JCM 800 reverb problem
markd
to a tech because of two problems: very high pitched feedback sound
when gain was set to 7 or above, and a separate lower-pitched but
louder feedback sound (at the time I they might be related somehow).
The seller swore he had it checked out before he sold it, and I could
only assume something happened during it's shipment across the US.
The tech found one of the power tubes was bad, and one of the
capacitors was loose. He replaced all preamp tubes with Sovteks, the
power tubes with Mullards and tighted up the capacitor. He also
checked the bias, and did basic diagnostics.
Everything seemed fine after spending time with the tech going over
everything and when I got home... but I discovered the low-pitched
feedback will assert itself simply by setting the reverb to 6 or
above. It only starts when there's no input to the amp (ie. not
playing/muting all strings), and slowly builds up to a high volume.
The problem immediately goes away as soon as I switch the reverb off
or turn it below 6. Is this a common problem with JCM 800 models of
this age (and do most peple just use a reverb pedal instead)? Anyone
have an idea what might be causing it? The tech that did the repairs
is 2+ hours of driving from where I live, so it's rather inconvenient.
It's obviously nothing he did to it since the behavior was there
beforehand.
Thanks
Phil_S
"markd" <mark...@NOSPAMgmail.com> wrote in message
news:s6ptn5tn8th6o2rub...@4ax.com...
> I recently bought a 1987 Marshall JCM 800 combo online. I brought it
> to a tech because of two problems: very high pitched feedback sound
> when gain was set to 7 or above, and a separate lower-pitched but
> louder feedback sound (at the time I they might be related somehow).
> The seller swore he had it checked out before he sold it, and I could
> only assume something happened during it's shipment across the US.
>
> The tech found one of the power tubes was bad, and one of the
> capacitors was loose. He replaced all preamp tubes with Sovteks, the
> power tubes with Mullards and tighted up the capacitor. He also
> checked the bias, and did basic diagnostics.
I hope you got back all the old tubes. Preamp tubes take a long time to get
tired and Sovteks are the cheapest, least toneful tubes out there. They
also have the lowest noise floor. If you didn't get them back, call him up
and ask him to send them to you. You own them, not him. Get the power
tubes, too.
>
> Everything seemed fine after spending time with the tech going over
> everything and when I got home... but I discovered the low-pitched
> feedback will assert itself simply by setting the reverb to 6 or
> above. It only starts when there's no input to the amp (ie. not
> playing/muting all strings), and slowly builds up to a high volume.
>
> The problem immediately goes away as soon as I switch the reverb off
> or turn it below 6. Is this a common problem with JCM 800 models of
> this age (and do most peple just use a reverb pedal instead)? Anyone
> have an idea what might be causing it? The tech that did the repairs
> is 2+ hours of driving from where I live, so it's rather inconvenient.
> It's obviously nothing he did to it since the behavior was there
> beforehand.
>
> Thanks
>
Are you saying it did this before you took it to the tech, didn't do this at
the tech's shop, but did it again when you got home? When your were at the
tech, did you do the exact same thing you did at home to produce the
problem? If so, it's the location, not the amp.
Take it over to a friend's house or even outside, and see what happens. Try
a different room, one that you know is on a different circuit branch. Turn
off all florescent lights, including those new fangled ones people are using
in place of incandescents. Do you live near power lines? Do you live near
a radio or TV broadcast tower?
Where are you located? 2 hours is too far a way for a casual visit. Maybe
you'll get a recommendation that's closer.
Phil Allison
"markd"
>
>I recently bought a 1987 Marshall JCM 800 combo online. I brought it
> to a tech because of two problems: very high pitched feedback sound
> when gain was set to 7 or above,
** That is either a microphonic tube ( ie 12AX7) or the result of the input
jack not shorting as it should with no plug inserted.
The latter is a very high pitched squeal and goes way if a lead in plugged
into the amp.
> ... but I discovered the low-pitched
> feedback will assert itself simply by setting the reverb to 6 or
> above. It only starts when there's no input to the amp (ie. not
> playing/muting all strings), and slowly builds up to a high volume.
** That my friend is a dodgy or worn out reverb tank - not un-common in an
amp that is 23 years old.
