biasing Rev E with zener mod

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biasing Rev E with zener mod

Postby Bill S » Fri May 06, 2016 1:06 pm

I'm finally getting time to assemble a rev E board I purchased several years ago. I purchased parts from Mouser using the parts list cut & paste. I purchased both the 10K adjustable pots in the parts list and also the 100 ohm listed under the zener mod. for use in positions R19,R22,R25 & R28. When I assembled the board recently I installed the zener diodes in positions R18,R21,R24 & R27. I must have not been thinking and installed the 10K ohm adjustable pots in R19,R22,R25 & R28. I had the bag of 10K ones labeled for these positions (forgetting that I also had the 100 ohm parts too) and also when I looked at the schematic it shows 10K in these positions. I didn't catch my mistake until I went to set the bias and my ohm readings from pin 3 of V3,V4,V5 & V6 weren't even close to the 400 ohms in the instructions. My question is: what is the proper method for setting the bias with the zener mod? I assume the 100 ohm pots are the correct ones to use in these positions.
Thanks, Bill
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Re: biasing Rev E with zener mod

Postby TomMcNally » Fri May 06, 2016 7:20 pm

Hi Bill -

Read this thread and also Shannon's reply to me that he quotes in another thread ... I think you'll find your answer.

http://www.diytube.com/phpBB2/viewtopic.php?f=1&t=6136

... tom
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Re: biasing Rev E with zener mod

Postby Bill S » Sun May 08, 2016 8:21 am

Many thanks Tom, It would be nice if there were more clearly written instructions for doing the zener mod. so someone else doesn't make the same mistake I made. I know now that when I was assembling the board I was carefully checking off items on the component list and when I came to these I also looked at the schematic and saw 10K pots in these and being late in the evening and being a bit tired I forgot about the 100 ohm ones that I'd also purchased for the zener mod.
Now for the task of removing and replacing these four adjustable pots. Desoldering and safely removing a component with multiple connections to the pc board is not one of my better skills.

Bill
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