tube amp "rustling sounds"
DJL
I have recently resurrected a non-master volume Riviera 725 by Pepco,
single channel amplifier. I am by no means a tube amp expert, and
need a little
advice. The amp has two 12AX7 9-pin sockets, a rectifier 5AR4 tube
socket, and 6L6 power tubes. The 6L6's are Sovtek, and the 12AX7's
are Jans Phillip, while the 5AR4 is made in China, Electronics brand,
or something. Anyhow, all brand new tubes.
I replaced both main caps, were 40uF-40uF units, replaced with
100uF-100uF units. I replaced the first 9-pin sockets, because
it was busted. I replaced the output transformer with one from
Hammond, wired for an 8 Ohm output. I also replaced numerous
caps (slightly larger values) and some resistors (same values) which
looked suspicious.
In short, it works, and sounds lovely, but there is a "rustling" sound
coming through the audio, even with nothing plugged in. It sort of
sounds like
paper flapping in the wind. When playing loudly, one cannot hear it,
and it seems to dissipate the warmer the amplifier becomes, but never
completely disappearing. I tapped the tubes, and the sound never
changes, and also ensured the tubes are securely in their sockets.
So, could it be any of the tubes, or something else? Any advice
appreciated, since I do not wish to fork out for another set of
power tubes if no one thinks that is the problem.
Regards.
PMG
retensioning?
Sometimes if an amp is biased a bit hot it makes all sorts of annoying
little sputtering and spitting sounds.
It doesn't sound like a matter of needing new power tubes to me.
Pete
ampmedic
or DeOxit.
Use a stiff tooth brush.
Clean up all around the sockets too.
Make sure you don't have cold or sloppy solder joints .
After you clean all the tube pins you may still hear
low volume sizzling sounds.
Plate resistors may need changing.
Don't use carbon comp.
The AmpMedic
Guitar Tube Amp
Servicing & Restoration
Serving The NY & L.I Area
Eml: me...@ampmedic.com
"DJL" <night...@hotmail.com> wrote in message
news:2d165cef.02091...@posting.google.com...
andrewunix
: Maybe the one 9 pin socket you didn't replace needs cleaning or
: retensioning?
:
: Sometimes if an amp is biased a bit hot it makes all sorts of annoying
: little sputtering and spitting sounds.
:
: It doesn't sound like a matter of needing new power tubes to me.
:
: Pete
A friend's Ampeg was doing this and it turned out to be plate resistors.
--
agreenbu @ nyx . net andrew michael greenburg
http://www.nyx.net/~agreenbu/
Dave Curtis
night...@hotmail.com (DJL) wrote:
>Hello Everyone,
>
>I have recently resurrected a non-master volume Riviera 725 by Pepco,
>single channel amplifier. I am by no means a tube amp expert, and
>need a little
>advice. The amp has two 12AX7 9-pin sockets, a rectifier 5AR4 tube
>socket, and 6L6 power tubes. The 6L6's are Sovtek, and the 12AX7's
>are Jans Phillip, while the 5AR4 is made in China, Electronics brand,
>or something. Anyhow, all brand new tubes.
>
>I replaced both main caps, were 40uF-40uF units, replaced with
>100uF-100uF units.
You may want to change the first cap in the PS
back to a 40. Most rectumfrier tubes have a max
value for the first cap and you don't want to
exceed it. I don't know the value for the 5AR4
right offhand, and as it's a controlled warm-up
tube it may not be a matter of concern.
> I replaced the first 9-pin sockets, because
>it was busted. I replaced the output transformer with one from
>Hammond, wired for an 8 Ohm output. I also replaced numerous
>caps (slightly larger values) and some resistors (same values) which
>looked suspicious.
It's usually a good idea to keep the signal cap
values the same (capacitance that is, voltage
ratings can increase). Try different values
(higher uF or lower) one at a time to see what
changes in the sound. Have you checked the values
of the resistors? They tend to drift, and are
quite affected by heat (carbon-comp thermistors).
>In short, it works, and sounds lovely, but there is a "rustling" sound
>coming through the audio, even with nothing plugged in. It sort of
>sounds like
>paper flapping in the wind. When playing loudly, one cannot hear it,
>and it seems to dissipate the warmer the amplifier becomes, but never
>completely disappearing. I tapped the tubes, and the sound never
>changes, and also ensured the tubes are securely in their sockets.
>
>So, could it be any of the tubes, or something else? Any advice
>appreciated, since I do not wish to fork out for another set of
>power tubes if no one thinks that is the problem.
Yes it could be tubes, or plate resistors, or
cathode resistors, or a bad connection... Hard
telling. It's definitely affected by heat. You
may be able to pin it down (if it's a resistor) by
hitting one resistor at a time with a "cold shot".
Good Luck,
-Dave
bill sundt
DJL wrote:
Try the simple thing first - borrow a 12AX7 and a 6L6 and try swapping
them for the tubes in the amp. If it is a bad tube you'll find out
quickly
and without even opening up the amp.
Bill Sundt
DJL
For future reference, I goofed. The power tubes are
6V6's, Electro-harmonix brand. I checked the
tension on that second 12AX7 socket, though the socket could
be dirty. I also swapped 12AX7 tubes, but not the
6V6 power tubes.
I also shot WD40 into the pots, and turned then, but
it made not difference in the rustling sound.
Also, before I open this thing back up, how do I dissipate
the caps? I never had to do it before, since the amp was
all in pieces when I first got it, and never had to worry
about it.
I will try everyone's suggestions, thank you.
andrewunix
:
: I also shot WD40 into the pots, and turned then, but
: it made not difference in the rustling sound.
I would recommend against using WD40 as a contact cleaner. It leaves a
residue that attracts dirt. The Caig Labs products are good for this
purpose.