Sometimes this problem can be fixed but the best option is to install a new
tank - Accutronics make them and they are readily available in the US for
under $30.
The part number is printed on the unit - something like " 8DB2C1B ".
.... Phil
Phil Allison
"Phil_S"
>
> I hope you got back all the old tubes.
** Nonsense.
> Preamp tubes take a long time to get tired and Sovteks are the cheapest,
> least toneful tubes out there.
** More nonsense.
The Chinese ones are the cheapest and crappiest.
> They also have the lowest noise floor.
** More nonsense - Sovtek X7s are notorious for hum and micophony problems.
> If you didn't get them back, call him up and ask him to send them to you.
** He has no obligation to do that and will have tossed those old tubes in
the bin by now .
>You own them, not him.
** Twaddle.
> Get the power tubes, too.
** Stupid and BAD advice.
Worn out and faulty tubes should never be returned to customers - lest
they try using them in the same or another amp and do harm or on sell them
fraudulently.
Rest of this utter cretin's brain dead drivel snipped to prevent me spewing
on the keyboard.
... Phil
Phil Allison
<Rednef>
markd
>>
>>Everything seemed fine after spending time with the tech going over
>>everything and when I got home... but I discovered the low-pitched
>>feedback will assert itself simply by setting the reverb to 6 or
>>above. It only starts when there's no input to the amp (ie. not
>>playing/muting all strings), and slowly builds up to a high volume.
>>
>>The problem immediately goes away as soon as I switch the reverb off
>>or turn it below 6. Is this a common problem with JCM 800 models of
>>this age (and do most peple just use a reverb pedal instead)? Anyone
>>have an idea what might be causing it? The tech that did the repairs
>>is 2+ hours of driving from where I live, so it's rather inconvenient.
>>It's obviously nothing he did to it since the behavior was there
>>beforehand.
>
>
> It's not a common problem
** Yes it is - you know nothing WANKER !!
Reverb tank feedback in old combo amps is very common.
> Take it back and demonstrate the problem.
** Ridiculous advice.
The OP can fix it himself in seconds for under $30.
.... Phil
Stephen Cowell
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:7u8rs0...@mid.individual.net...
> ** That my friend is a dodgy or worn out reverb tank - not un-common in
> an amp that is 23 years old.
What Phil's not telling us is that there's a rubber damper
inside the tank's transducer that sets the delay... this rubber
gets worn out.
Also, combo tanks should be inside a bag. I put mine
in bubble wrap, works great.
Any tech refuses to give me back *any* part of *anything*...
face full of knuckles, my man.
__
Steve
.
Phil Allison
"Stephen Cowell"
"Phil Allison"
>
>> ** That my friend is a dodgy or worn out reverb tank - not un-common in
>> an amp that is 23 years old.
>
> What Phil's not telling us is that there's a rubber damper
> inside the tank's transducer that sets the delay... this rubber
> gets worn out.
** That is ONE cause of reverb tank feedback, one that is not easily
fixed.
There are several others.
> Also, combo tanks should be inside a bag.
** Shame how many amp makers disagree.
> Any tech refuses to give me back *any* part of *anything*...
> face full of knuckles, my man.
** And then you do several years jail time for assault.
Right place for fucking shitheads like you.
... Phil
Phil_S
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:7u8sa0...@mid.individual.net...
<snip>
Even if I'm wrong, there's no reason to be such a jackass about it. You
only seem to know how to berate those who don't agree with you. It's ugly,
no doubt about it.
And I'm not wrong. That tech is incompetent. He shotgunned the tubes and
didn't fix the customer's complaint. IMO, those tubes are probably still
good and better than those Sovteks.
If he did fix it, which neither you or I think he did, it's like I said, the
OP lives under a radio tower or with too many of the wrong kind of light
bulbs, and can't replicate the problem at the tech's on account of it.
Have a nice day Phil. You don't need to bother calling me a cunt, either,
though I expect you will. It seems to be what rises from your limited
capacity for civil discourse.
Phil Allison
"Phil_Shithead"
>
> Even if I'm wrong, there's no reason to be such a jackass about it.
