OPL voltage problems (fixed) -> now PSU voltage problem

Testing/Troubleshooting
1

Hi everybody,

i have some voltage problems with my OPL module.
If i connect J2/1 or J2/2 to the core it doesnt boot anymore.
After searching the forum i found a topic which said to measure the following:

  1. With everything disconnected, what voltage do you read from IC1:12(Vss) to IC1:11(Vdd) on the core module?
    5V
  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?
    5V
  3. Does the LED light up with just the Core:J2 > OPL:J1 connection?
    Yes
  4. With no wires connected anywhere - What’s the resistance between the following pin pairs on the OPL module:
    IC3:4 and IC1:12 = 3,6M
    IC3:4 and IC1:1 = 3,8M

IC3:11 and IC1:12 = 0,2M increasing to 2,0M
IC3:11 and IC1:1 = nothing

J3:V+ and J3:Gnd = 0,1M increasing to 2M
J3:V- and J3:Gnd  = 0,2M increasing to 2M
J3:V+ and J3:V-  = 16M

  1. “I haven’t attached the pull-up resistor for the CAN Bus.” - the diode isn’t there either?
    No diode.

I guess there is something wrong with my +/- 12V right?

Are there any other connection that i can measure to find the problem?

 

Thanks a lot for your help!

 

Marxon

2

Hi, I’m probably not the best to troubleshoot with you but I’m knee deep in my own FM build. I say that it sounds like you don’t necessarily have a pwr problem. From your readings you appear to have correct Vcc on the logic side, no shorts.

“IC3:11 and IC1:1 = nothing” No connection between +5V and +12V, good.

“IC3:4 and IC1:12 = 3,6M”

IC3:4 and IC1:1 = 3,8M  No cables to PSU Right? No connection Between AVss and DVss. good

“J3:V+ and J3:Gnd = 0,1M increasing to 2M”  Filter Cap charging

“J3:V- and J3:Gnd  = 0,2M increasing to 2M”  Filter Cap charging
“J3:V+ and J3:V-  = 16M”  Lots of Caps between +12V and -12V

All so far looks OK.

When you say ‘won’t boot’ is there any sign of life on the LCD with the OPL brd connected? Can the core boot with nothing connected?  Can it boot with no OP amps stuffed, just the OPL and DACs? 

Check the Vcc voltage to GND when trying to boot. If steady, power down and do continuity checking from the PIC pins (right where the pin emerges from the plastic package) to their destinations on the OPL chip; not just the cable, the whole path. I also like to continuity check SMD pins; from device package to brd trace ( looking for cold solder joints), and from one pin to adjacent pins (solder bridges).

If you have been over every solder joint and cable then there maybe an issue with firmware.

Waiting to hear what you find, Good Luck

EDIT: Just remembered, On my OPL board the silkscreen labels for J2 are wrong. With the Component (DIP sockets) side up, and the J2 connectors closest to me; J2.2 is on the left and J2.1 is on the right. Pin 1 on both connectors is on the right side. Had to check and re-check this a few times myself.

3

Hi Yogi,

thank you very much for trying to help me!
Yes the Core does boot when nothing connected.
The Core-Opl interconnection test voltages are also OK (without Core - Opl J2/1 and J2/2 connection)
It does also boot with Core-OPL 5V connection (without Core - Opl J2/1 and J2/2 connection).
If i connect J2/1 or J2/2 the Core reboots again and again which means
i get the “boot-up midi-message” every 2-3 seconds and the 5V drops down to 4,3V(!)
So we getting closer to the problem, right?

 

 

Best regards

Marxon

 

EDIT:

I fear my OPL3 chip is dead :frowning:
When the OPL module is powered with 5V, nothing else connected,

which voltages should there be if i measure

the OPL:J2 module pins to Vss?

4

Yes the Core does boot when nothing connected.

 

So far so good. Core hardware and firmware seems OK

 

 

The Core-Opl interconnection test voltages are also OK (without Core - Opl J2/1 and J2/2 connection)

 

I assume that you have the correct OPL brd J2.1 and J2.2 as I mentioned above. 

