I would expect about -300 V with respect to ground on all LED terminals when they are all off. Was that 50 V across an LED or with respect to ground, and in the latter case, +50 V or -50 V?
OK, so that's not it.
If you can't measure the voltages without FPGA module because of the risk of damaging something (and you certainly shouldn't measure anything with FPGA module right now), maybe you can power down everything and see if either your eyes or an ohmmeter shows something wrong with the circuitry around Q8, Q9, Q10, U25 and U26.
If you can't measure the voltages without FPGA module because of the risk of damaging something (and you certainly shouldn't measure anything with FPGA module right now), maybe you can power down everything and see if either your eyes or an ohmmeter shows something wrong with the circuitry around Q8, Q9, Q10, U25 and U26.
Does this help? Red = +ve
My 85A2 lights up brightly (relatively, nice orange glow) in less the 5seconds.
You asked about ground conenction to chassis also. In the bottom left corner of the chassis in the first image you'll see a small PCB with a yellow disc capacitor - this is my grounding, using John Broskie's parallel capacitor/resistor/bridge arrangement to connect DAC ground to chassis safety ground.
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I hooked mine up the same way and the tube is barely lit when I turn the DAC on, though it shouldn't be on at all without the FPGA installed
EDIT:
Took some measurements.
3V3 is about zero
nswitch85A2 measured from R126 (FPGA side) to ground: ~14.3V
P1 to P5 of the tube socket: 0
EDIT:
Took some measurements.
3V3 is about zero
nswitch85A2 measured from R126 (FPGA side) to ground: ~14.3V
P1 to P5 of the tube socket: 0
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Ok, the ZTX558 are installed correctly. I measured them with my DMM and confirmed which leg is collector and emitter (higher voltage reading on diode mode on emitter side?). Nothing looks out of place, and I double checked all my solder joints.
The clipping light is still on without the module in. When I said it was off, it had come unplugged. So nothing has changed even after I re-did a few of the SMD joints.
The clipping light is still on without the module in. When I said it was off, it had come unplugged. So nothing has changed even after I re-did a few of the SMD joints.
+3V3 is as expected without FPGA module
Does P1 to P5 mean the voltage between P1 and P5? If so, then this also makes sense, as the -300 V or -215 V I wrote about was with respect to ground
14.3 V at nswitch85A2 is very wrong
Is there a short between the input voltage of the 5 V regulator and nswitch85A2? Or is the -300 V supply +300 V maybe?
Normally you would see the cathode of the 85A2 light up, that is, the rod at the centre. With reversed polarity, the anode would light up, that is, the cylinder around the cathode. It may be difficult to see due to the molybdenum gettering, though.
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I'm using a Maida for 300V and have it wired in at C126 like nauti. The positive output from the regulator is connected to the negative-labeled hole (closer to edge of board) and the ground output of the Maida is connected to the positive-labeled hole. I was fairly certain this was correct and hope I didn't mess that part up.
I think that's swapped. The ground output of the Maida is negative with respect to its positive output, so the ground output should go to the negative terminal of C126 and the positive output to the positive terminal of C126 - and there should be no connection between the ground output of the Maida regulator and actual ground anywhere.
I can't be sure, but I think you have a reasonable chance that nothing got damaged, except C126 itself if it was mounted and maybe some LEDs.
I can't be sure, but I think you have a reasonable chance that nothing got damaged, except C126 itself if it was mounted and maybe some LEDs.
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All other power supply voltage is good. Measured collector of Q10 to ground, 5V. Collector of Q8 to ground was -200V and I heard a ringing when measuring so I stopped quickly.
I checked all the transistors with the diode function and all seem to be ok still, with almost identical voltages to each other on both the collector and emitter.
I checked all the transistors with the diode function and all seem to be ok still, with almost identical voltages to each other on both the collector and emitter.
Do you measure a relatively low voltage, say < 10 V, when you measure the voltage across the 85A2, so with the negative meter terminal to -300 V? Do you use an ordinary multimeter with 10 Mohm or less input resistance?
If so, then I guess it's time to check which LEDs survived and whether the clipping LED was connected in reverse, and then to see what happens with the FPGA module installed.
If so, then I guess it's time to check which LEDs survived and whether the clipping LED was connected in reverse, and then to see what happens with the FPGA module installed.