It's possible that a pot has failed in such a way that cleaning it doesn't
fix the problem, too.
I would try replacing plate resistors before replacing pots, though.
: Also, before I open this thing back up, how do I dissipate
: the caps? I never had to do it before, since the amp was
: all in pieces when I first got it, and never had to worry
: about it.
Jumper the plate of a tube to the chassis with an alligator clip.
PMG
be referring to plates in the preamp section? That's the only place I
see any on any schematics I'm looking at (none for his amp though).
Pete
bill sundt
DJL wrote:
Try the simple thing first - borrow a 12AX7 and a 6L6 and try swapping
DJL
> 16 Sep 2002 08:10:11 -0700, night...@hotmail.com suggested:
> :
> : I also shot WD40 into the pots, and turned then, but
> : it made not difference in the rustling sound.
>
> I would recommend against using WD40 as a contact cleaner. It leaves a
> residue that attracts dirt. The Caig Labs products are good for this
> purpose.
Makes sense.
>
> It's possible that a pot has failed in such a way that cleaning it doesn't
> fix the problem, too.
True.
>
> I would try replacing plate resistors before replacing pots, though.
>
> : Also, before I open this thing back up, how do I dissipate
> : the caps? I never had to do it before, since the amp was
> : all in pieces when I first got it, and never had to worry
> : about it.
>
> Jumper the plate of a tube to the chassis with an alligator clip.
OK, this is where you got me. I do not know where the "plate"
is. Is this area somehow connected to the large caps? I need
to get myself a good book ...
Regards.
andrewunix
: andrewunix <agre...@nyx.net> wrote in message news:<slrnaocbu2....@nyx3.nyx.net>...
:>
:> : Also, before I open this thing back up, how do I dissipate
:> : the caps? I never had to do it before, since the amp was
:> : all in pieces when I first got it, and never had to worry
:> : about it.
:>
:> Jumper the plate of a tube to the chassis with an alligator clip.
:
: OK, this is where you got me. I do not know where the "plate"
: is. Is this area somehow connected to the large caps? I need
: to get myself a good book ...
The plate is a component of a tube. It will be attached to one or more
pins on the tube; this varies from one model to another. I would recommend
getting enough literature in front of you that you can at least identify
it.
DJL
OK everyone, here is the current status.
I tried new tubes, a little more quiet, but
not related to the rustling sound. I got myself
a book, and found what I thought to be the plate
resistors off the B+ supply and replaced them.
Still no dice. In my frustration, I plugged my
YJM308 overdrive into the front and nailed it.
Sounded awesome for all of 30 seconds, then no signal.
There was no smoke, or popping sounds that I could
hear, but you can still hear the power section "white noise",
yet no rustling. Before and after it stopped,
I tried component cooler, but could not locate the problem.
I plan on going in with a meter and testing the resistors
and caps. It would seem that the "bad" component has given out.
According to my book, this amp looks a lot like a Fender
circuit. Any other things I should check?
Regards.
Steve Cowell
...
> I plan on going in with a meter and testing the resistors
> and caps. It would seem that the "bad" component has given out.
> According to my book, this amp looks a lot like a Fender
> circuit. Any other things I should check?
Now that it's broke, you can fix it! Use an AC voltmeter and
find where the signal dies... easy as pie. No need to test all
the components of the amp... they might not test properly
with the meter anyway.
__
Steve
.
ampmedic
Have you changed all the plate resistors on the pre-amp tubes?
Did you suck out all the old solder from the joints before
installing the new components?
Any cold solder joints?
Bad grounds, especially at filter caps?
These are just the basics.
Did this amp work properly before you serviced it?
Why so high on the main caps?
Did you change the power resistors too?
The problem appears to be before the output.
Could be something you did (quite common) to contribute
to the problem.
The AmpMedic
Serving The NY & L.I Area
Eml: me...@ampmedic.com
"DJL" <night...@hotmail.com> wrote in message
news:2d165cef.0210...@posting.google.com...
DJL
Hello Everyone,
This is the current status. I replaced all resistors,
and capacitors. I also replaced the inductor. All resistors
have a 2% tolerance, and are at least 1/2W, mostly 1W.
And higher Watt values were replaced with such.
The power tubes, 6V6 are a matched set. When the amp
is on (standby switched on), one of the 6V6 tubes overheats.
I swapped tubes, and the problem remains with the particular
socket.
I recently bought Dan Torres' book, and have been reading
about bias. I am confused, because my amp's bias circuit
_looks_ nothing like any other the general schematics.
I have an analogue multi-meter, and the AC voltage on pin 5
looks to be around 26-28 volts, if I am reading it correctly.
There is a 220K load resistor from ground through pin 4 and
over to pin 8. Pin 8 also has a 0.1 uF capacitor (both sockets)
which goes off into the terminal strip. There is also a
330 Ohm 5%, 5W resistor from pin 3 of the bad socket,
to pin 4 of the good socket (used to be 350 Ohm).
The amp passes sound, and the rustling sound gets worse
as the one 6V6 starts to overheat. I made sure all the
pins were connecting.
I cannot find any red wire with a blue strype, the supposed bias
supply. I cannot find any diodes, or bias pots in the amp either.
Why is only one tube over heating? Are these 220K load
resistors the method used to set the bias? The only other
capacitors connected to the power tubes are the big filter
caps. I found one cold solder joint, and resoldered a bunch
of suspicious stuff. I always used a solder sucker, or
solder braid to clean, as well as alligator clip to heatsink.
Does anyone have a clue as to what I need to do now;
how to trouble shoot this? I know I could take it
in to a repair shop, but I resurrected this thing, and I
want to get it working correctly myself. Everything about the amp
was busted, missing, destroyed when I got it (for free).
Any help appreciated.
Regards.
