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May 20, 2022, 11:28:21 PM

Author Topic: B side voltage readings and LED  (Read 905 times)

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Offline Paul Birkeland

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Re: B side voltage readings and LED
« Reply #15 on: March 19, 2021, 04:14:13 PM »
Photo 3
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Birkeland

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Re: B side voltage readings and LED
« Reply #16 on: March 19, 2021, 04:18:54 PM »
From these photos it looks like a lot of the solder joints in this amp don't have enough solder.  It also looks like a few leads are poking out where they shouldn't be.  Specifically on one 9 pin socket I see a lead poking out of pin 5.  If that lead contacted the center post, it would do a lot of damage to the amp.


The 220 ohm resistor that goes to pin 1 on the B side isn't wired to the correct terminal, and that's why you aren't getting the correct voltages on that side of the amp.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline sfojws

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Re: B side voltage readings and LED (resolved, with one more question)
« Reply #17 on: March 20, 2021, 08:53:45 AM »
Hi Paul - Wow, what a difference it makes to have a second pair of eyeballs looking over the photos! After-routing the resistor in question, and reflowing & augmenting the solder joints, the voltage readings are (almost) all as expected.

The only discrepancy is at terminals 44 & 45, where the readings have been 76 volts, rather than zero. It appears that other builders have encountered this, and your advice has been to run the preamp for 50 hours, to allow the tubes to burn in. Am I reading this correctly?

It will be a few days before the interconnects, to connect the Reduction to the Moreplay, arrive, so I won't be in any hurry to put this to the test. Nevertheless, it will be great to get the Bottlehead components connected to the Hafler power amp that I assembled in 1985 (and the 1980 vintage Linn LP12 that I've rehabilitated). At some time, I'll also be curious to place (temporarily) the Crack into this setup. 

A thousand thanks for your assistance getting things into order.
John

Offline Paul Birkeland

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Re: B side voltage readings and LED
« Reply #18 on: March 20, 2021, 10:10:59 AM »
If all the other voltages are OK, the voltages at 44 and 45 also have to be OK.

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline niceguyjml

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Re: B side voltage readings and LED
« Reply #19 on: March 21, 2021, 08:08:08 AM »
I just completed my reduction build and have ~60 Volts at terminal 44 and 45 but all other voltages check out.  How was this resolved?

Offline Paul Birkeland

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Re: B side voltage readings and LED
« Reply #20 on: March 21, 2021, 09:10:13 AM »
There is no issue, different meters will read 44 and 45 differently.  We will be just taking these voltages out of the manual to prevent further issues.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man