leitrim_lad

Alesis Midiverb ii Problem
« on: January 08, 2011, 10:42:51 PM »
Hey everyone,

I have an alesis midiverb 2 and the ovld light is constantly on..

Im getting dry signal out of it but when i use the mix knob to mix with reverb the sound starts to disappear the more reverb i add..

Ive seen alot of people on google having the same problem but no one seemed to have answers in any of the posts i read.. 1 person said they sent it back to alesis and they said it was a problem with a filter cap and that alot of people have the same problem but thats where the post ended..

I know alot of people will think its probably not worth fixing but i kinda like it on some things and i just thought id throw it out there to see if any of ye kind people might have come accross this same problems on your travels and if so that you might have some information for me on how to go about fixing it..

Thanks a million


kazper

Re: Alesis Midiverb ii Problem
« Reply #1 on: January 08, 2011, 11:32:55 PM »
Find a schematic for the unit or start tracing down what circuitry makes the light turn on.

http://www.wolzow.com/analog/mvii.htm

I'd pop the top and just check for proper juice... as a start.

BTW what idea of a bad joke is all these cheesy PDF web sites that are clogging up the search engines...
« Last Edit: January 08, 2011, 11:34:51 PM by kazper »
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haima

Re: Alesis Midiverb ii Problem
« Reply #2 on: January 09, 2011, 05:46:46 AM »
Are you definitely using a 9v AC power supply (not DC)?

 

leitrim_lad

Re: Alesis Midiverb ii Problem
« Reply #3 on: January 09, 2011, 11:22:21 AM »
Hey thanks for the replies..

i cant seem to find a schematic for it ANYWHERE.. its a disaster. No one would have one here or be able to point me in a direction of one?
Ya im using the ac power.. I tried out 2 or 3 adapters in fact just to make sure because on some of the forms people said you might need one with more ma so i tried a 9v ac with more ma and it was the same result. I thought it could have been the pots so i took it apart and cleaned them but still no change..

Cheers

kazper

Re: Alesis Midiverb ii Problem
« Reply #4 on: January 09, 2011, 01:35:21 PM »
Honestly I've seen very few Alesis service documents. They seem to held them close at hand.

If you read into the link I posted, it talks about the software and how specific chips handle certain tasks etc..

If you read into what I was telling you is to take a look at the simple stuff. Get you DMM out, check the voltages from the 9V adapter. Check the voltages after the regulation. Check the voltages to the IC's. You can fix allot of stuff by simply looking at the boards and probing a little if you want to fix it.

After you figured out that life in the power world is ok, then you can start looking at the LED circuit.... what drives/turns on the light?

Kaz


You may try to contact Alesis and ask to purchase a service manual for it.
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jwhmca

Re: Alesis Midiverb ii Problem
« Reply #5 on: January 09, 2011, 02:17:28 PM »
More than likely one of the "RUN" supplies has died or is low. Either the + or - 9 or 12 or 15VDC (what ever it runs on) The Overload can be triggered by one of the supplies being low or missing. Check the main filter caps... usually the biggest in physical size closest to the power supply input. Are they puffed up? at all?

It is probably "regulated" look for the typical 78** IC.., e.g. LM7809 or 7812, 7815, and the NEG- counter part 79** 7912...etc. Do a google image search to see what they "look" like... then find and measure ALL the pins to ground. You will see a pattern (or get the Datasheet for the "now know part")

Say you find a set of 9 volt regs i.e. 7809 and a 7909.

One pin should be higher than 9 volts... say 12 or 15... maybe it's negative. Another pin might be 0vdc (ground) and the last will (working/good) 9 vdc, again maybe - neg.

Check them all (6) pins... find the pattern. One chip will either have no input ( the higher voltage) or no output... or the input will be too low causing the output to be too low.


 

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