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Problem with Equinox build
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Problem with Equinox build
stuii
I am new to Oakley, but with some (old) experience of soldering/kit building and of modular synths.

I have just built the Equinox phaser. The LFO is flashing red/green, so power seems to be fine. I get audio output from the audio input when there is no power connected, but I get nothing with the power connected.

I have looked at all soldering, there does not seem to be any dry or overflowing joints. I have looked at orientation of the components.

Any suggestions??

Thanks

Stu
catatemycaps
Have you checked wiring to the sockets?
stuii
I did check it when I built it. I am using the four socket board with linking cable.

I'll have another look.

Thanks

Stu

PS I will be out of the country for 10 days, so please expect me to be unable to respond until I'm back
stuii
Well, aren't I the clever one - not. You were right. I had wired up the sockets incorrectly - and I spent some time getting this wrong.

Thanks to Tony for correcting this.

Great service. Looking forward to building more Oakley modules (correctly).

Stu
Dragonsf
What is working: the LFO. The LED is blinking and reacts to the rate control. Output is also fine. Trouble here: the LFO output appears also at thye Audio out. Not visible and measurable shortcut. Happens with connecting cable or without.
Second problem: CV in signal vcan be traced up to U2/Pin7. After that, the signal can't be measured.
Third: the inpuit signal is lost after Q1. I have already replaced Q1 and Q4 with neew ones (though the old ones were tested OK).
I checked the power supply (which is fine)and the cables from the jacks to the PCB. Deep issue is not activated yet (send/return shorted).
I also shorted ground and chassis as recommended (dotcom power supply).
I tested the resistors around Q1 and Q4 as well as around Q7 and Q10.
(measurements were done with scope, voltmeter and transistor tester).
Any advice is appreciated. Thanks.
Update: the phaser itself is working: inserting the signal direct at R22 (after removeing C11), I can hear the phasing effect: Looks like the problem is in the input/mixing stage and CV.I also activated the deep issue and it's working too.

Voltages at Q1/Q4 seems to be strange:
Q1: 1: 14.2V 2: 8.5V 3:8.5V
Q4: 1:14.8 2:14.2 3:14.9
CV input stage:
Q7: 1,2:0 3: -0.6
Q10: 1:-13 2:-0.6 3:0

Q7/Q19 seems to be OK, as the effect varies with Mod depth and Tune.
Synthbuilder
Dragonsf wrote:
Update: the phaser itself is working: inserting the signal direct at R22, I can hear the phasing effect: Looks like the problem is in the input/mixing stage and CV.


How much CV is getting into the audio output? If it's a lot, over 1V or more, then I would suspect some sort of short or wiring fault. If it's a small amount, say 50mV or so, then that is to be expected as with large modulation depths there can be some CV breakthrough.

Can you detect audio signal getting through to Q1? That is, you should see a small audio signal on the base (middle pin) of Q1. If not check the wiring from the input socket to the board. Check too that the resistor values are correct around that input stage, particularly R12 which should be 470K and not something like 470R. Check also that Q1 is a BC550 or BC549, and Q4 is a BC560 or BC559.

Tony
Dragonsf
Synthbuilder wrote:
Dragonsf wrote:
Update: the phaser itself is working: inserting the signal direct at R22, I can hear the phasing effect: Looks like the problem is in the input/mixing stage and CV.


How much CV is getting into the audio output? If it's a lot, over 1V or more, then I would suspect some sort of short or wiring fault. If it's a small amount, say 50mV or so, then that is to be expected as with large modulation depths there can be some CV breakthrough.

Can you detect audio signal getting through to Q1? That is, you should see a small audio signal on the base (middle pin) of Q1. If not check the wiring from the input socket to the board. Check too that the resistor values are correct around that input stage, particularly R12 which should be 470K and not something like 470R. Check also that Q1 is a BC550 or BC549, and Q4 is a BC560 or BC559.

Tony
yes, Q1 gets and submits a correct signal. The signal is lost, when it gets into Q4. I checked both transistors and replaced them too. I'm using BC550 and BC560. The LFO amount is low (i.e. with my signal insertion, not audible at all). I also checked restinance bettween LFO out and audio out: 370K, not a problem.
Dragonsf
I removed Q4 and measured the voltages again and got reasonable 8V at pin 1, 2 and 14.8V @ 3. I replaced the BC560 with a different PNP, but after that change, the voltages are the same (14.8 at all pins).
Without Q4, voltages seems to be correct, does that mean, there is no fault in the wiring? And I also breadboarded the stage and got the same voltages (i.e. 14.8V). Can someone tell me the voltages on their board?
Dragonsf
Another experiment: I removed Q1 and shortcut Pin2 and 3. Result: I can hear the effect, but the dry signal is too strong.
Synthbuilder
Dragonsf wrote:
I replaced the BC560 with a different PNP, but after that change, the voltages are the same (14.8 at all pins).


That's not right. I would expect pin 3 to be around 15V (14.8V would be fine) and pin 2 to be 0.6V below that, ie. 14.2V in your case. Pin 1 will probably be around 7V or so.

Can you check your BC560 is working OK? Do you have a transistor tester you could use? The reason I ask is that someone fairly recently reported to me a problem with fake BC560 transistors.

Tony
Dragonsf
Synthbuilder wrote:
Dragonsf wrote:
I replaced the BC560 with a different PNP, but after that change, the voltages are the same (14.8 at all pins).


That's not right. I would expect pin 3 to be around 15V (14.8V would be fine) and pin 2 to be 0.6V below that, ie. 14.2V in your case. Pin 1 will probably be around 7V or so.

Can you check your BC560 is working OK? Do you have a transistor tester you could use? The reason I ask is that someone fairly recently reported to me a problem with fake BC560 transistors.

