Success!

After letting PRETUNE COR run for about five hours, I pressed Preset and stopped the cycle.

I had been sending source through 20 dB pad to R channel (no test set).

Replaced the 20 dB pad with an 8 dB pad in same path.

Re-did PRETUNE DEF (4 5) followed by PRETUNE COR (4 8); this time PRETUNE COR completed in a few seconds, ended with DONE, and after subsequent Preset it came back without start-up error message. Powercycling the unit had the same result.

I did this with both A9 CPU boards; the result was the same for both (and both now have their A9 CC jumpers back to normal position.)

Thanks for the getting-started advice, much appreciated!

Update - have started the SOURCE PRETUNE CORRECTION CONSTANTS procedure.

There are two steps -

First is "PRETUNE DEF" (test 45); this completed successfully (the manual says it would display "CORRECTION CONSTANTS NOT STORED" if the EEPROM were not written, so that's a good sign. That test ran instantly.

Second is "PRETUNE COR" (test 48). This has been running now for about half an hour. The signs of activity are

1. The test status says -IP- (probably "in process" or something to that effect)
2. A small arrow on the CRT to the left of the grid (at about line 6 from the bottom) is coming on and off at a 1 Hz rate
3. A vertical line, just to the right of the left axis of the grid, is varying in height (from the bottom) between about 2 divisions, and occasionally going all the way to full scale height. It appears to update about once a second.

I will need to leave it running at this point but will check on it from time to time. Hopefully it finishes by tonight!

Hi Chuck,

I think I have enough information to proceed --- I went back to the schematic of the A9 board, and the jumper pins E25 and E26 enable a write signal to go to the EEPROM, which is a 24-pin device that may be a 2816 type (the part on the CPU board here is an Intel D2817; found a datasheet for that online, so that means I should be able source replacement EEPROM(s), as the EEPROM back-up/restore facility in the 8753 depends on the 9122 series floppy drive (don't know if this can be done with HPIB interface, haven't checked.)

E25 and E26 are on the top pair of pins on my boards (both); they may be on the far right pair of pins on your board(s) where the header is horizontally oriented. Given that, I'm OK to proceed attempting to access EEPROM from the test/diagnostic menus in the 8753A. If there's a diagram of the board layout(s) anywhere in the documentation I've found online so far, I've overlooked the needed resource. Fortunately the boards are pretty well marked as to what major part is where.

Your two CPU boards are possibly from 8753B or 8753C; the 8753A never had option 006 (6 GHz) nor 002 (Harmonic mode), only option 010 (Time Domain. )

So, I think at this point I can proceed with attempting recovery of the 8753A with it's replacement CPU board.

Also, the other 00067 board I have here might be from the HP 8702A (lightwave analyzer, pretty much some early part of the 8753 family), but not sure. Anyway, gotta burn only one bridge at a time!

Thanks again for your time and exploration of your lab equipment on my behalf!

I'll report back (here) on whatever success/failure I encounter.

Dave

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Dave,

I got to both units.

The working one is #2828A04434, OPT 002 & 006
CPU board is 60079, Revision 3.0 Firmware.
The header is horizontal to the left of U36, marked from left E25, E27, E29, E31, blank. The run jumper is on the E25 pins

The bad CPU unit is #2807A04011, OPT 002, 006, 010
CPU board is 60129, Revision 2.01 Firmware
The header is also horizontal the same as above

As far as getting the board out without the lift tabs, I use a pair of vise grips at the center of the board edge where the pin header is located, doesn't take a lot of force to pull it up.

Hope this helps your problem.

Chuck

Dave,

The 60009 board is he one the manual says there is no docs for but it's similar to the 60079
board.
?
I'll open the working one this afternoon, I think there's another one with a bad CPU board in my storage shed that I just haven't wanted to spend time on, I'll look for that one too.

Chuck

On 12/7/2024 12:59 PM, David Feldman via groups.io wrote:

Thanks, Chuck - I really appreciate your time/interest in helping with this!

The A9 board number ends in 60009. I've got another A9 board (however, it's removal latches are missing and it's "distressed" at those corners due to some abuse in it's history) which ends in 60079. Both have a 5-jumper array in the lower left corner. Both are equipped with same version of EPROM 1.01 (6 parts, specific part numbers but sharing the same revision marking.)

Both A9 boards (I didn't include this info with original posting as it didn't seem relevant, but given the existence of A9 board versions for 8753A and your notes above) appear operational as far as I can tell (and in terms of the self-test diagnostic for internal tests which passes in both cases), but existence of incompatible EEPROM constants (that applied to whatever machine these previously lived in, long ago) is causing what appears to be pretune failure. I'm focusing on the 60009 board currently (as changing the CC jumper requires removal of the board and removal without the eject parts is doable but tedious).

