Right Channel hums and pops and this does not go away [solved]

[charleskeough]

Hi. Completed my stereomour this summer and am very happy with it!. However ever since I built it there has been humming and occasional loud popping in the right channel and the left channel is totally silent like it should be. Swapped the tubes and it stays in the right channel.  Here are my voltage measurements:

A1 A4     2.0 v AC
C1 C4     2.0 v AC

power supply pc board pads HV+   396

terminal strips
1            366
2            252
3            0
4            0
5            59
6-10       0
11          58
12          0
13          0
14          234
15          364
16          59
17          396
18          0
19          396
20          58

a1          59
a2          365
a3          0
a4          59

c1          59
c2          366
c3          0
c4          59

active load pc board
IA         395
IB         395
OA        251
OB        233
Kreg     2.47
-reg     0

[Paul Birkeland]

Popping is typically a funky solder joint in the amp.

With the amp running on your bench and a cheap test speaker plugged into the offending channel, try poking around with a wooden chopstick to see if you can poke anything to produce the pop.

You could also try a different 12AT7, just to be sure.

-PB

[charleskeough]

thanks for the very speedy reply!

So i poked around with a chopstick and did find one solder joint that was making noise when i touched it. So i resoldered the joint and now the amp is playing silently.

Previously if i moved the amp around it would play silently for a little while and then the right channel noise problem would come back. So Ill post back if thats the case also if it does not come back ill post back just to say so.

Thanks!

[charleskeough]

been running the amp for a few hours now and still dead quiet. Very happy! Problem definitely solved!

[dlefco]

Experiencing a low level hum (no popping)  in the left channel only. Right channel is silent. Any quick thoughts?

[Paul Joppa]

Quick thought is ... did you adjust the hum potentiometer? If yes, then swap the 2A3s side to side (and re-adjust the hum pots) - did the hum move or stay in place?

If you can do these things with a meter measuring the hum on the speaker leads (AC volts), that would be more informative - but the hum level should be around 2mV which not all meters can measure accurately.

[dlefco]

Thanks, Paul. I bought a pre-build so will be interesting troubleshooting, but I guess I have to get my hands dirty somehow. Any advice on the forum for folks like me who did not build but need to troubleshoot (advice other than go build one from scratch ?

[Grainger49]

The first question is do you have the manual?  If you do you will find the instructions to adjusting the hum pot in there, probably at the end of the assembly, after the resistance and voltage checks.  If not you should contact the builder for it.

Although it is late, you should read this:

http://bottlehead.com/smf/index.php?topic=1671.0

[dlefco]

I do have the manual which the seller sent immediately upon request. He is an active and involved member of both this forum and the Head-Fi community, and I couldn't feel better about him as a seller. Underside of build looks great- neat wiring, no noticeably branded plastic and clean joints. Perhaps in hindsight I'd have done the assembly myself, but c'est la vie. Just means I have to learn some of this stuff the harder way.

Will definitely look for those instructions on adjusting hum pot.

Many thanks,

Daniel

[dlefco]

Not finding anything in the manual about adjusting the hum pot, other than this in the troubleshooting section:

Deep hum without any buzz - this is 120Hz hum, and is usually encountered in DHT amps. Usually a touch up of the hum balance pot will eliminate it

Buzzy hum, like a bee - This usually means a lifted ground connection. Usually fixed with a careful examination of solder joints and an arbitrary re-solder job

[pdxgrampa]

Hum balance is on page 76

[dlefco]

Weird- the manual I have (v 12.17.13) only goes to page 43. Is there a different version I should be referencing?

[Paul Birkeland]

I just looked at an old Stereomour manual from 2011, and it has 80 pages.  Was the source of this manual the CD provided with the kit?   I ask because just the assembly instructions take up more than 43 pages.

-PB

[dlefco]

Thanks for the reply, Paul. Yes, the manual comes from the which the seller sent me. He says it was purchased during the Black Friday sale, so I assume the CD was part of that kit although I know he's owned the Crack several times so perhaps he sent an old CD. I can follow up with him too to find out more.

[fullheadofnothing]

Is the manual for the product you have? Which product do you have?

 The Crack manual is indeed 43 pages, and dated 12-17-13. The most recent version of the Stereomour manual is dated 2-3-14. You are posting in an old thread on the Stereomour board. I'm starting to think you have a Crack, and posting here is just causing multiple levels of confusion.