Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
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garrettm:

--- Quote from: SilverSolder on February 07, 2021, 06:21:58 am ---[...] 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.
--- End quote ---

Having replaced Controller modules between 8506A and 8505A units, I can confirm that the EPROMs contain firmware for both models. The only units not compatible are CT models which have special firmware due to hardware modifications (no rear input and special HV AC divider for 1kV range). The CT Controller can tell when not placed in a CT chassis, so somewhere on the mainboard or elsewhere is some sort of jumper or other feature that lets the Controller module know what model the unit is.
m k:
From M2764A manual

200 -2F1, -20F1
250 -F1, -25F1, -F6
300 -3F1, -30F1
450 -4F1, -45F1, -4F6
SilverSolder:

--- Quote from: m k on February 07, 2021, 12:34:20 pm ---From M2764A manual

200 -2F1, -20F1
250 -F1, -25F1, -F6
300 -3F1, -30F1
450 -4F1, -45F1, -4F6

--- End quote ---

Apparently the 8080A is only a "up to 4MHz" processor, so it is not picky about EPROM speed.

I wonder why Fluke chose a 15.36MHz crystal to run this board...  would that not run the CPU at 1.92MHz?


8080A     2.0MHz
8080A-1 3.125MHz
8080A-2 2.67MHz
8080B     4.0MHz


[edit: CPU speed]
garrettm:

--- Quote from: SilverSolder on February 07, 2021, 02:16:51 am ---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?

--- End quote ---

The 8505A with 505 firmware can be updated to 506 if you are feeling up to it.

The TL866CS is capable of producing the 21V peak programming voltage required by some of the early 2764 EPROMs. But the chips need to be erased first using a UV light source (~254nm wavelength). That requires pulling the label back to illuminate the die through a quartz window. Depending on the strength of the lamp, it could take a while to completely erase the contents. After proper erasure, the chip should be full of 1s. So before writing, you will want to check that the chip reads all 1s (or Fs in hex). After programming each chip, I would read the new contents and compare with the bin file to make sure everything worked. As Ronald Reagan once said, trust but verify.

And on that note, it also wouldn't hurt to read your EPROMs first and save the contents. The bins should match my V505/606 bins. If not, you will want to use Tiny Hexer to compare binaries and look if you can find "8505A   :8506A   :" in the U23 dump as a sanity check.
SilverSolder:

--- Quote from: garrettm on February 07, 2021, 04:38:03 pm ---
--- Quote from: SilverSolder on February 07, 2021, 02:16:51 am ---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?

--- End quote ---

The 8505A with 505 firmware can be updated to 506 if you are feeling up to it.

The TL866CS is capable of producing the 21V peak programming voltage required by some of the early 2764 EPROMs. But the chips need to be erased first using a UV light source (~254nm wavelength). That requires pulling the label back to illuminate the die through a quartz window. Depending on the strength of the lamp, it could take a while to completely erase the contents. After proper erasure, the chip should be full of 1s. So before writing, you will want to check that the chip reads all 1s (or Fs in hex). After programming each chip, I would read the new contents and compare with the bin file to make sure everything worked. As Ronald Reagan once said, trust but verify.

And on that note, it also wouldn't hurt to read your EPROMs first and save the contents. The bins should match my V505/606 bins. If not, you will want to use Tiny Hexer to compare binaries and look if you can find "8505A   :8506A   :" in the U23 dump as a sanity check.

--- End quote ---


My first UV EPROM eraser is on its way!  :D

For fun, I put the hex files through a crude 8080 disassembler - attached.  No guarantees that anything is right - I am utterly unfamiliar with 8080 assembly language.  Unfortunately, it doesn't include comments!  :D

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