ADVANTEST TR9403 - failed RAM

[Norbert67]

Hello!
I own an older TR9403 analyzer with a RAM failure. I would like to repair it because I think it´s still an excellent instrument to this day, but without a service manual or schematic I don´t know which RAM is failed. If somebody from this forum owns a measurement instrument like this and would be so kind and provide some schemes or help, I would be really happy. Thank You.


***FAIL RAM***
ADRS 050220      WR 107070       RD007070

[bidrohini]

Did you search the RAM here?
http://www.semistarcorp.com/product/advantest-parts-equipment/

[Norbert67]

Thanks for the tip.
Unfortunatelly the memory pcbs were not on the list.
I asked them how much they would wanted for the whole complete set of tr9403 with recorder and generator, but they did not answered.

[Norbert67]

For those who are interested in these Advantest Analyzers and have similar problems:
Even testing with ABI IC tester the RAMs seemed OK, but the problem persisted, which raises the question: how are these testers test these IC? I think just writing Os and 1s and not random values, which is for testing SRAMs not adequate.
Then I ordered a extender pcb board, managed to buy connectors to this, hoping I could monitor the data on rams with a oscilloscope, but unfortunately with extending the memory board the analyzer doesn´t work as intended.
So the only solution remained to buy a lot of these RAMs and change them one by one. So the problematic RAM was on memory board but still have no clue which one failed and what kind of ram failure we are talking about.
There were other little problems around the instrument, like the contacts of buttons, or bad tantalum caps, overload protection circuit failure (also tantalum + bad transistor), battery and so on, but now its in working condition and its a great spectrum analyzer. By the way after the instrument was not claiming any errors, the signal in oscilloscope mode was still a little rough, but changing all the rams for new ones the signal became much smoother than before.
I hope I help those, who struggle with the same problem.

[fzabkar]

IMO, the original error message points to L4/J4 or M8/K8, depending on whether AB16 or AB1 is the most significant bit. Obviously the data and address are in octal format.

https://elektrotanya.com/advantest_tr9403_memory_pcb_sch.pdf/download.html#dl

A neat trick that someone showed me is to piggy-back a good RAM onto a suspect RAM. Often the good RAM masks the bad one.

Another trick is to short DO to ground and then record the error message. Do this for 2 or 3 chips, and then you will recognise the RAM mapping. If the ICs are in sockets, then it's even easier and safer.

[Norbert67]

Thanks for the tips and tricks Fzabkar!