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Need help troubleshooting MBFM fault


LeTran
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Hi folks I've been following Midibox for a while now and have just completed my MBFM module :rolleyes:

However, it doesn't work.... :sad:

I have uploaded MIOS successfully to my core and I seem to get favourable responses from MIOS studio. I have uploaded the test tone program which appears to complete successfully. When I listen on the outputs I have nothing.

I have tested all the voltages and they appear fine (I'm doing the 0v linking of the 5v PSU and 12/-12v PSU).

I have put a scope probe on the inputs to the YMF262 and they all appear the same - the same as the clock freq ??!

Are there any steps I can take to narrow down the fault ?

Thanks alot.

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Make sure the wires from the Core to the OPL board are < 10 cm in length. Wilba had issues with longer lengths.

I tried making a special cable to avoid soldering to the bottom side of the board but it was a pain to debug and the OPL was a bit temperamental. Soldering straight to the bottom of the core (like the instructions say!) seemed to work better.

Good luck!

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Thank you - they are about 20cm in length on ribbon cable, maybe that's a bit too long? I also fixed up the LCD display and it displays the MIOS version and then states OPL3 testtone generator so I think the core is working properly.

What kind of tests can I do to see if my YMF262 chip is blown or not ?

thanks alot,

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Today I shortened the cables but unfortunately it's made no difference.

Well I say no difference, in fact the LCD won't display it's usual MIOS intro etc. If I uncouple the OPL3 module it displays fine.

Could something on the OPL3 board be the cause ?

I have another YMF262 chip so I'll try swapping it over and see what happens...

UPDATE: Still the same with a new YMF262 chip. Are there any jumpers I need to check ?

Edited by LeTran
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Unfortunately Java doesn't allow to send common MIDI events in SysEx packages. :-(

So, you have to find another solution, e.g. you could use MIDI-Ox (if you are using Windows) or MIDI-Pipe (if you are using MacOS)

This remembers me, that I wanted to add an alternative control to this application (e.g. switching pins via MIDI keyboard)

Best Regards, Thorsten.

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Could you please do me a favor and check the most recent mbfm_interconnection_test_v1d release?

-> http://www.ucapps.de/mios_download.html

I added the code which allows to control the pins with a virtual MIDI keyboard w/o testing it... it was the fastest solution to solve this issue.

Please let me know if it works.


C : Pin J2_1:RS = 5V
C#: Pin J2_1:A0 = 5V
D : Pin J2_1:A1 = 5V
D#: Pin J2_1:WR = 5V
E : Pin J2_1:D0 = 5V
F : Pin J2_1:D1 = 5V
F#: Pin J2_2:D2 = 5V
G : Pin J2_2:D3 = 5V
G#: Pin J2_2:D4 = 5V
A : Pin J2_2:D5 = 5V
A#: Pin J2_2:D6 = 5V
B : Pin J2_2:D7 = 5V

(the octave doesn't matter)
[/code]

Best Regards, Thorsten.

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Thanks TK - but I'm afraid it doesn't work.

I can only send modulation data on CH16 (not sure if this is correct or how to change) but pressing keys makes no difference.

The mod wheel still works though.

EDIT: Actually I'm only looking at the LCD display so if that part of the code isn't changed it may still work. I'll test properly.

Edited by LeTran
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I tested the core with MIDI-OX and it works fine.

TK if you do make a change to the interconnections prog then I'll happily test again.

Looks like my problem of dead OPL3 unit could be down to a second dead YMF262 chip ?

I was so careful to get those pins off though !

If anyone else has been down this road and can offer tips to try I'd be grateful. Thanks for the suggestions so far.

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TK if you do make a change to the interconnections prog then I'll happily test again.

So, does it mean that you are able to control the pins with the virtual MIDI keyboard of MIOS Studio as well?

This would be great - I will change the other test application as well if it works.

Looks like my problem of dead OPL3 unit could be down to a second dead YMF262 chip ?

I was so careful to get those pins off though !

Thats hard to determine.

If I remove the power +5v from J1 on the OPL3 board the LED still glows at about half the brightness.

Thats strange - it seems that there is a short between the data pins which leads to higher power consumption.

It's hard to say, if this is related to your soldering work, or if it's an internal short inside the OPL3 chip.

I've loaded up the MBFM software and with it set to the default, rhodes piano on CH1 I get +4.09v on pins D2, D4, D5.

Is this correct ?

