MBFM - white noise when LCD connected

Testing/Troubleshooting
1

Hi,

my MBFM (second approach) is weird.

  • see topic. If LCD connected, then after power on -> Beeps and white noise at full scale. Mostly noise all the time, plus the notes I play, if I do. The LCD shows all boot stuff regularly (“MIOS 1.9f”, and so on), then freezes at the main screen. (if I change patches, no changes on LCD)

  • Without LCD connected -> No white noise, but I noticed that every six notes I play, three of them are distorted (desoldered too hot OPL3 chip I guess, so maybe three out of six voices got damaged?)

hmmmmmmmmmm…

2

After some testing:

the problem has to be between LCD and OPL3 module… All voltages fine, core + LCD work when OPL3 module not connected. As soon as OPL3 interconnection connected, LCD hangs up and “noise data beeps” (reminding me of a very aggressive vintage modem) on the outputs.

I will check the YMF262, maybe it became too hot while desoldering… I have a spare one left.

3

Maybe there is no contact between the RD# pin of YMF262 and +5V?

The voice issue is probably related to a defective YAC512, or to bad solderings around this chip.

Best Regards, Thorsten.

4

It seemed to be a damaged YMF262. I soldered another one and it seems to work fine now. Still making an OPL3 bulk order to have enought spare chips though :smiley:

Thanks TK