On 5 Jun 2022, at 17:00, Kalle Kempe <kalle.kempe@...> wrote:

?Hello Everyone,
While working on my own E4407B I uncovered a few things. My own machine had an untuned YTF in the RYTHM which I have since successfully corrected. I discovered from the N7800 docs that no special equipment is used except an external synthesizer with great enough frequency range and a GPIB interface. I therefore set about looking for hidden commands for the SCPI interface.
Here are some that I have found so far, with my own notes on format/function calls.
Disclaimer: Using these commands can mess with your calibration data, making your unit worse. Please use with caution.

SCPI Command Function call

DIAG:CAL:ADC?\n

DIAG:CAL? nnn,n\n GetStateEEPROM, nnn,n = address

DIAG:CAL nnn,n,xxx.yyy\n SetStateEEPROMData (RAM), nnn,n = address, xxx.yyy = new value

DIAG:CAL:BEG\n SetStateEEPROMBegin

DIAG:CAL:STOR %s\n SetStateEEPROMStore

DIAG:CAL:END\n SetStateEEPROMEnd

DIAG:CAL:SOUR?\n GetStateCalSource

DIAG:CAL:SOUR %s\n SetStateCalSource

SYST:PASS %s\n SetStatePassword

DIAG:CAL:PIECE %s\n SetStateUpdate

DIAG:OPT %s\n SetStateEEPROMOption

DIAG:PARK:LO?\n GetStateParkLO

DIAG:PARK:LO %d\n SetStateParkLO

DIAG:CARD? %s\n GetStateInformation

DIAG:TEMP? %s\n GetStateTemperature

DIAG:LATC:VAL %f\n SetStateRAM

DIAG:LATC:SEL %s\n

DIAG:LATC:VAL?\nGetStateRAM

In addition, I have started mapping out the address space accessible with the DIAG:CAL? nnn,n command. Here a few of the addresses and their corresponding register contents

Addr: Keyword:
43,0 TG CAL OFFSET
43,1 TG CAL SLOPE
111,0 IF CAL LEVEL
112,0 RF CAL LEVEL
112,0
112,1 50 MHZ CAL ADJUST DAC (EEPROM)?
113,0 COARSE SET FREQ REF
113,1 FINE SET FREQ REF
114,0 LO LEVEL DAC (EEPROM)
115,0 COARSE RF GAIN DAC
120,0 BITG LO LEVEL DAC (EEPROM)
121,0 TG CORNER
122,0 TG MOD OFFSET
123,0 TG GAIN
124,0 TG A OFFSET
124,1 TG LB OFFSET
124,2 TG A SLOPE
125,0 TG X OFFSET
125,1 TG X SLOPE
126,0 TG F SLOPE
131,0 FEXT B1 LO LEVEL DAC
131,1 FEXT B2 LO LEVEL DAC
131,2 FEXT B3 LO LEVEL DAC
131,3 FEXT B4 LO LEVEL DAC
131,4 FEXT TG LO LEVEL DAC
131,5 FEXT B5 LO LEVEL DAC
131,6 FEXT MIX LO LEVEL DAC
132,0 YTF TUNE A0
132,1 YTF TUNE A1
132,2 YTF TUNE A2
132,3 YTF TUNE A3
132,4 YTF TUNE EXT 0
132,5 YTF TUNE EXT 1
132,6 YTF TUNE EXT 2
132,7 YTF TUNE EXT 3
133,0 FEXT YTF DELAY OFFSET 0
133,1 FEXT YTF DELAY OFFSET 1
133,2 FEXT YTF DELAY OFFSET 2
133,3 FEXT YTF DELAY OFFSET 3
133,4 FEXT YTF DELAY OFFSET 4
133,5 FEXT YTF DELAY OFFSET 5
133,6 FEXT YTF DELAY OFFSET 6
133,7 FEXT YTF DELAY OFFSET 7
133,8 FEXT YTF DELAY OFFSET 8
133,9 FEXT YTF DELAY OFFSET 9
134,0 B0 REF TEMP PA OFF 0
134,1 B0 REF TEMP PA OFF 1
134,2 B0 REF TEMP PA OFF 2
135,0 B0 REF TEMP PA ON 0
135,1 B0 REF TEMP PA ON 1
135,2 B0 REF TEMP PA ON 2
136,0 B1 REF TEMP 0
136,1 B1 REF TEMP 1
136,2 B1 REF TEMP 2
137,0 B2 REF TEMP 0
137,1 B2 REF TEMP 1
137,2 B2 REF TEMP 2
138,0 B3 REF TEMP 0
138,1 B3 REF TEMP 1
138,2 B3 REF TEMP 2
139,0 B4 REF TEMP 0
139,1 B4 REF TEMP 1
139,2 B4 REF TEMP 2
140,0 LO PRETUNE CONST 0
140,1 LO PRETUNE CONST 1
142,0 FEXT YTF DELAY SLOPE 0
142,1 FEXT YTF DELAY SLOPE 1
142,2 FEXT YTF DELAY SLOPE 2
142,3 FEXT YTF DELAY SLOPE 3
142,4 FEXT YTF DELAY SLOPE 4
142,5 FEXT YTF DELAY SLOPE 5
142,6 FEXT YTF DELAY SLOPE 6
142,7 FEXT YTF DELAY SLOPE 7
142,8 FEXT YTF DELAY SLOPE 8
142,9 FEXT YTF DELAY SLOPE 9
143,0 FEXT BREATHING ROOM 0
143,1 FEXT BREATHING ROOM 1
143,2 FEXT BREATHING ROOM 2
143,3 FEXT BREATHING ROOM 3
145,0 FEXT PULSE WIDTH
145,1 FEXT SWEEP DWELL
145,2 FEXT OVERTUNE FREQ
145,3 FEXT OVERTUNE STATE
145,4 FEXT MIX PULSE WIDTH
145,5 FEXT MIX SWEEP DWELL
145,6 FEXT MIX OVERTUNE FREQ
145,7 FEXT MIX OVERTUNE STATE
145,6 FEXT MIX OVERTUNE FREQ
146,0 B5 REF TEMP 0
146,1 B5 REF TEMP 1
146,2 B5 REF TEMP 2
147,0 EXT MIX REF TEMP 0
147,1 EXT MIX REF TEMP 1
147,2 EXT MIX REF TEMP 2

