[sparx]

My FM is sounding distorted and grungy.

I've checked the usual things and it all seems fine so what I can't rule out is that the surface mount chips aren't faulty.

Is there a fellow midiboxer, ideally in London UK area, who would be willing to try my board in their set up?
Its a long shot, but it really would be appreciated.

Thanks

S

[Echopraxia]

Is this a new build or is this a working MBFM that has recently been having problems?

In the USA so can't help there.

Wouldn't the op-amps have something to do with the quality of the sound? Anyone?

Are your power supplies still giving good voltage?

[sparx]

Its a newly completed build, certainly the board was working fine before the CS was finished, but now sounds distorted.
The original PSU was replaced as it was recycled and there was a smell of burning electronics and bits got warm which may have been normal, but with the new one the results are the same. Voltages are all fine.

Op-Amps are new as well.

As it stands, I can't rule out the OPL board or the PSU which is why I want to test the OPL board in a known working system.

Will throw the net a bit further, can anyone, anywhere assist me?

Thanks

S

[nILS]

Troubleshooting the whole thing is a lot harder than testing the individual parts. Start by disconnection everything.

First, check the PSU - measure all voltages, add some dummy loads (~7 LEDs in series for a 12V rail for instance), if everything checks out, move on to the core.

Connect it to the PSU, check voltages, upload something, all good? Move on to the DIN chain.

Hook up the DIN chain to the core use the ain64_din128_dout128_v2c app to see if all inputs are working. If that checks out move on to the DOUT chain with the same app.

If that works, disconnect DIN/DOUT again and hook up the OPL3 module and see if you can control it and everything sounds fine. If that works, hook up the CS again.

[sparx]

Thanks, all voltages are fine, CS works fine, uploads work fine, already tried to operate OPL and core with no CS, still grungy.

Which is why I think its possibly either the PSU or the OPL board.

Other thing I was thinking about doing, is running the OPL off a couple of batteries, has anyone tried this? If so can they post details?

Thanks

S

[nILS]

You can use 2 9V batteries. Simply connect them like this:

//      +9V        GND        -9V
//       |      ____|____      |
//       |     |         |     |
//     _[+]___[-]_     _[+]___[-]_
//    |           |   |           |
//    |           |   |           |
//    |           |   |           |
//    |           |   |           |
//    |           |   |           |
//    |           |   |           |
//    |           |   |           |
//    '-----------'   '-----------'

[sparx]

Thanks for that nILS, have seen various permutations of the "2 9V batteries as a bipolar supply" but never done it. I can confirm that this configuration will certainly power the Op-Amps in the OPL board should anyone else need to do it.

But alas, it looks like it is the SMD chips on the OPL which are at fault as I suspected.

Apart from replacing them, any way of testing them to see if its the sound chip, the DACs or both?

S

[Shuriken]

Not much you can do to test the components separatly.

I would suggest replacing one DAC. If you then still have distorted sound on that channel, replace the YMF262.

[sparx]

Yes replacing the DAC first makes sense, but guess what I don't have any spares of?
I'll post in the Fleamarket section too, but if anyone has any spare sets of chips, (think I'll do another one of these anyway) please let me know.

I do have a spare YMF262 so maybe that will get replaced first, guess its a 50/50 chance.

Thanks again

S

[Shuriken]

sparx, on 25 June 2010 - 15:48, said:

Yes replacing the DAC first makes sense, but guess what I don't have any spares of?
I'll post in the Fleamarket section too, but if anyone has any spare sets of chips, (think I'll do another one of these anyway) please let me know.

I do have a spare YMF262 so maybe that will get replaced first, guess its a 50/50 chance.

Thanks again

S

I see you killed you OPL3 board desoldering. I sure know how that feels

[sparx]

Yes, first of all it was ill and now its died.

Plus side is that now I can get on and do some other things whilst I wait for all the bits to arrive and when it does, the CS is there waiting for it.

It was really good whilst it lasted!

I see Mike has OPL sets but no sound chips.

S

[Shuriken]

sparx, on 30 June 2010 - 10:18, said:

Yes, first of all it was ill and now its died.

Plus side is that now I can get on and do some other things whilst I wait for all the bits to arrive and when it does, the CS is there waiting for it.

It was really good whilst it lasted!

I see Mike has OPL sets but no sound chips.

S

You could try the bulkorder, which is currently underway. I do have a YMF262 which is a pull. But you won't get very far withit without any YAC512.

This post has been edited by Shuriken: 01 July 2010 - 19:18

[sparx]

Thanks, I have a YMF and as you say it is not much use without the YAC.

Noticed the bulk order and will be joining that.

These chips and soundcards are getting really hard to find, so if anyone is thinking of building one of these, now would be the time to get the chips on order. Buying new is a better option than pulling chips off old soundcards.

Don't be put off by the surface mount either, just take it slowly and you'll get a cool synth.

S

[WhoopJohn]

sparx, on 02 July 2010 - 11:40, said:

These chips and soundcards are getting really hard to find, so if anyone is thinking of building one of these, now would be the time to get the chips on order. Buying new is a better option than pulling chips off old soundcards.

With a bit of confidence you can strip surface mount off boards. It often helps to clamp the board vertically and run a cow's hoof iron tip up and down one side while prising that side slightly off the board. The other side is then easy.

I keep seeing these new Yamaha with OPL cards on UK ebay for not much spondoolicks - there always seems to be someone selling them.
My link

[taximan]

HIya,
I couldn't help myself at that price and bought two (soundcards) .........gives me more confidence to experiment knowing I have cheap spares.
cheers
Paul


Just as an after thought...my mbfm sounded 'grungy' too.......it turned out to be the wires from the psu (amigadore/comoga) I just cut a couple of inches off the lead and soldered a new connector on and now it's fine.......except for one channel not working but I know that is due to crap soldering.

I have just looked through my receipts box but can't find where I got the four pin socket and plug from....I know it seemed expensive and I wasn't too happy with the quality...but it worked.
cheers
Paul

This post has been edited by taximan: 09 August 2010 - 22:47

[Shuriken]

I sure hope these cards actually contain a real opl chipset. By looking at the pcb i am not so sure about it. But since you already bought it, we will know soon enough.

[nILS]

When you get the cards, please list them here -> http://www.midibox.o...or_yac512_chips

[taximan]

Hiya,
The chip is a OPL ymf 718-s,it's a 100 pin smd and NO good for the mbfm...........but still I am enjoying trying to find a data sheet for the chip and it keeps me quiet as the missus says.


pssssssssssssstt.....anyone wanna buy a crappy souncard cheap?..lol

cheers
Paul