Another Crackly FM question

[JRock]

Hi. I can’t seem to get music out of my FM. It just sounds like digital noise.

[MBFM Ground.mp3](< base_url >/applications/core/interface/file/attachment.php?id=7882) This is the sound I get when Everything is hooked up the way it is in the interconnection diagram.

[MBFM unground.mp3](< base_url >/applications/core/interface/file/attachment.php?id=7883) This is the sound I get when I remove 5V and Ground from J1 and J3(on the OPL3)

Both of these are bootup then press some keys, then turn the modwheel.

I am using the PSU to Power the core module as well. I pulled 12V and Ground over to a 9V regulator and send that to J1 of the core module.

The interconnections test worked and when I got a very quiet testtone when I pulled the ground and 5V off of J1 and J3. I’ve heard very quiet melodic tones while I wsa trying different stuff out…

What Do I need to check? I’ve read a bunch of posts that are mostly similar. Do you think it’s the YACs or the 74s? Maybe the Crystal Oscillator?

I’m stumped.

[Janis1279]

1. You need 3 supply voltages for the OPL3 module;

+5Vdc and a bipolar voltage source ;

"Note that the OP amps are powered from a balanced voltage source (+/- 12V). I specified this large voltage range since it allows to take the same PSU like for the MBHP_AOUT module. The TL074s can be alternatively powered from +/-5V to +/-18V. "

Do you have stable supply voltages with connected the core and the OPL3 modules ?

2. The MBFM have the four audio outputs you can test it with the mbfm_testtone_v1c.zip application

3. may be you have wrong output settings .

sorry, my crystal ball is not so clear tonight.

regards,

Janis

[JRock]

I have a stable Bi-Polar PSU. I pulled the transformer out of a 1000mA 12VDC wallwart and built a Voltage doubler circuit.

I tested the outputs on J4 and J7. They both sound like the clip I posted.

The test tone played faint and distorted when I pulled the ground off. I couldn’t hear it with the ground on.

What voltages are you supposed to get on pins 1 and 4 of the 74s? I’m reading around 9V on the first two and closer to 14.5V on the third one. Maybe this sheds a little more light on things?

[Wilba]

I’m not so familiar with MBFM but I did have a lot of trouble because the cable between the Core and the OPL3 module was too long… it would pass interconnection tests but still not produce sound out of channels 3 and 4.

http://discourse.midibox.org/t/topic/12419

It’s probably not relevant, but something to check anyway.

[nILS]

Pin 1 is the output of the first opamp on a TL074. Whatever you get there depends on which IC it is.

Measure against ground:

Pin 4 should be +12V

Pin 8 should be -12V

see http://ucapps.de/mbhp/mbhp_opl3.pdf

Stop pulling the ground off. The grounds of the two PSUs need to be connected otherwise you’ll get random potential between the two.

Show a pic or some sketch of your wiring - what exactly goes where?

Do all the voltage tests - all all the voltages as expected?

[JRock]

I was just pulling the redundant grounding off. I wouldn’t touch the neutral from the +/-12V or the negative from the 5V.

From J2(Core) to J3(OPL3) to J4-J7(OPL3); and the +5V from J2(Core) to J1(OPL3).

The LED still lights when J2 to J1 is unhooked. I just assumed that was correct. I guess I’ll have to doublecheck that.

My ribbon cable is only about 6" (15cm?).

I’m sorting through a mess of components right now but when I finish that I’ll draw up a sketch, take a picture and post it up.

Thanks

[JRock]

Here’s How I’m connected.

All the voltages read correctly.

+/-12V on Pins 4 and 8 of the 74s.

If I don’t have +5 from J2core connected to +5 J1oPL3 the +5 pins on the YACs and the YMF read 2.82.

[Janis1279]

"All the voltages read correctly.

+/-12V on Pins 4 and 8 of the 74s."

you meant : +/-12V on Pins 4 and 11 of the 74s ?

The wiring look ok. The better is to connect the audio outputs gnd pin right to your power supply gnd .I think +/-12V common point.

If all the chips, a oscillator, electrolytic capacitors are the right placed, may be some soldering problems.

Regards,

Janis

[nILS]

All the voltages read correctly.

Where? What pins *exactly* do you measure and what voltages do you *exactly* get?

+/-12V on Pins 4 and 8 of the 74s.

What Janis said.

The LED still lights when J2 to J1 is unhooked. I just assumed that was correct. I guess I’ll have to doublecheck that.

Nope it’s not correct. At all. The LED is only connected to gnd and +5V via a resistor. If it lights up without 5V from the core you have a big fat soldering problem.

Remove the TL074s, unplug all data lines, find the bridge. It’s most likely somewhere between +5V and +12V around J3. Check continuity between the rails, … Do not power it up again before you find out why on earth the LED lights up w/o 5V.

[JRock]

I meant 4 and 11 of the TLO74s

I mean pins 1 and 3 on the YAC and Pin 1 in the YMF read 5V. (Like it says they ought to in the schematic)

Thanks.

[JRock]

Thanks guys. For your patience and your help. :flowers:

Ok.

The ribbon cable is the only connection between the core and the OPL3.

The core is working properly.

The +/-12V is not connected.

I get +3V @ J1oPL3, Pin 1 on the YMF and Pins 1, 3 and 7 on both YACs. and the LED is lit.

