Voltage problems

guf · 4624

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Offline guf

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Reply #15 on: January 22, 2013, 05:02:46 AM
I think i measured it right, turn on, clip terminal 4 and touch terminal 5, and set my meter on ac? 6.5



Offline Paul Birkeland

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Reply #16 on: January 22, 2013, 06:34:18 AM
Yes, 6.5V AC is correct.  Can you double check the capacitor orientation?  Somewhere along the way, you are losing a couple of volts from the heater circuit, and I'd be suspicious of a backwards cap or backwards diode.

Paul "PB" Birkeland

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Offline guf

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Reply #17 on: January 22, 2013, 03:05:19 PM
 my replacement 220 ohm 1/4w carbon composition resistors for A1 to 9 and B1 to 19, look different than the supplied ones that came with the kit. Those voltages continue to fluctuate around 20 instead of 0. Also I still can not locate the problem around the C2,C5,A8 loosing a few watts. They appear to be installed correctly as does the capacitor for C1 to C2, and the .1ohm wirewound resistor at C2/C5. One of the 4  Schotty diodes is different than the rest, not sure if that could be a problem.
Not sure if its unsafe to have these voltages off and use the amp....AND it annoys me not to have the numbers right but it sounds as i good as i expected it to. 
I appreciate any more suggestions. thanks



Offline Paul Birkeland

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Reply #18 on: January 22, 2013, 06:27:29 PM
How is the one diode different from the others?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline guf

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Reply #19 on: January 22, 2013, 07:53:19 PM
How is the one diode different from the others?
the writing is horizontal instead of vertical.
is there a way to test them while they are in place?



Offline Paul Birkeland

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Reply #20 on: January 23, 2013, 04:33:28 AM
That's not significant.  If the writing still says 1N5820, you're good to go.

Unplug the tubes from the sockets, then briefly measure the voltage at C1/C2 (IE - get your meter probes attached, plug the amp in with the power switch already on, check the voltage, then unplug the amp)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline guf

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Reply #21 on: January 23, 2013, 06:48:35 AM
The voltage with the tubes out and my clips at c1 and c2 was 8.6.

thanks



Offline Paul Birkeland

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Reply #22 on: January 23, 2013, 10:36:43 AM
Ok, good info, now do the same thing with one tube in socket A and no tube in socket B, then with one tube in socket B and no tube in socket A.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline guf

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Reply #23 on: January 23, 2013, 01:27:39 PM
socket a (and no b) 6.92
socket b (and no a) 6.88



Offline Paul Birkeland

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Reply #24 on: January 23, 2013, 03:31:15 PM
Alright, things are looking very good so far.

Try the same test with the other tube.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline guf

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Reply #25 on: January 23, 2013, 03:48:53 PM
oh i did. 

socket a was 6.86
socket b was 6.88



Offline Paul Joppa

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Reply #26 on: January 24, 2013, 04:12:54 PM
Then you have no problem.

Most of the voltage measurements on the heater power supply are a combination of AC riding on DC, and different meters will read them differently. Your heater voltages at the tubes are OK (they are a half volt high with one tube, which will come down with both tubes installed), and the tubes glow properly (indicating they are getting the right power) and the power transformer isn't vibrating noisily (indicating all four diodes are working properly) so enjoy the tunes!

Paul Joppa


Offline guf

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Reply #27 on: January 24, 2013, 04:32:11 PM
awesome paul thanks!