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 Post subject: Random popping noise
PostPosted: Fri Jun 08, 2018 4:19 pm 
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Joined: Sun Mar 11, 2018 6:53 am
Posts: 7
Hi, I've finished building my OSD kit, and there's just one problem... Here are the measured B+ voltages with tubes installed:

B+1: 440
B+2: 434
B+3: 425
B+4: 297
B+5: 289

So B+4 and 5 seem a little low. But all the controls seem to work, along with the switches. The problem is that there is sometimes a pretty loud pop. Like a short burst of static. It seems to get more frequent as the amp warms up. This happens with the volume and master all the way down.

I have the bias set to 18mA now...

Sounds like something is shorting maybe?

Oh, and when it pops, the sounds sometimes cuts out completely, and it will pop again, and the sound is back. The guitar doesn't sound distorted when playing (the clean channel) when the sound is working.

Update: the warmer the amp gets the more popping/static, until after about 15 miuntes, the sound cuts out completely. I've tried changing both the 6V6 tubes and the PI tube - same thing...


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Last edited by martianmale on Fri Jun 08, 2018 11:06 pm, edited 1 time in total.
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 Post subject: Re: Random popping noise
PostPosted: Fri Jun 08, 2018 4:37 pm 
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Joined: Sun Mar 11, 2018 6:53 am
Posts: 7
I just tried a different set of 6V6 tubes - same thing...


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 Post subject: Re: Random popping noise
PostPosted: Sat Jun 09, 2018 2:23 pm 
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Joined: Sun Mar 11, 2018 6:53 am
Posts: 7
Found it! :happydance: The problem was the wire that goes to pins 3 and 8 on V3 (the PI tube). The wire goes through pin 3 and jumps over to pin 8, and as the socket heats up, it was stretching the jumper and putting stress on the pin 3 solder joint - which I guess wasn't good - so intermittent contact and the PI tube was cutting in and out.

I properly terminated and jumped the pins (added a bit of stress relief in curving the jumper), and it works!

Just starting to explore the sounds - next is to install in the head cab.


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 Post subject: Re: Random popping noise
PostPosted: Wed Jun 13, 2018 2:21 pm 
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Holy Ghost
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Joined: Sun Mar 13, 2005 4:10 pm
Posts: 7418
Location: Brighton, Canada
martianmale wrote:
Found it! :happydance: The problem was the wire that goes to pins 3 and 8 on V3 (the PI tube). The wire goes through pin 3 and jumps over to pin 8, and as the socket heats up, it was stretching the jumper and putting stress on the pin 3 solder joint - which I guess wasn't good - so intermittent contact and the PI tube was cutting in and out.

I properly terminated and jumped the pins (added a bit of stress relief in curving the jumper), and it works!



Well, that's a new one to me!! Glad you found it.

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