Midiverb ii issues?
El Grillo
I'm an new electronic technician TRYING to grasp a hold of my
troubleshooting skills.
I have two Midiverb 2's on my bench currently.
One I was able to repair by replaceing some bad Filter caps, but the
other is still giving me all the indicator diodes are lit and the 2
digit screen is dead.
I tested all caps with an ESR meter and all is good.
Noticed one small decoupling cap looked funky and replaced, but no
luck.
(I'm also a bit unsure if I replaced with the right cap. I had a few
104 film caps in the shop).
SO...I'm asking for a bit of help from you all, if willing.
Any idea where I should be looking?
Thanks in advice for any help you can send my way.
nicholas
Arfa Daily
"El Grillo" <nra...@gmail.com> wrote in message
news:0b3f8d3e-ce83-4a8d...@k19g2000yqc.googlegroups.com...
Supply rails all correct voltages and clean (check with digital voltmeter
and 'scope) ? Processor chip receiving correct reset ? Processor clock
running ? No user control jammed in 'operating' position ? Such things can
cause a processor to 'loop forever' if it executes a bit of code during boot
up, to check for button presses that are part of a diagnostic entry
sequence, and the button that's being 'pressed' is not one that is being
expected.
Arfa
Meat Plow
> "El Grillo" <nra...@gmail.com> wrote in message
> news:0b3f8d3e-ce83-4a8d-
a032-59a...@k19g2000yqc.googlegroups.com...
All indicators lit but no numeric display? No processor bootstrap.
I have a couple of those BTW. Nice units for sound reinforcement.
El Grillo
Any ideas what could casue the processor to not boot?
Could this be a voltage issue maybe??
Tanks for your help!
n
On Jul 23, 12:33 pm, Meat Plow <mhyw...@yahoo.com> wrote:
> On Fri, 23 Jul 2010 17:16:34 +0100, Arfa Daily wrote:
> > "El Grillo" <nrad...@gmail.com> wrote in message
> > news:0b3f8d3e-ce83-4a8d-
>
> a032-59a743522...@k19g2000yqc.googlegroups.com...
>
>
>
>
>
> >> Hello,
>
> >> I'm an new electronic technician TRYING to grasp a hold of my
> >> troubleshooting skills.
> >> I have twoMidiverb2's on my bench currently.
El Grillo
My next plan is to check the voltages.
Without the schematic, I'm a bit fuzzy on where to check the voltages
and what they should be.
Do you have a method to track down the correct voltages??
Thanks again for your help!
n
On Jul 23, 12:16 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
> "El Grillo" <nrad...@gmail.com> wrote in message
>
> news:0b3f8d3e-ce83-4a8d...@k19g2000yqc.googlegroups.com...
>
>
>
>
>
> > Hello,
>
> > I'm an new electronic technician TRYING to grasp a hold of my
> > troubleshooting skills.
> > I have twoMidiverb2's on my bench currently.
Meat Plow
> Thanks for your help Meat Plow,
>
> Any ideas what could casue the processor to not boot? Could this be a
> voltage issue maybe??
>
> Tanks for your help!
If I had some service literature on it I might be able to point out
a few possibilities. The area of interest Arfa posted are what I would
start with but without being able to identify those areas and their
signals you're flying blind. You might try a little research on a factory
reset. Maybe Google 'midiverb II no boot' and see what pops up.
Gareth Magennis
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:Efj2o.333105$NW.10213@hurricane...
Gareth Magennis
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:Efj2o.333105$NW.10213@hurricane...
>
>
You might pay particular attention to Arfa's suggestion of the uP receiving
the correct reset.
The first thing I used to do with these old style microprocessor things,
after checking the power supplies, was to force a warm boot by taking the
reset line low or high - whatever is appropriate to force a reset. (get
the datasheet for the processor to find what is required and where) It was
surprising how many then suddenly burst into life.
Gareth.