** Fraid there is every need to get rid of know nothing bullshitting scum
like YOU.
> And I'm not wrong.
** YOU ARE UTTERLY WRONG !!!!!!!!!!!!
> That tech is incompetent. He shotgunned the tubes and didn't fix the
> customer's complaint.
** TOTALLY WRONG .
He fixed numerous faults and did all the right things.
The remaining slight issue with the reverb howling was either not noticed at
the time or deemed insignificant as it only affected high settings on the
control.
> IMO, those tubes are probably still good and better than those Sovteks.
** ROTFL !!!!!!!!!
YOU did not see the damn amp
YOU FUCKING TENTH WITTED LIAR !!!!!!!!!!!!!!
> If he did fix it, which neither you or I think he did, it's like I said,
> the OP lives under a radio tower or with too many of the wrong kind of
> light bulbs, and can't replicate the problem at the tech's on account of
> it.
** INSANE CRAP !!!
Straight to the nut house with SCUM like YOU.
> Have a nice day Phil.
** Drop dead
- you BULLSHITTING pile of Septic Shit !!
.... Phil
WB
>
>
> Also, combo tanks should be inside a bag. I put mine
> in bubble wrap, works great.
>
of my Earth PA beast ...
Stephen Cowell
"Phil Allison" <phi...@tpg.com.au> wrote
> ** And then you do several years jail time for assault.
>
> Right place for fucking shitheads like you.
At least you're munching knuckle sandwich...
*totally* worth it. I'll have to get in line, though...
__
Steve
.
jh
>
>
> "Phil Allison" <phi...@tpg.com.au> wrote in message
> news:7u8sa0...@mid.individual.net...
> <snip>
>
SNIP
> And I'm not wrong. That tech is incompetent.
Phil, offline IMHO we should avoid such general statements. As i
underestood, the amp had two isssues. We don't know whether the tech
claimd to have solved both -and- how much he charged.
I'm afraid to concur a bit with PA, but i'm also a bit partial to give
back troublesome tubes to the customer. You don't know what's happening
in "non-tech" hands. Most of the customers don't even want them back.
IMHO the trouble is feedback from the tank and it's likely that the tech
did not test the amp with the tank attachd and in the original combo. So
the problem might not have occured during the tests. Please don't ask me
why i look in that direction. BTDT
Jochen
RS
wrote:
>
>"Phil_S"
>>
>> I hope you got back all the old tubes.
>
>** Nonsense.
>
>> Preamp tubes take a long time to get tired and Sovteks are the cheapest,
>> least toneful tubes out there.
>
>** More nonsense.
>
> The Chinese ones are the cheapest and crappiest.
Sovteks 12ax7's sound absolutely rancid in many apps. I'd take the
sound of Chinese tubes over them, especially in places where the tube
can be overdriven.
>> They also have the lowest noise floor.
>
>** More nonsense - Sovtek X7s are notorious for hum and micophony problems.
Hum, microphony! Yes! Then definitely go with the Sovteks! (Phil S
obviously meant the lowest Signal to Noise.)
>> If you didn't get them back, call him up and ask him to send them to you.
>
>** He has no obligation to do that and will have tossed those old tubes in
>the bin by now .
Let's see...there's a bunch of possibly good tubes, probably still
working fine, and probably sounding way better than Sovteks. Yeah, he
definitely threw them in the bin. (Some repair shops are notorious
for swapping Sovteks and keeping old American/English tubes. And some
don't know any better. Phil S's advice is good...get the old tubes
back)
>>You own them, not him.
>
>** Twaddle.
>
>> Get the power tubes, too.
>
>** Stupid and BAD advice.
>
>Worn out and faulty tubes should never be returned to customers - lest
>they try using them in the same or another amp and do harm or on sell them
>fraudulently.
Which the repair shop definitely wouldn't do. Cause that's solely the
domain of musicians like the OP that do that kind of stuff.
>Rest of this utter cretin's brain dead drivel snipped to prevent me spewing
>on the keyboard.
Well, at least you've managed to present your argument in a calm,
logical way without showing too much anxiety [ahem...Keyboard
Tourette's]. So I trust that we can all continue this thread in a
civilized manner so that everyone can benefit from mutual knowledge...
