Author Topic: HP 3457A 8051 A/D controller replaced (Read 9616 times)

tppc · « **on:** May 04, 2018, 08:39:03 am »

Hi all,

I salvaged a nice clean Hp3457A from destruction.
The bad news is that the A/D hybrid U511 seems to be destroyed. (voltage at pin 1 never crosses 0).
All other signals on U511 pins seem to be OK, including slope selection and RUNUP signals at pins 6,7,8,9.

Yesterday, while probing with an oscilloscope, the A/D controler U501 started overheating.
I probably destroyed it by making accidental unwanted short.

So now, the question is : does anyone know where to find the following parts at reasonable price :

~~- 1QF6-0066 A/D hybrid (A2 U511)~~ salvaged one from a HP 44701A PCB
- ~~1820-3549 P8051 MASKED (A2 U501)~~ Replaced with AT89C51 + reverse XTAL1 & XTAL2pins (see last post)
or
- ~~03457-66502 PCB Analog assembly (used)~~

Thanks for your help
Kind regards

tautech · « **Reply #1 on:** May 05, 2018, 01:07:02 pm »

Place a listing for those bits here too:
https://www.eevblog.com/forum/buysellwanted/

Jwalling · « **Reply #2 on:** May 05, 2018, 03:35:12 pm »

Quote from: tautech on May 05, 2018, 01:07:02 pm

Place a listing for those bits here too:
https://www.eevblog.com/forum/buysellwanted/

That might be considered double posting...

ch_scr · « **Reply #3 on:** May 05, 2018, 04:07:11 pm »

The HP44701A uses the same A/D hybrid 1QF6-066. These HP44701 show up from time to time cheap on Ebay. The P8051 is called 1820-4881 in my unit.

tppc · « **Reply #4 on:** May 05, 2018, 10:07:28 pm »

Hi all,

thanks for your answers. As suggested by tautech, I placed a post in the Buy/Sell forum.

@ ch_scr, thanks for this valuable information. I knew the 1QF6-0066 A/D hybrid was used in the 3457A, 3468 and 3478 but I didn't know it was used in the HP44701 too.
This is very good news since these HP44701 seem to be very cheap on eBay.

Again, thanks for this information.
As for the P8051 used in the HP44701 I am not sure it uses the same mask ROM program as the one in the 3457a.

can anyone confirm this last point?

Thank you very much

.

ch_scr · « **Reply #5 on:** May 06, 2018, 06:59:00 am »

Well, information on the HP44701A is very sparse, if I did not have a picture from the inside of mine handy, i would have not been able to tell. Would love a component level service information on that one. I checked the SM of the 3457A, 3468A & 3478A.

3468A seems to use a ins8039n with external eeprom; all floating, interface, display and all.
3478A uses the 1820-2726 with transformer coupling, one TX and RX channel to the ground referenced side.
3457A uses the 1820-3549 with optocouplers, one TX and RX channel to the ground referenced side.
44701A uses the 1820-4881 with 4 Optocouplers, there is some kind of convoluted logic on the other side to make it into a parallel bus communication.

I believe it is safe to assume it would not be compatible

I suspect they all use the same P8051 but different masked rom.

tppc · « **Reply #6 on:** May 06, 2018, 07:43:57 am »

I didn't find any schematics for the 44701A either.
Well at least you found me a cheap source for the 1QF6-0066 A/D hybrid

hopefully I'll find a source for this P8051 too

Kind Regards

tppc · « **Reply #7 on:** April 06, 2019, 01:25:04 pm »

Hi all,

I am still fighting to revive my second HP3457a

As suggested here, I bought a used 44701a board and salvaged the A/D converter 1QF6-0066.

Unfortunately, this didn't help, since the A/D controller (A2 U501) seems to be faulty.

When I power it up, it shows :
ADDRESS-22 and immediately after, it shows
FAILED
it does not beep and the keyboard does not respond except the RESET key.

If I press RESET, it beeps and restarts but does exactly the same thing.

The main controller board (03457-66511) works fine, I tested it on my other HP3457a.
I also suspected the communication between the main controller A11 U601 and the A/D controller, replaced optocouplers A2 U509 + A2 U510 +A2 Q501 + A2 U502, it did'nt help.

As far as I know, A2U501 is a masked ROM P8051.
Is this something that could be "cloned" ?
I mean, somehow read the program from a good one, buy a blank programmable one and somehow flash it ?

Thanks for your help
Kind regard

coromonadalix · « **Reply #8 on:** April 06, 2019, 06:41:29 pm »

It could be read if there is no security bits involved

picburner · « **Reply #9 on:** April 07, 2019, 05:34:31 am »

If you can read the p8051 rom then you could use an AT89S51 that is pin to pin compatible and has a flash instead of a mask rom (if the code is equal or lower than 4K, naturally).

tppc · « **Reply #10 on:** April 07, 2019, 09:02:28 pm »

Hi all,
thanks for this information. I have very limited knowledge about microcontrollers.

What hardware and software do I need to program an AT89S51?

Kind Regards

feedback.loop · « **Reply #11 on:** April 08, 2019, 01:40:07 am »

For instance, cheap TL866 programmer can do it. They are sold all over eBay, but with different sets of adapters. Make sure you have 44PLCC adapter.
However, if yours is dead, I would not hope to be able to read it. Even if it were alive, it might have had a special read protection mode enabled. I would suggest to find the ROM dump (if they exist at all) before you spend money on a programmer.

coromonadalix · « **Reply #12 on:** April 08, 2019, 10:31:53 am »

buy the old tl866 version not the "plus" for future usage, the newest model "plus" goes up to 18volts not 21 as the old model.

tppc · « **Reply #13 on:** April 09, 2019, 05:10:53 pm »

Hi guys,

thanks for your answers.
Well, it looks like I won't need to buy any programmer, since the security bits are most likely set.

