R16

[dandeurloo]

Does R16 adjust out put? Between the two recent A12's I am putting together for a friend one of the pres has a lot lower output. When I measured R16 it was 1.2 with my DMM set at 200m. I now have it at 0V. Should this help? He took his other pre so i can't compare.

Thanks

[tpryan]

R16 does not adjust output. It adjusts the amount of offset voltage applied to U1. Set it for 0v at the output of U1 as described in step 35 of the assembly instructions.

[dandeurloo]

I have that done. Any idea whay the output may be different then the other pre? It is much lower.

[dandeurloo]

So I think I have it narrowed done to a bad switch. I was testing it more today and it started to only work in between when switching the switch. Tim or anyone, what is the mouser or digikey number so I can order one. Or do I have to order it from Grayhill? They probably wont send me one switch.

Also, how impossible will it be to de-solder all those pins from the board?

[tpryan]

It's easy to test the rotary switch with a meter. Check for continuity between the wiper pin and selected pin at each position. Do it for each deck.

When you say low output, do you mean low output before clipping or low gain compared to the working module?

[dandeurloo]

low gain, it actually only has output in a few positions, mostly in between positions. So now it is only working in between actual positions.

I went to my local electronic supply store and bought 2 grayhills (different models that don't have as many positions) to work with. One, to see how the insides work and one to try and repair the switch with. The one that came with the kit had a few pieces of small red plastic broken off in the middle of the rotary portion. So it must not have be actually hitting the wiper properly.

Anyway, long story short I tried to replace the guts of rotary housing portion of the switch with the other grahills guts but it still doesn't work. So it looks like I will have to find a solder sucker and try and get that switch off. Yikes.

Tim how do I get my hands on a new switch? Also, any ideas on the best way to de-solder this thing. Will the braided wire work on this at all?

[dkatz42]

The best way to do it, given that you're replacing it, is to clip the pins off so that you can desolder them individually (which then isn't too hard.) You'll probably have to disassemble and/or destroy the switch in place in order to reach all of the pins, but you're well-versed in taking it apart, from the sound of it.

I've always used one of the spring-loaded vacuum desolderers, clipping the lead as close to the board as possible and then sucking out the remains along with the solder. Don't heat the joint for too long and you shouldn't risk wrecking the PCB.

[tpryan]

We can sell you a replacement, send an e-mail to sales@seventhcircleaudio.com.

Allied also stocks this switch occasionally. Check their web site.

[dandeurloo]

I just ordered it from allied they have a few in stock. I'm gonna start clipping the old one out now.