Meter test [resolved]

jikolptijah · 25488

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Offline jikolptijah

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Reply #15 on: April 25, 2021, 11:33:51 AM
I lifted the three resistors off one terminal, plugged it in and the meter went to 60mA! Thanks again.

After leaving the amp on for several hours, the meter still drifts down 4-6mA. Is this normal?


Offline Paul Birkeland

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Reply #16 on: April 25, 2021, 11:53:45 AM
You'd want to see if the DC voltages at pins 1 and 4 on the 4 pin socket also drift down, as well as measuring the DC voltage between pins 1 and 4 on the 4 pin socket to see if that is dropping down over time. 

In essence it could be the meter having an issue, or it could be an electrical issue with the amp.  If all of the DC voltages are 100% stable, then it's the meter.  If you find that the DC voltages on pins 1/4 drop to around 55V or so after a few hours, then you would have an issue in the amp that would require additional investigation.

Paul "PB" Birkeland

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Offline jikolptijah

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Reply #17 on: April 25, 2021, 12:55:08 PM
I got 59.03V at pin1 and 56.66V at pin4. The meter read 50mA at the time these readings were taken. The amp had been on for ~5hrs. These seem pretty close to the previous readings when the amp had not been running for hours.  I plan to repeat measurements.

Do I clip one probe of the multimeter to pin1 and put the other on pin4 to measure the DC voltage between pins 1 and 4? I don't want to do anything stupid.


Offline Paul Birkeland

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Reply #18 on: April 25, 2021, 01:19:55 PM
Quote from: jikolptijah on April 25, 2021, 12:55:08 PM
Do I clip one probe of the multimeter to pin1 and put the other on pin4 to measure the DC voltage between pins 1 and 4? I don't want to do anything stupid.
Yes, that will tell you the filament voltage.  If that is not quite right, 2A3 operating current will drop.

The 59V and 56.6V would indicate proper 60mA draw provided your switch is on the higher current setting. 

It's entirely possible that you may just need to replace the meter.


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline jikolptijah

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Reply #19 on: April 25, 2021, 02:03:28 PM
I get 2.388V between pins 1 and 4 with the meter reading 50mA.


Offline Paul Birkeland

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Reply #20 on: April 25, 2021, 03:13:10 PM
That and the residual AC ripple will be adequate for full emission.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline jikolptijah

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Reply #21 on: April 26, 2021, 01:12:19 AM
Does that mean the problem is the meter?


Offline Paul Birkeland

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Reply #22 on: April 26, 2021, 05:32:19 AM
Yes, this is likely the meter not working 100%.

Paul "PB" Birkeland

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Offline jikolptijah

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Reply #23 on: June 08, 2021, 11:38:23 AM
Installed the new meter and everything is working perfectly. Thanks again Paul and thanks to everyone at Bottlehead!


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