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February 28, 2021, 01:15:49 AM

Author Topic: Failing resistance test at 3U  (Read 321 times)

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Offline Jlevine11

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Failing resistance test at 3U
« on: December 30, 2020, 03:56:27 PM »
Hi - I got my kit all assembled.  Doing my resistance checks, and I’m getting nothing at terminal 3.  All else looks fine.  I checked the red wire from ot-2 to terminal 3U, as well as the capacitor.  Any ideas?  Thanks.

Offline Paul Birkeland

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Re: Failing resistance test at 3U
« Reply #1 on: December 30, 2020, 04:13:30 PM »
How about the resistance at 11?  Terminal 10 on the OT?  Terminal 5 on the OT?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #2 on: December 31, 2020, 05:00:39 AM »
I’m also getting no reading at Terminal 11 and at OT 10.  OT 5 I’m getting a 0.

The B side seems to be all reading correctly.

Thanks for your help.

Offline Paul Birkeland

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Re: Failing resistance test at 3U
« Reply #3 on: December 31, 2020, 05:11:11 AM »
I'd be interested in seeing some build photos.  There's either something not quite wired properly on one channel, or debris causing weird readings.  In either case, this amp will be a fuse blower if you try to turn it on, so we'll have to figure out what's up first.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #4 on: December 31, 2020, 07:06:36 AM »

 Couple of notes - I accidentally clipped the brown/white pair coming off 6 & 7 and replaced those with a blue/white pair.  As a result, I didn’t have enough blue/white at the end, so I subbed a piece of orange/white off the volume pentometer. I hope that’s not too confusing.

Let me know if I can send any clearer photos.

Offline Paul Birkeland

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Re: Failing resistance test at 3U
« Reply #5 on: December 31, 2020, 07:37:14 AM »
There's a random wire poking out around terminal 3, what is that?  I would use a lot more heat and resolder all the joints on the terminal strips up front.  The lower joints in particular look not at all flowed out.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #6 on: December 31, 2020, 10:22:18 AM »
Thanks - I think that did the trick.

On the question of the random wire, that’s the black wire coming down through the chassis that I clipped and head wrapped.  I can’t seem to find a good place to tuck it out of the way. Any suggestions?

Offline Paul Birkeland

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Re: Failing resistance test at 3U
« Reply #7 on: December 31, 2020, 10:26:34 AM »
This one?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #8 on: January 02, 2021, 04:28:25 AM »
Sorry - no.  That was a random clipped lead that was lying on the chassis.

I resoldered a few areas, and A side is now looking good.  I have unfortunately now lost some of my B side.  Specifically I’m failing at 17 & 24 - getting no readings on either.  Any suggestions?


Offline Paul Birkeland

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Re: Failing resistance test at 3U
« Reply #9 on: January 02, 2021, 05:14:15 AM »
I would reflow all of your joints.  When your readings change as you move the chassis around, that's an indicator of loose components that aren't properly captured by solder.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #10 on: January 02, 2021, 05:19:01 AM »
Thanks Paul.  Any chance you’d be up for a quick FaceTime call to make sure you’re not seeing something obvious that I’m missing?

Offline Deke609

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Re: Failing resistance test at 3U
« Reply #11 on: January 02, 2021, 07:45:43 AM »
Also check this area out - see yellow arrow in attached pic. it looks like an unclipped resistor lead may be contacting the socket frame and grounding out.

I'd follow PB's suggestion of reflowing all the joints with A LOT MORE HEAT. Of the solder joints that are visible in your posted pic, I'd say at least half look like "cold joints" with a lot of "solder blobs" -- i.e., solder has been melted ONTO the joint, but not INTO it.  More heat and making sure that the soldering iron tip contacts both the wire and terminal/lug at the same time should fix this.

cheers and good luck, Derek
« Last Edit: January 02, 2021, 07:48:02 AM by Deke609 »
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Jlevine11

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Re: Failing resistance test at 3U
« Reply #12 on: January 02, 2021, 08:37:39 AM »
Thank you - will give that a go