Need help Diezel VH4 switching failure

[fusionbear]

A client brought me a VH4 to repair, but the problem is in the midi board. It is switching constantly at a high rate of speed. It won't reset. Main Chip? any ideas? I am not that versed in these midi switching boards.

[LeftyStrat]

I might first try to replace the opto-isolator or the gates. It sounds like the processor is working (doing the switching), it's just getting garbage from some other component. If the processor was bad, it wouldn't switch at all.

Here's some specs:

http://www.midi.org/techspecs/electrispec.php

[LeftyStrat]

The other thing could be a power supply issue which keeps resetting the microprocessor. Might try checking the caps and power to it.

Normally, when a microprocessor goes bad, it just stops working. When it does crazy stuff, it's either getting bad input, or being reset constantly.

[fusionbear]

Thank you, that is very helpful. I will let you know how it goes...

[fusionbear]

Its the main chip. Power is OK Optoisolator OK. Got to get in touch with Diezel and see if he will sell me one for my client...

[fusionbear]

Peter Diezel is sending a new switching processor. His customer service is awesome!!!

[vibratoking]

Don't know what processor is in there, but there are quite a few PIC micros that are known to enter that type of failure mode.

[fusionbear]

Yup, he said he is using a different one now...

[LeftyStrat]

Well, learn something new every day. Bad processor would have been my last guess.

Glad you got it straightened out.