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July 05, 2022, 03:42:48 PM

Author Topic: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP [resolved]  (Read 100 times)

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Offline [email protected]

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Hello there.
I'm working on the Eros II pre-amp.
I'm stuck on the Shunt Regulator step and not sure where my build is going wrong.

Here is what I know:

The previous tests for transformer voltages, power stage measurements and seeing if all tubes light up all passed.

At the shunt regulator test, the MJE tabs read at 374V and hold that voltage steady for several minutes, the voltage does not lower.
The LEDs do not light up. At no point of testing and retesting did these LEDs light up.
I worked through the shunt regulator steps four different times (found a couple of mistakes and fixed them) and followed up with a continuity check on connections that might be off.
I reheated/reflowed all solder points on board and tube socket D.

Usually, when I encounter errors with kits, the error is mine. I find it, fix it, and move on.
This time, I cannot find my error. Likely, I don't see my error. Maybe a component is bad? I'm hoping you see something and have some advice.

In the photos, you'll see a weird looking connection made on R4. This is one of my errors, which I believe I fixed. I put the 1W 220k resistor in the wrong 220k resistor place. Since the leads were already trimmed, I made a crude shunt to connect the breg point and +reg solder pads. It's pretty ugly, but I'm reasonably sure that the path is in the right order.

Attached are photos of my build. I hope they are clear enough for what you are looking for. If you need different angles, please say so.
Any advice is good advice.
Thank you for your time,

Bradley

p.s.


Sifting through this forum, I found these voltages are asked about:

A Side:

MJE - 371V
Kreg - 371V
Breg - 371V
+reg - 371V
-reg - 373V
I - 373V
O - 370V

B Side:

MJE - 371V
Kreg - 371V
Breg - 371V
+reg - 370V
-reg - 371V
I - 374V
O - 370V
« Last Edit: June 13, 2022, 05:04:31 AM by Paul Birkeland »

Offline [email protected]

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #1 on: June 12, 2022, 07:57:40 AM »
photo 1

Offline [email protected]

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #2 on: June 12, 2022, 07:58:19 AM »
photo 2

Offline [email protected]

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #3 on: June 12, 2022, 07:58:42 AM »
photo 3

Offline [email protected]

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #4 on: June 12, 2022, 07:59:21 AM »
photo 4

Offline Paul Birkeland

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #5 on: June 12, 2022, 09:08:26 AM »
What happened here?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #6 on: June 12, 2022, 10:34:06 AM »

From my original post:
In the photos, you'll see a weird looking connection made on R4. This is one of my errors, which I believe I fixed. I put the 1W 220k resistor in the wrong 220k resistor place. Since the leads were already trimmed, I made a crude shunt to connect the breg point and +reg solder pads. It's pretty ugly, but I'm reasonably sure that the path is in the right order.

I said it was weird looking. That is my ugly shunt.

You would probably recomend that I pull at of that out and use the remaining (2) 220k resistors that came with the kit?
I have 1/2W resistors on hand. Would that be a suitable substitute for this circuit?

Offline Paul Birkeland

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #7 on: June 12, 2022, 11:00:24 AM »
Let's not worry about that just yet.  Do you have the 12AU7 in the D socket and is it glowing?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #8 on: June 12, 2022, 11:27:21 AM »
The tube glows, yes.

Offline [email protected]

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #9 on: June 12, 2022, 12:18:51 PM »
To be more specific, the 12AU7 is in the D socket and it glows.
I appreciate your help.

Offline Paul Birkeland

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #10 on: June 12, 2022, 03:02:20 PM »
The black wire leaving the power supply board above the power transformer is connected to the wrong terminal.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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Re: Eros II Shunt Voltage Way Too High - LEDs Not Lighting UP
« Reply #11 on: June 12, 2022, 03:34:07 PM »
You caught it, Eagle Eye!
Thank you kindly.