Alesis Midiverb II strange problem

[samgraysound]

Hi All,

I'm looking at an Alesis Midiverb II. I got a power supply for it. It powers up fine and passes signal. But all the presets sound messed up. They either have crazy screechy feedback or just sound like garbage generally.

What could be causing this?

 

[samgraysound]

I recapped the power supply and now the overload light is constantly on and it just puts out a very loud tone.

 

[Bo Deadly]

Probably need to break out the scope, look at the ins and outs of the A/D and D/A and hope it's not just something horked in the DSP chip. Assuming that's the topology. Is there a schem?

 

[samgraysound]

I've only found a schematic for the power supply

 

[Adrian55]

I've only found a schematic for the power supply

Could you tell me what are the values for small blue film capacitors (decoupling ones)? I've got one that friend and identifies now as resistor

 

[mjrippe]

Google to see if there is a hardware reset. Often holding down one or more buttons while powering on.

 

[Ike Zimbel]

I recapped the power supply and now the overload light is constantly on and it just puts out a very loud tone.

Did you keep the old caps? If so, have a close look at the leads and see if any of them have a copper collar around the part that goes through the board. If so, you have pulled a via out when you removed them so may have broken the circuit between the top and bottom of the circuit board. I have seen some Lexicon boards of that vintage have this happen really easily, even with proper desoldering technique. The fact that the fault changed and got worse after you recapped the power supply board points to there now being an issue with the PS. What frequency is the tone?

 

[Diabolical Artificer]

Something else to look at is a back up battery. Not sure if the Midiverb has one but my Quadreverb does. If yours does check it's voltage.

Also if you've re-capped it,did you get the caps in backwards? The Quadreverb has an odd supply, getting a split rail supply from a non tapped transformer. If the Midiverb is the same.....

Lastly, check, re check and check again your work. Where you have been is often where the fault is. Screwing up is very easily done.

Andy.

 

[tubejay]

I've had a few of these come across my bench lately that had a bad tantalum cap. In all three cases they were in different spots on the board. The caps themselves were discolored, with a burned look to them. In once case, it burned up before my eyes, so I could see it, and in all cases they are quite hot to the touch. I'd say we'll see more and more of that as these caps are getting old. In all three cases, the red overload LED was lit up, and while it'd pass audio, no effects were passing, and in some cases coupled with hum and other issues.