1st gen opl board corrections?

MIDIbox FM
1

I’ve got some 1st gen OPL boards from smash that are being built now, I remmber that the resistor numbers printed on the board are wrong,

If anyone has the correct values, could they let me know?

2

Yep, the wrong resistors numbers made me to desolder lot of then when I looked it. The correct resistances distribution is on the Eagle file (.brd): 

http://www.ucapps.de/mbhp/mbhp_opl3_v1.brd

or in the gif:

http://www.ucapps.de/mbhp/mbhp_opl3_v1.gif

But not in the PDF. These are not good.

Regards

3

thanks very much for your help fizzicato, my friend has already soldered one board, so some desoldering required i think

4

write a short pm to TK. thx

5

I’ve just been looking at the files on uCApps.

The .GIF is wrong when compared to the parts list and the Yamaha data sheet.

The sample and hold capacitors should be 2.7nF and the filter caps 68pF.

The problem seems to be that the SmashTV board and the original uCApps boards use different parts numbering.

The parts list on SmashTV’s site is correct for his board: http://www.avishowtech.com/mbhp/mbhp_OPL3R1.html

I’ve just noticed I’ve forgotten a link, so one of the IC sockets has to come off. Grrr!

If it’s a very old board, you’re going to have to check back with the schematic. Just don’t put 68nF caps on - you might not get much sound at all, that’s a 25% increase in time constant!

HTH

Mike

6

I corrected the mistakes, and re-arranged the labels in the hope, that they are a little bit more readable now.

(However, I must admit that it still looks ugly)

-> http://www.ucapps.de/mbhp/mbhp_opl3_v1a.gif

-> http://www.ucapps.de/mbhp/mbhp_opl3_v1a.brd

Best Regards, Thorsten.

7

Wow! that was fast!

It’s a lot more readable too - for my rather poor eyesight, having the component values in a contrasting colour help a bit too.

I was talking the other day with a PCB designer friend, and he said that the modern trend on SMT boards is to leave most of the silk screening off, just label the connectors etc. The makers figure that no-one but themselves are ever going to work on them, and they might as well save the space. A scary thought for future modders.

Best wishes

Mike

8

So if I went the way Smash said, what will this do? I put together a smash board for FM some time ago and it never worked at all, are the components damaged or do I only need to swap out the correct parts for the mistakes listed?

Also, I’d like a copy of the original gif or pdf so I can compare what exactly would be wrong on the board. I can’t find any copies of what I have already made.