Is my next step plugging in the module? I have switch C on so that the selected s/d and filter should light up.
Yes, I think it is. The 85A2 should light up after a second or two. If I remember well, the LEDs turn on much later, after the ECC81 crystal oscillator has started up.
The FPGA has 3 lights on it. The 85A2 is lit, but different than before and not very bright. No LEDs turned on after about two minutes of run time, and I changed settings and tried Surprise to no avail.
Could it be that the LEDs are lit, but very dimly? Is the voltage at the collector of Q8 around +2.5 V with respect to ground when the 85A2 is lit?
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They don't appear to be lit at all, and the clipping LED was bright when lit yesterday. I'm getting 2.5V at the collector, and -210V pin 5 of 85a2 to ground. The three LEDs on the module remain lit. I'm wondering if I should attempt a reflash.
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Previously the clipping LED was running at about 4.5 mA, while they only get 0.55 mA when everything works as intended. You should see something at 0.55 mA, though.
What voltage do you measure across R129, so at ignited85A2 with respect to ground? Does MUTEREL (a.k.a. collector of Q15 or pin 10 of the output relays) go low within two minutes?
Do you have an oscilloscope at your disposal and if so, what's its bandwidth?
What voltage do you measure across R129, so at ignited85A2 with respect to ground? Does MUTEREL (a.k.a. collector of Q15 or pin 10 of the output relays) go low within two minutes?
Do you have an oscilloscope at your disposal and if so, what's its bandwidth?
OMG, I came back inside and turned the DAC on again and now it's working? I don't have an input or filter board attached, but the lights are working. When I change settings, the appropriate light engages. Progress!
So next step is to adjust the trimpot and variable capacitor?
EDIT: Getting 3.3v across r129
So next step is to adjust the trimpot and variable capacitor?
EDIT: Getting 3.3v across r129
Yes, the trimpot and variable capacitor of the crystal oscillator (R42 and C7). The trimpots at the DAC outputs don't matter yet.
I think I've run into my first damaged part from my mistake? I'm getting 0V across R52 and it's not changing when I adjusted R42 and C7
I had noted continuity across C7, but after looking at the schematic, there is continuity through the inductors, so that doesn't seem like an issue.
And now the LEDs have stopped working...
I had noted continuity across C7, but after looking at the schematic, there is continuity through the inductors, so that doesn't seem like an issue.
And now the LEDs have stopped working...
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When the LEDs were reacting to the switches, did you hear the mute relays clicking when you switched to a different setting? If so, then the crystal oscillator must have worked. (I have to check my Verilog code to see if the fact that the LEDs were working already means by itself that the crystal oscillator was working.)
I don't think they were clicking, but hard to tell over snap of the switch, and I wasn't listening for it. I accidentally turned the DAC on without the ECC81 installed, and since then the indicator LEDs no longer work. All the previously measured voltages are still good and the FPGA has 3 lights still. The R52 measurement was taken before I screwed up and had the tube out, so that wouldn't have caused that issue.
I can't think of any way that starting it up without the ECC81 could damage anything. Whether the LEDs work could depend critically on the settings of C7 and R42.
Do you have an oscilloscope with a bandwidth of at least 20 MHz? If not, do you have a spare through-hole resistor with a value between 1 kohm and 100 kohm?
I can't look in my own Verilog code right now, that will have to wait until tomorrow or the day after.
Do you have an oscilloscope with a bandwidth of at least 20 MHz? If not, do you have a spare through-hole resistor with a value between 1 kohm and 100 kohm?
I can't look in my own Verilog code right now, that will have to wait until tomorrow or the day after.
I don't have a scope, but I should have a resistor. Taking a break from it for now, getting depressing lol. I should have just used all the on-board PSUs rather than getting fancy. I need to ask nauti about his 6.3V reg, because mine seems to be working fine but the diodes are really hot.
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A way to check if the crystal oscillator works would be:
A. Power everything down and wait a few minutes
B. Solder one wire of the 1 kohm...100 kohm resistor to a terminal of R124 (the 33 ohm SMD termination resistor for sdclock)
C. Connect a voltage meter between the other terminal of the extra resistor and ground
D. Turn everything on and wait for two minutes
E. If the meter shows a value above 2.9 V, then the oscillator probably doesn't work
The purpose of the extra resistor is to keep the capacitance of the leads of the meter and of the meter itself from loading the clock buffer, that's why it has to be placed close to R124 and not at the meter's side of the lead.
If the oscillator doesn't work, slowly turn C7 from minimum to maximum capacitance to see if that changes anything. If not, reduce R42's resistance and try again.
A. Power everything down and wait a few minutes
B. Solder one wire of the 1 kohm...100 kohm resistor to a terminal of R124 (the 33 ohm SMD termination resistor for sdclock)
C. Connect a voltage meter between the other terminal of the extra resistor and ground
D. Turn everything on and wait for two minutes
E. If the meter shows a value above 2.9 V, then the oscillator probably doesn't work
The purpose of the extra resistor is to keep the capacitance of the leads of the meter and of the meter itself from loading the clock buffer, that's why it has to be placed close to R124 and not at the meter's side of the lead.
If the oscillator doesn't work, slowly turn C7 from minimum to maximum capacitance to see if that changes anything. If not, reduce R42's resistance and try again.
I got a reading of -0.099V when messing with C7, R42 at about half. -0.099V was as low as I could get (measuring across R52, red lead on P3 side). I then used R42 to adjust the voltage to -0.500V.
Do I now adjust C7 again to go as low as possible, then use R42 to get back to -0.5 again?
Do I now adjust C7 again to go as low as possible, then use R42 to get back to -0.5 again?
Ok so I kept adjusting until I got it settled in on -0.500V. It's not very steady and seems to slowly decrease over time, it's about -0.545V after 10 minutes.
No, LEDs never started working again. The voltage across R52 isn't very stable, could that indicate an issue? Also, there is no relay clicking. I wonder if the reversed 300V damaged the tubes?