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May 19, 2022, 07:04:02 PM

Author Topic: Failed Resistance Checks [resolved]  (Read 74 times)

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Offline paddington206

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Failed Resistance Checks [resolved]
« on: May 13, 2022, 04:02:22 PM »
Hi,

So I've gotten to the final resistance check for the stock Crack build and my measurements at terminals 7, 9, B3, and B6 all read 1.7Kohm instead of 2.9. The center pins for the RCA jacks are also reading 5Kohm instead of 90-115. All other terminals pass. I've attached images of the terminals that failed. Any idea on why the resistances are so low?

« Last Edit: May 13, 2022, 11:15:03 PM by Paul Birkeland »

Offline Paul Birkeland

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Re: Failed Resistance Checks
« Reply #1 on: May 13, 2022, 05:21:45 PM »
Your meter may be able to resolve the 2.49K resistors on the headphone jack that are in parallel with the 3K cathode loading resistors but isolated by the 100uF coupling caps, so I wouldn't worry a ton about that.

The 5K on the RCA jacks is odd, but that wouldn't stop me from turning the amp on necessarily.  If you attempt to measure the resistance of one of the 22.1K resistors (which you can do while they are soldered in the circuit), what does the meter show?

The wire routing to B4 is incorrect and it may pick up hum from the green twisted pair of wires it now runs on top of.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline paddington206

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Re: Failed Resistance Checks
« Reply #2 on: May 13, 2022, 06:41:58 PM »
So I tested the 22.1K resistors and when that also read 5K I figured my multimeter was either old and broken or I didn't know how to use it. So I ran out and bought a new one that's easier to use and now I'm getting all the correct readings. 2.6K for 7, 9, B3, B6, and 105K for the RCA center pins.  I also rewired the wire to B4 correctly, guess I didn't know that wire routing was that important.

Thanks for suggesting the quick sanity check! Now on to the voltage tests...

Offline paddington206

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Re: Failed Resistance Checks
« Reply #3 on: May 13, 2022, 07:52:17 PM »
Voltage tests passed and the music is flowing! Now I just have to wait for my ZMF Atriums to come in  8)

Thanks again for the help!

Offline Paul Birkeland

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Re: Failed Resistance Checks
« Reply #4 on: May 13, 2022, 11:14:55 PM »
Awesome, I'm glad you managed to resolve that issue.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man