Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: johnnys on March 26, 2019, 07:26:16 PM

Title: Voltage help on 2015 Crack Model
Post by: johnnys on March 26, 2019, 07:26:16 PM: Hey All,
I'm thinking I've got some cold solder joints, and I was hoping you could help me identify them. This is an April 2015 model Crack that I put together ages ago but am just now getting around to troubleshooting. All resistances check out and both tubes light up evenly when it powers on, no trouble with the fuse. The bottom LED lights, but the top LED running to A8 does not. One strange occurrence was that the 6080 tube did not light up the first time i powered up the amp, but after removing and replacing the tube it fired up just fine the next time. No idea if that means anything, was just curious.

Photos are attached, let me know if others would be helpful. Appreciate all the help here.

Voltages are as follows:
1. 153***
2. 170.9
3. 0.5
4. 170.9
5. 78.2
6. 0.3
7. 153***
8. 1.1
9. 105.4
10. 0.4
11. 74-60*** got different measurements two times
12. 0
13. 170.9
14. 0.1
15. 195.1
20. 0.3
21. 218.9

A1. 78
A2. 0.9
A4. 0.1
A5. 0.1
A6. 153***
A7. 0.7
A9. 0.1

B1. 153***
B2. 170.9
B3. 153***
B4. 77.6
B5. 170.8
B6. 105.1
B7. 0.1
B8. 0.1

Photos:
(https://i.imgur.com/5a9R7Mo.jpg)
(https://i.imgur.com/7qjPKxI.jpg)
(https://i.imgur.com/q1ypPbQ.jpg)
(https://i.imgur.com/xLHFc0H.jpg)
(https://i.imgur.com/LSDbNQQ.jpg)
(https://i.imgur.com/UrtbsuS.jpg)

Thanks again,
John
Title: Re: Voltage help on 2015 Crack Model
Post by: Paul Birkeland on March 27, 2019, 04:27:34 AM: If these two diode leads touch, you'll have other problems.

Can you measure the DC voltage at A8?

-PB
Title: Re: Voltage help on 2015 Crack Model
Post by: johnnys on March 27, 2019, 09:22:20 AM: Thanks for your reply, Paul.

Yes, those diodes were touching, Iâ€™ve separated them at the point that you circled.

My DC voltage at A8 is 8.2.
Title: Re: Voltage help on 2015 Crack Model
Post by: Paul Birkeland on March 27, 2019, 09:53:42 AM: You have a damaged diode going to that terminal. You can run a wire from A3 to A8 and your amp will likely work properly (and your voltages should fall into line).

-PB
Title: Re: Voltage help on 2015 Crack Model
Post by: johnnys on March 27, 2019, 10:03:08 AM: Roger that. I will get that done tonight. I'm assuming I should remove the damaged diode while I'm at it?
Title: Re: Voltage help on 2015 Crack Model
Post by: Paul Birkeland on March 27, 2019, 10:16:19 AM: You can leave it in if that's more convenient. It has failed open.
Title: Re: Voltage help on 2015 Crack Model
Post by: johnnys on March 27, 2019, 08:41:53 PM: Alright, I bridged A3 to A8 with a wire. After turning the amp on to test the tubes the input tube flashed brightly 2-3 times. Now, only one side of the input tube glows and I believe both LED diodes are now blown as my multimeter diode tester now longer lights up the LED A3.

A3 and A8 now reading at 34.4 DC. Other anomalous readings coming in at about the same as before.

I actually have the speedball upgrade kit which I believe has 8 more of these diode LEDs. I can use those for the time being to replace these, but need to figure out whatâ€™s frying them.

Thanks again for the help.
Title: Re: Voltage help on 2015 Crack Model
Post by: Deke609 on March 28, 2019, 03:24:37 AM: Quote from: johnnys on March 26, 2019, 07:26:16 PM

I'm thinking I've got some cold solder joints,

Hi John - I'd try redoing the solder joints at and around the PT. The 2 circled below look particularly suspect.

Good luck!