So, if you are able inspect the A9 board in your 8753A and suggest which is the CC position, that should apply to both boards here (i.e., is the "CC" position at the top of the 5x2 header, or other position; the normal operating jumper position appears to be at the bottom of the header pin group from your initial response and by inspecting both boards here.)

As an aside, I read through the section in the PDF service manual on adjustments/calibration constants; it appears the pre-tune issue has a specific diagnostic step which can regenerate the parameters and those get rewritten to an EEPROM somewhere on the CPU board, and from seeing a few other posts on the issue (need follow a procedure after A9 module replacement) this is a common situation (such as these things would go nowadays!)

So, again I appreciate your willingness to pitch in and advise!

Dave WB0GAZ

--

See Early TV and Vintage Test Equipment

Chuck Azzalina

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Dave,

The 60009 board is he one the manual says there is no docs for but it's similar to the 60079
board.
?
I'll open the working one this afternoon, I think there's another one with a bad CPU board in my storage shed that I just haven't wanted to spend time on, I'll look for that one too.

Chuck

Thanks, Chuck - I really appreciate your time/interest in helping with this!

The A9 board number ends in 60009. I've got another A9 board (however, it's removal latches are missing and it's "distressed" at those corners due to some abuse in it's history) which ends in 60079. Both have a 5-jumper array in the lower left corner. Both are equipped with same version of EPROM 1.01 (6 parts, specific part numbers but sharing the same revision marking.)

Both A9 boards (I didn't include this info with original posting as it didn't seem relevant, but given the existence of A9 board versions for 8753A and your notes above) appear operational as far as I can tell (and in terms of the self-test diagnostic for internal tests which passes in both cases), but existence of incompatible EEPROM constants (that applied to whatever machine these previously lived in, long ago) is causing what appears to be pretune failure. I'm focusing on the 60009 board currently (as changing the CC jumper requires removal of the board and removal without the eject parts is doable but tedious).

So, if you are able inspect the A9 board in your 8753A and suggest which is the CC position, that should apply to both boards here (i.e., is the "CC" position at the top of the 5x2 header, or other position; the normal operating jumper position appears to be at the bottom of the header pin group from your initial response and by inspecting both boards here.)

As an aside, I read through the section in the PDF service manual on adjustments/calibration constants; it appears the pre-tune issue has a specific diagnostic step which can regenerate the parameters and those get rewritten to an EEPROM somewhere on the CPU board, and from seeing a few other posts on the issue (need follow a procedure after A9 module replacement) this is a common situation (such as these things would go nowadays!)

So, again I appreciate your willingness to pitch in and advise!

Dave WB0GAZ

Thanks, Chuck - I really appreciate your time/interest in helping with this!

The A9 board number ends in 60009. I've got another A9 board (however, it's removal latches are missing and it's "distressed" at those corners due to some abuse in it's history) which ends in 60079. Both have a 5-jumper array in the lower left corner. Both are equipped with same version of EPROM 1.01 (6 parts, specific part numbers but sharing the same revision marking.)

Both A9 boards (I didn't include this info with original posting as it didn't seem relevant, but given the existence of A9 board versions for 8753A and your notes above) appear operational as far as I can tell (and in terms of the self-test diagnostic for internal tests which passes in both cases), but existence of incompatible EEPROM constants (that applied to whatever machine these previously lived in, long ago) is causing what appears to be pretune failure. I'm focusing on the 60009 board currently (as changing the CC jumper requires removal of the board and removal without the eject parts is doable but tedious).

So, if you are able inspect the A9 board in your 8753A and suggest which is the CC position, that should apply to both boards here (i.e., is the "CC" position at the top of the 5x2 header, or other position; the normal operating jumper position appears to be at the bottom of the header pin group from your initial response and by inspecting both boards here.)

As an aside, I read through the section in the PDF service manual on adjustments/calibration constants; it appears the pre-tune issue has a specific diagnostic step which can regenerate the parameters and those get rewritten to an EEPROM somewhere on the CPU board, and from seeing a few other posts on the issue (need follow a procedure after A9 module replacement) this is a common situation (such as these things would go nowadays!)

So, again I appreciate your willingness to pitch in and advise!

Dave WB0GAZ

Should the original brand have been spelled "Teac"??

?

?

