Help with voltage checks

Loquah · 1743

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Offline Loquah

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on: November 12, 2012, 04:39:15 PM
Hi all,

Not sure if this belongs here or in the technical thread so apologies if it's misplaced.

I have just finished building my Crack and in voltage tests everything tested well except for a significant voltage difference coming off pins B4 and B1. I read 80V on B4, but 87V on B1. The manual says that 10-15% variation is expected, but everything else was much closer to the readings in the manual so I thought it was worth checking in.

I'm a complete newbie to circuit design. Good with a soldering iron, but no knowledge of what each component is doing within the circuit!  :)

PS I am using 240V as I'm in Australia (in case that makes any difference)

Check out my reviews on YouTube - https://youtube.com/c/passionforsound


Offline Mosez

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Reply #1 on: November 12, 2012, 05:49:03 PM
Could be the variation in the value of the 22k1/1W resistors? Should be fine, but wait for confirmation on this one please - I don't want to be the one to say go ahead and plug in your tubes and have you fry your Crack and say bugger!  ;)

Daan Zweers


Offline Paul Birkeland

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Reply #2 on: November 12, 2012, 06:11:06 PM
I read 80V on B4, but 87V on B1.

Looks good, provided you are seeing the same voltages at 1 and 5.

This voltage varies by the emission of the 12AU7, which can vary a bit, especially between a new production tube and an old stock tube.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Loquah

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Reply #3 on: November 12, 2012, 06:12:23 PM
OK, great. Thanks.

It sounds sweet so all OK. I was worried that it might have affected the L/R balance or something, but seems all good.

Check out my reviews on YouTube - https://youtube.com/c/passionforsound