RonSonic
This is confusing as all hell.
Does pin 8 connect directly to ground? If so, there should be a
negative DC voltage on pin 5 something about 12-15VDC. Check.
First suspect the capacitor that couples from the previous stage's
plate to the grid of this tube. Other suspects are the largish
resistor going from pin 5 to the negative bias voltage source (100 to
220K), and the smallish resistor (1K5 - 22K) in series with the
coupling capacitor to the grid.
IF pin 8 goes to ground through a resistor capacitor network, then
that largish resistor on pin 5 goes to ground. The other suspects
remain the same.
>The amp passes sound, and the rustling sound gets worse
>as the one 6V6 starts to overheat. I made sure all the
>pins were connecting.
>
>I cannot find any red wire with a blue strype, the supposed bias
>supply. I cannot find any diodes, or bias pots in the amp either.
What amp is this anyway? Ignore crap like what color a wire is
supposed to be, that's worse than TV movie bomb defusing. There may or
may not be a diode for a bias supply. There may be a selenium or it
may be cathode biased.
What amp is this?
>Why is only one tube over heating?
Compare voltage and DCR measurements from the good tube to the bad
tube. For the live measurements use a 60 or 100W bulb in line with the
power cord so you can work on it for more than a few moments before it
melts down.
>Are these 220K load
>resistors the method used to set the bias? The only other
>capacitors connected to the power tubes are the big filter
>caps. I found one cold solder joint, and resoldered a bunch
>of suspicious stuff. I always used a solder sucker, or
>solder braid to clean, as well as alligator clip to heatsink.
>
>Does anyone have a clue as to what I need to do now;
>how to trouble shoot this? I know I could take it
>in to a repair shop, but I resurrected this thing, and I
>want to get it working correctly myself. Everything about the amp
>was busted, missing, destroyed when I got it (for free).
Cool. If you don't have a schem, then LOOK AT THE AMP ON YOUR BENCH.
Presumably it did once work. all we need to do is determine what was
where back then. First figure out what sort of bias circuit it used to
have, then figure out what is different between the working and the
non-working tubes.
Be prepared to find a miswiring in your work. Not that I question your
ability, but it's a possibility any tech must consider when
"everything's been replaced but it still has a problem."
Ron
Steve Cowell
"RonSonic" <rons...@tampabay.rr.com> wrote in message
news:1pn5ruod5jrsj8q60...@4ax.com...
...
> What amp is this anyway? Ignore crap like what color a wire is
> supposed to be, that's worse than TV movie bomb defusing.
Hey Ron... ever see that British TV series "Danger: UXB"?
Now *that's* some real-life bomb defusing; amazing detail.
Opening shot, first episode... guy listening to a fuse with a
stethoscope, takes a hammer and chisel to the lock ring,
and **BOOM**. "Of course, there were no remains"...
highly recommended, and available on video.
__
Steve
.
RonSonic
I saw it when it first aired. Very good. I've read up on those guys
and their battle with the German bomb designers. Unreal what people
can do when they feel they must.
Not at all the same as the cliche argument over what damn color code
the bomber used.
Ron
DJL
numbers on the socket are quite useful if ONE READS THEM!
Maybe my eyes are failing. ;)
RonSonic <rons...@tampabay.rr.com> wrote in message news:<1pn5ruod5jrsj8q60...@4ax.com>...
[snip]
> This is confusing as all hell.
I bet it was!
> Does pin 8 connect directly to ground? If so, there should be a
> negative DC voltage on pin 5 something about 12-15VDC. Check.
>
> First suspect the capacitor that couples from the previous stage's
> plate to the grid of this tube. Other suspects are the largish
> resistor going from pin 5 to the negative bias voltage source (100 to
> 220K), and the smallish resistor (1K5 - 22K) in series with the
> coupling capacitor to the grid.
>
> IF pin 8 goes to ground through a resistor capacitor network, then
> that largish resistor on pin 5 goes to ground. The other suspects
> remain the same.
This sounds right, looking at my now correct drawing.
Pin 8 on the good socket goes directly over to pin 8 on the bad
socket. The 5W 330 Ohm resistor goes from pin 8 on the bad socket
to pin 1 on the good socket, which is connected to ground.
I hope this makes more sense.
>
> >The amp passes sound, and the rustling sound gets worse
> >as the one 6V6 starts to overheat. I made sure all the
> >pins were connecting.
> >
> >I cannot find any red wire with a blue strype, the supposed bias
> >supply. I cannot find any diodes, or bias pots in the amp either.
>
> What amp is this anyway? Ignore crap like what color a wire is
> supposed to be, that's worse than TV movie bomb defusing. There may or
> may not be a diode for a bias supply. There may be a selenium or it
> may be cathode biased.
>
> What amp is this?
I will ignore all crap from now on. It is a Pepco Riviera 725 from
the 1960's.
Thanks, I believe it is a miswire also. I looked back at my notes,
and one wire on the terminal strip is draw to one location on one
drawing, and another location on another drawing. I will recheck
everything now that I have read the pinouts right!
Regards.
RonSonic
>First, let me say I read the pins wrong. Those little
>numbers on the socket are quite useful if ONE READS THEM!
>Maybe my eyes are failing. ;)
>
>RonSonic <rons...@tampabay.rr.com> wrote in message news:<1pn5ruod5jrsj8q60...@4ax.com>...
>[snip]
>> This is confusing as all hell.
>
>I bet it was!
>
>> Does pin 8 connect directly to ground? If so, there should be a
>> negative DC voltage on pin 5 something about 12-15VDC. Check.
>>
>> First suspect the capacitor that couples from the previous stage's
>> plate to the grid of this tube. Other suspects are the largish
>> resistor going from pin 5 to the negative bias voltage source (100 to
>> 220K), and the smallish resistor (1K5 - 22K) in series with the
>> coupling capacitor to the grid.