 

 

It does also boot with Core-OPL 5V connection (without Core - Opl J2/1 and J2/2 connection).

 

OK seems like the Vcc and Vss on both brds are good.

 

 

If i connect J2/1 or J2/2 the Core reboots again and again which means

 

So there seems to be a problem with the interconnection. Are there any messages/characters on LCD when OPL brd is connected? Retrace the Core to OPL connections as per http://ucapps.de/mbhp/mbhp_opl3_interconnections.pdf For now, test with no ±12V and no op amps installed, this will narrow things down.

 

 

I get the “boot-up midi-message” every 2-3 seconds and the 5V drops down to 4,3V(!)

 

4.3V is not necessarily a dead short, but it may be enough to cause the Core to reset. So the problem could be in the Digital side of the OPL brd, U1, 2 or 3, if your Core-to-OPL connections are correct.

Do any of the YM chips get hot? Check for solder bridges. Check that all top side jumpers are installed. (where did you get the OPL brd, mine is from SmashTV). Check that 'litics filter caps are correct, ‘- - -’  to unmarked hole (GND side) of footprint (Not the one marked ‘+’). 

Make sure chip orientation is correct. Looking at back of board, with J2 connectors closest to me: Pin 1 of YMF262 is upper left pad, Pin 1 of both DACs are to the bottom left of their footprints.

 

 

 

I fear my OPL chip is dead :( When the OPL is powered with 5V, nothing else connected, which voltages should there be if i measure the OPL:J2 pins to Vss?

 

d7:0 are bi directional (I think), they should be floating, may be any where between 0 and 5. the rest are inputs to the OPL so about the same, floating. Generally speaking, unconnected inputs are not a good condition for most chips, it can cause oscillations and runaway current draw. With just Vcc  and GND connected, do you see the drop to 4.3V?

The symptoms do point to a chip with an internal short, pulling too much current, but checking for solder bridges should be the first thing. I can’t speak to the ruggedness of the YM chips, but some of these ‘old’ chips can take quite a beating, more so then modern chips, so if there is a soldering problem then the OPL may ‘come back from the dead’.

Don’t give up!

5

Kind of messed up my last post with the ‘qoute’ thing, so my my notes are interspread with your quotes. Sorry, makes it hard to read.

6

The Core-Opl interconnection test voltages are also OK (without Core - Opl J2/1 and J2/2 connection)

It does also boot with Core-OPL 5V connection (without Core - Opl J2/1 and J2/2 connection).

The more I re-read this the more I feel that there is a problem with your J2 connections. If I understand correct- Core boots normal with just  the +5V and GND connected to OPL brd In other words, both boards powered up with no logic connections?  So with this setup: the OPL board is not overloading the PSU, and causing the PIC to reset.

I would look very close at U1.8:6,  pins 6 and 8 are on either side of a Vcc pin. If either pin was bridged to the Vcc pin: disconnected from core=no problem but when connected to core, PIC would at some point try to pull low=dead short.= voltage drop.

.  

7

I have tested every single Core(PIC)-Opls(YMF) line to
figure out if a certain one causes the problem:
-Core (Testtone app) and Opl module powered with 5V,
-LCD connected (LCD shows “Testone Generator”)
Result:
CORE PIC:pin24 to OPL J2:WR (YMF:pin6,8)
was the problem! But there was no short circuit to see…
So it has to be under the YMF :smile: I tried to bend it up a little bit, very carefully.
And then i blowed as strong as i can from all sides to the chip, connected everything again:
It works!
Unfortunately, now it doesn´t boot with +/-12V connected.
But i guess tomorrow after some sleeping, it will be fixed too.
So far, thanks for your supoort yogi!

