[FIXED] Agilent 34970A GPIB controller chip

[Jwalling]

Got one of these on the bench for repair with serial prefix MY44.
The GPIB controller is shot. Looking at the service manual BOM it's a 1822-0639 and that's what's in this particular unit. The find-a-part website description is NFTS IC ASIC HPIB Controller, Keysight Trade Restricted. Not orderable, Contact Keysight for repair service. 

In the schematics in the same damn manual it's a 1821-1721 TMS99C14FN PLCC 44 

I can probably find an older TI TMS99C14, but I don't know if the pinout is the same or whether it will work. Does anyone happen to know?

Jay

[Kleinstein]

It's not only the pin-out that has to match. Also the firmware must be compatible, either detecting the chip used or same register use.

[Jwalling]

There seems to be a lot of Chinese vendors that are claiming to have stock, but that's about it.
http://www.aliexpress.com/w/wholesale-1822%25252d0639.html?spm=2114.01010208.0.51.UcXmBE&site=glo&g=y&SortType=total_weight_score_desc&SearchText=1822-0639&initiative_id=SB_20160721081927&shipCountry=US&needQuery=n

I wonder if any of these are for real. If anyone has any experience with any of these sellers I'd like to hear...

Jay

[pelule]

The TMS9914 was a standard peripheral device (NEC offered a similar product, the uPD7210). Thus nothing to program but to setup/control via registers (like a PIO or CTC in the old times).
It was offered in different packages, the FN package was the PLCC44 pin, the "C" was a mre modern CMOS version.
So you get the TMS99C14FN.
Here the link to the data sheet: ftp://ftp.whtech.com/datasheets%20and%20manuals/Datasheets%20-%20TI/TMS9914A_dataSheet_Jun89.pdf
An yes, National Instrument offers it, but the price is a bit crazy.
A smarter solutin may to buy a "part only" gear.
PeLuLe
 

[Jwalling]

Thanks PeLuLe.

I do have some TMS99C14FN parts on some scrap 34401A boards. I think I will probably try this.
See https://www.eevblog.com/forum/buysellwanted/wtb-agilent-1822-0639-gpib-chip-for-34970a/

Jay

[Jwalling]

Thanks PeLuLe.

I do have some TMS99C14FN parts on some scrap 34401A boards. I think I will probably try this.
See https://www.eevblog.com/forum/buysellwanted/wtb-agilent-1822-0639-gpib-chip-for-34970a/

Jay

Success! the TI part works fine!
The last part I had to remove was the 16C550 UART (it was corrupting the ALE signal from the 8751 micro) Now it talks on the GPIB bus. Had to replace 5 other 74XXX/75XXX glue logic chips as well.
Not surprising when you see the picture of the 34907A plug-in. Some Idjit must have wired it to 120VAC!

Purchased this off Ebay http://www.ebay.com/itm/122031822097?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks to all who contributed!

Jay

[DoricLoon]

Hi Jwalling,

I have a 34970a which I purchased from ebay with error 625. Both the main processor and the IO processor are sending data across the opto link.
Don't know if the data is correct or no? but levels are sound and appear to be the correct timing. I was wondering if the failure could be due to the IO processor missing it's reply window because it's not happy with the IO.
I can change the interface type on the unit and it does alter the interupt state of the GPIB and UART controller.
The IO processor is reseting and switching backplane power on.
Tried to connect via RS232, connection manager detects an instrument but doesn't identify it and any attempt at communication fails with a time out.

I have purchased a couple of TMS9914AFNL listed as new old stock hopefully they will do if needed?

What error did you have before you started?

[Jwalling]

Hi Jwalling,

I have a 34970a which I purchased from ebay with error 625. Both the main processor and the IO processor are sending data across the opto link.
Don't know if the data is correct or no? but levels are sound and appear to be the correct timing. I was wondering if the failure could be due to the IO processor missing it's reply window because it's not happy with the IO.
I can change the interface type on the unit and it does alter the interupt state of the GPIB and UART controller.
The IO processor is reseting and switching backplane power on.
Tried to connect via RS232, connection manager detects an instrument but doesn't identify it and any attempt at communication fails with a time out.

I have purchased a couple of TMS9914AFNL listed as new old stock hopefully they will do if needed?

What error did you have before you started?

It was error 625. I think this is my log entry for that unit...

MY44020108 Another error 625 BPPWR was high. U302-1 tied low ERPONRST from MC34064 voltage monitor. Turned out that U302 74HCT132-1 pin shorted internally.
after replacing the ACT132, no GPIB function. The GPIB chip appears bad – runs very hot!
I replaced the chip with a TI part from a 54542A, and it passed!

[DoricLoon]

Had another go at the 34970a today and think I may have found something?

I can change the baud rate of the RS232 interface and see the baud clock on the TL16C550CFN alter so the IO processor is definitely responding to main processor command.

I checked the data lines between the IO processor and the two bus management IC's and could see data switching. I then selected GPIB and each of the data lines shows the same signal. As per attached PNG. I'm an electrician trying to learn electronics so my knowledge is pretty rudimentary. Looking at the signal it appears to me that the rise time of the signal is way off. With GPIB selected the signal is constant. RS232 selected and data is changing but after taking a closer look that horrible rise time still exists.

Should I desolder the GPIB controller and see if the data lines improve?  I'm guessing pot luck as to which of the three bus devices is causing the problem? The only reason I suggest GPIB initially is I can see responces from the IO processor and the RS232 chip.

[Jwalling]

The rise time is determined by the pull-up resistors on the data lines. They are 46.4K so I don't see a problem.

[DoricLoon]

The rise time is determined by the pull-up resistors on the data lines. They are 46.4K so I don't see a problem.

Thank you for the pointer. I expected to see nice clean square edges on data lines, never considered the capacitance of the components or the board.

[f14]

Hi all
sorry for bump old topic. but I need you guys help me fix issue code 625
I use flir for check temp all ICs and only two U311 & U310 ( 75xxx) get warm . all ICs is cool(U309,307,305) . I checked U302 it no short but  I got short-circuit between pin 12 & 6 in PCB .it's still normal ?
Have any idea to fix this ?
today I had replace two U310,310  and TMS9914 from good working GPIB chroma ac source board but still got 625 code . after that I remove 16C550 and nothing better . maybe the error come from MCU 89s52?
thank you!