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November 30, 2021, 12:27:11 PM

Author Topic: New crack build stopped working - v hot transformer - [Resolved]  (Read 339 times)

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Offline Msb72

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Hello
I need some help. I have completed my crack first  build. I checked the resistances and voltages all of which were within range. I then proceeded to use the crack which worked for around 30 mins perfectly well before the transformer became very hot and the tubes stopped glowing. I have resoldered all the joints to the transformer and checked all the other joints and rechecked the resistances which again fall within the specified range. However now on powering up the tubes don’t glow and leds don’t light. The transformer also became hot so have powered off before measuring volts.
I enclose photos of my build
How should I proceed next to troubleshoot?
Many thanks
« Last Edit: August 30, 2021, 06:17:03 AM by Paul Birkeland »

Offline AB2KH

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Re: New crack build stopped working - v hot transformer
« Reply #1 on: August 29, 2021, 05:38:12 AM »
Msb72 could you post some more photos of the 3K 10w cathode resistors from the 12AU7 side of your build.

Offline Msb72

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Re: New crack build stopped working - v hot transformer
« Reply #2 on: August 29, 2021, 06:02:29 AM »
Here are more photos from the 12AU7 side
Thx

Online Paul Birkeland

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Re: New crack build stopped working - v hot transformer
« Reply #3 on: August 29, 2021, 06:19:39 AM »
The power transformer's running temperature will depend a lot on the DC voltages in the amp.  Without knowing the DC voltages, it's tough to give you any guidance.

One wire at B7 doesn't look to be well soldered. If the LED going to A8 is allowed to touch A7, then you will have major problems.

By the way, can you tell us about the solder and flux (if applicable) that you used? 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Msb72

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Re: New crack build stopped working - v hot transformer
« Reply #4 on: August 29, 2021, 07:05:24 AM »
I used Cardas eutetic solder thoroughout which is a lead/tin/silver/copper ultra pure electronics solder. I will make the voltage measurements and post them if you think it is ok to do this even though the tubes are no longer glowing.
Thx

Offline AB2KH

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Re: New crack build stopped working - v hot transformer
« Reply #5 on: August 29, 2021, 07:11:53 AM »
What Paul said! A bad connection at B7 would cause the tubes not to light. No heat in the tube(s)= no conduction therefore the LED(s) would not light.

Offline Msb72

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Re: New crack build stopped working - v hot transformer - Resolved
« Reply #6 on: August 30, 2021, 06:09:59 AM »
Many thanks - resoldering B7 resolved the problem

Offline AB2KH

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Re: New crack build stopped working - v hot transformer - [Resolved]
« Reply #7 on: August 30, 2021, 07:27:08 AM »
Msb72, good to hear your crack amp is up and running. With a GOOD set of HI-Z cans you are going to realize a whole new level of resolution in what you listen to.