CUNTHEAD! <g>
Stephen Cowell
<Rednef> wrote
> I always bag things i've replaced right down to a burned 1/8 watt
> resistor and present them to the customer. If they want to chuck the
> stuff that's their option. Most do.
Defnitely ask the customer if you can toss the shorted final...
if they want it back, sharpie skull-and-bones warnings on it.
The warning about disreputable shops swapping out desirable
old pre tubes for new crappy tubes is important... *know* what's
in your amp, have ID marks on the important expensive bits.
Don't let shysters get away with murder of this kind. Same thing
happens in motorcycle shops.
__
Steve
.
RS
wrote:
>The tech found one of the power tubes was bad, and one of the
>capacitors was loose. He replaced all preamp tubes with Sovteks, the
>power tubes with Mullards and tighted up the capacitor. He also
>checked the bias, and did basic diagnostics.
MarkD, I agree with Phil_S (the UN-rabid Phil): I've found that Sovtek
12ax7s can sound horrible, though there are different versions. It
may also be personal preference to some extent, but you could see for
yourself by swapping a known-good tube in for the first preamp
section. Post here for help on determining which socket that is (if
you're still reading).
None of this is intended to cast doubt on your tech. I think people
are just trying to coach you on how -not- to go wrong. I also agree
with most other posters that you should be able to get the original
parts back. I've always found that reputable techs won't have any
problem with this.
I have always done that as a matter of good faith; replaced components
get returned in a sealed poly bag with clear markings that the parts
are bad. Stephen's comment about marking original tubes, and marking
any returned shorted tubes or components with a big X is very valid...
You don't want to inadvertantly use those for anything, but it should
be your option to pitch them.
Phil_S
"Rednef" wrote in message news:3hlmce....@news.alt.net...
>
> Damn who is this Allison tard? Reads like he has a rattail file shoved
> up his arse.
Philthy passes through here from time to time. He's got a limited
vocabulary and doesn't tolerate disagreement at all.
Phil_S
"jh" <j...@org.de> wrote in message
news:hlo316$mlm$1...@news.eternal-september.org...
> Phil_S schrieb:
>> And I'm not wrong. That tech is incompetent.
>
> Phil, offline IMHO we should avoid such general statements. As i
> underestood, the amp had two isssues. We don't know whether the tech
> claimd to have solved both -and- how much he charged.
>
> Jochen
>
Of course. No real disagreement here (on general statements), but I've got
my doubts.
Read down....I'm not the only one who thinks parts should be returned to the
customer. In the US, most states have a law that says an auto repair shop
is required to return parts to the customer. Of course, no one wants a
greasy old CV boot, so it's probably rare. Nevertheless, most shops have
you sign a waiver when you drop your car for service. I think this is a
good practice. On occasion, I've asked for stuff, which was bagged and left
in the back when I picked up the car.
jh
Hi Phil,
to be honest, I would really "thank" my auto repair shop, if I had to
inestigate my car for scrap after a visit in the shop, t avoid that i
had to scrap it myself....
I'm used to say "don't scrap it - i want to have it/see it", otherwise
it's gone ...
With tube amps, it's almost the same for me. If a customer says "i want
it back", he gets everything.
If the gear comes with "valuable stuff" and "working stuff", these items
are of course still in there, when the amp goes back to him. Propably a
lot of black sheep out there.
But - a microphonic ax12, a burnt out EL34 or something else????
Burnt resistors, old caps? Sorry, i'd have to get them to a specialised
dumpster, who makes sure that those items don't end in our environment.
Jochen
Phil Allison
"jh"
>
> With tube amps, it's almost the same for me. If a customer says "i want it
> back", he gets everything.
> If the gear comes with "valuable stuff" and "working stuff", these items
> are of course still in there, when the amp goes back to him. Propably a
> lot of black sheep out there.
> But - a microphonic ax12, a burnt out EL34 or something else????
> Burnt resistors, old caps? Sorry, i'd have to get them to a specialised
> dumpster, who makes sure that those items don't end in our environment.
>
** Here in Australia, it is almost unheard of for a customer to ask for
faulty parts back - invoices contain a list of parts that have been
replaced and anyone can inspect the unit and verify that IS the case.
