by Ty_Bower » Fri Sep 21, 2012 1:45 pm
Cut & jumper is a little tricky, but not too bad. Converting back to VT-137 would be rather difficult, so I'd consider this a permanent change. Flying wire would involve soldering wires into the V2 and V3 holes on the board, and using chassis mount sockets off to the side. You could easily re-arrange the leads to the socket to accomodate whichever tube type you prefer.
Cut & jumper instructions:
1) On the upper side of the board (marked "PUT SOCKET ON THIS SIDE"), cut the trace at V2 leading to pin 3. Cut the trace at V3 leading to pin 2. You might use a sharp hobby knife (X-acto) to cut the traces, or try using the cutoff wheel in a rotary (Dremel) tool. You want to cut the trace near the socket pin, but don't damage the through-hole plating.
2) Flip the board over to the underside of the board. Cut the following traces:
- at V3 leading to pin 3
- at V3 leading to pin 5
- at V3 leading to pin 8
- at V2 leading to pin 2
- at V2 leading to pin 5
- at V2 leading to pin 8
3) As you stuff the board, you will need to install eight jumper wires (insulated solid copper, 18 or 20 gauge). I would install all the jumpers on the underside of the board. Leave enough tail when you cut the excess leads off the resistors so that you can make an easy connection to the jumper wire. It might not hurt to make a little hook or loop before you connect the jumper. The socket holes should be large enough to fit both the pins from the tube socket and the end of the jumper wire, so no worries there.
Jumpers for V3
- from the "3" end of R13 to pin 1
- from the "R" end of R15 to pin 2
- from the "R" end of R17 to pin 3
- from the "R" end of R25 to pin 8
Jumpers for V2
- from the "4" end of R14 to pin 1
- from the "R" end of R16 to pin 2
- from the "R" end of R20 to pin 3
- from the through board via located between R18 and R20, to pin 8
Check my work before you start cutting and jumping. I probably made a mistake somewhere.
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