>>
>> IF pin 8 goes to ground through a resistor capacitor network, then
>> that largish resistor on pin 5 goes to ground. The other suspects
>> remain the same.
>
>This sounds right, looking at my now correct drawing.
>
>Pin 8 on the good socket goes directly over to pin 8 on the bad
>socket. The 5W 330 Ohm resistor goes from pin 8 on the bad socket
>to pin 1 on the good socket, which is connected to ground.
>
>
>I hope this makes more sense.
Yeeeaaassss it does. Okay. You've got a cathode biased amp. There's
going to be a capacitor across that 330 R. The grid, pin 5, will have
a large resistor going to ground as a reference, if that is open or
unconnected, it'll let that tube runaway. Measure VDC from grid to
ground with the amp on no tubes, if you've got anything over a stray
mV or so then the coupling cap is bad.
Plug tubes in, measure from ground to cathode (pin 8) should be the
same on both tubes, else bad connection.
Tube pins are numbered clockwise from below (the natural view), pin 1
is just to the right of the key, or the gap in a 7 or 9 pin tube.
HTH,
Ron
DJL
Hello Ron,
I do not recall what the exact measurement was from ground to cathode,
but I do remember them being the same. I do not want to mislead anyone
here, and want to clarify that I have never had this amplifier working
correctly, and with the tubes being new, I believe this may be a bias
issue.
I measured the bias using the transformer shunt method (one VOM lead on
the rectifier tube, the other connected to the power tube). The "bad"
tube read 41 to 42 DC mA, and the other tube read 34 to 35 DC mA. The
plate voltage is about 440 VDC. Looking at my charts, the bias should
be 16.9 DC mA, or thereabouts.
Now, I would guess that each power tube has a resistor associated
with it, which would need to be increased in order to decrease
the current draw. I posted a partial schematic (ugly) on my
web site, because I am a little confused. The one tube has a 1.1K
resistor (for the one drawing 41 mA), but the wiring for the other
tube (drawing 34 mA) has thrown me for a loop. It looks to have
a 69K resistor, yet there is a wire coming from pin 6 of the
second 12AX7 tube. Am I looking at the correct resistors, or
should I look elsewhere?
http://www.angelfire.com/on4/ontariomtovision/schem.jpg
Regards.
RonSonic
Well yeah, it is a bias issue.
>I measured the bias using the transformer shunt method (one VOM lead on
>the rectifier tube, the other connected to the power tube). The "bad"
>tube read 41 to 42 DC mA, and the other tube read 34 to 35 DC mA. The
>plate voltage is about 440 VDC. Looking at my charts, the bias should
>be 16.9 DC mA, or thereabouts.
>
>Now, I would guess that each power tube has a resistor associated
>with it, which would need to be increased in order to decrease
>the current draw.
That would be the 330R going to ground.
BUT. you've got somewhat different behavior between the two tubes. One
is cooking the other isn't. The coupling caps are still suspect. It
may well be that both these tubes are too hot to run in this amp. BUT,
you report IIRC that the one socket is the one where the glowing is
going on even when you swap tubes. This says there's a problem with
that socket which doesn't exist for the other. Either the coupling cap
is bad or those 220K's aren't making it to ground. Pull the outputs
and measure DCV from pin 5 to ground with the amp on.
>I posted a partial schematic (ugly) on my
>web site, because I am a little confused. The one tube has a 1.1K
>resistor (for the one drawing 41 mA), but the wiring for the other
>tube (drawing 34 mA) has thrown me for a loop. It looks to have
>a 69K resistor, yet there is a wire coming from pin 6 of the
>second 12AX7 tube. Am I looking at the correct resistors, or
>should I look elsewhere?
>
>http://www.angelfire.com/on4/ontariomtovision/schem.jpg
There's going to be another 69K resistor going from pin 8 to ground on
the PI tube - I'm guessing you didn't draw it. I'm thinking that 1K1
belongs on the other side of the coupling cap and that there should be
one on the other side.
Check for DC+ on the grids first.
Ron
DJL
You guys are going to think that I am daft, maybe you already
do. I went and added two 1K in parallel, for 500 Ohms, in
series with the 330 Ohm resistor. I also put a 47 uF cap
in parallel with it. This brought the current draw
right down to 17 mA for _EACH_ tube. No more overheating.
This confuses the living daylights out of me, since when
one was overheating, it was pulling more current (34 vs 41).
I triple checked before and after adding the new resistors
and cap, same results. I played through the amp for 15
minutes, with no change in readings afterwards, and no
overheating. The only explanation I can think of is that
when the one tube overheated it drew more current, due to
maybe a slight variance between the tubes? Anyhow, that
is taken care of.
Ron, double checking the amp, there is no other 69K on
the other side, The 1.1K is in series with the coupling
cap also. Maybe I should neatly draw out the entire
circuit, so everyone else can preview my monster. All
for kicks of course, or in case some other sorry soul
gets a hold of one of these amps!
Anyhow, back to the original issue, the rustling sound.
In replacement of every capacitor and resistor in this
amplifier, the sound has never left. Of course, it became
less loud once all the resistor were replaced, but since
old resistors drift in value, the gain of the signal could
have went down with new resistors. The sound is not
effected by the volume control, once standby is switched
on, the sound is there. The following were
mentioned previously:
1. Improperly ground filter caps.
- the caps are the can type, with tabs that are soldered
to the chasis for the ground. There are four tabs.
Would a bad solder joint on one of these tabs cause
issues even if the other three have good solder contact?
2. Bad solder joint.
3. Dirty contact.
Would these be the main areas to check? Anything else?
Regards.