I’m not finding any bridges or connections that aren’t supposed to be. That probably cause I’m not looking in the right spots.

[Janis1279]

I remember another older topic with the Led is lit without +5V connected to the OPL3 board.

http://discourse.midibox.org/t/topic/13607

may be it somehow helps.

Regards,

Janis

[Echopraxia]

Did you get your opl3 board from Smash? If so you have to fix a trace on the board that was not processed properly at the factory. Just a thought.

I had a lot of problems with my MBFM before I got it to work. I found that using a flux paste/gel on your smd pins, tweezers with micro tips and small diameter solder wire will get you nice clean solder joints. If you can’t get good solder joints on the smds nothing is gonna work. I had somewhat similar weird noises and the smds were the problem for me. I would try to resolder your smds with flux and get the magnifier out.

Don’t give up.

[JRock]

Thanks guys.

I did get my board from Smash. What Trace needs fixing?

I was pretty meticulous about the SMDz. That doesn’t mean I’m infallible but they look pretty good. I’d hate to bugger up the board so that will be my last resort.

Thanks for the Link Janis. Yeah, I had read that thread a couple times. That’s why I thought it might be the YACs. I guess I’ll try to fix this trace (as soon as I find out what it is) first, try a different XO, then see where I’m at.

[nILS]

I did get my board from Smash. What Trace needs fixing?

http://discourse.midibox.org/t/topic/10078

[JRock]

Again, Thanks for all your help and your input :flowers:

I got Rev.2 so all should be good.

So my core works normally. It boots up and wants to play. The LCD is working fine.

With the core wired to the OPL3 via J2(1) and J2(2) and the core powered on, the LCD lights cause Pin 1 (Vdd) of the YMF is getting 3V from somewhere. The +/-12V is not connected and nothing is connected to J1oPL3.

I checked the YMF262M Datasheet and I can’t decipher what the internal connections are. Probably pretty complicated.

The only closed circuits with pin 1 of the YMF are pin 7 of the YMF (/RD) and the 5V rail for the

YACs: pins 1, 3, 7 and 9, as well as the Vdd pin for the XO; and the +5V for J1oPL3.

Has anybody gotten this?

What voltage does your 5V rail read when J1 and J3 (OPL3) is not connected to any power?

[nILS]

Your 5V rail should always be 5V.

With the core wired to the OPL3 via J2(1) and J2(2) and the core powered on..

…the core should be doing exactly the same thing as if that connection were missing and the YMF should have 5V on pins 1 and 7. Pin 12 should be ground.

With the opl module connected via Core J2 > OPL J1: Do you still get 5V on the core module or does the voltage drop there as well?

Post (good) pics of the OPL module, both top and bottom view.

Since you’re already having problems with the 5V rail, remove the opamps and leave ±12V unplugged for now.

[Imp]

I remember having some troubles too, when i build my FM.

Did you use a PIC18F452 or a PIC18F4685 ?

I accidently ordered a 18F4685 and only got the fm working by uploading the MIOS files for the '452 to it.

edit: 20 secs after posting this, i found what i searched for, for about half an hour…

With the Fm , the LCD should be wired as 8bit and the Pull-up for CAN must be left out, cause otherwise it messes up communication with the OPL.

This might clarify what i’m talking about

[JRock]

I have a couple more pics but I can’t get anymore to load right now.

When I hook Core J2 - Opl3 J1 It’s 5V.

When It’s just the core to Opl3 J2(1-2) The voltages read like so:

-.7V

-.7V

3.9V

3.9V

-.7V

3.9V

-.7V

-.7V

4.17V

-.8V

around 2.5V but it fluctuates +/-.1 rapidly

4.19V

I have an 18F452 and I haven’t attached the pull-up resistor for the CAN Bus.

After I took these pics I took out the 74s and I am not gonna hook up the +/-12V till I figger out what’s goin’ on.

Thanks guys

[nILS]

I have a couple more pics but I can’t get anymore to load right now.

Do you know anyone that has a real camera? It’s kinda hard to see anything on the pics…

The main problem that I have in trying to figure out what’s wrong is that I have no clue whatsoever regarding what works, what doesn’t and what in the name of sweet baby Jesus you’re measuring. I am guessing the list of voltages is what you measure on J2_1 and J2_2? What did you measure that agains? Ground? If so, where? It should be impossible to negative readings… Besides, those are data pins and the voltage of those doesn’t really help.

So, this is my last try. Answer the following questions, or I’ll give up.

1. With everything disconnected, what voltage do you read from IC1:12(Vss) to IC1:11(Vdd) on the core module?

2. When you connect Core:J1 to OPL3:J1 only - what voltage do you read from IC1:12(Vss) to IC1:1(Vdd) on the OPL board?

3. Does the LED light up with just the Core:J2 > OPL:J1 connection?

4. With no wires connected anywhere - What’s the resistance between the following pin pairs on the OPL module:

IC3:4 and IC1:12

IC3:4 and IC1:1

IC3:11 and IC1:12

IC3:11 and IC1:1

J3:V+ and J3:Gnd

J3:V- and J3:Gnd

J3:V+ and J3:V-

3. “I haven’t attached the pull-up resistor for the CAN Bus.” - the diode isn’t there either?