In 30+ years, I can only recall one person who made a fuss about getting a
regulator IC back from his Crown IC150 pre-amp. When pressed, he could give
no reason at all for wanting it back.
Must be an American phenomenon to expect a bag of junk presented with each
repair job.
As I posted previously, there are DAMN GOOD reasons for NOT returning the
removed parts - particularly tubes.
It is just TOOOO tempting for some to re-install tubes that have serious
faults and hence do damage to an amplifier and THEN complain that the repair
tech did a bad job and want it fixed again for free. Others may even offer
the faulty tubes for sale on eBay or some similar criminal fraud.
I have even heard of a case where a customer took a returned part to a
relative with very little knowledge who " tested " it and declared it to be
OK - WHEN IT WAS NOT !! An entirely ABSURD argument ensued because of
this, the kind that any service tech DOES NOT NEED !!
If some rabid customer stands on his hind legs and demands " his property "
back - there IS a simple solution. Return the parts in such a way they
cannot be re-used - ie cut ALL component leads back to nothing, break
some or all the pins off the tubes and maybe create a permanent fault any
part that previously showed intermittency.
Game over.
..... Phil
Greasehorse
wrote:
>
Some people include replaced parts on collectors amps but I agree
otherwise unless asked..
Rednef
<phi...@tpg.com.au>wrote:
>** Here in Australia, it is almost unheard of for a customer to ask for
>faulty parts back - invoices contain a list of parts that have been
>replaced and anyone can inspect the unit and verify that IS the case.
As I repair I collect everything I replace. It's bagged and offered to
the customer at pick up. Some people are curious, some could care
less. 99% tell me to shit can the parts but there is always that one
in a hundred that wants parts back after I've chucked them in the
trash. So I save them as I go just in case. It also is a way to keep
track without writing down each piece pulled from stock.
markd
<psymond...@comcast.net> wrote:
>
>
>"markd" <mark...@NOSPAMgmail.com> wrote in message
>news:s6ptn5tn8th6o2rub...@4ax.com...
>> I recently bought a 1987 Marshall JCM 800 combo online. I brought it
>> to a tech because of two problems: very high pitched feedback sound
>> when gain was set to 7 or above, and a separate lower-pitched but
>> louder feedback sound (at the time I they might be related somehow).
>> The seller swore he had it checked out before he sold it, and I could
>> only assume something happened during it's shipment across the US.
>>
>> The tech found one of the power tubes was bad, and one of the
>> capacitors was loose. He replaced all preamp tubes with Sovteks, the
>> power tubes with Mullards and tighted up the capacitor. He also
>> checked the bias, and did basic diagnostics.
>
>I hope you got back all the old tubes. Preamp tubes take a long time to get
>tired and Sovteks are the cheapest, least toneful tubes out there. They
>also have the lowest noise floor. If you didn't get them back, call him up
>and ask him to send them to you. You own them, not him. Get the power
>tubes, too.
No, I didn't get the old tubes back - never even thought of it to be
honest. I was just glad the amp worked...and so were my dogs! The
feedback before taking it to the tech would literally have them
running to the back door to get out of the house.
I don't mean to start a holy war, but the tech claims he does work for
lots of guys that gig a lot, and the Sovteks in his opinion offer good
tone for the money - and he was considering the type of music I'd be
playing, which is mostly hard rock/old-school metal. Hard for me to
argue with him since I simply don't know any better. The amp's clean
and boost channels sound great to me, my wife and kids. Granted it
has the reverb problem, but it's playable, has all new tubes, and
didn't cost me a fortune to get it back. I was concerned there might
be something horribly wrong with a lot of components, so to be told it
just needed tubes and that the rest of the components tested fine gave
me warm fuzzies at the time. ;-)
Any suggestions for 'better' tubes that I might like even better? My
understanding is the preamp tubes can be replaced w/o any biasing?
True/false? I sure don't want to take the thing in again just to swap
out tubes. The tech charged me $80 total for the 5 Sovtek 12ax7LPS
and 2 Mullards EL34s.