The data pins are toggled with high frequency, you cannot measure the correct voltage w/o a scope.

Therefore the test application supplies static voltages.

With the interconnection test, do you always read 5V on the selected pin, and 0V on all other pins? This would help to exclude a short.

Best Regards, Thorsten.

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So, does it mean that you are able to control the pins with the virtual MIDI keyboard of MIOS Studio as well?

No that function doesn't work I'm afraid.

With the interconnection test, do you always read 5V on the selected pin, and 0V on all other pins? This would help to exclude a short.

Yes.

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I've attached a picture of just J2-2 connected. As you can see, the LED is lit.

Not sure what to do now really. I've tried 2 YMF chips.

I seem to have noticed this behaviour with my mbfm aswell. Which seemed kinda odd to me.

I don't have any problems though.

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I've just been checking the parts over.

I'm using TL074CN op amps - are these OK ?

Yes, i used the same.

But i was looking at your picture. And it seems to me that the polarity of C16 is wrong. Uh nevermind...it seems mine is wrong :pinch: .

Maybe you could post some detailed pictures of top and bottom of the pcb?

Edited by Shuriken
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Yes - here's two. the brown wire on the underside was just to eliminate an earth to the 5v side only.

I've made progress !! With a scope i managed to find that my clock freq was dead. Replaced and now the YMF262 gives good clock signals and I can see the output clocks too.

I can trace them into the YAC512 but I'm not getting anything out of it. I presume that the output is now analogue, albeit small.

Could anyone post a pic of what waveforms to get on the YAC512 outputs when running the test tone program ?

I had two others soldered in but I swapped them out for this one to see if the lot had been blown.

post-7118-126218987885_thumb.jpg

post-7118-12621898882_thumb.jpg

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Yes - here's two. the brown wire on the underside was just to eliminate an earth to the 5v side only.

I've made progress !! With a scope i managed to find that my clock freq was dead. Replaced and now the YMF262 gives good clock signals and I can see the output clocks too.

I can trace them into the YAC512 but I'm not getting anything out of it. I presume that the output is now analogue, albeit small.

Could anyone post a pic of what waveforms to get on the YAC512 outputs when running the test tone program ?

I had two others soldered in but I swapped them out for this one to see if the lot had been blown.

Are your YAC512 pin 2 connected to GND ? !

I clean my pcb's, if need it with isopropyl spirit.

Regards, Janis

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Wow - thanks so much for spotting that !!

Must have been part of the etching process missing off a bit.

I'm going to double check all the connections again.

Without the 12v power connected or any of the TL074's in, I've took some pics of my waveforms running the testtone program.

I know that I need the feedback from the opamps for some signals but surely you'd expect something from YAC512 pins 16, 13, 11, 10 ?

Thanks again for all the help so far - I'm determined to get it working and I'll have learnt loads by the time I'm done !

EDIT :- The picture names are wrong. From left to right they are pin 5(clock), pin 7(smp2), pin 8(smp1), pin 12(swin) and pin 4(din).

post-7118-126228232084_thumb.jpg

post-7118-126228233382_thumb.jpg

post-7118-126228234132_thumb.jpg

post-7118-126228234875_thumb.jpg

post-7118-126228235622_thumb.jpg

Edited by LeTran
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I fixed the bug in the mbfm_interconnection_test and released a new one:

In order to compare your scope snapshots, I would have to open my MBFM case... very timeconsuming :-/

However, it seems that they are looking good. Now it's time to check the audio output buffers (IC6)

Just unplug IC3 and IC5, and tap an audio signal from a (known working) audio source to pin IC3:O4, IC3:O3, IC5:O4 and IC5:O3 (since you own a scope, I guess that I don't need to explain more details about the testing procedure)

If audio is buffered correctly (1:1), then the remaining error must be located between the YAC chips and IC3/IC4 - I don't have the testing procedure for that (only trial&error&visual inspections)

Best Regards, Thorsten.

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Thanks TK - as soon as I sort this issue I'll test the interconnections prog.

I tested the op amps as you suggested and they all work fine so no problems there.

I suspect the YAC512 chips as nothings coming out of them. I have a bulk pack of 25 brand new (unused) ones coming to me soon from USA.

Once it's working I'll no doubt have some spare chips going which I will sell on for a reasonable price. Email me if you're interested.

Thanks once again to all who have helped me. I'll post when it's working :rolleyes:

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