Forum Vibe Dim Bulb r48/R49 Question

[Philthy]

Hi Guys - posted this over at FSB and haven't had a reply yet so I thought I'd try here (apols if that is poor form...)....Appreciate any help.

I just completed a Forum Vibe vintage using the Classis Amplification v5 board. I put it in a wah enclosure (yes it was tight ) and have the pedal working. I stepped up 9vDC using a Madbean road rage doubler with a LT1054 and am getting 18V at the board. My 9v supply is 600mA - plenty.

My the bulb is pretty dim with the trimmer max'd and as a consequence the throb is not as pronounced as other vibes I've used.

Then I noticed what I think is a discrepancy regarding R48 and R49, the bulb bias R's, in the populated layout which I used to as the primary reference for the build. Here: http://www.classicamplification.net/fv/ ... t2n_02.htm

Unpopulated layout here: http://www.classicamplification.net/fv/ ... t2n_03.htm.

Parts list here: http://www.classicamplification.net/fv/ ... int_05.htm

The parts list shows R48 being 100k and R49 being 48k - as per the schematic. However the layouts contradict this ie: thay are showing R48 as 47k and R49 as 100k.

So I need to know if the populated layout or the unpopulated layout is correct?

[slacker]

Unless I'm looking at the wrong thing, I can't tell from the layout which resistor is which, the traces aren't visible. If you can see the traces on the PCB see which resistor is connected to the collector of Q13, that one should be 100k. If you can't see the traces you could use the continuity tester on your meter to do the check instead.

[Philthy]

Thanks for the reply
My board is very difficult to get out and I've had to mount the two resistors in question (and adjacent parts) on the underside of the board to allow the jacks to fit in...
Was hoping that someone here might have built one of these before and could comment before I attempt what essentially is a total disassembly of all the hook ups to get the board back out to inspect the traces...,,

[Philthy]

Had a play with this again last night.

Swapped the 100k/47k with no luck - LFO stopped working.
Removed the 150R limiting resistor - light became brighter. LFO still not working.
Swapped the 100k/47k back to where I had them (ie: in accordance with this: http://www.classicamplification.net/fv/files/fv5_vint2n_02.htm ) and voila, we have a working univibe
Still had some rotation left in the trimmer at the optimal spot. Measured my voltage at the board and I was getting 17v now so maybe I am a little low and the additional 150R was too much.
I did try the pedal at 12v(22v at the board) at is sounded relatively harsh at the revised sweet spot on the trimmer. I think the preamp is seeing too much voltage @22v.