Best regards
Marxon

8

Can´t sleep… must fix it :rolleyes:

 

Here my next tests:

 

PSU:+12/-12V/Gnd –> OPL:J3
PSU:Gnd          –> Core J2:Vss
PSU:+5V          –> Core J2:Vdd and OPL J1:Vdd
no LCD connected
RESULTS:
OPL J3:-12V to OPL J3:Gnd = -12V
OPL J3:12V  to OPL J3:Gnd =  12V
OPL J1:Vdd  to OPL J3:Gnd =   5V
Core boots up.

next:

PSU:+12/-12V/Gnd –> OPL:J3
PSU:Gnd          –> Core J2:Vss
PSU:+5V          –> Core J2:Vdd and OPL J1:Vdd
LCD connected
RESULTS:
OPL J3:-12V to OPL J3:Gnd = -12V
OPL J3:12V  to OPL J3:Gnd = 6,5V
OPL J1:Vdd  to OPL J3:Gnd =   5V
Core does not boot.

next:

PSU:Gnd          –> OPL J3:Gnd and Core J2:Vss
PSU:+5V          –> OPL J1:Vdd and Core J2:Vdd
LCD connected
RESULTS:
PSU:+12 to PSU:Gnd = +12V
PSU:-12 to PSU:Gnd = -12V
PSU:+5  to PSU:Gnd = +5V
Core boots up.
LCD is working.

 

Strange?

9

<p>Great! You’r welcome, just glad to be able to help some.</p>

<p>On the ±12V side, start without any amps installed. If it won’t boot without any amps installed then its a problem on the board.</p>

<p>Double check solder joints; can also re-heat any that don’t look ‘bright’. More then once I’ve had a board that looked 100% but didn’t work; till I re-heated some joints. </p>

<p>Without the OP amps installed, you should be able to connect the +12v and GND then test; then only the -12V and GND. This will narrow down which raid is a problem.</p>

<p>Double check the polarity of the filter caps, the ones on the -12V rail will have the ‘+’ side of the cap to GND; C16, C20, C22 and C26. The silkscreen on this board is correct.</p>

<p>On my board, one of the traces from J3, a +12 trace, passes under U3. There is a solder mask on this board, but without it you could get a bridge under U3 to this trace with too much soldier.</p>

<p>Other possible areas to look at:</p>

<p>Land for R5 and U3.9</p>

<p>Land for wire jumper under U3 and U3.9:8 pins</p>

<p>Land for R13 and U5,9</p>

<p>Land for C11 and U5.1</p>

<p>Land for R6 and U6.1</p>

<p>Land for R15 and U6.12</p>

<p>These spots are very close together, but not connecting; good candidates for solder bridges.</p>

<p>Don’t spare the solder wick on a ‘iffy’ joint, just clean the joint and re-solder it.</p>

<p>After you’ve checked and double checked, and the core will boot,  install one amp and test. If it works then install another and test again, then the next. If any of these are a ‘no-go’, replace it with a new one. Remember that U6 is ‘upside down’ compared to the other two amps.</p>

<p>Keep it up.</p>

<p>EDIT: Didn’t see your latest post before I Hit the ‘POST’ button :)</p>

10

Looked over your latest test results. Very good.

To summarize; with LCD connected to core, +12V rail fails at OPL board. With no ±12V to OPL board, LCD & core works and ±12V rails stable at PSU. With no LCD connected, Core boots and ±12V rails are stable at OPL board. Hummm

So common connections between LCD and OPL board- RB7:0, and RD6:5 should be looked at. I’m not ruling out the points I covered in last post, but most bridges would effect the +12 rail regardless of the LCD being connected. The OPL3 and DACs ( and LCD) do not have any direct link to the +12V rail other then by U3 & 5.

This is strange and seems like a grounding issue; I’ll have to think some more on how this could be caused. Best advice I could give is still what I laid out in the last post. If all that fails then we’ll have to widen the search.

11

Hi again yogi and all others!