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Dave,

Which CPU board do you have? 08753-60079 or 08753-60067? There was an earlier one but
manual says no documentation for it believe it was -60006.

The drawing in the manual has no labels shown on the header pins and it does show it as being a 4pin header. The schematic lists labels as E7-E22.

The CPU board (60079) layout appears to show a 5pin header with the run jumper across the second set of pins (from bottom) for the run position. The board layout shows U35 to the right of the header.

I have a A model and can check the header for you if you need.

Chuck

Hi Chuck,

Thanks for the ASCII-Art depiction.

Just want to re-confirm, so could you take a look at this?

I found a 5-pair (not 4-pair) jumper header set, oriented vertically, in the lower left (holding board, bottom down, facing component side) of the board. Just to the left of the header set is the bottom of the large CPU chip. To the right of the header set is an IC labeled U35.

From top to bottom, the five jumper position pairs are labelled as follows:

E25 E26  (top)
E27 (blank)
(blank) (blank)
E31 E32
E33 (blank)   <-   this is the only pair that currently (in run position) has a jumper

While I suspect from your description that the normal running position is on E33/blank, and the CC position is at the top, E25/E26? Does this appear to be correct?

Thanks!

Hi Chuck,

Thanks for the ASCII-Art depiction.

Just want to re-confirm, so could you take a look at this?

I found a 5-pair (not 4-pair) jumper header set, oriented vertically, in the lower left (holding board, bottom down, facing component side) of the board. Just to the left of the header set is the bottom of the large CPU chip. To the right of the header set is an IC labeled U35.

From top to bottom, the five jumper position pairs are labelled as follows:

E25 E26 (top)
E27 (blank)
(blank) (blank)
E31 E32
E33 (blank) <- this is the only pair that currently (in run position) has a jumper

While I suspect from your description that the normal running position is on E33/blank, and the CC position is at the top, E25/E26? Does this appear to be correct?

Thanks!

开云体育

Dave:

Here is crude diagram of the CC jumper location.
_______
|????????? |
|????????? |
|????????? |
| cpu??? |
|????????? |
|????????? |
-----------?? J4
??????????????? __
?????????????? |. .| jumper position to load correction constants
?????????????? |. .|
?????????????? |. .|
?????????????? |. .| jumper position to operate
?????????????? -----

Pull jumper off pins in lower position and push it on the upper position pins as shown above
to enable load constants

Reverse procedure when finished loading constants

ChuckA

On my HP 8753A VNA, I am trying to follow the instruction for enabling adjustments to stored calibration constant data (needed after replacing A9 CPU module with a different unit and getting related start-up errors).

Working with HP 8753A_B_C Service manual 08753-90156, readily available online, I downloaded from:


In the section (indexed as "Adjustments", titled "Adjustments and Correction Constants", starting at PDF page 159:

The instruction text is this:

"A9 CC (CORRECTION CONSTANT) JUMPER POSITION" 
"Move the A9 CC jumper, as explained next, to the ALTER position to change..."
however, where (in the next few bullet points) this is explained, the assumption evidently is that the reader knows where on the A9 CPU board the CC jumper is located.

---> I am unable to find any jumper labeled CC on the CPU board (unless it's totally obvious and I keep missing it!) <---

Thanks for a description, pointer or other advice (or request for clarification, however, I'm hoping this is a basic problem that is fairly self-explanatory!)

Dave

On my HP 8753A VNA, I am trying to follow the instruction for enabling adjustments to stored calibration constant data (needed after replacing A9 CPU module with a different unit and getting related start-up errors).

Working with HP 8753A_B_C Service manual 08753-90156, readily available online, I downloaded from:


In the section (indexed as "Adjustments", titled "Adjustments and Correction Constants", starting at PDF page 159:

The instruction text is this:

"A9 CC (CORRECTION CONSTANT) JUMPER POSITION"
"Move the A9 CC jumper, as explained next, to the ALTER position to change..."
however, where (in the next few bullet points) this is explained, the assumption evidently is that the reader knows where on the A9 CPU board the CC jumper is located.

---> I am unable to find any jumper labeled CC on the CPU board (unless it's totally obvious and I keep missing it!) <---

Thanks for a description, pointer or other advice (or request for clarification, however, I'm hoping this is a basic problem that is fairly self-explanatory!)

Dave

On Fri, Dec 06, 2024 at 07:44:16AM -0800, gsl via groups.io wrote:

Is it possible to buy one of these converters? I have the same problem on my HP54542C!
Thanks.

Yes, possible. I've responded off list with details, provided I got the
email address right.

-Alex