Tony

I tested the BC560 is it seems to be OK. I tried several other BC560 with the same result. And yes, I also expect pin 1 to be around 7V. More and more I suspect the culprit is Q1, because afetr removing Q1, the voltage at Q4 seems to be reasonable. FIY the test results for the bc560 are: hFE:552, uf 668mV and Q1 is hfe 525, uf=673mV.
Synthbuilder
I'm not sure what else to suggest at the moment. I still suspect the transistors especially if you've recreated the circuit on breadboard and it does the same thing as on the Equinoxe PCB. Some of your voltage readings show you are getting base-emitter voltages of 0V. This does point to a problem. Pin 2 and pin 3 should normally be around 600mV apart - the base being 600mV more positive in the NPN (Q1) and 600mV more negative in the PNP (Q4).

A lot of these fake transistors are actually transistors but they are not what they say on the front. So they may be a poorly made 2N2906 printed up as a BC550. It may then be that the pin out is not what it should be. Does your tester tell you the pin out? It should be CBE reading from pin 1 to pin 3.

Tony
Dragonsf
Synthbuilder wrote:
I'm not sure what else to suggest at the moment. I still suspect the transistors especially if you've recreated the circuit on breadboard and it does the same thing as on the Equinoxe PCB. Some of your voltage readings show you are getting base-emitter voltages of 0V. This does point to a problem. Pin 2 and pin 3 should normally be around 600mV apart - the base being 600mV more positive in the NPN (Q1) and 600mV more negative in the PNP (Q4).

A lot of these fake transistors are actually transistors but they are not what they say on the front. So they may be a poorly made 2N2906 printed up as a BC550. It may then be that the pin out is not what it should be. Does your tester tell you the pin out? It should be CBE reading from pin 1 to pin 3.

Tony

I'm on the same page. Transistor tester says 1:C, 2:B and 3:E. I tried several diffrent PNP types, but show the same results (on the BB).
Maybe I shoud vary the resistors a bit.
Synthbuilder
Dragonsf wrote:
Maybe I shoud vary the resistors a bit.


Unless there is an incorrect value in there it really should work. There's certainly something not right but right now I have no idea what it could be.
Dragonsf
I reassembled the BB and I'm getting now somewhere: the Voltages at Q4 (12.6, 13.2, 15) look alright to me, but the output at Q4 is only the negative wave. Output of Q1 is perfect. Any advice?
Synthbuilder
Can you try another PNP transistor in position Q4 on your breadboard? Not a BC560 but something like a 2N3906. It will have a different pin out so fit it so that CBE are correctly connected.

If that works then I would suggest the BC560s you have aren't what they should be. If the new circuit does exactly the same as before then I am completely at a loss of what to suggest next.

Tony
Dragonsf
Synthbuilder wrote:
Can you try another PNP transistor in position Q4 on your breadboard? Not a BC560 but something like a 2N3906. It will have a different pin out so fit it so that CBE are correctly connected.

If that works then I would suggest the BC560s you have aren't what they should be. If the new circuit does exactly the same as before then I am completely at a loss of what to suggest next.

Tony

I replaced the Q4 with a2N5087 (EBC), but the same: positive part is cut off. Maybe the base bias is wrong?
Synthbuilder
Dragonsf wrote:
I replaced the Q4 with a2N5087 (EBC), but the same: positive part is cut off. Maybe the base bias is wrong?


OK it was worth a try. This probably rules out the transistors so the problem is likely to be with the resistor values or the connections within the circuit. Now since the breadboard and the PCB both show the same voltages then that would suggest that the resistor values are wrong somehow.

What signal level are you using to get the loss of positive part? The base of Q1 isn't expecting anything above 1V (peak) and it must be AC coupled (via a capacitor - C4 in the Equinoxe) and not directly coupled.

On the Equinoxe board what is the voltage across R12 with no audio signal applied? Also what is the voltage across R17. Finally, what is the voltage across R2?

Tony
Synthbuilder
For a working Equinoxe the voltages (with no audio input) should be something like:

Q1 (NPN)

1 (C) 14.4V
2 (B) 5.8V to 6V
3 (E) 5.2V to 5.4V

Q4 (PNP)

1 (C) 8V to 9V
2 (B) 14.4V
3 (E) 15V

Audio gain from base of Q1 to collector of Q4 should be around +2. ie. 1V(pk) on base of Q1 will end up as 2V (pk) on collector of Q4 with no change of phase.

Base-emitter voltages should both be around 0.6V.

The voltage across R12 will be around 0.1V. The voltage across R17 will be around 5V. The voltage across R2 should also be small perhaps 0.1V or so.

Tony
Dragonsf
My Voltages are across R2: 0.1V, R12: 0.4 and R17 8.5V.
Input at Q1B: 1V, output: 1V.
Q1:
C 14.2
B 8.8
E: 8.5
Q4:
C 14.9
B 14.2
E 14.9

Update: I replaced all the relevant resistors and getting a better result (i.e. 2V output after Q4). Still no phasing, but that's the next step. Thanks for your patience, I'll be back.
New values:
Q1:
C 14.3
B 5.7
E: 5.3
Q4:
C 10.3
B 14.2
E 14.9

Next problem: no signal after R22 (i.e Pin 4 U3)

I had to replace Q7 and Q10, now I can modulate the LFO with depth. Without inserted U3/U4, I can see a nice modulation signal at U3/U4/Pin1/16, but with inserted IC: nothing.
Toe make sure, it's not the IC, I replaced U3 with a new one. Behavior is the same.
Dragonsf
Eventually, I could solve the case: Q5 was also defective. After replacing it with a working one, the phasing is working. Also the deep issue is fine. Thanks for the support and patience, Tony.
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