Need help from computer / transputer folks ...please!

[Tracker]

Hello,
Seeking help from someone with transputer and RAM debug experience...
The fault is on an R&S FESM spectrum analyser, the detector board is not processing the signal.
Selftest points to the Fast Measurement RAM module which is a plugin module.
In addition, when I run the analyser at <1Hhz  Resolution BW, the problem goes away.
However when Resolution BW is above >1Khz , the detector card is used and the fault arises... the signal line is flat across the top of the display...
Below 1KHz the Detector card is not used and a Digital IF card is used instead.

Having searched the internet in vain, I am left trying to debug the module.
(My plan B is to purchase a full Detector board, but I really hope I can fix the one I have.)

The DRAM module is mainly made up of the following:
2 x MT4C16257DJ-6  256x16 60ns Fast DRAM CMOS IC’s
1 x IMST805-F25S 32bit transputer … I hope this is not faulty as its quite hard to get.

To put things in perspective, I have attached some parts of the repair manual which show where the DRAM module is located and how it functions.

I'm not great at logic debug, I'm more comfortable with RF... so hopefully someone can help point me to some tests which may narrow the fault down.
For example, are there pins on transputer which could indicate a problem DRAM?
Or similarly is there a way to determine if the DRAM is working?


fingers crossed !!!

[tggzzz]

To not answer your question, I'll observe the maxim of repairing old test equipment: "it is always the capacitors".

So, have you checked all power supplies for DC value and ripple? Marginal values could easily result in logic failures, either complete or subtle or intermittent.

[coromonadalix]

And i would add   Not being rude

This is maybe more elaborated than you think for some repairs, i don't know your experience in soldering high count pins

the ram chips are relatively easy to get and not expensive, the other transputer chip, yes   can be very very expensive, seen 150$ up to 500$ for it.

Have you tried to contact  R&S  for support or repairs ??  this is not a toy  even i with years of experience would play in it


Do you have a complete service manual for it ??  if not  you'll be  ''guessing''

Do you have  hot air tools ??

my 2 cents

[Haenk]

Maybe ask R&S (or it might be in the service manual) if there is a more verbose failure/debug log available.
If not, I'd rather replace both DRAMs as a start - these do fail as well.
Obviously check supply voltages first.

[Tracker]

Thanks for the advice folks.
Yes I'm leaning towards a gunshot approach and just replacing the DRAM.
Yes I've got the skill and hot air equipment to do this.
Power supplies check out fine.

I believe the problem occurred when I accidentally powered down the unit as it was going through its power on routine... this may have caused a problem I guess.

[tggzzz]

I believe the problem occurred when I accidentally powered down the unit as it was going through its power on routine... this may have caused a problem I guess.

I would be a little surprised if that was the cause. Exception: if there is non-volatile storage somewhere, it might have been corrupted.

Is there any form of "global reset to factory settings" anywhere?

[Haenk]

check if the memory board and the chips get their voltage right (and clean, check with scope)
maybe also check caps on the memory board and surrounding the connector on main PCB

[Tracker]

Cheers guys,
Measuring voltages on board is a little tricky,  I don't have an extender card, so I'll need to solder fly leads onto the various points.  I'll try that next.

There is a Factory reset but it also loose all calibration, so thats my last ditch step.

I've emailed Q&S asking if there are deeper debug commands, and explained the symptoms,  hopefully someone's there can give some insights.

[Tracker]

While I patiently await the response from R&S...

I took a deeper look at the service manual and noticed there are deeper Service Tests which can be performed on each board , but this requires a Password.

Anybody?

[strawberry]

carefully desolder and do read/write check in some programmer

[Tracker]

Thanks Strawberry, thats not a bad idea!
I have a programmer, hopefully it covers the DRAM part number....

PS, I found the Service Password... with this there are no extra tests, it just allows various cal corrections to be disabled and EPROM contents to be dumped etc... Not sure it's going to help.

Cheers!