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12-19-2006, 05:39 PM
| #1 |
| Member Join Date: Oct 2006
Posts: 44
| tube screamer woes
I repackaged my ts-5 and since I took it apart yesterday, it distorts even with the drive knob at 0. What might cause this?
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12-19-2006, 06:22 PM
| #2 |
| Senior Member Join Date: Jun 2006 Location: Southwest U.S.A.
Posts: 141
| short?
Maybe somehow you shorted the connection on the drive control so it has max resistance in the feedback loop.
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12-20-2006, 04:07 PM
| #3 |
| Senior Member Join Date: May 2006
Posts: 1,124
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Alternatively, depending on the way the pot is wired, if the little rivet securing the middle lug to the wiper is loose now then the pot can behave like it is always at max. I often find I have to get in there and "pinch" the rivets of some pots to make them behave again. Just be gentle.
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12-20-2006, 04:24 PM
| #4 | |
| Member Join Date: Oct 2006
Posts: 44
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12-21-2006, 05:35 AM
| #5 |
| Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA
Posts: 10,366
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I think you have two threads going on the same repair. I mentioned elsewhere that you likely have an open resistor in the voltage divider that provides that bias V.
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12-21-2006, 03:09 PM
| #6 | |
| Member Join Date: Oct 2006
Posts: 44
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12-21-2006, 07:28 PM
| #7 |
| Member Join Date: Oct 2006
Posts: 44
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If you look at the schematic I've attached, you can see what I have done to the circuit. It's hard to see in the clipping section, but I show the switch between sets of diodes. The circled components are removed. Also, should I remove R27 and R28 since those transistors are removed (In other words, does it still need that bias voltage)? Is there anything that I should not have done? I put in a tpdt switch for true bypass. Also, see this thread for a little more background. HC Forum thread Last edited by msclford; 12-21-2006 at 08:23 PM. Reason: add pic |
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12-22-2006, 02:38 AM
| #8 |
| Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA
Posts: 10,366
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Where is that voltage divider, I don't spot it? Is there 4.5v at its center? Measyre at each end of each resistor, and there should be 9v at the top, 4.5at the junction, and zero at the bottom. Where is the path for emitter current through TR3? All I see is caps. If you removed the switching JFETs, then R27 and C15 seem irrelevant. If that is a jumper in place of Q2, then R28 is no longer needed. |
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12-22-2006, 03:06 AM
| #9 |
| Member Join Date: Oct 2006
Posts: 44
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I was wrong about the voltage. It does measure 4.5v, I just measured it wrong. That eliminates one problem, but I still think that it has a lot of distortion going on, it sounds like a metal distortion pedal instead of a tube screamer! It doesn't seem like it had this much gain before. I did swap C10 for a slightly different value, but that wouldn't cause it to boost the gain, would it? About the emitter current, there is a 10k resistor to ground off of that leg of the transistor. The person who drew up that schematic just missed it. |
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