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October 17, 2021, 11:10:45 AM

Author Topic: Please help: weak output from new Crack build ZA [resolved]  (Read 302 times)

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Offline andrzej.suski

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Please help: weak output from new Crack build ZA [resolved]
« on: August 06, 2021, 02:55:03 AM »
Hi,

I seem to have a similar outcome as beatcomber - extremely weak sound, thin sound from both channels with the volume pot maxxed out. As, I live in South Africa with 230v supply, I am not sure the voltage checks I do are supposed to be the same as those printed in the manual. They are similar in their relativity (i.e. change of magnitude between different points). Perhaps more importantly, the diodes don't seem to emit any light.

All the test resistances were spot on.
Resistances suggested in the thread with the HD6xx plugged in are 0,26 for both channels.

I have re-soldered all the iffy connections but with no effect.
The tubes glow as they should.

Thank you very much in advance for your suggestions!
« Last Edit: August 28, 2021, 05:26:52 AM by Paul Birkeland »

Offline Paul Birkeland

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Re: Please help: weak output from new Crack build ZA
« Reply #1 on: August 06, 2021, 03:31:16 AM »
Can you post your voltages on terminals 1-10?  Being in a different country does not change what those voltages should be.  If they are not correct, it's extremely important that you don't try to use your amp.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline andrzej.suski

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Re: Please help: weak output from new Crack build ZA
« Reply #2 on: August 13, 2021, 06:39:06 AM »
Hi Paul,

Apologies for the delay - I started a new job this week. And thank you for your initial response!
I can't quite configure my multimeter to show voltages in the order of magnitude from the manual, but on the DCV 20 setting I get:

T1: 1.6
T2: 2
T3: 0
T4: 2
T5: 1.6

T6: 0
T7: 1.4
T8: 0
T9: 1.5
T10: 0

Thank you!

Offline Paul Birkeland

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Re: Please help: weak output from new Crack build ZA
« Reply #3 on: August 13, 2021, 06:42:36 AM »
Just about all of the voltages in the manual are over 20V.  What settings does your meter have?  Are you able to measure a 9V battery?

You should absolutely positively never, ever, ever try to use an amp that hasn't passed its DC voltage checks.  At the end of the day an operational problem that would be super obvious from failed voltage checks may damage your headphones or injure you, so for now please don't try to listen to the amp until you're absolutely certain that the voltages are OK. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline andrzej.suski

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Re: Please help: weak output from new Crack build ZA
« Reply #4 on: August 13, 2021, 10:50:30 AM »
Hi,

I guess I have "used it" only once as I wasn't sure what those voltage readings meant...

I don't have a 9V battery, but I measured a 1.5V one on the same setting on the meter (DCV - 20) which read 1.5. The same setting results in the voltages measured at the terminals above.

Apologies, I'm just a complete novice...
Andrzej

Offline Paul Birkeland

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Re: Please help: weak output from new Crack build ZA
« Reply #5 on: August 13, 2021, 11:11:59 AM »
Almost all the voltages in the kit are over 20V.  Reading them on the 20V scale won't give useful measurements.

You'll either need to switch it to a higher DC voltage range or get an auto-ranging meter.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline andrzej.suski

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Re: Please help: weak output from new Crack build ZA
« Reply #6 on: August 14, 2021, 04:29:02 AM »
Hi,

The reading remains the same on the 200 setting. Is it possible that something went wrong in a way that produces such low voltages?

Andrzej

Offline Paul Birkeland

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Re: Please help: weak output from new Crack build ZA
« Reply #7 on: August 14, 2021, 06:14:10 AM »
Can you post the voltages you are measuring on terminals 1-10 with the meter set to 200V?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline andrzej.suski

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Re: Please help: weak output from new Crack build ZA
« Reply #8 on: August 28, 2021, 05:25:09 AM »
Paul, I asked a friend to have a look and he spotted the problem. I installed one of the power supply capacitors the wrong way around. It needed to be replaced along with the resistor next to it. Everything works beautifully now!

Thank you for your patience and help!

Offline Paul Birkeland

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Re: Please help: weak output from new Crack build ZA [resolved]
« Reply #9 on: August 28, 2021, 05:27:04 AM »
A second set of eyes is a very useful tool!
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man