It is unbelievable how many different connections somebody can measure, before
locating the real problem :smile:
Ladys and Gentelman: it is the PSU!
As long there is less current drawn from 5V
(only the Core without LCD for example :wink:
everything is ok.
But if there is more current drawn  
5V drops to
+12V drops to 6,8V
-12V remains -12V

I am using this PSU from the forum:

Only difference: i have “dual” transformer with 2x15V outputs.
I connected the outputs like this:

 

At the 7812 +12v output i connected an additional 7805 circuit (2200uF-330nF-7805-10uF-100nF) to get the 5V.

So what could cause this behavoir?
I guess the 7812 is faulty, but right now i have no other one for testing.
Any other ideas?

Best regards
Marxon

12

Great to hear! 

I think in your case it may be more to do with the 7812 followed the 7805. This is a good way to limit heat at the 7805 but if you are loading close to max, 1-1.5A, on the +5V rail, that load is also seen at the output of the 7812. So trying to draw off of  the +12 rail overloads the 7812 and you end up with voltage sags on +12 and/or the +5V rails.

You could try a second +V reg ahead of the 7805, say a 7809 or 7812, parallel to your original 7812. So you have one 7812 for the +12v rail and a 78XX followed by a 7805 for the +5V rail. What is the amps @ 15V ac for your xformars? Should be fine at 2-3A

Very glad you found the issue, truly I was thinking that this would be the next place to search. Like they say, ‘Its always the last place you look’ :wink:

13

I guess you are right.

Just checked the datasheet from my LCD:

The led backlight already needs 300mA.

I will try your suggestion with the second +V rail.

Have some 7809 here… My transformer has 2x1,6A

Some 2x3A is allready ordered :smile:

OK lets start the next round…

 

Again, thanks a lot for your support!

 

Best regards

Marxon

 

 

EDIT:

any recommendations which capaciator values to use?

14

Marxon, a 7809 would work well. As far as filter caps, there is allot of range. These caps do two things, smooth ripple and shunt HF noise to GND, in essence a very, very, VERY low Frequency, low pass filter. For input, you want a large 'litic in the 100uF -10,000uF range (bigger is better) to absorb the raw ripple, BUT make sure it is rated 3-4X the voltage (voltage spikes when switching on and off). You can also use parallel caps to increase the uF, I.E. two 100uFs in parallel = 100+100=200uF. Lots of trade-offs depending on space, cost and whats in the junk box. Along with that, a small .1 uF range cap to shunt HF noise; most cerm disc caps are rated +50V or more so V rating isn’t too much of an issue. On the output, again the same configuration, but you are at a lower voltage and you have far less ripple, so the 'litic can be < 100uF range. Between the 7809 and the 7805 you can apply the same ‘output rule of thumb’. Remember that 78xx TO-220s are rated at 1.5Amps with heat sinks; you can get the 78XXs in the TO-3  5 Amp package, but heat sink/mounting becomes a problem.

Most datasheets show the min values; most engineers want to use just what is necessary, only!  2 cents saved per unit adds up on 10,000 units :wink: Our goal is to have very good sound!

You are very welcome; just glad to be ABLE to help. The older I gets, the more I want to pass along the little bits of hard earned knowledge the world has taught me; at least till my wife tells me to ‘Shut Up!’ :wink: )  

15

Kind of messed up my last post with the ‘qoute’ thing, so my my notes are interspread with your quotes. Sorry, makes it hard to read.

There. I fixed it.

16

Thanks nILS. After I had posted it and realized what happened, I tried Editing it, but couldn’t seem to break things apart. Guess I need a bigger hammer! I’ll just sit over here with my ‘fool’ hat on. :shifty:

I don’t even know what the #*%$ happen in the other post with the "<p>"s at the start and end of each line!?!  That’s what I get for post in the middle of the night.

17

Boy, I don’t know if this issue is fixed or not from the posts being bounced back and forth. But I suspect it hasn’t been fixed. I am surprised that nobody has asked to measure the AC voltage across the rectifier as seen on post #11. This should be a strong 30vac. If its not, then you have one of the polarities of the 2 ac transformers wired backward. When I say backwards I mean switch the 2 black wires on only one of the transformers. I suspect that you are seeing only a half wave rectified DC voltage from the bulk supply which will drop drastically under load rather than a full wave one.

