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SE330 calibration troubleshooting
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author SE330 calibration troubleshooting
vaktmesterj
Hi people

pin 1 of U12 is 3,3v

pin 1 of U32 is 3,3v

pin 7 of U12 and pin 7 of U32 is around 15 volts and not affected by the trimmer.

Anyone knows what could this indicate?
Synthbuilder
Quite possibly you have some wrong resistor values around those op-amps. Check R123 and R130. But you may have a problem with the right hand triangle LFO - based around the right hand sides of U2, 3, 4, 10 & 11. Check that pin U11 pin 7 is slowly oscillating and can be turned to near zero volts when the triangle level pot is fully down.

Tony
vaktmesterj
Thanks alot!

Checked the resistors next to the amp and they are all correct.

pin 7 of U11 is around 15v, and every pot is turned fully down.

Whats next?
Synthbuilder
vaktmesterj wrote:
Whats next?


You need to find out why your right hand triangle oscillator is not working. The usual suspects are board shorts, wrong components and maybe failed components.

The right hand triangle LFO can be found in the middle on the second page of the schematics. If U4 pin 7 isn't oscillating the problem is with the LFO itself. If it is oscillating then it'll probably be a problem with the VCA based around U10b and U11b.

If you only have a DVM and no scope then turn the LFO speed right down and you should see the meter reading fluctuating wildly when you monitor the LFO output.

Tony
vaktmesterj
In all the spots which require a 470nF, 63V polyester, i have used one that says "47k63". Would that explain the problem?
vaktmesterj
According to the color code of the resistors, the ones who are suposed to be 390r, are 380r. Could that be it?

Edit: I meassured one from the box and its 390, so its all good.
vaktmesterj
Appart from that, ive checked that everything on page 2 is as it should.

Edit: Btw, what do you mean by "U10b and U11b", whats the "b" for?
vaktmesterj
Alot of times its something very stupid. I mistook pin 8 for pin 7, seems good now, i guess its too late so ill continue tomorrow. Thanks for all the help so far
Synthbuilder
vaktmesterj wrote:
what do you mean by "U10b and U11b", whats the "b" for?


For an IC package with several identical sections it is common to identify them by a letter. For a dual op-amp, the first op-amp in the package is a and the second b. For a quad op-amp, you'd have a, b, c and d. U11b is therefore the second section of the dual op-amp, namely the pins 5, 6 and 7.

Tony
vaktmesterj
Okay so its alive, but sounds a little miserable.

Here is a soundclip after i did the calibration, would much appreciate if you (or anyone) could have a listen.

https://www.dropbox.com/s/0is2ck6qrflkzsf/se330%20calibration.mp3?dl=0

First is just a A tone with triangle modulation. Then its an a chord, and the last one is quad mode. Doesnt sound right? :p

The s_freq trimmer does not do anything. The sine depth pot has an effect when i turn it around, but it does not oscilliate.

There also seems to be little or no difference between dimension and quad.

Hoping this could be just a simple error eek!

Edit: I just read another thread here, and understand that dimension and stereo should sound pretty similar. But still, the mangled chord and quad mode doesnt sound right to me.

Edit: Also the output is very low, i have to crank my preamp up almost max to get an audible sound
vaktmesterj
So i went over it again

Chords get mangled
Low output
S_Freq does not do anything
Sine rate pot does not do anything
Quad mode sounds weird

Edit: U39 and U40 atleast heats up, is that normal?

Edit: In the schematics it says R187 should be 7k5, but in the builders guide it says 15k. Which one is right?

Edit: At the RPSU board, which one of the power pins is pin 1? The one farthest from the "switch" header?
vaktmesterj
Okay, so U23 has -15 on both pin 8 and 4, when 5 should have +15, i guess that can explain why the sinewave stuff isnt working
vaktmesterj
...and that was because the pin wasnt soldered to the board. Sinewave modulation works now, but the sound is still very distorted, especially when i try to play chords.