Dave Curtis
Well, the typical complaint for this isn't exactly described as a
rustling sound :o)
> - the caps are the can type, with tabs that are soldered
> to the chasis for the ground. There are four tabs.
> Would a bad solder joint on one of these tabs cause
> issues even if the other three have good solder contact?
Not likely. I've seen some (a lot) with just one tab soldered. Most
are made so that when you twist the tab it has fingers that will hold
it securely in place (once all 4 are twisted). One soldered tab makes
the connection to the case which is the common negative terminal for
all caps in the can (usually).
>2. Bad solder joint.
Ayuh. Sometimes impossible to see. Doesn't normally make a rustling
noise, but it's a possibility.
>3. Dirty contact.
Yessah. Usually found by "swirling" the (preamp) tube in it's socket
with everything up & running at moderate volume. The closer you get to
your output tubes when doing this, the louder the (probable) pops will
be, so if you want to give your driver or output tubes a wiggle, you
may want to hit the standby first...
>Would these be the main areas to check? Anything else?
(inhaling)-->Ayuh. Tubes themselves. More than once I've had
"suspected good" tubes turn out to be the culprit (even new ones).
Try this (if you haven't already):
With only the power tubes and driver installed, power up. Noise?
It's in this stage. No rustle? It comes frome the previous stage.
Pop in the next tube upstream from the driver. Noise? It's in this
stage. No noise? It comes frome the previous stage, etc, etc.
HTH,
-Dave
Tony Hwang
Do you have scope? Maybe parasitic oscillation?
Couple pico farad between plate and grid, you know what.
If it is, will be able to see with scope.
Good luck,
Tony
DJL
> > - the caps are the can type, with tabs that are soldered
> > to the chasis for the ground. There are four tabs.
> > Would a bad solder joint on one of these tabs cause
> > issues even if the other three have good solder contact?
>
> Not likely. I've seen some (a lot) with just one tab soldered. Most
> are made so that when you twist the tab it has fingers that will hold
> it securely in place (once all 4 are twisted). One soldered tab makes
> the connection to the case which is the common negative terminal for
> all caps in the can (usually).
All four are soldered on each cap, so I _should_ be able to rule this out.
> >2. Bad solder joint.
>
> Ayuh. Sometimes impossible to see. Doesn't normally make a rustling
> noise, but it's a possibility.
Rustling, popping, spitting. But I suppose a bad solder joint
would must likely cause intermitant signal, and/or ground hum.
>3. Dirty contact.
>
> Yessah. Usually found by "swirling" the (preamp) tube in it's socket
> with everything up & running at moderate volume. The closer you get to
> your output tubes when doing this, the louder the (probable) pops will
> be, so if you want to give your driver or output tubes a wiggle, you
> may want to hit the standby first...
>
> >Would these be the main areas to check? Anything else?
>
> (inhaling)-->Ayuh. Tubes themselves. More than once I've had
> "suspected good" tubes turn out to be the culprit (even new ones).
> Try this (if you haven't already):
I have two brand new sets of tubes (power, preamp, rectifier) that I tried,
same problem. I also tried a bunch of old preamps tubes I had.
The ones I am currently using are the Tesla JJ ECC83, JAN Phillips 6V6,
and a Sovtek 5AR4. All my power tubes are matched.
>
> With only the power tubes and driver installed, power up. Noise?
> It's in this stage. No rustle? It comes frome the previous stage.
> Pop in the next tube upstream from the driver. Noise? It's in this
> stage. No noise? It comes frome the previous stage, etc, etc.
>
> HTH,
> -Dave
Well, with both preamp tubes out, same noise.
With both preamp tubes out, and one 6V6 out,
no noise. Swapped the 6V6 to the other socket, noise.
Switch 6V6, swap sockets, no noise, switch back, noise.
Is this a feasible test to pull one of the power tubes?
If so, should I attempt to resolder all the pins of the
"noisy" socket?
Regards.
DJL
> Hi,
> Do you have scope? Maybe parasitic oscillation?
> Couple pico farad between plate and grid, you know what.
> If it is, will be able to see with scope.
> Good luck,
> Tony
No, unfortunately I do not have a scope.
Are you suggesting that I put a small value
(pico farad) capacitor across the plate
and grid? By grid, do you mean the control
grid, or the screen grid?
Regards.
CompUser
> Well, with both preamp tubes out, same noise.
> With both preamp tubes out, and one 6V6 out,
> no noise. Swapped the 6V6 to the other socket, noise.
> Switch 6V6, swap sockets, no noise, switch back, noise.
>
> Is this a feasible test to pull one of the power tubes?
> If so, should I attempt to resolder all the pins of the
> "noisy" socket?
Hey Dave,
Where you also the guy that was saying one 6V6 was
glowing red, but not the other...?
Could you be getting some arcing going on in the
"noisy" socket? Check to see if the control
grid contact on both 6V6 sockets is showing similar
voltage (-34 VDC or so, measured to chassis), and take a
good look at the "noisy" socket to see if all the contacts
appear to be in good (similar) condition and making
correct contact with the tube pins.
What do you *real* amp techs think? Check screen
resistors too?
Did you ever get around to checking the bias on the
6V6's? I think I asked this a while back (if it was
you), but I missed your answer...
Steve
hobbyist type, one each.
DJL
> > Well, with both preamp tubes out, same noise.
> > With both preamp tubes out, and one 6V6 out,
> > no noise. Swapped the 6V6 to the other socket, noise.
> > Switch 6V6, swap sockets, no noise, switch back, noise.
> >
> > Is this a feasible test to pull one of the power tubes?
> > If so, should I attempt to resolder all the pins of the
> > "noisy" socket?
>
> Hey Dave,
>
> Where you also the guy that was saying one 6V6 was
> glowing red, but not the other...?
Yes.
