Fuzzface q1 failure

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Smoky Black
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Post by Smoky Black »

I have a fuzzface on my breadboard, ge, and q1 keeps failing. I play the fuzz for awhile and the next time I use it, q1 is dead. I’ve had 3 transistors die.

Could q2 be the cause? Anyone have this problem?

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plush
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Post by plush »

Smoky Black wrote: 14 May 2020, 04:38 I have a fuzzface on my breadboard, ge, and q1 keeps failing. I play the fuzz for awhile and the next time I use it, q1 is dead. I’ve had 3 transistors die.

Could q2 be the cause? Anyone have this problem?
Which transistors do you use
Schematic you are using
How do you power your circuit
?

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Smoky Black
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Post by Smoky Black »

It’s the arbiter GE fuzz face, except I’ve replaced the fuzz pot with a bias control, the cap is wired as full on fuzz, and I’ve got a 1k pot with a 680 ohm resistor at the emitter of q2 to bias,

Q1 is a 2n2625, hard to read, I have a lot of these.

Q2 is a hitachi 2sb175 or 176. It’s powered with a battery.

Due to the direct coupling, I’m wondering whether a problem with q2 could cause a q1 failure.

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plush
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Post by plush »

Smoky Black wrote: 14 May 2020, 11:03 It’s the arbiter GE fuzz face, except I’ve replaced the fuzz pot with a bias control, the cap is wired as full on fuzz, and I’ve got a 1k pot with a 680 ohm resistor at the emitter of q2 to bias,

Q1 is a 2n2625, hard to read, I have a lot of these.

Q2 is a hitachi 2sb175 or 176. It’s powered with a battery.

Due to the direct coupling, I’m wondering whether a problem with q2 could cause a q1 failure.
I beleive it's simply because you got defective 2n2625s.
Also, 2n2625 has a very low hfe for a FF. Why did you decide to use them?

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Post by Smoky Black »

I double checked and it’s a 2n2672 in q1, with 3 failures, and a Hitachi 2sa15 in q2.

The 2n2672 is still low hfe, I found them at an electronics surplus store many years ago and bought around 25 because they were cheap. I pick out the ones that are in the 60-70 range.

It’s real frustrating because I get this thing dialed in, and then the transistor fails.

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Post by plush »

Smoky Black wrote: 14 May 2020, 13:56 I double checked and it’s a 2n2672 in q1, with 3 failures, and a Hitachi 2sa15 in q2.

The 2n2672 is still low hfe, I found them at an electronics surplus store many years ago and bought around 25 because they were cheap. I pick out the ones that are in the 60-70 range.

It’s real frustrating because I get this thing dialed in, and then the transistor fails.
Have you measured their leakage? 60-70 is very unusual for 2672, they could be leaky as f and/or already dead.

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Post by Smoky Black »

No, I didn’t measure leakage. I thought the leaky ones were the ones that wander really high when testing hfe.

They seem to develop a short from base to emitter. A good one has over 4 meg resistance, and the failed ones 120 ohms at best.

Seems strange to have so many failures, but it could be they’re just messed up. I was just wondering if anyone had ever experienced anything similar. They sound good before they fail...

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