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I have an 8594E spectrum analyzer that gives CAL: SPAN SENS FAIL when self-calibrating.
I went through the internal service-diagnostic routines and?
passes:? 2V reference detector, ground reference detector
fails:? main coil driver, FM coil driver, sweep ramp, 10V reference detector, -10V reference detector

The service guide points to the A7 Analog Interface for all of these failures.? So...simple enough, I just need to swap A7 boards.
And I did, and nothing has changed...exact same fails.

So either I got an A7 with the exact same failures as my original, or something else is actually wrong.
Any suggestions would be greatly appreciated!

On Tue, Apr 30, 2024 at 10:17 AM, Scott Townley wrote:

I have an 8594E spectrum analyzer that gives CAL: SPAN SENS FAIL when self-calibrating.
I went through the internal service-diagnostic routines and?
passes:? 2V reference detector, ground reference detector
fails:? main coil driver, FM coil driver, sweep ramp, 10V reference detector, -10V reference detector

The service guide points to the A7 Analog Interface for all of these failures.? So...simple enough, I just need to swap A7 boards.
And I did, and nothing has changed...exact same fails.

So either I got an A7 with the exact same failures as my original, or something else is actually wrong.
Any suggestions would be greatly appreciated!

===
Are all supply voltages correct?

+10V/-10V diagnostics are very basic tests, it is easier to debug them which hopefully shows the root cause. +10V reference starts from U25 pin6 and its buffered version shows up at emitter of Q150 also J-22 on A7 board. If you don't see +10V at that location, either +15V/-15V supplies are missing or you have a board with a faulty reference section like the original one (unlikely).

Assuming you see +10V reference at emitter of Q150, this voltage goes through test muxes U15A->U17->right side of R17 (J1-31) with 1/10 attenuation and shows up as 1V during +10V diagnostic routine. If the muxes don't pick the right input there could be an issue with address/data bus in the connector of A7.

If you see +1V (attenuated 10Vref) at J1-31 during +10V test, and -1V at -10V test next possibility is ANA_TEST input of U64 in processor board is damaged (or ANA_TEST trace is damaged, worth checking the connectivity). 2V reference is passing, which is another input to the same mux so rest of the chain looks fine. If you have another processor board (08590-60365 ? ) you could swap and check. You can also look at output of U64 (or U45 with x1.68 gain) in 10V and 2V reference routines.?

I don't know if the test voltages stay static of pulsed during diagnostic tests, if DVM doesn't show expected voltages at mux outputs you may need an oscilloscope.
Ozan
?

Ozan,
Thank you for the tips.? My observations:
1. I was able to verify +15VF, +5A and +10UF voltages directly on A7.? I need to get an extender to really dig into it :-(
2. In the system diagnostics, +10V Reference (presumably +10UF?) is quite unstable
3. In verifying +10UF, I measured at one end of R105, which connects +10UF to V(REF)+ of the DAC in the third converter ref_cal circuit.? Not knowing which end was which, it was easy enough to find the +10UF (and checking with an o-scope it's quite stable, unlike the system diagnostic), but as it happens the other side of R105 has a very small voltage on it (less than 100 mV).? This doesn't seem right to me.??
As I await my extender, any further insights would be appreciated!

On Fri, May 3, 2024 at 05:38 AM, Scott Townley wrote:

Ozan,
Thank you for the tips.? My observations:
1. I was able to verify +15VF, +5A and +10UF voltages directly on A7.? I need to get an extender to really dig into it :-(
2. In the system diagnostics, +10V Reference (presumably +10UF?) is quite unstable
3. In verifying +10UF, I measured at one end of R105, which connects +10UF to V(REF)+ of the DAC in the third converter ref_cal circuit.? Not knowing which end was which, it was easy enough to find the +10UF (and checking with an o-scope it's quite stable, unlike the system diagnostic), but as it happens the other side of R105 has a very small voltage on it (less than 100 mV).? This doesn't seem right to me.??
As I await my extender, any further insights would be appreciated!

===
Hi Scott,
Other end of R105 goes to a virtual ground inside the IC , seeing ~0V is expected. Current through R105 becomes the reference current for the DAC.

+10V test voltage should go through muxes mentioned in the previous message and show up as 1V at top of R18 (ANA_TEST). If you see 1V then this board is fine, the issue is either connectivity between this board and the CPU board or the MUX on the CPU board is damaged.?

Instead of extenders I usually solder kynar wires to critical test points and take out for measurement. At the measurement end I put different number of knots to distinguish which wire is which. A battery powered soldering iron works well for these small soldering jobs.?
Ozan