Another Crackly FM question

[JRock]

Ha Ha :thumbsup:

No. I doublechecked. J3 reads +/-12V and ground...

[nILS]

Um. Then you have some very interesting problems.

IC3:4 == V+ == +12V

IC3:11 == V- == -12V

If the voltage reads okay on J3, it should also read okay on IC3:4 and IC3:11.

So... Something doesn't add up, at all.

Check for continuity between J3:V+ and IC3:4

Check for continuity between J3:V- and IC3:11

[JRock]

They are both open.

And with Only J3 connected IC3 (YAC512-M):4 should be receiving +12V

IC3 :11 -12V

I can't be that interesting :hmm:

I must be doing something stupid.

I hadn't taken the TL074's out. With them out IC3:4 = 0V

IC3:11 = 0V

On IC5:4 I get 12V

IC5:11 = -12V

That's where the +/-12V should come from?

[nILS]

Wait wait wait...

And with Only J3 connected IC3 (YAC512-M):4 should be receiving +12V

IC3 :11 -12V

IC3 would be channel 1/2 TL074 opamp, not the YAC.

For future reference: I am going by the schem on ucapps.de, which apparently doesn't match Smash's PCB when it comes to the part designators...

The +-12V should be on pins 4 and 11 of the opamps.

I must be doing something stupid.

Like not looking at the schematic and wondering why I ask you to check for 12V on the YACs? :whistle:

Seeing that you were measuring somewhere other than I thought, your results make a little more sense now. :yes:

So, to make sure we've not missed anything:

One last time, check the voltages of all pins marked as +5V, +12V and -12V on the schem against ground on OPL:J1.

Do that with all the parts mounted. Do that with both the +-12V and 5V supply connected.

[JRock]

A Ha! I thought I might have crossed my signals at some point. That's why I wrote the YAC in there, to make sure we were on the same page. That all makes a lot more sense. It's been a couple days since I looked at the schematic but I didn't think the YAC was supposed to get 12V. OOps.

I'll check everything again and double check with the schematic

Sorry to waste your time. Thanks for helping me!

[JRock]

Ok...

IC1:1 = +5V

IC1:7 = +5V

IC2/4:1 = +5V

IC2/4:3 = +5V

IC2/4:6 = +5V

IC2/4:9 = +5V

IC3/5/6:4 = +12V

IC3/5/6:11 = -12V

J1 = +5V

J3 = +/-12V and Ground

[nILS]

Okay, so your voltage problems seem to have magically vanished :)

What's the audio like now?

[JRock]

Magic! :sorcerer:

I'll make the connections to the PIC and find out.

I forgot to mention that a bunch of other pins on IC1 also read +5V :pinch:

Guess I was in a rush to hit post.

[JRock]

Now I get no sound besides the crackle of the 74s when I connect or disconnect power.

All the voltages I just posted are still the same.

[Shuriken]

Is the big hum gone now?

[nILS]

a bunch of other pins

Not helpful. Which pins?

New audio sample?

Trace the sound from the YACs output (if there's any) and see where it dies.

[JRock]

There is no sound from either YAC (pins 10 and 11) output. There is distorted tonal music coming from the YMF!! From pins 21 and 22.

Is the big hum gone now?

Yes.

I think just because I have it grounded properly. I have it connected the same as before.

I am just not experimenting with the ground connections.

There is not much to sample from the main output. Would it be helpful to hear what is coming from the YMF? It plays to Midi and the pitch bend works. It's on the Rhodes Piano.

Now I get +5V on these pins with the PIC connection in place...

IC1:1/3/5/6/7/8/15 = +5V

Thanks!

[Shuriken]

Good to hear the hum is gone.

Pin 21 and 22 is Serial Data Output for channel AB and CD. That's why it's distorted. If it wasn't distorted, why would one need the YAC512.

Since there is no hum and you can hear a pop, it is very likely the problem is related to the YAC512. If all the voltages check out and you cannot find any solder/component problem on the board, i would recommend to replace one to see if that solves the problem.

[JRock]

That's what I was thinking. Ugh. I wonder why they're beat?

I think they were new.

Electrostatic? The 6N138 is still going strong. I didn't blow the 74s... (I think they are pretty tough though.

Guess I'll scrounge up some more and see what happens.

Thanks!

[mazatta]

Let me know if you need any YAC512, as I have some spares tucked away somewhere.

[JRock]

PM'd you. Thanks!

[JRock]

Just to Follow up, I replaced the YAC512s and I am getting some music!!!!

I still have to construct the Control Surface, But I'm getting a Musical tone out of Output 1.

I'll update again once I confirm that everything is as it should be :thumbsup:

I would try it out on the JSynthLib, but I still don't have a reliable USB to midi.

[JRock]

It's Aliiivveee!!!! AAHAHAHAHA!!! :frantics:

You guys Fuckin' Rock!!! Thank You So Much!!!

I'll treat you all to a song :flowers:

(as soon as I figger' out how to use this thing)

[Schrabikus]

I have a similar problem. Permanent backgound noise, even with LCD and control surface disconnected.

MBFM_noise.mp3

[Shuriken]

You should really make a seperate topic for your problem.

[Schrabikus]

Sorry, Occam's razor is on my mind =)