I have a second 3457a in good working condition.
Maybe some day, I'll take time to desolder both controllers and try to swap them... I don't know yet.

Kind regards

tppc · « **Reply #14 on:** April 13, 2019, 12:24:33 pm »

Hi guys,

I suggested I could desolder the A/D controllers from my HP2457A DMMs… and so I did!

Here is the result :
The known good DMM equiped with the suspected bad A/D controller reacts exactly as the bad one.

ADDRESS-22
FAILED

I didn't try the known good controller in the bad meter (too scared to burn the good controller

).
Well, at least, now I know for sure that the A/D controller (A2U501) is dead.

Now, the question is :
- If I buy the TL866 programmer, how do I know if the lock bits are set? and is there a risk that I screw up the good P8051 while trying to read it on the TL866?

Regards.

coromonadalix · « **Reply #15 on:** April 13, 2019, 12:37:57 pm »

well if the bits are set normally you wont be able to read it, and put it back in the meter it should still work okay, but if you desolder it or simply remove it from a socket, take anti static precautions.

tppc · « **Reply #16 on:** April 13, 2019, 01:01:58 pm »

I already desoldered it and installed a socket in the meter. This allows me to swap the controllers.
To be honnest, I Don't have anti static straps, but you are right, I will get one and use it on my next experiments.

Thanks for your help.

Kleinstein · « **Reply #17 on:** April 13, 2019, 01:09:22 pm »

With a new programmer, a first thing would be to test it with some less critical parts.
The main danger to the chip would be from ESD and wrong connection / setting at the programmer (e.g. wrong supply).

If it is an really old chip chances are there may not even be protection bits on the chip available.

tautech · « **Reply #18 on:** April 13, 2019, 01:17:26 pm »

Quote from: tppc on April 13, 2019, 01:01:58 pm

I already desoldered it and installed a socket in the meter. This allows me to swap the controllers.
To be honnest, I Don't have anti static straps, but you are right, I will get one and use it on my next experiments.

Thanks for your help.

A little guidance from Defpom about how he reprogrammed an HP chip:

Programmer:
https://youtu.be/VDg1dgE4AFk?t=390

The doing:
https://youtu.be/xhbnW1zHTX8?t=1169

tppc · « **Reply #19 on:** April 13, 2019, 01:50:22 pm »

Quote from: Kleinstein on April 13, 2019, 01:09:22 pm

With a new programmer, a first thing would be to test it with some less critical parts.
The main danger to the chip would be from ESD and wrong connection / setting at the programmer (e.g. wrong supply).

If it is an really old chip chances are there may not even be protection bits on the chip available.

Here is a picture of the good controller installed back in the good meter with a socket.
Is it old enough to be sure no protection bits involved?

@Tautech,
thanks for the links, I will watch the videos.

Regards

tppc · « **Reply #20 on:** April 28, 2019, 12:17:44 pm »

Hi all,
I found what seems to be a backup of 3457A A/D controller binaries.
http://bbs.38hot.net/thread-756595-1-1.html

Unfortunately, it is on a Chinese Website and I can't download it.
Even with Google translate I can't find out how to subscribe and how to gain access to this file.

Can anyone help?
(please see attached screenshot)

Thanks for your help.

picburner · « **Reply #21 on:** April 28, 2019, 01:22:42 pm »

Here are the two files from the posted link:

tppc · « **Reply #22 on:** April 28, 2019, 01:36:38 pm »

oh waaaaouh! That was fast!

Thanks very much.
Hope it is the actual program and not a fake

Anyway, I ~~will~~ did order the TL866 programmer and an 5 AT89S51 today.

I will let you know if it works when I receive my programmer.

Again, thank you very much!

picburner · « **Reply #23 on:** April 28, 2019, 01:56:33 pm »

I notice now that the file (...p8051.zip) is more than 8KBytes long while the AT89S51 cpu has a Flash memory of 4KBytes only.
The content of this file from 1000h to 203Fh is all 0FFh, you probably need to reduce the file size when loading it into
the eprom-programmer.

tppc · « **Reply #24 on:** May 04, 2019, 06:54:21 pm »

Hi there,
I received my TL866 programmer today

.
Unfortunately the µC's AT89S51 didn't arrive yet.

Anyway, I couldn't wait any longer, so I played with the TL866...

Tried to read the fried 8051AH -> FAILED "OverCurrent Protection! External short or IC reverse or incorrect package!"
Tried to read a C8751H (UV ROM) pulled from my 44701A -> FAILED "OverCurrent Protection! External short or IC reverse or incorrect package!"

Tried to read the 8051H extracted from my other HP3457A (in good working condition) and guess what…
the dump is identical to the backup I found on the Chinese site (once again, thanks to picburner

).

Looks like I will revive my second HP3457A

By the way, will the AT89S51 work exactly as the P8051AH?
I mean, is there any chance that the meter somehow reads the chip ID? (which may differ from the 8051AH)

Regards.


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Author Topic: HP 3457A 8051 A/D controller replaced (Read 9616 times)

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