Jeff Liebermann
>Supply rails all correct voltages and clean (check with digital voltmeter
>and 'scope) ? Processor chip receiving correct reset ? Processor clock
>running ? No user control jammed in 'operating' position ? Such things can
>cause a processor to 'loop forever' if it executes a bit of code during boot
>up, to check for button presses that are part of a diagnostic entry
>sequence, and the button that's being 'pressed' is not one that is being
>expected.
I have a Midiverb II, Microverb III, and some other Alesis boxes. I've
had to go inside to fix every one at various times. The big 1000uf
and 2200uf filter caps are all junk in most Alesis boxes. If you have
an oscilloscope, you'll see lots of ripple on the power supply buses.
There are also 0.1uf decoupling caps, which like to short out.
No display sounds like no power. Even a comatose processor should
show some lit segments on the display. I agree with Arfa's approach.
Follow the power.
Note that the wall wart might be 9V AC or 9V DC. Alesis used both
with identical connectors. An AC box will actually run with a DC
power supply, but will also do strange things. Checking the Alesis
web pile, it's a 9V 830mA AC P3X110 adapter.
If you have problems working on it with zero information, these sites
might be useful:
<http://www.synthzone.com/alesis.htm>
<http://www.wolzow.com/analog/mvii.htm>
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Arfa Daily
"Gareth Magennis" <sound....@btconnect.com> wrote in message
news:y1%2o.220782$U%7.143992@hurricane...
Yes, good advice. A forced reset is a good test. However, the OP's
experience of dealing with this sort of problem appears limited, so if I
were he, I think I would definitely be looking for some schematics, as
without them, it's going to be difficult for him to troubleshoot this ...
Arfa
Arfa Daily
"Gareth Magennis" <sound....@btconnect.com> wrote in message
news:y1%2o.220782$U%7.143992@hurricane...
>
>
Yes, good advice. A forced reset is a good test. However, the OP's
Gareth Magennis
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:7N43o.336958$m87.69552@hurricane...
If you get the datasheets for the uP and ROM/RAM chips, you can scope each
data and address line and sometimes come across one that just doesn't look
right, e.g. it has values that are not 0 or 5 volts, but something in
between. Forcing a reset can sometimes help by providing a few cycles of
program to watch before the unit hangs.
Cut bus tracks til you find out which chip is fouling the line.
I have managed to fix quite a few units this way where the schematics were
not available.
(By the way, I'd always change the program RAM chip first if feasible, as
these used to be the most likely chip to fail)
Gareth.
El Grillo
I will try to work out some of the issues tomorrow at the shop.
Also, if a filter cap tests good using a ESR meter, could it still be
bad??
n
On Jul 26, 3:10 pm, "Gareth Magennis" <sound.serv...@btconnect.com>
wrote:
> "Arfa Daily" <arfa.da...@ntlworld.com> wrote in message
>
> news:7N43o.336958$m87.69552@hurricane...
>
>
>
>
>
>
>
> > "Gareth Magennis" <sound.serv...@btconnect.com> wrote in message
> >news:y1%2o.220782$U%7.143992@hurricane...
>
> >> "Arfa Daily" <arfa.da...@ntlworld.com> wrote in message
> >>news:Efj2o.333105$NW.10213@hurricane...
>
> >>> "El Grillo" <nrad...@gmail.com> wrote in message
> >>>news:0b3f8d3e-ce83-4a8d...@k19g2000yqc.googlegroups.com...
> >>>> Hello,
>
> >>>> I'm an new electronic technician TRYING to grasp a hold of my
> >>>> troubleshooting skills.
> >>>> I have twoMidiverb2's on my bench currently.
tm
.Thank you everyone for your help!
.
.I will try to work out some of the issues tomorrow at the shop.
.
.Also, if a filter cap tests good using a ESR meter, could it still be
.bad??
.
.n
A shorted cap will check good with an ESR meter. You should do a sanity
check on what it is telling you.
tm
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Meat Plow
> Thank you everyone for your help!
>
> I will try to work out some of the issues tomorrow at the shop.
>
> Also, if a filter cap tests good using a ESR meter, could it still be
> bad??
If there is a doubt, sub it. As far as I'm concerned if it passed the ESR
test it's good (for the time being)
JW
Well, it could be shorted. Somewhat rare for electrolytics IME, though.
