Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
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joeqsmith:
If I change over to use the external trigger while monitoring the sync, again it seems to alias long before it should.   

Here you can see the serial port being used with the external trigger.  It will keep up at 22Hz but at 23Hz it will start to miss. 


--- Quote from: SilverSolder on February 07, 2021, 12:00:13 am ---Snowstorm tomorrow, perfect time to get GPIB working! :D

I may be misremembering the speed of the Fluke:  it was quite a while ago, it may have been an old HP 59313 A/D converter that I got running that fast...  Time to get some accurate numbers. 

I will check what firmware revisions I have as well, it would be cool if we could upgrade all of them to the latest version!  (Assuming the hardware is compatible throughout...)

--- End quote ---

That would be great as I am really at a loss.  Maybe I just don't understand the manual.   S0 should be 1 sample/reading and they claim a digitizing time of 4ms.  2ms when using line asynchronous.  If I set the number of samples higher to allow the meter to collect at a faster rate, the sync rate stays the same.  It's just looks like it's a much slower than they claim.   
SilverSolder:

My max versions are:
 
  8505A -  v5.0.5
  8506A -  v6.0.7

I have no idea what the actual latest revisions actually are.

There seems to be a big difference between v.6.0.6 and v6.0.7 for the 8506A, they behave quite differently in many subtle respects.

I have never tried burning eproms, but I do have a TL866CS here that might do the job?
garrettm:

--- Quote from: joeqsmith on February 06, 2021, 09:41:08 pm ---This meter has version 603 installed.   Looks like its just a couple of 2764s.   If you have the images already archived, yes please, upload them and we can at least get on the same firmware. 

If I change to use the internal asynchronous trigger, you can see the packet is now just five bytes rather than the six.  There is no CR.   Also notice that the meter sends the data slightly faster but again, no where near what I would expect.     

Maybe SilverSolder's meter has different firmware as well which may explain why their meter is faster.    It's also VERY possible I am still not doing something properly which is throttling the system.

--- End quote ---

603, that’s positively ancient! Until now, I've never seen a firmware version below 605 out in the wild. It very well could be a software glitch holding your unit back. What year do you think you Controller module was made?

I haven't read my ROMs yet but I have a TL866II PLUS from XGecu that I can use to get them. I'm quite keen to see what differences you observe between revisions. It would be nice if we can put that enhanced baud rate on the Bit Serial Interface to good use!

I believe versions 1.0.1 for the CT variant and 607 for the standard 8506A are the last firmware revisions. The controllers with these versions had date codes of 1993 on the chips.

I've attached a picture of the elusive CT model and a couple of different Controller boards that had bad calibration memory. The CT Controller from 1993 looks basically identical to the others dating to 1983 and 1987 which both have version 606.

Here's a thread I made about that repair.

https://www.eevblog.com/forum/repair/fluke-8506a-repair/msg1002513/#msg1002513

I'll upload the newer 607 firmware here in a bit.
SilverSolder:
Judging by the picture of the controller posted at Xdevs (reproduced below), it seems that the firmware in the EPROMS apply to both the 8505A and the 8506A - somehow, the code must figure out what it is when it boots.  The reason I think that is because firmware on 8505A always appears to be 5.x.x whereas it is always 6.x.x on the 8506A, based on the units I have seen.  Note the label on the EPROM in the picture lists two revision numbers...  one for each model!  So, the newest ROM image might be a good upgrade for both models!  (Note, this is just a wild guess and it could be completely wrong...)



I am not very experienced with EPROMS, so this next "conclusion jump" may be wrong:  I noticed that the crystal in the controller is nearly 16MHz, we are probably dealing with an 8MHz CPU - which was fast in 1982.  Does that mean the grade of EPROM has to be the faster 200ns or better kind, to avoid introducing wait states in the CPU?  I have noticed EPROM is available in several speed grades...  I haven't looked under the labels of any of mine yet to confirm or deny this theory so it may well be incorrect.

garrettm:
I got the V506/607 EPROMs read from my meter. And since I had a spare Controller board with V505/606 firmware I read the EPROMs from it too.

The zip file contains the U23 and U24 bins along with datasheets for the different UV EPROMS used on each controller, photos of the actual chips and some notes. Should be pretty self contained.

I read the contents of each chip three times and compared the results to ensure I got good reads. I then compared the contents of each version and found a string for "8505A   :8506A   :" in both U23 binaries which gave me confidence that I read them correctly.

*Corrected a minor typo in the 8505A_8506A_Firmware.zip, where I wrote V505_607 instead of V506_607.
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