U39 and U40 gets very hot
vaktmesterj
...so i had forgotten another pin, pin 16 on U28 VCA (V2164D).

I soldered it in, turned it on and nothing works. I can hear a faint sound comming through at full volume, but the peak led is not lighting up and there is no BBD action, only faint modulation when i turn the pots.

Now i really dont know what to poke at, i guess something shorted when i soldered pin 16 on U28, because before that i had the ensemble sound, it was just a little low and weird.

Could the V2164D have shorted?
Synthbuilder
It's difficult to say what could be wrong. I would check again all your solder joints from the underside of the board - I use a magnifying glass. Each solder joint should look like a mini volcano with the stump of the component's lead sticking out the top.

No component should be getting hot. If U39 and U40 are getting hot I'd check again that they are the right way around and the correct part. Normally if something is too hot too touch then that component has been damaged permanently.

Unfortunately, the V2164 is easy to kill if the power supply pins are not connected properly. You may be OK since pin 16 is the +15V supply and it is the -15V pin that can cause instant death. However, if all is looking well with the rest of the circuit and you still have no sound it could well be the V2164 that is dead.

Tony
vaktmesterj
Hi!

All joints seems fine, i resoldered suspicious ones. It was fun tracing and meassuring with the schematics, first time ive done that.

Well, everything semi-worked before i soldered that last pin of the V2164, then everything went dead (green led still on tho) so i guess atleast that chip is shorted?

Ive ordered a new one + a couple of OPA's to replace the ones that got hot.

Thanks for helping out
vaktmesterj
Hi

Would it be safe to remove all IC's, power up the unit to meassure all IC sockets?
vaktmesterj
I replaced the chips that got hot. They are still getting hot.

The chips are U39 and U40. I meassured them, and they are getting the voltage they are supposed to have. What could it be that heats them up?
Synthbuilder
vaktmesterj wrote:
Would it be safe to remove all IC's, power up the unit to meassure all IC sockets?


Yes, it will be safe and it's a good thing to do.

Tony
Synthbuilder
vaktmesterj wrote:
What could it be that heats them up?


The two main reasons for overheating chips:

1. The voltage applied to their pins is too high.

2. The resistative load connected to the pins is too low.

Both problems can be caused by shorts and/or incorrect resistor values. Someone recently on this forum found they had a shorted pair of IC socket pins due to a solder blob inbetween the board and the socket. It will be worthwhile checking to see if you have something similar.

Tony
vaktmesterj
Hi

I was going to order another board, but decided i wouldnt give up.

So, i systematicly meassured every socket, and all + and - 15v pins are correct. Does this rule out anything? Could it still be a solder blob or incorrect resistor?
Synthbuilder
vaktmesterj wrote:
So, i systematicly meassured every socket, and all + and - 15v pins are correct. Does this rule out anything? Could it still be a solder blob or incorrect resistor?


You know now that the ICs are getting their power correctly. If any devices are getting too hot - ie. you can't put your finger on them for more than 10 seconds - then you still need to find that problem.

And the mostly likely cause is a solder short or wrong value somewhere.

It'll be worth building yourself an audio probe to find the audio fault:

http://diy-fever.com/misc/audio-probe/

These are actually useful even if you have a scope.

You should be able to trace the audio signal from start to finish as it moves through the SE330 with this probe. Found out where the audio goes bad.

Tony
vaktmesterj
Thanks alot

Can i probe without the IC`s in their sockets?
Synthbuilder
vaktmesterj wrote:
Can i probe without the IC`s in their sockets?


You can but it's main use is in tracking the audio through the full circuit. And that means all the chips should be be in place. However, those hot chips are the final amplifier stages so you can leave them out for the moment and make sure the rest of the circuit is working. You should be hearing the modulated signal on both pins 1 and 7 of U29.

U39 and U40 are both OPA2134 - it maybe worth trying TL072s in there and see if they get hot and, if not, whether you get any audio output. If all now seems well you may just have had some bad OPA2134s.

Tony
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