Reduction Hum and No Playback [resolved]

OverAnalyst · 3252

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Offline OverAnalyst

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on: August 12, 2020, 05:00:30 AM
Thought it would be better to start my own troubleshooting post/topic instead of using someone else's.

Here's what I posted previously (yesterday morning):
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Here are my resistance measurements for the following terminals:

38 - 7.7ohms (should be *)
39 - 1.1kohms, not fluctuating (should be *, but per the previous reply, if not 0, should be okay?)
41 - same result as 39
42 - same result as 38

For the following, I get very similar to Neuronal, so I’m assuming they’re ok?

45 - * (should be 0 ohms)
46 - .7 ohms (should be OL)
47 - * (should be OL)

And assuming those resistance values are okay, I went ahead and proceeded with voltage checks. Here are my off-nominal readings:

44 - 78V (should be 180V)
45 - 77 V (should be 0V)
47 - 175V (should be 0V)

The manual I’m using is dated 7.21.19

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So I plugged her in, and instead of music, I get a hum on both speakers. The tubes do light up (so did the LED’s when doing the voltage checks). I tried the different line source selections on my preamp, and still humming.  Photos below. Know the issue?
« Last Edit: August 13, 2020, 06:43:17 AM by Paul Birkeland »



Offline OverAnalyst

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Reply #1 on: August 12, 2020, 05:02:51 AM
more pics...



Offline OverAnalyst

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Reply #2 on: August 12, 2020, 05:08:59 AM
pics...



Offline OverAnalyst

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Reply #3 on: August 12, 2020, 05:09:24 AM
pics...



Offline OverAnalyst

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Reply #4 on: August 12, 2020, 05:09:43 AM
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Offline OverAnalyst

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Reply #5 on: August 12, 2020, 05:10:03 AM
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Offline OverAnalyst

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Reply #6 on: August 12, 2020, 05:10:26 AM
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Offline OverAnalyst

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Reply #7 on: August 12, 2020, 05:10:41 AM
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Offline OverAnalyst

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Reply #8 on: August 12, 2020, 05:10:58 AM
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Offline OverAnalyst

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Reply #9 on: August 12, 2020, 05:11:13 AM
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Offline oguinn

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Reply #10 on: August 12, 2020, 05:22:25 AM
Don’t listen to an amp that hasn’t passed its resistance and voltage tests. PB and others can jump in with more specific advice.

Jameson O'Guinn

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Main System: Schiit Bifrost MB, Rega Planar 6 with Exact cartridge, Eros 2, BeePre, Kaiju/Stereomour II, Jagers, Mainline

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Offline Doc B.

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Reply #11 on: August 12, 2020, 05:55:12 AM
I'm away from the office and PB is a bit under the weather, so our responses may be a little spotty for the next few days. As advised, don't fire up the amp again until this is resolved. Terminal 45,46 and 47 resistances are OK, as you have determined. Sorry about the misprint there, the misprinted version of the manual you got seems to be caught in our library as a ghost that won't disappear. The correct version is dated 10-3-19. We can send a link to a current version if you email us at [email protected].

With respect to 38,39,41 and 42 these resistance measurements will most likely fluctuate or progress in one direction to a high value as capacitors in that part of the circuit charge up. The 7.7 ohms at 38 and 41 looks to be a problem. One possibility is it is actually 7.7 Megohms and thus is OK. Checking your meter settings and remeasuring the resistance would be in order here to determine if that is the case. Another possibility is that the terminal is miswired and is actually reading 7.7 ohms, in which case it must be corrected before proceeding to voltage measurements.

I'm not spotting an obvious miswire in your photos. You might start by reflowing the lower holes in terminals 39 and 41 and remeasuring resistance. From the angle of the photo it's not possible to see if they are completely soldered.


Dan "Doc B." Schmalle
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Offline Paul Birkeland

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Reply #12 on: August 12, 2020, 06:47:55 AM
A quick example of where you can run into trouble: the cap mounted over at 31U has the lead poking out toward 32.  If that lead touches 32, you will ground out the signal.  I would go through and bend all the leads like that in your build over the terminal strips, then reheat the solder in those areas so it flows around the bent leads. 

If your voltages on the forward 4 terminal strips are OK but you aren't getting signal, this will be a solder joint issue more than anything.  I have also seen the RCA jacks installed improperly and that caused signal not to pass properly.  It's also possible for debris or solder to touch between the center pin of the RCA jack and the outside body, and this will also short signal out. 

If you don't see something obvious, let me know what AC voltage ranges your meter has and we can send some signal into your Reduction and look for where it gets hung up. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline OverAnalyst

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Reply #13 on: August 12, 2020, 10:42:17 AM
Per Doc’s comments, I do indeed get 7.7ohms and not Mohms for both 38 and 42.

Per PB, I did go thru and remove some of the excess wiring, and improved the attachment and reflowed. And per Doc’s comment, I did reflow 39L and 41L.

I did another round of resistance measurements, and still get the same result. Everything checks out except for 38 and 42. Still showing 7.7 ohms.

Something I want to mention but not sure if it means anything. The first time I did resistance checks, I did get a * for both 38 and 42. But of course, being the anxious person I am, I proceeded to power on and perform voltage checks. Now 38 and 42 show this relatively low resistance. Did I screw something up here? Any possible damage to nearby components?



Offline Paul Birkeland

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Reply #14 on: August 12, 2020, 10:44:59 AM
How are those resistances with no tubes in the sockets?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man