>>
>> Everything seemed fine after spending time with the tech going over
>> everything and when I got home... but I discovered the low-pitched
>> feedback will assert itself simply by setting the reverb to 6 or
>> above. It only starts when there's no input to the amp (ie. not
>> playing/muting all strings), and slowly builds up to a high volume.
>>
>> The problem immediately goes away as soon as I switch the reverb off
>> or turn it below 6. Is this a common problem with JCM 800 models of
>> this age (and do most peple just use a reverb pedal instead)? Anyone
>> have an idea what might be causing it? The tech that did the repairs
>> is 2+ hours of driving from where I live, so it's rather inconvenient.
>> It's obviously nothing he did to it since the behavior was there
>> beforehand.
>>
>> Thanks
>>
>
>Are you saying it did this before you took it to the tech, didn't do this at
>the tech's shop, but did it again when you got home? When your were at the
>tech, did you do the exact same thing you did at home to produce the
>problem? If so, it's the location, not the amp.
>
>Take it over to a friend's house or even outside, and see what happens. Try
>a different room, one that you know is on a different circuit branch. Turn
>off all florescent lights, including those new fangled ones people are using
>in place of incandescents. Do you live near power lines? Do you live near
>a radio or TV broadcast tower?
>
>Where are you located? 2 hours is too far a way for a casual visit. Maybe
>you'll get a recommendation that's closer.
The problem existed before I took it to the tech, so it's nothing he
did, and doesn't matter what room I'm in, etc. We went over the amp
at length, but for whatever reason he/I didn't push the reverb all the
way up while I was there. Had I known it was the source of the
problem, I certainly would've verified it was ok. My focus was the
horrible feedback from the gain, and for all I knew it was somehow
related to the other feedback issue.
I'm concerned the guy isn't as great as the music store claims that
frequently uses him. Would a 'good' tech have been able to discover
that with basic diagnostics? He obviously didn't mess with the reverb
either, but I also never indicated to him it was a problem (since I
didn't know it was the source). If the reverb tank needs to be
replaced, should his 'bench test' have shown that? Again, I'm asking
out of sheer amp electronics ignorance.
markd
wrote:
>
Thanks for the feedback (no pun intended). So it's just a simple swap
out w/o any other adjustments necessary? I'm guessing that's the
case, but figured I better ask before making things worse!
>.... Phil
>
>
>
>
White Spirit
> Any suggestions for 'better' tubes that I might like even better? My
> understanding is the preamp tubes can be replaced w/o any biasing?
> True/false?
True. I'd recommend EH 12AX7s. You need to buy tested ones as many are
microphonic but they are the best sounding current production valves
IMO. JJs are good quality but I hate the way they sound in a Marshall.
Original Mullards and Brimars are very nice but it can be difficult to
get hold of ones that are usable for a reasonable price and you won't
really notice the different in the channel switching 800s IMO.
It's worth buying a few different brands and experimenting with which
one sounds best in V1 and then see which sounds best in V2 and so on.
Stephen Cowell
"markd" <mark...@NOSPAMgmail.com> wrote
> Any suggestions for 'better' tubes that I might like even better? My
> understanding is the preamp tubes can be replaced w/o any biasing?
> True/false? I sure don't want to take the thing in again just to swap
> out tubes. The tech charged me $80 total for the 5 Sovtek 12ax7LPS
> and 2 Mullards EL34s.
The important position is informally called the 'gain hole'...
usually the one closest to the input jack, or left side of the
amp, from the front. There are many brands of tubes, some
of the best (and most expen$ive) are not made anymore.
How deep do you want to go? Are you satisfied with what
you've got? It might be worth some bux to put a real classic
tube into the V1 gain hole position on your amp... then again,
maybe not. That's one reason you should have kept your
old pre tubes... you can swap them in and see how they
sound. Pretty soon you'll have a good idea of what a
crappy pre tube sounds like (tap them when the amp is on
to check for microphonics) and what a good one sounds
like. Most of the 'tone' comes from the gain hole position tube.
