Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Jimb0 on June 18, 2018, 08:04:07 AM

Title: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 08:04:07 AM

So I finished building two Crack with Speedball kits a few days ago. I turned it on to check the voltages, then two of the 2.49Kohm resistors on the headphone jack overheated and smoke appeared. I quickly turned it off after that. I tried it on the second kit I built and the same thing happened.

I ran through the kits again to see if I had any bad solder joints. In the first kit I didn't solder the unbanded side of a 100uF 160V properly to 9U. On the second kit I didn't find any problems, but resoldered all the 100uF 160V joints just to make sure.

What tests should I perform before retrying the 2.49Kohm? I have already taken out the resistors to be replaced with new ones.

Thanks in advance

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Doc B. on June 18, 2018, 08:13:56 AM

Sounds like you have a miswire on the first amp that you have reproduced on the second amp. Post pictures.

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 08:48:31 AM

Thanks Doc! Will be uploading them shortly.

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Paul Birkeland on June 18, 2018, 08:52:03 AM

Those resistors fry when:

1. The 100uF caps are in backwards.
2. There is a short between terminals 6 and 7 and/or 9 and 10.

If the current iteration of the instructions are followed, it's actually nearly impossible to burn up these resistors, is this an older kit?

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 08:56:53 AM

These are the newest kit that just arrived last week. I'll check those terminals out.

Just a side note, I was using the old method of soldering the 2.49kohm resistors slanted instead of horizontally but I'm guessing this is unrelated.

Here are some pics of the first kit. I'll upload the second one in a minute.

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 09:09:31 AM

Second amp

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Paul Birkeland on June 18, 2018, 09:15:00 AM

You have a miswire on the octal socket. The 6080 cathodes connect to terminals 7 and 9, not 6 and 10.

The change in headphone jack wiring removes the brief voltage spike as the coupling caps charge when no heapdhones are plugged in.

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 09:21:21 AM

Thank you PB. :)

Thanks for that piece of info. That will definitely be wired accordingly then.

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Kitchener on June 18, 2018, 10:33:49 AM

Nice wiring, Jimb0  :)

Title: Re: Fried 2 2.49Kohm resistors on two kits
Post by: Jimb0 on June 18, 2018, 09:55:21 PM

Quote from: Kitchener on June 18, 2018, 10:33:49 AM

Nice wiring, Jimb0  :)

Thanks Kitchener :) I really appreciate that and I'm glad you like it.

Quote from: Caucasian Blackplate on June 18, 2018, 09:15:00 AM

You have a miswire on the octal socket. The 6080 cathodes connect to terminals 7 and 9, not 6 and 10.

The change in headphone jack wiring removes the brief voltage spike as the coupling caps charge when no heapdhones are plugged in.

I'm glad that the problem was just a miswire and an easy fix. Thanks again PB.