>
> Could you be getting some arcing going on in the
> "noisy" socket? Check to see if the control
> grid contact on both 6V6 sockets is showing similar
> voltage (-34 VDC or so, measured to chassis), and take a
> good look at the "noisy" socket to see if all the contacts
> appear to be in good (similar) condition and making
> correct contact with the tube pins.
I re-crimped the tube pins last night to ensure good contact.
I will measure the control grid voltage tonight.
>
> What do you *real* amp techs think? Check screen
> resistors too?
All the resistors, caps and inductor have been replaced in
the amplifier. The noise has never gone away, so I would
guess it is in a contact that I have not touched as of yet.
> Did you ever get around to checking the bias on the
> 6V6's? I think I asked this a while back (if it was
> you), but I missed your answer...
>
> Steve
> hobbyist type, one each.
Yes, the bias was high. I changed the resistor from
330 Ohms to a series/parallel setup for a total of 830 Ohms.
Now the bias is about 17 DC mA per tube. My charts show
16.9 DC mA for 440 plate volts, so I tought this was a pretty
close match.
Regards.
CompUser
> I will measure the control grid voltage tonight.
The "tube pins"?? Or the socket contacts??
Did the look ok, before you started?
> Yes, the bias was high.
What does "bias was high" mean??.
> I changed the resistor from
> 330 Ohms to a series/parallel setup for a total of 830 Ohms.
"The resistor" was...what resistor? What's a
"series/parallel setup"??
> Now the bias is about 17 DC mA per tube. My charts show
> 16.9 DC mA for 440 plate volts, so I tought this was a pretty
> close match.
Sometimes thinking gets us in a peck o' trouble ;-)
What was PLATE voltage on 6V6s, when you were getting
the 16.9 mA (need to to the P=IE and get the watts for
what each 6V6 is dissipating @ idle). The 16.9mA kinda is
useless by itself...
Steve
DJL
> > I re-crimped the tube pins last night to ensure good contact.
> > I will measure the control grid voltage tonight.
>
> The "tube pins"?? Or the socket contacts??
> Did the look ok, before you started?
Sorry, the socket contacts that receive the pins.
>
>
> > Yes, the bias was high.
>
> What does "bias was high" mean??.
One side read 41-42 mA, the other 34-35 mA at 440V plate.
>
> > I changed the resistor from
> > 330 Ohms to a series/parallel setup for a total of 830 Ohms.
>
> "The resistor" was...what resistor? What's a
> "series/parallel setup"??
The one connected to pin 8 of the power tubes. I put two 1K Ohm in parallel
and wired that in series with a 330 Ohm.
>
> > Now the bias is about 17 DC mA per tube. My charts show
> > 16.9 DC mA for 440 plate volts, so I thought this was a pretty
> > close match.
>
> Sometimes thinking gets us in a peck o' trouble ;-)
>
> What was PLATE voltage on 6V6s, when you were getting
> the 16.9 mA (need to to the P=IE and get the watts for
> what each 6V6 is dissipating @ idle). The 16.9mA kinda is
> useless by itself...
>
> Steve
Looks like it has crept up a bit, to around 464V.
How does anyone ever get this right, one must have
tonnes of patience.
I assume I should increase the resistance on pin eight.
It never occurred to me that the plate voltage would go up. Does
any of this make sense? Wait a minute, I had to
replace the inductor with a resistor, because it started
to fry, so I stuck a 330 Ohm 10 W in its place. Would
this be the likely cause of the increase?
Does anyone know where one can buy good inductors on the
net?
Previously when you said check the voltage at the control
grid on the 6V6s, did you mean pin five? I get nothing.
Negative contact to pin five, positive contact to ground
(analogue meter). Now there is a 220K load resistor from
pin five to pin one, then to ground, so is this the reason
I am reading zero volts, or am I totally misunderstanding
this?
Regards.
CompUser
>
> One side read 41-42 mA, the other 34-35 mA at 440V plate.
Yipes...these are 6V6's?!? That's something like 18 and
14 watts dissipating at idle...sounds like right at
the bleeding edge of tube melt down!
> >
> > > I changed the resistor from
> > > 330 Ohms to a series/parallel setup for a total of 830 Ohms.
> The one connected to pin 8 of the power tubes. I put two 1K Ohm in parallel
> and wired that in series with a 330 Ohm.
Ok, so you changed the kathode resistor...why? Too cool
down the idle? Sounds like it worked (see below). The
question this leads too is "why did it get so hot in there,
in the first place?"
> >
> > > Now the bias is about 17 DC mA per tube. My charts show
> > > 16.9 DC mA for 440 plate volts, so I thought this was a pretty
> > > close match.
While the tubes will last a lot longer at 7.4 watts (one
of the *actual techs* here can probably tell ya how much
longer) than 18 or 14 watts, you might not like the sound
of a the amp. I took my Laney up from about 7.5 to 9.5
watts at idle, and it was as if the thing came alive!!
I wonder if the "rustling sounds" could have been
arcing inside the tubes, if the plate and screen
were starting to deform/droop/etc, passing all that
current.
> Looks like it has crept up a bit, to around 464V.
> How does anyone ever get this right, one must have
> tonnes of patience.
As you tweak the bias, the plate voltage can change...
you're letting more or less of it leak thru the power
tubes.
>
> I assume I should increase the resistance on pin eight.
> It never occurred to me that the plate voltage would go up. Does
> any of this make sense?
See above :-)
> Wait a minute, I had to
> replace the inductor with a resistor, because it started
> to fry, so I stuck a 330 Ohm 10 W in its place. Would
> this be the likely cause of the increase?
Ooops, you got my non-tech butt there...inductor, where
did *that* come from?!? Might this be a filter choke?
I have *zero* knowledge on chokes in B+ supplies...don't
know if subbing a resistor for one is cool, either...
