Video Teardown, Repair and Analysis of an Agilent E3642A DC Power Supply

[Hugoneus]

In this episode Shahriar attempts a repair of an Agilent E3642A DC Power Supply which is completely non-responsive. After presenting a teardown of the power supply, the GPIB interface is used to verify the functionality of the power supply. The problem is traced to the main display unit which communicated with the main power supply via a serial interface.

After disassembly of the display, it is revealed that the entire unit has suffered a catastrophic failure due to the VFD display drive IC. All components must be individually removed and replaced. Unfortunately the main processor is a Mask ROM IC version (80C51) and cannot be sourced. Can you help Shahriar find a replacement part?

Watch the video here: [54 Minutes]
http://youtu.be/quOQ-Wedxjc

More videos at The Signal Path:
http://www.TheSignalPath.com

[free_electron]

yeah . i most likely have em. same as in a 34401 multimeter. has same mask code

[pickle9000]

Well at least you have some cookies.

[c4757p]

The cookies are strangely adorable.

[vaualbus]

Sadly I think that the processor is programm at the factory.
On the schematics of the 33120 function generator, that share almost the same front pane board excpet of course a different vfd display, on the service manual that have the schematics in the part list the description of the micro is:  87C51 PROG so I suppose it mean intel 87C851 programmed. Somebody have to donate to you the chips.
Good luck!

[HighVoltage]

I also have the Agilent E3642A and it was bought broken on ebay Germany.
Turned out to be only a bad rotary encoder.
Agilent had the rotary encoder in stock in Germany and after replacement the unit worked perfectly.

I did not think about using the GPIB for remote control and test the unit remotely with the broken rotary encoder.
Great idea!
Thanks for another great repair video, especially for me, since I worked on the same unit.

[Hugoneus]

yeah . i most likely have em. same as in a 34401 multimeter. has same mask code

Awesome! Should I PM you then?

[Monittosan]

awesome video Shahriar keep up the good work! 

I have one of these power supply's and do you think that the high heat output from the VFD driver is a concern ? And may have caused this failure mode? I only ask as from the video we have learnt that failure of this component can be quite costly to repair. hmmm

[Hugoneus]

awesome video Shahriar keep up the good work! 

I have one of these power supply's and do you think that the high heat output from the VFD driver is a concern ? And may have caused this failure mode? I only ask as from the video we have learnt that failure of this component can be quite costly to repair. hmmm

Any repair will require the proper mask ROM controller no matter what.

[electronic_eel]

Nice video, I really like the repair & teardown videos you do.

Doesn't help with the mask rom though, but here are the schematics anyway:
E364xA_User_and_Service.pdf

Agilent revised the manuals of all their power supplies and pulled the schematics on the newer versions of the manuals. Stupid move on their side.

Don't you have another E36xx supply in your lab? Just try to connect it's front panel to the broken one. Does it work? That may widen your options in searching for a replacement.

Maybe take a look at the protocol between display and main unit.

[free_electron]

The good : i found a bunch of front panels.
The bad: non of em had the pcb's in em
The good (2) that means i have those pcb's somewhere... i never toss em because they hold valuable parts like those cpu;s m, the supertex drivers etc. most likely these machines had broken glass.

my lab is still a bit in turmoil . havent quite done the final cleanup. that'll be for this weekend. i'm sure i will find the boards then

(pictures below are only half of it ...)

[Hugoneus]

Sweet god of Neptune... That lab needs a clean up!

Where do you live, I can drop by to give you a hand. 

[romantao]

FYI, very nice approach

http://adamsblog.aperturelabs.com/2013/01/fun-with-masked-roms.html

[SeanB]

Sweet god of Neptune... That lab needs a clean up!

Where do you live, I can drop by to give you a hand. 

Silicon Valley, but you had better bring a large truck and trailer..............

[ion]

Worst case you can always decap the IC and read off the ROM bits!  A few months ago I came across this software that can extract the bits from an image of the die:

https://github.com/ApertureLabsLtd/rompar

That said, I don't know how easy it would be to turn a stream of bits into usable code.


Edit: romantao got there first.  I guess it's doable if you know the instruction set!

[radioFlash]

Another nice video, good luck with getting a replacement processor!

[DJ]

Sweet god of Neptune... That lab needs a clean up!

Where do you live, I can drop by to give you a hand. 

Silicon Valley, but you had better bring a large truck and trailer..............

Google "jim williams bob pease lab" and banish thoughts of order as being prerequisites for excellence.

(Linear Tech even had a puzzle of it!)

[SeanB]

I can almost guarantee that if you ask Vincent where a particular part is in his work area, he will be able to immediately go to the correct area, and probably to the correct box as well and find it. Then he will ask if you need a second or third just in case.

[Zucca]

FYI (I am just copy/pasting stuff)

Looks like here vtp was able to dump out the 80C51:

https://www.eevblog.com/forum/repair/hp-34401a-repair/msg614164/#msg614164

and the big free_electron was thinking about this Agilent E3642A issue.
As suggested by him

simply flash it into a 8751 and it will work

I am temped to try to read out a 80C51 with my cheap ass MiniPro TL866 and see if it works...