Hi Yuri; I am late to this thread, but if you have not tried this, reseating the 4 or 2 eproms which are socketed near the rear may solve the problem. I am currently having the same problem with one of mine and in the past this have solved the problem on other units. Good Luck; Thomas Knox NIST 4475 Whitney Place Boulder Colorado 80305 1-303-554-0307 tomk...@nist.gov
Quoting "Yuri Ostry" <y...@ostry.ru>: > Hello, > > Tuesday, January 20, 2009, 17:26:00, Richard M. Hambly wrote: > > R> One of my 53132As, an Agilent unit, s/n KR01202209 fail the power-on self > R> test with a FAIL:ROM error message. > > Cannot say anything about your particular counter, but very often such > error is due to 'leaked' EPROM chip, that change value of some memory > cells over time. Last years I seen such problems 5 or 6 times with 15+ > years old equipment, and in most times original EPROM image still can > be read out if you have a EPROM programmer that allow to set arbitrary > Vcc for a chip in programming socket. > > Some background: Erased EPROM cell (actually small piece of > metallization between two layers of silicon oxide, acting both as a > capacitor and as a gate of MOSFET transistor on underlying layers) > reads as logical "one". When it is charged during programming, it > start read as "zero". > > If some cell have small defects in insulating oxide, or just got a hit > of some high energy particle, part of charge can be lost and > "programmed" bit that should read as "zero" starting to read as "one" > under normal conditions (nominal Vcc). > > There is a chance (very good chance, according to my own experience) > that you can find such "partially discharged" bits by lowering > (gradually) Vcc and saving read images to disk for further comparsion. > > Usually I start from 5.0V, make 10-20 reads, saving each one to > separate file in a 5V0 directory, then switch to 4.9V, and do the > same, saving to 4V9 directory, and so on... Usually it is enough to go > below to 4V0... > > When you analyze saved images later, first compare all files in each > directory to each other, you can find some bits that reads unstable at > given voltage. Then compare images between nearby voltages and if > there is any changes, it may be your "lost" zero bits. > > If you go too low, some EPROMS that was written before and then erased > to program current image may show you some of former programmed bits > as zeros - you need to be careful. There was some "erased" EPROM chips > that read as blank under 5V but read out their previous content (and > CRC perfectly match) when read out at Vcc little below 3.8V (not all > brands of EPROM operational at that voltage, though)... > > If there is a CRC on a EPROM label, it may be very useful in > determining that your recovered image is really good. Some devices do > CRC check on startup and you can feel yourself safe enough if checksum > error is gone. > > Always keep your original EPROM chip intact and do not expose it to a > UV or sunlight (if there is no label that cover their window) until > you are completely sure that you have correct image on hand. Use spare > EPROM of same type for experiments. > > > BTW: Looks like it is a good idea to have images of EPROMS and > calibration EEPROMs (if any) for all equipment in a safe place. > > -- > Best regards, > Yuri, UA3ATQ/KI7XJ mailto:y...@ostry.ru > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.