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January 15, 2021, 03:24:11 AM

Author Topic: BeePre 1 Channel Down [resolved]  (Read 344 times)

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Offline Kevin

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BeePre 1 Channel Down [resolved]
« on: December 22, 2020, 06:48:46 PM »
Happy holidays everyone!
I have built the BeePre a while back and enjoyed it with no issues. Work has been super busy the last couple of months and I hadn't had time to kick back and turn the amp on. I tried turning on everything today and noticed a loud hum in the left channel. It looked like the left 300B tube did not turn on at all. I took some pictures of the left side components.

The resistance measurements pretty much all checked out on both sides, but the voltages were a little concerning:
1   4.82
2   87.4
3   0
4   8.89
5   0
6   144.7
7   0
8   0
9   0

10   186.7
11   190.2
12   0
13   0
14   0
15   192.8
16   0.78
17   188.9
18   0
19   0.98

20   0
21   0
22   214
23   0
24   0
25   214
26   0
27   0
28   0
29   -5.34

30   -5.34
31   2.51
32   0
33   0
34   13.9
35   6.93
36   6.93
37   0
38   0
39   0

40   218
41   0
42   0
43   218
44   0
45   0
46   218

A2 87.1

Thank you for the help!
« Last Edit: January 08, 2021, 06:43:34 AM by Paul Birkeland »

Offline Kevin

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Re: BeePre 1 Channel Down
« Reply #1 on: December 22, 2020, 06:56:23 PM »
More pictures

Offline Paul Birkeland

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Re: BeePre 1 Channel Down
« Reply #2 on: December 23, 2020, 06:16:58 AM »
Did you have to install 300Bs when you got this preamp back out?  Are you 100% sure you put the fat pins on the 300B into the rear pair of socket holes?

What DC voltage do you have at POS IN and POS OUT on the side that's not working?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Kevin

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Re: BeePre 1 Channel Down
« Reply #3 on: December 23, 2020, 12:35:38 PM »
The preamp never left my setup. Never touched the tubes. I just couldn't find the time to turn it on and let it warm up to enjoy some music. I just confirmed that both the 300B tubes are oriented properly with the fat pins towards the transformers.

On the bad side, POS IN is reading 1.008v and POS OUT is reading 36 mv, but drifts up
« Last Edit: December 23, 2020, 12:39:40 PM by Kevin »

Offline Paul Birkeland

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Re: BeePre 1 Channel Down
« Reply #4 on: December 24, 2020, 04:36:04 AM »
Disconnect the wire leaving POS Out, then recheck those voltages.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Birkeland

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Re: BeePre 1 Channel Down
« Reply #5 on: January 06, 2021, 01:53:01 PM »
Is there any update on this issue?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Kevin

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BeePre 1 Channel Down - Repost (Original thread locked)
« Reply #6 on: January 06, 2021, 07:31:05 PM »
For some reason, the original thread is locked and I couldn't post a reply. Not sure if that was my doing or if there was an error, but I tried the email option and flagging option to try to reach somebody about the post but to no avail.. But to summarize the last thread:

I have built the BeePre a while back and enjoyed it with no issues. Work has been super busy the last couple of months and I hadn't had time to kick back and turn the amp on. I tried turning on everything today and noticed a loud hum in the left channel. It looked like the left 300B tube did not turn on at all. I took some pictures of the left side components.

The resistance measurements pretty much all checked out on both sides, but the voltages were a little concerning:
1   4.82
2   87.4
3   0
4   8.89
5   0
6   144.7
7   0
8   0
9   0

10   186.7
11   190.2
12   0
13   0
14   0
15   192.8
16   0.78
17   188.9
18   0
19   0.98

20   0
21   0
22   214
23   0
24   0
25   214
26   0
27   0
28   0
29   -5.34

30   -5.34
31   2.51
32   0
33   0
34   13.9
35   6.93
36   6.93
37   0
38   0
39   0

40   218
41   0
42   0
43   218
44   0
45   0
46   218

A2 87.1

Quote
Did you have to install 300Bs when you got this preamp back out?  Are you 100% sure you put the fat pins on the 300B into the rear pair of socket holes?

What DC voltage do you have at POS IN and POS OUT on the side that's not working?

The preamp never left my setup. Never touched the tubes. I just couldn't find the time to turn it on and let it warm up to enjoy some music. I just confirmed that both the 300B tubes are oriented properly with the fat pins towards the transformers.

On the bad side, POS IN is reading 1.008v and POS OUT is reading 36 mv, but drifts up

Quote
Disconnect the wire leaving POS Out, then recheck those voltages.

With the POS OUT wire removed, the POS IN voltage fluctuates a bit between ~1.5v-1.7v. The POS OUT fluctuates between ~0.62v-0.79v.

« Last Edit: January 06, 2021, 07:32:51 PM by Kevin »

Offline Kevin

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Re: BeePre 1 Channel Down - Repost (Original thread locked)
« Reply #7 on: January 06, 2021, 07:34:10 PM »
More pics

Offline Paul Birkeland

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Re: BeePre 1 Channel Down
« Reply #8 on: January 07, 2021, 05:49:06 AM »
Pull the filament regulator board on that side and post photos of what's underneath.  The low voltage power supply isn't making it into the board, which could just be something as easy as a loose connection.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Kevin

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Re: BeePre 1 Channel Down
« Reply #9 on: January 07, 2021, 08:52:59 PM »
That seemed like the issue.. I unscrewed the board to take some pictures and decided I might as well just flow some solder over all the transformer joints. Nothing really seemed loose, but when I tested the voltages, POS IN was showing 16v and POS OUT was showing 10V. I reconnected the POS OUT wire and rechecked everything and it matched the other side.

All the LEDs turned on and the tube warmed up. Will hook everything back up to my system tomorrow and give it a listen.

Thank you so much for your help!