Perhaps with the community's help we can find out more on these units and work together on keeping them running going forwards.
Best regards

Ozan and Raymond,

Q502 was it. Emitter-base junction was wide open.? Replaced it with the most similar PNP I could find in a 2n5771. E42 error is gone, and I have a full sine wave at both full positive and negative offset. The 5771 is not really a small signal transistor, but will see what happens in due time.

Will need to calibrate, but these 8116A are almost a whole day affair to cal. Looks dead on at first glance though. Probably will stay up late this evening and fix her up after I let her run for a couple of hours.

If both of ya are close, I'd take ya out for a beer. If ya don't drink, i'd get ya a coffee.

Hope this post helps others with the same fault I had in the future by reading this thread, and what a good resource this group is.

Thanks for the help,
David

On Jun 5, 2022, at 14:44, Matt Huszagh via groups.io <huszaghmatt@...> wrote:

?I've performed some of the microwave troubleshooting described in the HP
8971C service manual. The microwave circuitry in the 8971C test set
consists of a number of paths selected with relays. These paths consist
of a simple pass-through for low frequencies directly handled by the
8970B and filters and a downconversion mixer for higher frequencies (to
translate RF frequencies to an input frequency the 8970B can
handle). I've attached an image from the service manual showing these
paths.

The first part of the troubleshooting section involves injecting an RF
signal, selecting a path, measuring the signal gain, and comparing it
with the gain computed from the individual component gains. I've also
attached an image showing these individual component gains.

The gains I measure differ a fair amount from the predicted gains.

In SSB (single sideband) 1 I'm measuring a gain of approximately 23 dB
instead of the expected 15 dB. Moreover, this gain is pretty flat across
the bandwidth as tested by moving the RF signal in 100 MHz steps.

In SSB 2, I also measure a gain in excess of the predicted value. In
this case, 24 dB instead of 19 dB expected.

In SSB 3, I measure a gain of about 16 dB instead of the 20.5 dB
expected. If I move the RF signal by 10-20 MHz (without adjusting the LO
frequency) the gain moves up more toward the expected value.

