Beepre voltage question

Jamus · 5849

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Offline Jamus

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on: February 01, 2016, 02:56:21 PM
2 terminals have voltages out of spec, not sure if this is something to be concerned about...
Terminal 17: should be 90-110v. Mine is 125v
Terminal B2: should be 90-110v. Mine is 135v
All others terminals were good

Thanks!
Jamus
« Last Edit: February 02, 2016, 01:52:22 AM by Jamus »

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #1 on: February 01, 2016, 03:36:26 PM
17 and B2 are connected by a piece of wire and cannot be different by 10V.

If you swap 300B's between channels, does this voltage move to A2?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #2 on: February 01, 2016, 04:18:01 PM
Before switching tubes I rechecked voltages and this time they were equal (142v each).
I swapped tubes and the error followed. Now terminal 2 and A2 are both 135v. Terminal 17 and B2 are both 99v. Bad tube?

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #3 on: February 02, 2016, 07:00:49 AM
Before switching tubes I rechecked voltages and this time they were equal (142v each).
That's a 300B that's not conducting.
I swapped tubes and the error followed. Now terminal 2 and A2 are both 135v. Terminal 17 and B2 are both 99v. Bad tube?
I would take your soldering iron and reheat the pins on the 300B that's acting up, with a special emphasis on pin 2.  If you have enough heat to get the solder to flow, there's a small hole on the end of each pin, and a little extra solder can be added.

If these are old 300B's with years and years of use, this may not do you any good.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #4 on: February 02, 2016, 07:25:14 AM
Thanks PB, I'll try that tonight. This is a brand new Sophia Electric mesh plate, still under warranty. In my shoes would you just send it back or is this a pretty minor but permanent fix? I just don't want to end up right back here after warranty lapses in 30 days.

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #5 on: February 02, 2016, 07:32:55 AM
Oh, I would send it back and not solder on the pins.  If the factory has any questions about the operating point of the 300B, let us know and we can help with that. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #6 on: February 02, 2016, 08:42:36 AM
Thanks again, this is helpful information.
Jamus

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Jamus

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Reply #7 on: February 12, 2016, 12:08:47 PM
I got replacement tubes today and rechecked voltages. Now all 4 relevant terminals (2, A2, 17, B2) all measure 121v. This is only 10% over spec (90-110v) so I assume this is okay (?). All other voltages were within spec.

Next I hooked up CD player and BH crack to listen. All sounded great at first, listened for about 5 minutes. I left it playing for about 30 minutes to continue warming up. When I came back to listen there was almost no volume.

I took the BeePre out of the chain and the Crack works fine. I let everything cool down for a few minutes (top plate on BeePre was very hot). When I fired everything back up it sounded normal for about 5 seconds, then volume dropped down again.

Any suggestions on where to start with troubleshooting?


Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #8 on: February 12, 2016, 12:11:49 PM
Recheck all the voltages after the sound drops out.
-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #9 on: February 12, 2016, 01:45:02 PM
Now those same four terminals (2, B2, 17, A2) measure 142v each. All other spots are still in spec.

For what it's worth when I sent the last tubes back to Sophia, they said they remeasured both and they worked fine.
« Last Edit: February 12, 2016, 01:46:47 PM by Jamus »

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #10 on: February 12, 2016, 01:46:18 PM
You have 142V and still ~5V DC or so on the ungrounded end of each parallel pair of 8 Ohm resistors?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #11 on: February 12, 2016, 01:49:01 PM
Correct. 5.11 and 5.16

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650


Offline Paul Birkeland

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Reply #12 on: February 12, 2016, 01:54:20 PM
Can you very, very carefully take a measurement of the DC voltage at pin 3 on each 4 pin socket? 

This is sounding a lot like a missed or flaky solder joint somewhere, but it's strange that it happens in both channels.

You have plate voltage, heater voltage, and bias voltage, so it is likely a mechanical connection that isn't allowing current to flow properly. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Jamus

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Reply #13 on: February 12, 2016, 01:59:24 PM
0V for both

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
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Offline Jamus

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Reply #14 on: February 13, 2016, 09:24:22 AM
I reheated all terminals around this area (1-20, 4 pin sockets, C4S boards). No change.

Going back to the resistance checks these 4 terminals only reached 75k ohms. Could that be a clue to what is going on here?

Rega Planar3/Elys2 - Eros - BeePre - Kaiju - Klipsch Forte I's
Marantz CD5005
Crack w/Speedball - Senn HD650