Beepre 2 Coarse Attenuator resistance measurement [resolved]

denteom · 3401

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Offline Paul Birkeland

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Reply #30 on: December 16, 2022, 10:31:48 AM
No, switch the fine control to a different setting and be sure that doesn't influence the reading you're getting.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #31 on: December 17, 2022, 08:59:31 PM
Hi PB, tried switching the fine attenuator, sometimes it stayed at 5 kohm sometimes it goes to 0 kohm at Terminal 7 of the coarse attenuator.  It is not on a fix switch setting.  Initially I thought it was the fine attenuator Terminal 2 and 8 but turning it to different positions the results become variable but always 5 or 0 kohm. The resistance at terminal 1 was stable at 5 kohm despite switching different positions. 
Finally a ray of hope. Think that narrows down the problem, but I'm not sure what is still causing the problem.  Hoping to fix this soon, before Christmas.



Offline denteom

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Reply #32 on: December 18, 2022, 04:21:01 AM
PB:
I pulling up the metal plate where the attenuators are secured.  Noticed it had a lesser chance of getting a 0 kohm reading. Must be the metal plate shorting it with something.  How do I get rid of that?  Do I put back the standoffs and see what happens or do I add some insulators in between?



Offline Thermioniclife

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Reply #33 on: December 18, 2022, 05:19:45 AM
You would have to use nylon spacers instead of metal, but you should actually find the short and correct it.

Lee R.


Offline Paul Birkeland

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Reply #34 on: December 18, 2022, 05:34:59 AM
There would need to be debris or a contact between the metal hardware of the switch and the actual switch terminals themselves.  This should be easily visible if you inspect the switches closely.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #35 on: December 18, 2022, 08:49:07 PM
Finally resolved the problem did 3 things:
1. I changed the number 6 washers to paper washers that I stashed away in my tool kit. I harvested those from my old personal computer motherboard those were used to prevent shorts from the chassis to the computer MOBO.
2. I tightened the hexagonal washers that locks the attenuators to the metal plate.  noticed when the shaft touches the metal plate it also caused a short.
3. Sprayed and brushed the contact points.  And Voila, shorts gone.
Thank guys.  Guess I'll be hearing Christmas carols on my pre-amp after all.



Offline denteom

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Reply #36 on: December 19, 2022, 03:14:12 AM
I've got a new problem, after completing the upgrade and inserted the tubes and turned on the pre amp the left tube is not lighting up and it does not even warm up. How do I trouble shoot it?



Offline denteom

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Reply #37 on: December 19, 2022, 03:45:39 AM
also no sound from the left channel but the right channel seams to be ok



Offline Paul Birkeland

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Reply #38 on: December 19, 2022, 05:33:19 AM
I would recheck your voltages. The twisted green pair of wires leaving the first PC board you installed in the original build is what makes the tube glow, but you could have a loose solder joint going to pins 1 or 4 on that socket as well.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #39 on: December 20, 2022, 01:43:49 AM
Hi PB:
I tested the filament voltage supply at the Reg+ Reg - that is connected to the B1 and B4. show a voltage around the 2.5.  The other side Reg+ and Reg - supplying the A1 and A4 was correct 6.3 volts.
Do I desolder and resolder again the incorrect Reg+ Reg-? shaking it still reveals a firm connection.  Hope it just a simple problem



Offline Paul Birkeland

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Reply #40 on: December 20, 2022, 05:10:24 AM
On the front of that board there are pads that say "+ DC -", what voltages do you see at each set?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #41 on: December 20, 2022, 05:33:45 AM
The ones on the front both are 8 DC volts.
Just a correction on the Reg+ Reg- connected to the B1 and B4 show a DC voltage of 1 volt.  While the Reg+ Reg- connected to the A1 and A4 show also 8 volts



Offline Paul Birkeland

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Reply #42 on: December 20, 2022, 05:56:44 AM
Neither regulator appears to be working, or there's an issue with your meter that's not letting you resolve the measurement properly. 

The 1V could be because there's a short at the socket wiring that's pulling the regulator down, or there could be a soldering issue on the board itself. I would pull out either the wire leaving Reg+ or the wire leaving Reg - (you don't need to do both, just the one that's easy), and see if the voltage coming out of the board pops back up to 6V.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #43 on: December 21, 2022, 01:44:22 AM
Verified that my tester is correct, used my friends multi-tester.  So What we did unscrewed the filament board and re-checked and added solder to some joints we think has loose joints.  After which we checked again the voltage is now correct, and both tubes now light up.
I thought that was it, when we turned on the music.  I still have no sound on the left channel. But the right channel sounds great!

I'll check again later tonight. I'll begin with the speaker cables just in case something also got loose.

I also tried switching the cables to channel two and three still no sound on the left channel.
Where do you suggest I check inside the pre amp?




Offline denteom

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Reply #44 on: December 23, 2022, 03:39:31 AM
I found the voltage problem causing no sound on the left channel:
Having the Black terminal at 14
These are the readings on the red terminal:
Terminal 25= 13 VDC
Terminal 30= 13 VDC
Terminal 6 = 120 VDC
Terminal 16= 65 VDC
I've already installed the first upgrade. Are the values for the original build still holds true?  The Beepre Manual says Terminal 25 and 30 should be 10.  Is 13 volts still okay?
What could be the problem at Terminal 16, is it just loose or just improper soldering at Terminal 16?
Hoping this is the last problem