Any thoughts on what might be going wrong here? SSBs 1 and 2 suggest to
me that maybe the attenuator (AT3) is passing the signal through
un-attenuated. However, the test for SSB 3 indicates that if this is
true, then the YIG filter + attenuator combo is attenuating the signal
by a margin even more than that predicted by the third test on it's own,
which is concerning. Unfortunately, I've only been able to test SSB 3
operation at the low end of its range (2.5 GHz). I'm using my 8340 as
the LO and the only other RF signal generator I have is an 8663A, which
tops out at 2560 MHz. I've got an 8341 too, but it needs repairs.

An obvious solution to these problems would be to open up the instrument
and test components individually. Unfortunately, I can't do that yet as
I bought this unit in a supposedly functional state and may lose my
right to return it if I open it up.

All thoughts appreciated.

Thanks
Matt

"Harvey White" <madyn@...> writes:

Just looking at the schematic, I wonder about a few things:

did you measure the current through (or voltage drop across) R23?

This would be both in power on and power off.

I'm assuming (as a fault mode) that the switch circuit may fail, or be
partially on when power is off.? This would be either (or both) CR3
failing or Q1 failing, which makes the battery try to drive the +5 volt
line all by itself.? In that case, I can see the backup battery going to
zero in very little time at all.

This is a good point.

The current through R23 when off is in the low nA range, same as when
the instrument is powered on. This seems to be consistent with the
measurements performed with the external supply.

I also measured the DC resistance through the parallel path of CR3
(reverse bias) and Q1 and it seems to be an open circuit; at the very
least > tens of MOhm. As an additional check, I measured the forward
drop of CR3 which came out to just under 0.6V so that seems fine.

Anyway, I think I *may* have identified the culprit. There's some
corrosion on the battery holder that I think could have effectively
removed the battery from the circuit. I wasn't measuring the voltage
across the actual battery terminals, but at accessible connection points
on the PCB. So, I think the full reserve supply was being powered by the
capacitor, which is why it couldn't meet the current demands.

I applied some deoxit to the battery holder terminals and I now see a
steady 3.18V measured on the PCB at the connections to the battery.

Matt

"Bruce" <bruce@...> writes:

There is a rather simple solution: Scan only the oversized pages.
Typically, the theory sections only change slightly over the life of
an instrument. You could scan some of the sections referring to
debugging techniques that changed over the life of the instrument and
possibly the updates section. No need to scan the entire manual.

In theory, yes, but I think it's preferable to scan the entire manuals
for 2 reasons:

1. The rest of the pages are easy to scan and it would be nice for all
the page numbers to line up. It's really nice to have consistent,
complete, high-quality manuals and I think this is worth a bit of extra
effort up front.

2. The 8663A manual is a bit weird and is incomplete in some
respects. For instance, parts the digital troubleshooting section say to
refer to signature analysis codes, but these aren't actually provided
anywhere in the manual. There's a chance these were added in this
manual. We could look for these specifically, but it would be a shame to
find out at some later point that there was another omission in the
earlier manual revisions that we'd missed the opportunity to scan.

Matt

"Richard Parrish" <Richard@...> writes:

I'm sure that these are rare. I was in a place 10 years ago that I was able to purchase a number of the end-of-life manuals with all the updates, expensive but I thought it worth it. I couldn't do it again even if they were available. The irritating thing about the manuals is that Agilent expanded single page schematics and put them in the large page format which then made a single page schematic, onto 3 11.5x18" pages; hence the large size of the manuals. I wouldn't have an issue with having someone who has the right equipment scan the manuals but it's going to be a lot of work for someone since the theory and parts lists are on 11x8.5" pages followed by the schematics or block diagrams on 11x18" (?) pages.
I purchased the full set from Keysight which is 4 volumes but I can't locate Vol1 at the moment.

Thanks Richard, it's generous of you to be open to this. I've looped in
Dave at Artek who scans these manuals as a business and does a nice
job. I expect he has a scanner that can do the large pages in one piece
and can stitch the parts together, but he can confirm. If not, I've been
looking at a used scanner that can do that size (which I've been
considering anyway) and do them myself. I know of software that can
stitch images like this together and would be willing to put in the
effort, though I've never used this before so will have to give it a
test run first.

Where are you located? Obviously something local would be preferred, but
would you be open to shipping them (which others can subsidize) if not?

Matt