Voltage reading off, Basic Crack

clams · 2633

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Offline clams

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on: February 14, 2012, 07:01:14 AM
Hey everyone,

I just finished building my amp and had these voltages off. Also one of the LEDs was off. I reflowed the joints connecting to all the problem terminals but the voltage readings are the same. Is this a damaged LED? i've tried to measure the resistance of the LED that is off but my ohmmeter reads "overloaded"

TerminalMeasured VoltageExpected Voltage
1153V90V
6900
7150V100V
1040V0V
A6152V90V
A812.4V1.5V

Thanks for any help!
« Last Edit: February 14, 2012, 03:15:57 PM by clams »


Offline Paul Joppa

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Reply #1 on: February 14, 2012, 04:00:00 PM
Sounds like the LED is either busted or backwards.

Paul Joppa

Offline clams

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Reply #2 on: February 14, 2012, 04:26:30 PM
I checked and its in the correct orientation. Would a broken LED really have the potential to throw off all of those voltages?


Offline Paul Joppa

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Reply #3 on: February 14, 2012, 06:47:45 PM
If you have more than 1.5-1.6 volts at A8 (and A3) then the respective LED is not conducting. Either it is backwards, or it is not soldered successfully, or it is damaged. In that case, the driver plate voltage will be very high, and that is connected to the output tube grid which will be high, causing the output cathode to be very high and the current to be too high, which drives the power supply voltage down a bit.

Yes, it messes up everything.

Paul Joppa

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