Need help with hum and faint left channel on my S5 Electronics kit - diyAudio
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Old 14th January 2007, 01:02 AM   #1
Neville is offline Neville  United States
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Angry Need help with hum and faint left channel on my S5 Electronics kit

I have everything setup in my Hammond chassis with Hammond 1609 trannies, but I get a hum with very faint music in the left channel. With the help of another DIY gentleman I have successfully "cleaned" out my wiring, keeping wires as short as possible and a few other things, but still get the hum.

Now I did notice that with the stock pot, if i disconnect the ground lead to the left channel, music comes thru but with a lot of hum/buzz and if I connect the ground lead to anywhere on the pot housing, I get clear sound but cannot use the pot to control volume. I have used a new pot and still have the same issue.

Going crazy here ..... can somebody please offer a newbie advice or anything that might help me ?


btw I have soldered the resistors and caps on the otherside of the pcb so I could have the tubes protrude thru the holes in my chassis. I also have checked all resistor values and they are good. I have checked and double checked and triple checked all solder joints. With my very limited knowledge in tubes/diy , I suspect I have a short either in my RCA left input or going out to my speakers but don't know how to resolve it. I also do not feel comfortable taking voltages with the amp on so have only done it disconnected.


Thx
Neville
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Old 14th January 2007, 02:10 PM   #2
Neville is offline Neville  United States
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I have read posts that mention checking that the rca inputs and speaker connections do not touch the chassis. I'm pretty sure that is not the case but decided to put electrical tape around the parts that could touch it. Still have the issue.

Regarding grounding, I have the 3rd green IEC wire attached to the chassis. Hammond 1609 are wired to the chassis ground.
RCA inputs have a single ground going to the back of the PCB where the trannies can be grounded. POT does not have any ground, did not make any difference with or without the ground lug.

I dont think this issue is specific to the S5 kit but more of a "always do this or that when grounding" or something procedural.

Any advice ?
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Old 14th January 2007, 02:18 PM   #3
SY is offline SY  United States
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Photos are often helpful in situations like this.

Basic rules: Make sure that the IEC green wire is securely attached to the chassis, and that all other circuit grounds come together at a common point near the input. The circuit grounds can be attached to the chassis at that point either directly or through a small (10-30R) resistor. Some people use back-to-back paralleled diodes to tie the circuit ground to the chassis.
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Old 14th January 2007, 08:58 PM   #4
Neville is offline Neville  United States
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http://good-times.webshots.com/photo...00225152RmYNCx

I have upload a few other pics to this site.

Both switch and volume do not have any plastic or rubber grommets between it and the chassis.
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Old 15th January 2007, 11:58 PM   #5
Neville is offline Neville  United States
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Join Date: Jul 2004
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Success at last ! I grounded the pot with the lug and also added electrical tape to the sides and that worked. Now I have both channels working apart from the humand I can live with the hum. I sometimes have to knock the case when it goes to the right channel ???????

but I am happy just doing that-pretty sad but a milestone for me
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