HP-8753E Opt 010 - H/W or S/W Option

[TheSteve]

I'd be more concerned about pin 13, it looks like there is solder on it. If you remove it from the socket and reform the legs chances are it will still make contact - unless the leg(s) fall off of course. I believe you can backup the cal parameters to a floppy - I hope you've done this already.

[AJ3G]

I have not backed up the cal parameters yet. I have some 3.5” disks due to arrive today, so I will. I will take a look at that pin too. Would you happen to know if that EEPROM is buffered from the CPU, or does it get written directly?

My plan at the moment is to look at some of the lines (CS, RD, and WR) with my Logic Analyzer. I suspect read is ok, or the instrument would not work whatsoever. I will then try to set those option bits over and over again and see if I can monitor any activity on the three pins above.

Rich

[AJ3G]

Steve:

I made an error, the pin I was complaining about is Pin 13 that is DQ0. I am looking at it kind of upside down myself, so that may explain the confusion. I did the pin count wrong when reviewing the data sheet. I will correct my previous message so it’s clear, I apologize.

Datasheet for EEPROM: https://html.alldatasheet.com/html-pdf/55462/AMD/AM29F010-70JC/223/4/AM29F010-70JC.html

Rich

[AJ3G]

All:

I just wanted to give a status update. I finally got this all sorted out. I managed to secure a second CPU Board to use as a test article. Both CPU Boards would not except license keys for their respective serial numbers. I also discovered the information I needed to change is on U402. The EEPROM map posted by Steve is valid despite coming from a HP-8753D model. Here is how to modify the EEPROM:

- Address 0x00 - 0x02 must be populated with "F7 F7 F7"  (NOTE This activates OPT 006, 10, and 02)
- Address 0xBC - Populate with 01 to activate and 00 to disable. (NOTE: This activates/deactivates OPT11)

When completed you should see a the enclosed picture of the boot up. Ideally you want to confirm all test pass too.

Rich

[EduardGede]

Hi,

I got confronted with the same issue of being unable to activate the options
with the upgrade code from Ceasar.

Changing the data in U402 in the first 3 addresses with F7F7F7 will result in RF not working.

The culprit was the fact that the Rchan-in and the Rchan-out where bridged.

So disconnect all.
Set S400 A8 dipswitch on A9 CPU board.
Start VNA and do your thing according manual instructions 9018-40043.pdf.

Cheers

[EE-digger]

Be sure to give Caesar the correct SN and model number.  The bits are all the same but this controls access to them.

I'm sure you guys can all type though 

added:   Steve - I have a very vague recollection of there being two different CPU assemblies.  Perhaps the correct switch is not being thrown??

[AJ3G]

I ultimately was able to troubleshoot this problem to an issue with an IC around the EEPROM, which was not allowing the correct lines to be thrown to write to the PROM.  Once this was corrected, the activation code worked without issue.

I also was able to socket the EEPROM and write to it, so this too worked, but was not the source of my particular issue. Other than having to replace the inverter board after this, the 8753E has been rock solid.

Rich