But, if you really did a big reduction in the idle current,
that would increase your "available" B+...you're simply
not bleeding off as much thru the power tubes.
>
> Does anyone know where one can buy good inductors on the
> net?
If no one jumps in on this, you might post it again
as separately titled query...be sure and specify the
model amp ;-)
> Previously when you said check the voltage at the control
> grid on the 6V6s, did you mean pin five? I get nothing.
> Negative contact to pin five, positive contact to ground
> (analogue meter). Now there is a 220K load resistor from
> pin five to pin one, then to ground, so is this the reason
> I am reading zero volts, or am I totally misunderstanding
> this?
Yes, control grid on 6V6, pin five...I was wondering if your
amp has "fixed bias" (where idle current is controlled by
imposing a NEGATIVE DC voltage onto the control grid) or by
"cathode biasing" (uses relationship between cathode/cathode
resistor/grid to make cathode appear positive to grid).
Sounds like your amp's using cathode bias. Since Pin One
is not connected in glass bottle 6V6's, they just used the
Pin One contact as a mount point for the grid-to-gnd
resistor. If you had fixed biasing, you'd have seen
something around -35 on Pin Five..
There's a very useful article on biasing by Lord Valve,
on the AGA web site, http://aga.rru.com ...other excellent
articles at Randall Aiken's site, http://www.aikenamps.com .
Again, I'm not a pro, or a tech...but I do enjoy this
stuff, and I believe I haven't led you astray with anything,
so far! [1]
Steve
Steve Cowell
...
> Ooops, you got my non-tech butt there...inductor, where
> did *that* come from?!? Might this be a filter choke?
> I have *zero* knowledge on chokes in B+ supplies...don't
> know if subbing a resistor for one is cool, either...
> But, if you really did a big reduction in the idle current,
> that would increase your "available" B+...you're simply
> not bleeding off as much thru the power tubes.
That value of resistor is unsuitable for subbing for a choke...
the voltage is way high, explaining why you had to up
the cathode resistor. You should have used a bigger
resistor, probably 2k, 2w or thereabouts.
You really should put a choke back in... AES has them:
Good luck.
__
Steve
.
DJL
> > > What does "bias was high" mean??.
> >
> > One side read 41-42 mA, the other 34-35 mA at 440V plate.
>
> Yipes...these are 6V6's?!? That's something like 18 and
> 14 watts dissipating at idle...sounds like right at
> the bleeding edge of tube melt down!
Yep, 6V6s. Well one was glowing :).
> > >
> > > > I changed the resistor from
> > > > 330 Ohms to a series/parallel setup for a total of 830 Ohms.
>
> > The one connected to pin 8 of the power tubes. I put two 1K Ohm in parallel
> > and wired that in series with a 330 Ohm.
>
> Ok, so you changed the kathode resistor...why? Too cool
> down the idle? Sounds like it worked (see below). The
> question this leads too is "why did it get so hot in there,
> in the first place?"
Yes, to cool down the idle. I had never had it running
before, never had tubes in it, so this was the first
tube set in it.
> > >
> > > > Now the bias is about 17 DC mA per tube. My charts show
> > > > 16.9 DC mA for 440 plate volts, so I thought this was a pretty
> > > > close match.
>
> While the tubes will last a lot longer at 7.4 watts (one
> of the *actual techs* here can probably tell ya how much
> longer) than 18 or 14 watts, you might not like the sound
> of a the amp. I took my Laney up from about 7.5 to 9.5
> watts at idle, and it was as if the thing came alive!!
>
> I wonder if the "rustling sounds" could have been
> arcing inside the tubes, if the plate and screen
> were starting to deform/droop/etc, passing all that
> current.
I blew up my multi-meter, tried to do voltage when the
meter was on current. Blew the fuse as well as the
main board in the meter. One would think that the fuse
should below before damage like that occurred, mass
produced garbage with too big of a fuse. Anyhow, I went
and blew a wad on a new spiffy digital multi-meter.
With my current setup in the amp, the plate is reading
450V at the plate, and 15.5 DC mA per tube. A little
low, but anyhow. The new meter is _WAY_ more accurate,
so I suppose the old one getting nuked was a blessing in
disguise. I am guessing I should buy another set of
power tubes, and give it another round. Now that the
idle current is down, if I get another matched pair that
draws the same current as the old ones, then I should
be good to go, if this is the problem.
[snip]
> > Wait a minute, I had to
> > replace the inductor with a resistor, because it started
> > to fry, so I stuck a 330 Ohm 10 W in its place. Would
> > this be the likely cause of the increase?
>
> Ooops, you got my non-tech butt there...inductor, where
> did *that* come from?!? Might this be a filter choke?
> I have *zero* knowledge on chokes in B+ supplies...don't
> know if subbing a resistor for one is cool, either...
> But, if you really did a big reduction in the idle current,
> that would increase your "available" B+...you're simply
> not bleeding off as much thru the power tubes.
It looks like a comp. resistor, but there is five bands on it.
I already posted another message to see if any one can identify
it. I tried different resistor values in place of the "inductor",
but the plate did not seem to change. A book by Dan Torres says
one can perform a replacement like this, though it will change
to sound.
[snip]
> Sounds like your amp's using cathode bias. Since Pin One
> is not connected in glass bottle 6V6's, they just used the
> Pin One contact as a mount point for the grid-to-gnd
> resistor. If you had fixed biasing, you'd have seen
> something around -35 on Pin Five..
Makes sense.
> There's a very useful article on biasing by Lord Valve,
> on the AGA web site, http://aga.rru.com ...other excellent
> articles at Randall Aiken's site, http://www.aikenamps.com .
> Again, I'm not a pro, or a tech...but I do enjoy this
> stuff, and I believe I haven't led you astray with anything,
> so far! [1]
>
> Steve
You are _most_ helpful.
