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December 07, 2021, 01:37:51 PM

Author Topic: Repair service [resolved]  (Read 729 times)

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Offline preston.ezell

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Re: Repair service
« Reply #45 on: October 16, 2021, 08:36:00 PM »
And @AB2KH as a direct response to what you were suggesting, I measured and I have around 207V at the point where the B+ connects to the small board.  I have around 75V where the board connects to the AU7 plate from terminal 5.  I have 0V where the board connects to the AU7 plate from terminal 1.

So perhaps this will come down to a replacement of the small board.

Offline Paul Birkeland

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Re: Repair service
« Reply #46 on: October 17, 2021, 04:06:38 AM »
You can e-mail queen(at)bottlehead(dot)com to request a repair box.  Be sure to paste a link to this thread so she knows you've been here. 

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline AB2KH

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Re: Repair service
« Reply #47 on: October 17, 2021, 07:15:50 AM »
Put your amp in the base as you would operate it. Place it in a dark area and turn it on, cheque the 12AU7 and confirm that both sides of the tubes heaters are glowing orange, you should see two of them one for each triode section.
Let us know the results.

Chris/AB2KH

Offline preston.ezell

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Re: Repair service
« Reply #48 on: October 17, 2021, 10:57:42 AM »
Last time I did this check both were glowing, but I will check again after work and report.

Offline AB2KH

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Re: Repair service
« Reply #49 on: October 17, 2021, 03:42:56 PM »
My thinking in my previous post is not sound so please disregard it.

You have supply voltage but no output voltage and the LED's are not lit and they should be on regardless of wether there is a plate load present or not. So that would confirm that there is/are components that are "tutafineut". PB is correct, the best/easy answer is go for a new board and parts.

I would be curious as to the final results so keep us posted.

Chris/AB2KH

Offline preston.ezell

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Re: Repair service
« Reply #50 on: October 17, 2021, 04:17:11 PM »
So, although they might be dim (I’m not sure of what brightness level would be considered normal) both sides are lit.

https://drive.google.com/file/d/1a00w5hmAVk5NLZ5j4J2NKWaBUBzQ7H_H/view?usp=drivesdk


Offline AB2KH

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Re: Repair service
« Reply #51 on: October 17, 2021, 04:44:49 PM »
Touch up the solder pads on those LES's they look a bit sketchy

Chris/AB2KH

Offline preston.ezell

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Re: Repair service
« Reply #52 on: October 17, 2021, 05:48:57 PM »
I’m sorry if this is a dumb question, but again I’ve never done this sort of thing before.

What is the LES?

Offline preston.ezell

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Re: Repair service
« Reply #53 on: October 17, 2021, 06:07:16 PM »
Did you mean LEDs?

Offline Paul Joppa

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Re: Repair service
« Reply #54 on: October 17, 2021, 06:25:35 PM »
I think AB2KH meant LEDs, and I suggest not touching them up yet - they are so small they can easily be overheated.
Paul Joppa

Offline AB2KH

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Re: Repair service
« Reply #55 on: October 18, 2021, 05:33:11 AM »
Good day all,

Yes I meant LED's, sorry for the confusion. Paul my thinking was and is at this point he really has nothing to loose.

Chris/AB2KH

Offline Paul Birkeland

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Re: Repair service
« Reply #56 on: November 05, 2021, 08:21:41 AM »
I got this repair on the bench today, and the PN2907 did not survive being installed backwards and was shorted out, and this pretty much tanked that half of the small PC board up front.  One LED on the 9 pin socket was open also.  The LED problem and some other soldering related issues look to be from using an iron that's not hot enough to properly flow out the solder quickly.

Fixing up the front PC board, I was then left with one dead channel and one half of your rear PC board that just wasn't passing any current. When I unscrewed your rear board and moved it, all of the wires broke in a way that's consistent with using a wire stripper on too small of a setting, which will cut into the solid core wire and weaken it so it snaps off. When I went to work replacing these, I discovered that all of the wire ends going to the terminal strips were just resting on the terminal strips with some solder, not passing through the terminal strip holes themselves, so I had to replace every wire required for Speedball installation because connections like those are likely to pop loose later on their own.

After installing all of the new wires, there was also some distortion in the previously working channel which I tracked down to a damaged transistor on the other side of the large PC board. 

With all of those issues addressed, this amp is now up and running.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline larcenasb

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Re: Repair service
« Reply #57 on: November 06, 2021, 07:47:07 AM »
So thorough, nice work, Paul. :) Hope you had some good coffee beforehand!

Offline Paul Birkeland

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Re: Repair service
« Reply #58 on: November 06, 2021, 08:11:51 AM »
I split the work between two different days, so that helped a lot!
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline AB2KH

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Re: Repair service [resolved]
« Reply #59 on: November 06, 2021, 08:47:48 AM »

Paul,

Thanks for your up date on this mystery. From the sound of your repair report this thread could have gone on for ever.

Preston,

Hope you enjoy your amp, it is truly a top shelf piece of audio equipment.

Chris/AB2KH