Lar/Mar Bias Question
Moderator: VelvetGeorge
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Chevelle
- Senior Member
- Posts: 83
- Joined: Sat Oct 10, 2009 2:34 pm
- Just the numbers in order: 7
- Location: Los Angeles
Re: Lar/Mar Bias Question
Thanks Toner and Neikeel. I think I'm going to give a new pot and cap a try to eliminate all possibilities.
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Chevelle
- Senior Member
- Posts: 83
- Joined: Sat Oct 10, 2009 2:34 pm
- Just the numbers in order: 7
- Location: Los Angeles
Re: Lar/Mar Bias Question
So as a follow up, I was getting ready to change the pot on my LarMar and decided I better just wire it up without the MV to make sure there isn't something else wrong. Well, I did and there is a problem. For some reason, after the amp is on for about 10 to 15 minutes or so, the negative voltage at pin 5 of v4 and v5 starts dropping (or should I say rising since its negative?) to near zero and the redplating begins. Not sure what to look at next, but any advice would be very welcome.
UPDATE: I resoldered the entire bias section and it seems to be working now. I've tried it for a few days without the LarMar installed and have no signs of redplating. I put the LarMar back in and it seems to be working fine as well. Must have been a cold solder joint or something in the solder connection I guess. As a side note, I always has a problem where the most negative voltage I could get on pin 5 was -32v and when I was looking at the bias section, I noticed the bias resistor in series to the pot was measuring only 44K. I switched that out for a 56K and now I can get -50v on pin 5.
UPDATE: I resoldered the entire bias section and it seems to be working now. I've tried it for a few days without the LarMar installed and have no signs of redplating. I put the LarMar back in and it seems to be working fine as well. Must have been a cold solder joint or something in the solder connection I guess. As a side note, I always has a problem where the most negative voltage I could get on pin 5 was -32v and when I was looking at the bias section, I noticed the bias resistor in series to the pot was measuring only 44K. I switched that out for a 56K and now I can get -50v on pin 5.