[time-nuts] Agilent 53132A Needs Help

[tomknox at nist.gov]

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
tomknox at nist.gov



Quoting "Yuri Ostry" <yuri at 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:yuri at ostry.ru
>
>
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