Crack headphone output resistors

dickymint · 1445

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Offline dickymint

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on: February 22, 2020, 05:27:28 AM
Hello folks, I recently got hold of a Crack kit with the Speedball upgrade, it needed building and I built it as I was told by the nice instructions. The voltages are all around those on the sheet but once up and running for a while, it starts to fizzle through the headphones. I thought, go back to basics and check all my solder joints, did so and then found that the two resistors that bypass the headphone socket are partly burnt and one of them has even melted part way through the white cable going to the socket, as it was touching the resistor. Are these supposed to run that hot and what could possibly be causing them to run so hot, if they are not meant to? Apart from the Speedball, the kit is as it came, just not a bag of bits anymore...
RF

Richard Faulkner


Offline Paul Birkeland

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Reply #1 on: February 22, 2020, 05:51:28 AM
Can you post some photos of your build? 

Are the 100uF coupling caps installed properly? 

Are the wires that leave terminals 7 and 9 and go to the octal socket actually attached to 7 and 9? 

Whatever you do, DO NOT use this headphone amp!!!!!!  You will destroy any headphones that you plug into it pretty quickly.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dickymint

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Reply #2 on: February 22, 2020, 09:31:57 PM
Thanks for the reply Paul, the wiring is as per the drawing, I did find a bad solder joint on the octal base and a faulty power supply capacitor, which I replaced. And last night I tried with T50RP's and the sound was free from all crackling and popping and was pure liquid glory. I will double check your info and send a picture but  I am off working for a few days and will do it when I get back.

Richard Faulkner


Offline Paul Birkeland

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Reply #3 on: February 23, 2020, 05:52:51 AM
None of the work you've done would resolve the kinds of issues that will cause burnt resistors at the headphone jack.  I would still not use the amplifier.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline dickymint

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Reply #4 on: March 01, 2020, 04:59:58 AM
Hello Paul,
Finally back home again. I have gone through the wiring again and can find nothing amiss so far but you might be able to spot something. I don't seem able to add any photo's do you have an email address I can send them to?
Richard.

Richard Faulkner


Offline Paul Birkeland

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Reply #5 on: March 01, 2020, 05:21:05 AM
Can you post the voltages you have on terminals 1-10?

My e-mail is pb(at)bottlehead(dot)com

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man