New Build Stereomour II [resolved]

amritdesai · 21375

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Offline Paul Birkeland

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Reply #15 on: January 09, 2016, 11:30:12 AM
If you have 2.53V there, then the 2A3 will glow.  If the tube isn't glowing, try remeasuring that voltage with the 2A3 plugged in.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #16 on: January 09, 2016, 11:37:40 AM
Sorry for the confusion. I am getting 3.35v without the tube and 2.53v with the tube in the socket. My common (black) probe on D4 and my red probe on D1 with my meter on AC.

Thanks.



Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #17 on: January 09, 2016, 01:33:48 PM
With that voltage there, the 2A3 should be glowing, and you should see ~60V DC from pins 1 and 4 to ground.  If you don't see the tube glowing, you will want to double check that both tubes don't glow in that socket, as well as that the socket is installed properly with the big pins facing the rear of the chassis (You mentioned that the initial voltage checks were OK, which would mean that the socket is where it needs to be).

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #18 on: January 09, 2016, 02:01:34 PM
Hi Paul,

Previously, when everything was working both tubes were glowing quite bright emitting a blue band. Now only the right tube is doing that. The tube on the offending side is glowing slightly but now no blue color and much darker than before. There is no audible music coming from that channel as well. Both sockets are in the correct orientation - big pins facing the rear of the chassis.

I measured pins 1 and 4 to ground and ~0V DC on the left channel. On the working right channel it measures ~60V DC like it should. Also, the two LEDs closest to the potentiometer are no longer illuminating like they were previously. Just to describe more thoroughly what happened - i put my probe precisely on terminal 32 while the unit was plugged in and turned on. There was a spark and a LOUD POP at that terminal.

I really appreciate you taking your time to help me! Thank you so much.

Amrit


Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #19 on: January 09, 2016, 03:16:26 PM
What DC voltage do you get at D2?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #20 on: January 10, 2016, 05:49:56 AM
Paul,

At D2 I am getting a negative value -2.27VDC. This value is also slowly changing. After a few seconds it has worked its way to -2.05VDC
At A2 I am getting constant 391 VDC.

Amrit

Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #21 on: January 10, 2016, 07:22:30 AM
What voltage do you have at T20?  How about T19? And T34?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #22 on: January 10, 2016, 08:10:40 AM
T19: -2.13 VDC
T20: -2.14 VDC
T34: -2.17 VDC

Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #23 on: January 10, 2016, 08:14:24 AM
How about 31?  31 and 44 tie together through one of the little 130 Ohm resistors, then 31 feeds 34 through another one.  You have no B+ at 34, and I suspect maybe no B+ at 31 either, but we know you have high voltage at 44. 

Therefore, it is most likely that there is a loose resistor or a blown resistor that is preventing your Stereomour from working.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #24 on: January 10, 2016, 08:27:48 AM
T31: 122 VDC
T44: 434 VDC

Amrit

Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #25 on: January 10, 2016, 09:10:27 AM
Carefully poke at the resistor between 31 and 44 with something that doesn't conduct (chopstick).  I would be willing to bet that it's loose.  Also be aware that you have some voltage on the capacitor at T31 that may not have a convenient way to bleed off.

If the resistor is not loose, try measuring it with your meter to confirm its value (again, be careful of high voltage persisting after the amp is shut down).

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #26 on: January 10, 2016, 09:46:23 AM
The resistor is not loose.

Going to T31 I am not getting a reading from the 130 ohm resistor. Going to T30 I am getting ~128 ohms.

You are correct the 130ohm 2W metal film resistor going to T31 seems to be blown.

Any other worthwhile measurements to I should take?

I am so grateful for your help! Thank you so much.

Amrit

Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #27 on: January 10, 2016, 11:13:12 AM
I would just replace the resistor, then recheck your voltages.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline amritdesai

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Reply #28 on: January 20, 2016, 10:10:12 AM
Paul,

I had to replace two of the 130 ohm resistors near the offending area. I rechecked everything and am happy to report the amp is powering up and tubes are glowing. Thank you so much for your help!

After a couple of hours last night listening there was some noise coming from the left channel - the offending channel. It was mostly static with some popping and would grow then disappear entirely, then would come back. I figured maybe a capacitor has been affected based on the irregularity and behavior of the noise.

I listened briefly for an hour this morning - no noise or popping whatsoever. So I'm going to wait a few days before making any conclusions.

Thanks again Paul, your diagnosis was spot on.

Amrit

Zu Audio soul Mk II, w radian 475
Zu Mission Cables
Stereomour II, JJ 2a3 40
Clearaudio Concept Wood Ortofon Black
Eros Phono Pre
Schiit Bifrost DAC
Synergistic Research Black Fuses

Offline Paul Birkeland

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Reply #29 on: January 20, 2016, 11:34:59 AM
I've never had a capacitor present the problem you are describing.  When you have a capacitor issue, it is generally very obvious.

Crackling is most often bad solder joints or a tube that needs to run in for a while.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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