Weird resistor problem.....

Started by Bucksears, November 23, 2003, 10:38:49 AM

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Bucksears

I'm building JD's Boutique Fuzz and it's not working; no sound at all. So, I'm measuring each cap/resistor on my DMM to make sure the values/connectivity is showing up correctly. All of them are fine except for the 100k resistor between the transistors: it reads at about 50k. I replaced it with another and got  the same thing. I went back and measured the first resistor that I took out and now it reads correctly (about 98.7k). I measured the new one before putting it in and it read correctly. I can get some voltage readings from the trannies a little later today when I get the off-board stuff wired back on.
Is this supposed to happen? i.e. because it's connected to the base of Q1 and the emitter of Q2, it's pulling on the resistor?
Thanks,
Buck

petemoore

Although I do it sometimes, the readings [Rvalue] can't be trusted.
 Alternate paths are available [ie the electrons go around the other way and can bypass the resistor 'depending']
 Often times the readings [in ckt] will be what the color code on the R states, other times not...if it is the same then kool, if not I don't concern myself with it.  Testing in ckt resistors is not on any debugging pages I've ever read, I try not to recommend it...there's too many 'if so's thens' and 'if not thens'...I just do it once in a while cause once in a while I get somewhere that way.
 I would measure the voltages on the transistors: collecotr base and emitter, post them here...I or someone will probably be able to tell you where in the ckt to start looking [if there's a miswire] etc.
Convention creates following, following creates convention.

Bucksears

OK. Here are the voltages that I was reading on the two transistors:
Q1
C = .1mv
B = .2mv
E = -.0mv

Q2
C = -.0mv
B = .5mv
E = -.0mv

Any thoughts, kind sir's? Bad transistor(s)?

Thanks,
Buck

petemoore

Especially around the collector.
 Most likely a miswire, or bad connection as it's sitting at 0v
 You could try a different Q [did you socket the transistors] in Q2, but the completely bad transistor scenario I think is unlikely.
 Did you check out the DIY FAQ, the debugging page has lotso' info you can use.
 Check that 9v is getting to the top rail [the 'top' of the 33k and whatever you have for resistor above Q2.
 I sometimes check that connection is made [say in this case]from the Q2 collector lead to the Q2 collector resistor lead] using DMM ' continuity check beeper. Actually I sometimes check all comp connections this way, and have found missed connections that 'looked' fine.
Convention creates following, following creates convention.

Bucksears

Thanks, Pete. I'll check over everything again. I started out using sockets I made from an IC socket, but took them out when I didn't think I was getting a good connection. I'm going to try some other Q's and see if it was the ones I was using.
Buck