> I'm concerned the guy isn't as great as the music store claims that
> frequently uses him. Would a 'good' tech have been able to discover
> that with basic diagnostics? He obviously didn't mess with the reverb
> either, but I also never indicated to him it was a problem (since I
> didn't know it was the source). If the reverb tank needs to be
> replaced, should his 'bench test' have shown that? Again, I'm asking
> out of sheer amp electronics ignorance.
Tanks are normally an order item unless you have a common type...
Marshall reverb is not something folks write home about, much.
I wouldn't put too much stock in the tech missing it, but if you'd
brought it in for a reverb complaint, that would be different.
Profit margins are higher on the cheaper tubes... he populated
your amp with the cheaper variety. If you can't hear the difference,
then great. It's going to take some self-education on your part
in order to start being able to tell the difference. Having a selection
of new and used classic pre tubes around is a first prerequisite.
Mullard, Brimar, Telefunken, RCA... these are the respected brands.
They are no longer made and command high prices, even used...
I just bought two Mullards and a Telefunken from a radio repair
geek... $50, used, tested good. They're probably 50 years old.
The difference in my amp is startling... crazy highs, full tone...
and that's from installing just *one* of them in V1.
You have three choices, with a spectrum in between:
1.) Take your amp to a mediocre tech... put up with the results
2.) Take your amp to a stellar tech... pay for the results
3.) Educate yourself on the inner workings of your amp...
enjoy the results.
By far, the most expensive of your time and effort will be choice
#3... and by far, the most rewarding.
__
Steve
.
Phil_S
>>Sometimes this problem can be fixed but the best option is to install a
>>new
>>tank - Accutronics make them and they are readily available in the US
>>for
>>under $30.
>>
>>The part number is printed on the unit - something like " 8DB2C1B ".
>
> Thanks for the feedback (no pun intended). So it's just a simple swap
> out w/o any other adjustments necessary? I'm guessing that's the
> case, but figured I better ask before making things worse!
>
Typically, this is as simple as it appears. If you are at all handy, you
should be able to do it. Probably the most common error with a reverb tank
is reversing the cables. Take pictures so you don't rely on memory for
reinstallation.
I think Accutronics will sell you a tank direct. The model number tells
them the orientation, size, number of springs, and resistance. You'll need
to find the label on the old one before you order. I guess you've got to
remove it anyway.
Phil_S
> I don't mean to start a holy war,
There's disagreement and there's disagreeable. Someone here can't
distinguish. It's not you're doing.
Dave Curtis
<psymond...@comcast.net> wrote:
>"markd" <mark...@NOSPAMgmail.com> wrote in message
>news:ts65o5pbanmrkevd7...@4ax.com...
>>>Sometimes this problem can be fixed but the best option is to install a
>>>new
>>>tank - Accutronics make them and they are readily available in the US
>>>for
>>>under $30.
>>>
>>>The part number is printed on the unit - something like " 8DB2C1B ".
>>
>> Thanks for the feedback (no pun intended). So it's just a simple swap
>> out w/o any other adjustments necessary? I'm guessing that's the
>> case, but figured I better ask before making things worse!
>>
>
>Typically, this is as simple as it appears. If you are at all handy, you
>should be able to do it. Probably the most common error with a reverb tank
>is reversing the cables. Take pictures so you don't rely on memory for
>reinstallation.
Actually he could try reversing them now; sometimes for who knows what
reason they get crossed-up.
>I think Accutronics will sell you a tank direct. The model number tells
>them the orientation, size, number of springs, and resistance. You'll need
>to find the label on the old one before you order. I guess you've got to
>remove it anyway.
I'm sorry, I might have missed it but, has it been tested yet? Hey
Mark, Do you have a multimeter?
markd
Hasn't been tested, and yes I have a multimeter.
Tell me what to check... please? ;)
Phil_S
"Dave Curtis" <dbaud...@roderunner.com> wrote in message
news:ub96o552dugmn88sh...@4ax.com...
Excellent catch, Dave!
Stephen Cowell
"markd" <mark...@NOSPAMgmail.com> wrote
> Hasn't been tested, and yes I have a multimeter.
>
> Tell me what to check... please? ;)
Measure ohms on both connectors of the tank.
Use this guide to find your tank.
http://www.accutronicsreverb.com/prodspec.htm
Click on the picture to read the specs... when they
say 'four springs' it's really two springs, joined in
the middle.. the 'six spring' tank has three springs.
