It had a faulty power supply. I repaired it and now all voltages are in spec. I have no control of anything on the front panel and all lights are on. Only noise on screen, no characters. Processor board has ROM17 light on. I think the processor or memory board has failed.
Looks like the ROM is corrupted. Anyone have a programmer for 27HC641. Looks like I can still get chips. $94 each. Some have modded the 27c64 to work that are much cheaper. Iam still hoping to pick up a memory board. One on eBay in the US but they won't ship outside the US.
The fact it lost its memory does not neccessarily mean the IC itself is bad, EPROMs are guaranteed to hold up their memory something like 20 yers or so, now that instrument is well past that, so maybe simply reprogramming the old chip could also help, you'd still need a programmer though. You better ask Casey, because he read back some NEC EPROMs for me a while back...
Post by thelasttubewarrior on Jan 23, 2018 23:46:42 GMT -5
I've had a couple units in that series. Two 492s and the then-top-of-the-line 494AP.
They're beastly spectrum analyzers and they were the state of the art in their day.
But they're not good for modern digital modulation modes. That's just way beyond the state of the art when they were designed.
I had a pair of Rohde & Schwarz FSEA30s which were much more useful with digital modulation schemes. And with an ultimate noise floor of -163 dBM in baseband, they were very sensitive and very precise machines.
There was a time when I had a very decent test bench. A local company that built cellular base station equipment downsized and I got to buy up all their surplus equipment for pennies on the dollar. I equipped my bench and also made a pile of money.