Arfa Daily
"JW" <no...@dev.null> wrote in message
news:ht1056l7egepmdrn9...@4ax.com...
In the past, I have seen many electrolytics that were serving as rail
decouplers, that have gone short. The little purple 10uF's that Panasonic
used to litter everything that they built with, were favourites for failing
short. As you say, doesn't seem to be as common an occurrence these days as
it once was, though. Interestingly, I had a s/c electrolytic just today (see
my post regarding some Restek speakers). It was one of those brown plastic
'Siemens' types that you used to see a lot of in Grundigs and B&O's.
Arfa
Michael A. Terrell
It was very rare with American built electronics. Most failures were
open filter capacitors, or damaged 160 mF, 250 V 'Low Power Factor'
electrolytics used in the voltage doubler power supplies. BTW, 'Low
Power Factor' were rated in the ripple current they could handle.
Today, they would be a Low ESR rating.
The only shorted electrolytics I remember in American built
electronics was the low voltage caps used in the cathode circuits of
audio amps.
Arfa Daily
"Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
news:0IadndnEp-heA83R...@earthlink.com...
Interesting. I wonder why the difference ? A few years back - say 10 or so -
I would have said that I saw as many short circuit electrolytics, as any
other problems with them such as open circuit, low value, leaking, bulging
etc. Now though, short circuit is comparatively rare. As to cathode caps, I
think that I have probably seen more that were open circuit than short. Used
to be a big problem in the frame output and audio output stages of TV sets,
back in the day ...
Arfa
Michael A. Terrell
Sprague had high standards, but you paid for it. Japanese crap hit
the US hard in the early '70s and you saw a lot more failed
electrolytics. Sprague started shutting down their plants as demand for
high quality electrolytics dropped. I still have a roll of aluminized
mylar from the Orlando plant, along with a partial roll of 'component
lead' they used on their famous 'Orange Drop' capacitors.
Arfa Daily
<snip>
>>
>> Interesting. I wonder why the difference ? A few years back - say 10 or
>> so -
>> I would have said that I saw as many short circuit electrolytics, as any
>> other problems with them such as open circuit, low value, leaking,
>> bulging
>> etc. Now though, short circuit is comparatively rare. As to cathode caps,
>> I
>> think that I have probably seen more that were open circuit than short.
>> Used
>> to be a big problem in the frame output and audio output stages of TV
>> sets,
>> back in the day ...
>
>
> Sprague had high standards, but you paid for it. Japanese crap hit
> the US hard in the early '70s and you saw a lot more failed
> electrolytics. Sprague started shutting down their plants as demand for
> high quality electrolytics dropped. I still have a roll of aluminized
> mylar from the Orlando plant, along with a partial roll of 'component
> lead' they used on their famous 'Orange Drop' capacitors.
Now there's another interesting thing. I wouldn't have thought that Orlando,
given the extremes of humidity that it suffers, would have been a very good
place for manufacturing capacitors, or was it just 'wet' electrolytics that
were made there ? Or was the whole plant environment-controlled ? Guess you
wouldn't be able to afford to do that these days ...
Arfa
Michael A. Terrell
Air conditioned factories were, and are common for electronics in the
US. When you consider the time it takes to wind a mylar capacitor and
dip it into epoxy, there isn't much time to adsorb moisture. If the
humidity is too low you will build up a static charge on the mylar, then
it will to stick to the rollers in the handling and winding machines.
The Microdyne plant where I worked was fully air conditioned, and it
was about two hours north of Orlando.
--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Meat Plow
I don't suppose a plant manufacturing capacitors has to be very big. At
least the assembly building. It's easy enough to imagine a climate
controlled assembly room. And Mike is right about the history of
capacitors. I lived through the era when manufacturing stopped giving a
shit about quality over pumping out volumes of crap.
Michael A. Terrell
Sprague continued to make them, but most manufacturers had been taken
over by MBA bean counters by then. They were still making high quality
parts, till Vishay bought them.
El Grillo
nicholas
On Jul 29, 1:41 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote: