Layout alternative

MIDIbox FM
1

Hi,

After untold troubles with my OPL module I am contemplating the alternative layout on the wiki,here.

But the links give me a 404 (see stryd’s opinion on offsite documentation!). I however do have the files downloaded already :slight_smile:

My questions are:

Has anyone actually used this layout successfully?

Has anyone got a MySpace account where they could ping selfservice, the guy who did this layout, so that I could ask if he minds me putting it on the wiki? (sorry but I’m boycotting MySchmace)

TIA for any help (hoping that some others get on board with MBFM so I can get answers to my troubleshooting questions :D)

Dave mK

2

Wow,

I thought I was the only one not doing MySpace. Looks like my fellow boxers are with me :slight_smile:

But seriously, anyone?

D

3

What was your problem with the original layout and what makes you think a different PCB version would increase the chance of getting a working MBFM in any way?

S

4

MySpace is teh ghey. hehehe

seppo is on the right track though…

5

Hi seppo and stryd,

Well I have been working on MBFM on and off for a couple of years now :slight_smile: [in fact i just checked through the forum and my first message re: MBFM is from 2005, yikes!] I’m in no way criticising the original OPL3 board layout, just exploring ways of finishing this project before 2010  :smiley:

Anyway, a brief recap: my YMF and YAC chips are from the first bulk order. I have the original OPL3 board hooked up to a V2 core. My PSU is an AC wallwart hooked up to the appropriate caps and regulators mounted on veroboard. I can upload apps to the core fine, so I’m sure MIDI is working fine. The core has the latest version of MIOS and MBFM. Running the MBFM interconnect test app, I’m sure that the core is sending the appropriate signals to the OPL3 board.

The problem is that when running the MBFM firmware I get absolutely no sound from the OPL3 board. Simple as that. The LED on the OPL3 board comes on, there’s + and -12V at the power input on the OPL3 board. I’ve tried two batches of TL074s (hadn’t realised they could be sensitive to static the first time I built the OPL3!). Still nothing.

My current crystal oscillators both seem to be from NOS, I’ve not got a scope so I can’t think of a way to test they are actually working. Any suggestions how to rule this out?

Unfortunately I can’t find the appropriate crystal oscillator here in Prague, so I’m contemplating building the oscillator adapter from gyorgy’s page:

http://web.t-online.hu/gyurek/midibox.htm#oscillator

Anyone explored this option?

My current OPL3 board is from Mike, so there’s no solder screen and some of the tracks are really close together. Although I’ve been over the board with a magnifying glass and scraped every single possible solder bridge, still not a single sound. I’m currently considering either ordering a new OPL3 board from Smash with solder screen to see if that makes a difference, or trying the alternative layout I originally mentioned. The reason for this is that the tracks seems to be more spaced out and therefore less chance of bridges… what do you guys think?

One thing that I did do when testing was to measure the voltages at the YMF chip and YAC chips. Obviously I was very careful, but is there any chance these could get killed by static?

Well, as you can see, now I’m pretty stuck. So any suggestions more than welcomed :slight_smile:

TIA

Dave

6

I got bad vibes here.. I was reading along, thinking to myself, “Well tested…He still hasn’t ruled out damage to the FM chips though…” then I see:

One thing that I did do when testing was to measure the voltages at the YMF chip and YAC chips. Obviously I was very careful, but is there any chance these could get killed by static?

Err, yep. You ougtta be wearing a grounded static strap at all times handling these goodies, especially when the power is on. (hint: ankle straps stay out of the way)

Edit: didin’t that core rev need hardware changes to run the latest MIOS?

7

Hiya Stryd,

As ever thanks for taking the time to read such a detailed post and trying to help, it’s most appreciated!

Err, yep. You ougtta be wearing a grounded static strap at all times handling these goodies, especially when the power is on. (hint: ankle straps stay out of the way)

Aha there’s something new to me. Ah well, one lives and learns :slight_smile: Luckily I always buy 2x parts in group buys so looks like I will have to order the nice solder screened OPL PCB from Smash for attempt 2…

Edit: didin’t that core rev need hardware changes to run the latest MIOS?

Yup but I’m pretty sure I implemented this. (Will double check tho just for my sanity).

Just as a matter of interest is there any way to verify the crystal oscillator other than a scope?

Well I’m off to buy an ankle strap before I kill anything else :smiley:

Thanks

Dave

8

Good news is that static straps be mighty cheap :slight_smile:

As for the oscillator I think you’d need to build a circuit to make it drive a led or something… Probably easiest to swap it with a new one in that case, if you don’t have a scope…

I know a few times ppl have grabbed the wrong type of xtal for the FM, are you sure you got it right?

9

Hi, sorry for being a bit late…

Why you didn’t gave me a scream via myspace? i’ve heard of the problem only few days ago after almost an year away from TK website…

I’ve fixed the links in the wiki!

Byee!!

10

I was in a similar position as yourself. Although i had a sort of working MBFM, i couldnt get my finger on the problem (I did have sound however it was faint and with lag).

I decided todo a complete rebuild of the OPL3 module. I ordered a new pcb from Mike and ordered all the parts myself. Only reused the IC sockets and the TL074.

Two weeks ago i soldered the whole thing together and to my surprise it was actually working. If u need it, i may have a spare YMF262 for you. It is a pull though, not a new one.