Quickie problem: One Chanel does not work [solved]

oxide2k · 2906

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Offline oxide2k

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on: February 14, 2014, 09:33:52 AM
Happy Valentine day to all!  8)
I completed my Quickie 3 days ago. It was fun!
It was my first electronics DIY. I was little confused on how do resistance check. I did some testings but was not sure about results. So I went though and connected it to the amp. Only one channel was working. The working channel was great. So I went back to testing. After some struggling I understood how to test this preamp.
I noticed that some problems.
Could higher voltage at terminal 1 be the problem? As you could see below terminal 1 has 37 volts. Could the resistor be fatly?
I tested the solder and soldered it again. Still same problems.
Voltage check
1-37v 
6-29v
2-38v
7-37v
4-7v
9-2.3v
Rotary d -8.7v
Rotary c-3.8v

Resistance has problem too. 
Terminal
4-nothing
9-1.07
Rotary
8,9-1.08k
11,12-no
Volume
A-side-0
Please help. Any suggestions.
« Last Edit: March 05, 2014, 10:15:02 AM by Caucasian Blackplate »



Offline Paul Birkeland

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Reply #1 on: February 14, 2014, 09:47:33 AM
Faulty resistors are nearly always visibly faulty.  They crack, sizzle, and pop to the point where they just look terrible, then you know to replace them.

In your Quickie, I'm wondering if the 2nd step on page 18 was followed closely.  That would be that the upper and lower lug on the volume pot closest to terminal 3 should be wired together. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline oxide2k

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Reply #2 on: February 14, 2014, 12:04:36 PM
Thanks Paul.
I wished for so easy solution. It would be one solder joint away  :)
I looked at it again. Here is the photos.  Looks like how it should be?



Offline aragorn723

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Reply #3 on: February 14, 2014, 03:24:36 PM
Hi, your potentiometer is wired like mine, so that's probably ok.  Is it the A side that doesn't work or b side?  It's kinda hard to see how the bottom wires are on the potentiometer, but it looks like the 4k resistor (if I remember the value correctly) on the b side in one of your pics looks like the terminal isn't filled with solder all the way, is that resistor pretty solid if you try to wiggle it?  I'm assuming the tubes were installed during the resistance checks?  Just looking at a few numbers too, is there continuity between 4L and A5?  Thanks,

Dave
« Last Edit: February 14, 2014, 03:41:29 PM by aragorn723 »



Offline Paul Birkeland

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Reply #4 on: February 15, 2014, 06:20:40 AM
There's a 1.07K resistor between 4 and 5.  In your photo, it is kinda strangely positioned in the amp, and is potentially not making good contact.

Can you verify that both resistors across the output RCA jacks are 475K?

If you put one 475K between 4 and 5 by accident, you would essentially create the problem you're experiencing.

(Also - did you try swapping tubes between channels?)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Bonzo

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Reply #5 on: February 15, 2014, 07:30:27 AM
It seems also the heater cable of the A channel is a bit burned.
Did you check continuity?

Ciao!

Bisogna avere orecchio!


Offline oxide2k

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Reply #6 on: March 05, 2014, 08:22:41 AM
Thanks for all help!
I mixed placing of resistors.  It was dark so I did not see difference between resistors.  :o stupid me.
It works great now!