someone please help

[foozertone]

The following readings are from an Ampeg Scrambler from the GGG layout. I've gone over the layout numerous times and I can't spot any problems altjough I know there are somes because I get no effected signal. Please help me figure ou how to get this running. I've read all the debugging pages but still I am incapable of getting it to work. Here are the transistor readings:

Q1  E:0.10     Q2  E:1.05     Q3  E:0.00      Q4  E:0.00
      B:9.23           B:0.65           B:5.26            B:5.48
      C:9.24           C:7.86          C:9.24            C:9.24



I'm reasonably sure I have the transistors in the right pinoiut but...?
PLEASE someone help me figure out how to use these readings.

Thanks

Jeff

[aron]

You have a problem with Q1. The base and the collector should not be the same voltage. if you used a socket, pull the transistor and try a continuity test on the base and collector pads and see if they are shorted.

Start with that problem first.

[aron]

Ooh one more thing. The Ampeg Scrambler looks to be a negative ground circuit, so your collector should be zero and the emitter higher. Either the transistors are backwards or your battery is connected backwards.

[foozertone]

Okay I went ahead and changed the transistors around and I tested Q1 and it measured a short. Does that mean it's bad or is there more to it? Your help is so welcomed.

Jeff

[dxm1]

Ooh one more thing. The Ampeg Scrambler looks to be a negative ground circuit, so your collector should be zero and the emitter higher. Either the transistors are backwards or your battery is connected backwards.

I B confuzed... The schematic I pull up from GGG show a negative ground, all NPN circuit. The collectors of both Q1 and Q3 are tied to the positive rail, and so shouldn't both be battery voltage? Also, Q1 is biased with a pair of 1M resistors between hot and cold, so shouldn't the base of Q1 be about 1/2 battery voltage?

[foozertone]

yeah   someone please to sort this out for me? Is my transistor bad that it shorts between the base and collector?

Thanks
Jeff

[aron]

Maybe you have a short right at the base and collector OR maybe the short is somewhere else. Anyway, assuming that the board is correct, then it's probably either a solder blob (causing the short) or some kind of other wiring error.

[foozertone]

Maybe you have a short right at the base and collector OR maybe the short is somewhere else. Anyway, assuming that the board is correct, then it's probably either a solder blob (causing the short) or some kind of other wiring error.

I don't know if this matters but I tested Q1 out of the circuit and it read a short in the transistor. Does this mean it's bad or what?

Thanks

Jeff

[frankclarke]

Measure the base voltage on the transistor socket with no transistor.

[foozertone]

okay, I didn't have Q1 socketed buit I took it out and measured the pads and got this:
Q1 E:0.00
     B:4.20
     C:8.83

Please tell me what to do with these results

Thanks

Jeff

[dxm1]

Those look _much_ better - pop in a new transistor for Q1 and measure again.

[foozertone]

I don't have another 2n5306 to replace Q1 but I replaced it with a 3904 and got the following readings:
Q1; E:.01
      B:5.58
      C:0.00

Would a 2N5457 work better?

Thanks
Jeff

[dxm1]

I don't have another 2n5306 to replace Q1 but I replaced it with a 3904 and got the following readings:
Q1; E:.01
      B:5.58
      C:0.00

Bummer. Assuming there is no solder bridging or device overheating going on when you install the transistor, it may be just incorrect orientation. It looks like the 2N5306 can come in two different pinouts - EBC and ECB. Do you know which you have (had)?

If it were me, I'd take the old one and try it again with both pin configurations.

If it were really ECB, it may produce the voltages you first listed. You would have been connecting the base to +9V.

The first stage should look like this:



If it has the ECB pinout, the circuit would look like this:

Would a 2N5457 work better?

Thanks
Jeff

No.