Regards.
CompUser
> meter was on current. Blew the fuse as well as the
> main board in the meter.
I did something similar to mine (a Harbor Freight
Salvage, all of $4.99 I think).
> The new meter is _WAY_ more accurate,
> so I suppose the old one getting nuked was a blessing in
> disguise.
There ya go, same here!
> It looks like a comp. resistor, but there is five bands on it.
> I already posted another message to see if any one can identify
> it. I tried different resistor values in place of the "inductor",
> but the plate did not seem to change. A book by Dan Torres says
> one can perform a replacement like this, though it will change
> to sound.
Yes, you got a reply from one of the more experienced (than
me, heh!) folks on that inquiry...a resistor, and the
explanation for your higher B+, to boot!
>
> You are _most_ helpful.
>
My pleasure...I've gotten *lots* of helpful info
from many folks in AGA, since I bumped in here in
spring of 2000. I'm glad to help someone else!!
Steve
Tony Hwang
Newer Simpson has circuit breaker built-in which works quite fast/well.
For under 100.00 we can get true RMS reading DVM now.
Tony
Dave Curtis
<steve762u...@yahoo.com> wrote:
>> I blew up my multi-meter, tried to do voltage when the
>> meter was on current. Blew the fuse as well as the
>> main board in the meter.
You also probably took a *lot* of life out of that particular 6V6 at
the same time. That's probably why they aren't matched anymore.
FWIW, if you'd had the amp plugged into a series-wired light bulb
(poor man's variac), you would have most likely averted extensive
damage to the meter or the OP tube. (don't ask me how I know this...)
:o) Not to mention the light bulb going off would remind you that
you just screwed up. Using a high enough wattage bulb will keep the
voltage to the amp at fairly close to line voltage. I use a PowerStat
after the bulb to make sure the amp gets 125 VAC.
My .02 dB,
-Dave
BTW, try looking at the amp in total darkness and see if you can see
any arcing going on during the noise. I have a feeling new OP tubes
are going to help.
Good luck, and keep us posted!
DJL
> On Sun, 27 Oct 2002 04:59:23 GMT, CompUser
> <steve762u...@yahoo.com> wrote:
>
> >> I blew up my multi-meter, tried to do voltage when the
> >> meter was on current. Blew the fuse as well as the
> >> main board in the meter.
>
> You also probably took a *lot* of life out of that particular 6V6 at
> the same time. That's probably why they aren't matched anymore.
True, but the "non-matchiness" probably happened when the amp
was biased so hot previously. Either way, my current 6V6s are
rather "cooked". :)
> FWIW, if you'd had the amp plugged into a series-wired light bulb
> (poor man's variac), you would have most likely averted extensive
> damage to the meter or the OP tube. (don't ask me how I know this...)
> :o) Not to mention the light bulb going off would remind you that
> you just screwed up. Using a high enough wattage bulb will keep the
> voltage to the amp at fairly close to line voltage. I use a PowerStat
> after the bulb to make sure the amp gets 125 VAC.
And I have just the light bulb for the job.
>
> My .02 dB,
> -Dave
>
> BTW, try looking at the amp in total darkness and see if you can see
> any arcing going on during the noise. I have a feeling new OP tubes
> are going to help.
Good suggestion, thank you.
>
> Good luck, and keep us posted!
Will do.
Regards.
DJL
> Dave Curtis <dwav...@yahoo.con> wrote in message news:<kbmnruoflsvgksgd9...@4ax.com>...
> > On Sun, 27 Oct 2002 04:59:23 GMT, CompUser
> > <steve762u...@yahoo.com> wrote:
> >
> > Good luck, and keep us posted!
>
> Will do.
>
> Regards.
Hello Everyone,
This experience is making me want to go out a buy a new tube amp :|.
Anyhow, the show must go on.
I replaced the #1 resistor in the FC section with a 3.9K 2% 2W,
which is the closest to 3.8K I could locate. Now, even with
the _old_supposedly_toasted tubes I turned it on, and I swore
I heard no noise for a bit, then "pfft". There was no smoke,
or noise. I went and check all the resistors for a short and
found none (continuity check). Now, I started swapping in my
new tubes, same noise. I have two "old" sets, and two "new" sets.
Then again that "pfft" noise could have been my imagination. I
am going to put the other (330 + 330) 660 Ohm 10W back in to check.
With any of the four sets in the amp, the bias is all screwed
up now. Plate voltage reads a steady 454V. The current draw
on one tube is 15.3 DC mA, while the other is 17.6 DC mA.
Old tubes, new tubes, no difference. What in the world could have
happened now? Cathode biased amp. I have about 1150 Ohm in the
cathode at the moment.
Thoughts, suggestions, locations of a good bridge to leap from? ;)
Regards.
DJL
> With any of the four sets in the amp, the bias is all screwed
> up now. Plate voltage reads a steady 454V. The current draw
> on one tube is 15.3 DC mA, while the other is 17.6 DC mA.
> Old tubes, new tubes, no difference. What in the world could have
> happened now? Cathode biased amp. I have about 1150 Ohm in the
> cathode at the moment.
I just read a FAQ by Lord Valve, and it indicated that my tubes
may not be "closely" matched, and that a few mA difference is nothing
to sweat over. I find it bizarre that before I put in that
3.9K resistor, that the current was _always_ the same on both tubes.
Then again, maybe the circuit was not operating the way it should,
when 660 Ohms were in the #1 FC position, and not the "more original"
3.9K Ohms.
With respect to the crackling and popping. Are there specific pins I
should start with? The volume knob does not seem to affect the
noise, so I suspect, like we all discussed before, that it is in
the power section. Should I start by resoldering specific pins,
or clean and resolder every power tube pin?
Regards.