 

Pete

18

Hi Pete, My impression from the posted photo, is he has the primary phasing correct, but you may be right.

 

I am surprised that nobody has asked to measure the AC voltage across the rectifier as seen on post #11. 

Yes a prudent test, but I would expect to see problems on the -12V rail also. 

 I could be totally wrong here; from the git-go I have been making assumptions based on the tests that are done and trying to relate a fail mode to them. Can’t troubleshoot everything, at all at once; just trying to test and verify one section at a time. 

 

 I suspect that you are seeing only a half wave rectified DC voltage from the bulk supply which will drop drastically under load rather than a full wave one.

Again, wouldn’t this effect the 7912 also? With a half wave rect., wouldn’t the GND point be at 1/2 of the secondary xformer Voltage, 6.5V referenced to the ‘-’ bridge connection? From Marxon’s photo/sketch, it appears he has ±16V from the bridge, but at this point my eyes are going a bit crossed :wink:

 

Looking at the the output of the 7812, under heavy load, it drops to 6.8V; looks like the regulator’s circuit protection is kicking in. It ‘smells’ like a load current related problem, to me, ASSUMING there are good heat sinks and full power from the transformers.

The OPL board doesn’t load either 12V rail very much, 3 op amps for <75mA total?, But the 5V rail is pulling ~1A or more, close to the 7805’s max with good heat sinking, and in turn, passing this load, plus the '05’s losses, to the 7812. 

There still could be other issues: a bad op amp, undetected short, a damaged regulator or thermal overload to name a few. Time will tell. For myself, as I build sections, I test and re-test till I’m confident that it’s “known good”. Once all sub systems are integrated, one symptom can be caused by a host of possible faults.

This PSU design, two xformers, though very similar to a center tapped bi-polar, is not ‘the run of the mill’. Only considering the overall size of the PSU, my choice would have been a center tapped xformer, but in the end it’s Marxon’s decisions. Just trying to help him sort it out.

19

Hi again and happy Eastern,

sorry for neglecting this topic but

i started building a Midibox NG, too so the FM Synth had to take a little break :wink:

This is the current status:

I am using a second transformer now to power

the +5 rail.

Unfortunately the FM still dont work.

OPL powered with J3 (+12V/GND/-12V) and J1 (+5V)

-> correct Voltages on IC sockets (no TL074 plugged)

-> correct Voltages YMF262 (Pin 1, 7): J3 (Vss)

-> correct Voltages YAC512 (Pin 1, 3, 5, 9): J3 (Vss)

-> OPL power led = off

same as 1) and OPL connected to Core

via J2_1 and J2_2 except D6 and D7

-> correct Voltages

-> Core boots up (FM Testtone)

-> OPL power led turns on 1 sec after powering

same as 2) and D6 or D7 connected

-> Core does not boot

-> OPL power led off

-> +5V drops +3,8V.

Solderings and connections are 100% OK

Double and tripple checked.

I am afraid the YMF has died during all my fix attempts..

Any other Ideas are welcome :smile:

Best regards

Marxon

20

Don’t give up on your OPL3 yet–though they’re not very expensive on eBay.

 

I haven’t followed all your earlier posts, but I did notice something:

  • The OPL3 board power LED is connected directly to J1 (well, through a resistor). Whenever the board is receiving +5V, that LED will be on; if it’s going on a second after you power on, something is shorting/drawing too much current for 1 second. The LED should light dimly even if the board only has +3.8V. If the YMF262/YAC512s are getting +5V/Gnd like in your first example, the LED will be on. If not, you can start there. If you have a multimeter with this capability, you can also try hooking it up in “current” mode and wiring it in series with J1, to see how much current the OPL3 board is drawing. According to the datasheet, the YMF262 draws 10 mA, and each of the YAC512s should be about the same. If the +5V rail is being loaded by the OPL3 board by more than 100 mA, there’s some short, internal or external.

 

Good luck!