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February 23, 2020, 10:10:51 AM

Author Topic: Something was wrong and then I made it worse. [solved]  (Read 2495 times)

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Offline corndog71

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Something was wrong and then I made it worse. [solved]
« on: February 22, 2014, 10:09:48 AM »
I got the shunt regulator board installed and fired it up for testing voltages.  I noticed the leds on the shunt board were all lit as were the two on the left channel tube. 

The right channel leds on the tube were not lighting up. 

I checked the voltage on the metal tabs of each MJE5731. 

Left side was 105VDC, right side had 0VDC.  I figured I didn't solder it in good enough so I shut it down and resoldered all 3 pins.

I turned it on again and the right tube leds were still not lighting up.  I probed the outer pins of the MJE5731 and got 120VDC and then my probe slipped and hit the center pin and I heard a snap.  All four leds on the shunt board stopped lighting up. 

So the question is how do I figure out which parts I broke?
 
« Last Edit: February 23, 2014, 04:53:44 PM by Caucasian Blackplate »
The world was made for those not cursed with self-awareness.

Rob

Online Paul Birkeland

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Re: Something was wrong and then I made it worse.
« Reply #1 on: February 22, 2014, 12:50:26 PM »

So the question is how do I figure out which parts I broke?
 

You don't, you build a new PC board.

(It was very likely the center leg of the MJE-5731A, or an issue with  the black jumper)
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline corndog71

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Re: Something was wrong and then I made it worse.
« Reply #2 on: February 22, 2014, 01:07:53 PM »

So the question is how do I figure out which parts I broke?
 

You don't, you build a new PC board.

(It was very likely the center leg of the MJE-5731A, or an issue with  the black jumper)

The black jumper checks out.  Are you saying I need to replace all of the parts on the board?  Surely some of them are salvageable.
The world was made for those not cursed with self-awareness.

Rob

Offline corndog71

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Re: Something was wrong and then I made it worse.
« Reply #3 on: February 22, 2014, 03:03:40 PM »
So I took the shunt regulator board out as well as the two 1K resistors, reconnected the B+ wires and turned it on to make sure it still worked in stock form. 

The tubes lit up but I thought I heard a slight crackling sound so I shut it down.

Going back to resistance checks I found some off readings.

39 - 7.2K
41 - 7.2K
42 - 8R

50 - 982R
51 - same as 50

52 - 1.952K   The reading jumps around but then builds up to here and stays there.
53 - same as 52

56 - 0.6R
57 - same as 56  Bad cap?

58 - 982R  It jumps a bit then settles here.
59 - same as 58

The 1K resistors between the power supply caps are still good.
« Last Edit: February 22, 2014, 03:27:19 PM by corndog71 »
The world was made for those not cursed with self-awareness.

Rob

Online Paul Birkeland

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Re: Something was wrong and then I made it worse.
« Reply #4 on: February 23, 2014, 06:18:46 AM »
I guess my biggest question is whether the stock Reduction was functioning or not. 

56/57 being 0 and 58/59 being 1K means that you have a short at 56/57.

Can you provide a photo of that region?

It's also possible that one of the red wires leaving that region got moved to a ground connection.  (T5 would be the logical mistake here)

Generally, you won't kill one of the power supply caps unless it's in backwards, which is also possible.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline corndog71

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Re: Something was wrong and then I made it worse.
« Reply #5 on: February 23, 2014, 06:56:36 AM »
Arrgh!  I found it.  I connected the new B+ wire from the shunt board to 5 instead of 4.  :-[
The world was made for those not cursed with self-awareness.

Rob

Online Paul Birkeland

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Re: Something was wrong and then I made it worse.
« Reply #6 on: February 23, 2014, 07:38:37 AM »
No biggie, 'ish happens. 

You can e-mail replacement parts and we'll get you a care package with a fresh SR PCB.

If you'd like, you can build and install the C4S section w/o the SR section in place.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline corndog71

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Re: Something was wrong and then I made it worse.
« Reply #7 on: February 23, 2014, 01:43:11 PM »
Whew!  It's working!  Back to stock with proper voltages and lit leds.   I probably could've gotten it all working had I not zapped the shunt board.  All because of one poorly placed B+ wire.  I'm surprised I didn't mees up the leds on the tube.

I guess I could add the C4S boards. 

Thanks for the help, Paul.
The world was made for those not cursed with self-awareness.

Rob

Offline corndog71

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Re: Something was wrong and then I made it worse. [solved]
« Reply #8 on: March 25, 2014, 06:55:57 AM »
Just wanted to follow up on this.

I installed the C4S boards and definitely heard a lower noise floor and over all improvement.  I recently got replacement parts for the shunt regulator board and was able to assemble that without messing it up and now it's all complete.  It sounds very good and retains a ton of information even at low volume levels.  Even at an average listening level of just 50-60 db I could still hear the drum heads vibrating and the space of the recording.  It sounds both relaxed and musical with sometimes scary dynamic shifts!  Thanks again to Queen Eileen for the parts and excellent customer service.
The world was made for those not cursed with self-awareness.

Rob