bluezplaya
Well-known member
I could sure use some help right about now! I have racked a pair of Quad Eight 137 cards. They both have the original 3442 transformers for outputs and I'm using the Cinemag 3440a input transformers mounted to JLM Go-Between Plus cards with no zobel resistor. I can't seem to find a specific schematic for the 137 card but have been looking around the forum and finding schematics for the 127 card, and some pinout info.
After getting the voltages correct on the JLM psu at +/-28V and 48V, I put the edge pin connectors on the cards and within seconds R11 (36r) on channel 1 was fried in a puff of smoke. I unplugged channel 1 and I turned the power back on to test just channel 2 but all I got was some hum and no audio signal.
So here is the pinout I've got:
1 = +28v
2 = -28v
3 = ground
4 = out trans (-)
5 & 6 shorted together
7 = out trans (+)
8 = n/c
9 = leg 2 of gain pot
10 = leg 3 of gain pot (330r in series with pot)
11 = n/c
12 = n/c
13 = input (-) from JLM GB
14 = input (+) from JLM GB
I'm using mic cable to connect the XLR ins to the Go Between input but using two wires twisted from the mic out (+ and - from GB) to the 137 on 14 and 13.
I'm using mic cable to connect pins 7 and 4 from the 137 to the XLR out. The shield is connected to the XLR but not connected to the 137 anywhere.
Any insight or help would be tremendously appreciated.
Adam
After getting the voltages correct on the JLM psu at +/-28V and 48V, I put the edge pin connectors on the cards and within seconds R11 (36r) on channel 1 was fried in a puff of smoke. I unplugged channel 1 and I turned the power back on to test just channel 2 but all I got was some hum and no audio signal.
So here is the pinout I've got:
1 = +28v
2 = -28v
3 = ground
4 = out trans (-)
5 & 6 shorted together
7 = out trans (+)
8 = n/c
9 = leg 2 of gain pot
10 = leg 3 of gain pot (330r in series with pot)
11 = n/c
12 = n/c
13 = input (-) from JLM GB
14 = input (+) from JLM GB
I'm using mic cable to connect the XLR ins to the Go Between input but using two wires twisted from the mic out (+ and - from GB) to the 137 on 14 and 13.
I'm using mic cable to connect pins 7 and 4 from the 137 to the XLR out. The shield is connected to the XLR but not connected to the 137 anywhere.
Any insight or help would be tremendously appreciated.
Adam