The ohms will be approximate... you'll read slightly
less than the audio impedance when you measure
DC ohms... it's an electronical thing.
Order your tank from:
Have fun.
__
Steve
.
Phil Allison
"markd"
> Hasn't been tested, and yes I have a multimeter.
>
> Tell me what to check... please? ;)
** There is no reason to do an ohm meter check on a unit that works and
where you have the model number printed on it.
.... Phil
Phil Allison
"markd"
> Hasn't been tested, and yes I have a multimeter.
>
> Tell me what to check... please? ;)
Stephen Cowell
"Phil Allison" <phi...@tpg.com.au> wrote
Yes, I agree... if you've got the model number, you
have the whole enchilada, spread beaver, in toto.
__
Steve
.
Morris Slutsky
<stephenleeNOSPAMcow...@gmail.com> wrote:
> The important position is informally called the 'gain hole'...
> usually the one closest to the input jack, or left side of the
> amp, from the front. There are many brands of tubes, some
> of the best (and most expen$ive) are not made anymore.
> How deep do you want to go? Are you satisfied with what
> you've got? It might be worth some bux to put a real classic
> tube into the V1 gain hole position on your amp... then again,
> maybe not. That's one reason you should have kept your
> old pre tubes... you can swap them in and see how they
> sound. Pretty soon you'll have a good idea of what a
> crappy pre tube sounds like (tap them when the amp is on
> to check for microphonics) and what a good one sounds
> like. Most of the 'tone' comes from the gain hole position tube.
Hi Steven,
I've never really understood the 'gain hole' concept. I'm a hobbyist
but not a collector and haven't really done much tube rolling or
seeking out of vintage items. To some extent I consider it a duty to
support current tube manufacturers in order to ensure that there will
continue to be a supply of them. I think it's a great thing that it's
even possible to get some of these tubes that have been in production
for over 50 years, newly made - whereas semiconductors even 10 years
old are often irreplaceable. But I don't have the experience so I
really wouldn't know about tube swapping.
However, I don't get the idea behind the 'gain hole'. I understand
that this position has to be the quietest, as there's the most gain
ahead of it - the least hiss, the least hum, and the least
microphonics. What I don't understand is how it contributes to any of
the distortion/overload of the amplifier.
In a classic amp with no master volume, as you turn it up, it
distorts. The first stage to distort is the output stage, the power
tubes. As you push it harder, you start to distort the preamp stages,
working backwards towards the input. If you have a master volume
control, and you turn it way down, and then push the amp into
distortion, the first stage to distort will be the final preamp stage
and again it'll work backwards from there. So for the most part,
stages go into overload finals first, preceding stages second, and so
on all the way back to the input. But the input tube never really
overloads unless you run a really, really hot signal source, something
more than a basic electric guitar perhaps. And even if it does, the
odds are you've already got so much distortion in the succeeding
stages that the distortion from the first tube will be completely
clipped off by the next stages and you'll never hear it anyway - so
why does the 'gain hole' matter so much for overdrive character?
I'm just asking. I don't want to start a subjective-objective flame
war I just want to understand what you've seen, heard, and thought
about the issue.
Stephen Cowell
"Morris Slutsky" <morris....@gmail.com> wrote
> But the input tube never really
> overloads unless you run a really, really hot signal source, something
> more than a basic electric guitar perhaps. And even if it does, the
> odds are you've already got so much distortion in the succeeding
> stages that the distortion from the first tube will be completely
> clipped off by the next stages and you'll never hear it anyway - so
> why does the 'gain hole' matter so much for overdrive character?
Because it's where the meat of the tone comes from...
it's not the tube you're clipping that contributes the
tone, it's the first tube in the string, the one that gets
the electro-mechanical and turns it into electronic.
> I'm just asking. I don't want to start a subjective-objective flame
> war I just want to understand what you've seen, heard, and thought
> about the issue.
All you have to do is get a bunch of pre tubes and
start swapping... the simpler amps give you a better
sense of what you're getting... like a Champ would
be perfect for testing 12AX7's.
__
Steve
.