Midiverb ii issues?
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From: Meat Plow on 25 Jul 2010 13:46 On Sun, 25 Jul 2010 10:05:05 -0700, El Grillo wrote: > 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.
From: Gareth Magennis on 25 Jul 2010 13:58 "Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message news:Efj2o.333105$NW.10213(a)hurricane... > > > "El Grillo" <nradina(a)gmail.com> wrote in message > news:0b3f8d3e-ce83-4a8d-a032-59a743522db2(a)k19g2000yqc.googlegroups.com... >> Hello, >> >> I'm an new electronic technician TRYING to grasp a hold of my >> troubleshooting skills. >> I have two Midiverb 2's on my bench currently. >> >> One I was able to repair by replaceing some bad Filter caps, but the >> other is still giving me all the indicator diodes are lit and the 2 >> digit screen is dead. >> >> I tested all caps with an ESR meter and all is good. >> Noticed one small decoupling cap looked funky and replaced, but no >> luck. >> (I'm also a bit unsure if I replaced with the right cap. I had a few >> 104 film caps in the shop). >> >> SO...I'm asking for a bit of help from you all, if willing. >> >> Any idea where I should be looking? >> >> Thanks in advice for any help you can send my way. >> >> nicholas > > Supply rails all correct voltages and clean (check with digital voltmeter > and 'scope) ? Processor chip receiving correct reset ? Processor clock > running ? No user control jammed in 'operating' position ? Such things can > cause a processor to 'loop forever' if it executes a bit of code during > boot up, to check for button presses that are part of a diagnostic entry > sequence, and the button that's being 'pressed' is not one that is being > expected. > > Arfa
From: Gareth Magennis on 25 Jul 2010 14:05 "Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message news:Efj2o.333105$NW.10213(a)hurricane... > > > "El Grillo" <nradina(a)gmail.com> wrote in message > news:0b3f8d3e-ce83-4a8d-a032-59a743522db2(a)k19g2000yqc.googlegroups.com... >> Hello, >> >> 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 > > 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 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.
From: Jeff Liebermann on 25 Jul 2010 15:24 On Fri, 23 Jul 2010 17:16:34 +0100, "Arfa Daily" <arfa.daily(a)ntlworld.com> wrote: >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 jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: Arfa Daily on 25 Jul 2010 20:37
"Gareth Magennis" <sound.service(a)btconnect.com> wrote in message news:y1%2o.220782$U%7.143992(a)hurricane... > > > "Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message > news:Efj2o.333105$NW.10213(a)hurricane... >> >> >> "El Grillo" <nradina(a)gmail.com> wrote in message >> news:0b3f8d3e-ce83-4a8d-a032-59a743522db2(a)k19g2000yqc.googlegroups.com... >>> Hello, >>> >>> 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 >> >> 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 > > > 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. 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 |