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Want to buy 495P v9.7 EPROMs which are installed on the A54 memory board. P/Ns 160-8316-00 and 160-8315-00. Or, complete working A54 board with these EPROMs installed.

RIck
K8EZB

On Wed, 25 Jul 2018, Rick Boswell wrote:

Want to buy 495P v9.7 EPROMs which are installed on the A54 memory board.
P/Ns 160-8316-00 and 160-8315-00.

There are 9 EPROMs in v9.7 firmware in 494AP that should be the same as you
have. They are part numbers 160-8315-00 to 160-8323-00. First 2 are on that
memory board, rest is on GPIB board. I have all firmware images and can send
'em to you so you would be able to program your own chips.

There is another thing -- it is _NOT_ just those switches that tell the
firmware what instrument it runs on. There is also another MCU on the front
panel that runs its own firmware. Main instrument firmware asks the front
panel MCU about hardware version and that is taken into consideration when
deciding what hardware it runs on. For example, 494AP and 2756P have EXACTLY
SAME switches configuration and main firmware decides what it runs on based
on what front panel controller told. 494AP and 2756P are identical inside
just case and front panel is different. 2756P has full-blown 494AP chassis
inside sans front panel and its own front panel. Part of the case not
occupied by 494AP chassis is simply empty. If you remove that chassis and
install a 494AP front panel on it the thing will tell you it is 494AP and
will happily run as 494AP without flipping a single switch.

And BTW, did you replace _ALL_ electrolytic caps in the power supply except
those 2 big ones protruding through its cover? If you didn't start with this
first -- it is almost 100% probability that most (if not all) of those
capacitors are dead and your instrument just acts erratically.

There is absolutely no reason to even start doing anything on any part of
the instrument until you have the power supply refurbished.

You should also make sure the fan is working properly -- unlike some other
instruments in 49x it is CRITICAL. If it doesn't work your PS will overheat
in almost no time.

---
*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*

Sergey,

Thanks for your detailed post. I am new to SA's in general and to the 495P specifically but am learning. I have spent considerable time with the two-volume service manual (700+ pages) as well as reviewing various online resources such John Miles notes, the KO4BB website, and others. Some responses & questions re your comments:

Firmware: I am familiar with the physical distribution of the firmware on the A54 memory board, GPIB board, and front panel. Thanks for your offer to provide images to allow me to program the EPROMs I am looking for. At present, I don't have the devices or programmer to do this, and since my need is almost certain to be a one-time need, I'd like to avoid programming my own EPROMs if I can purchase what I need. I am also familiar with the front panel MCU. I own two 495Ps, one of which I purchased in essentially new condition and which works well. Along with this one I received a "parts" 495P which I find works as it should if I simply install a known good A54 memory board which has v9.7 EPROMs installed.. It boots up as a 495P, indicates v9.7 firmware is installed and v1.1 firmware on the front panel processor. So, it would seem that my issues are a result of a defective A54 memory board. I have obtained an A54 memory board from an older 494 unit with v9.0 firmware, and am looking for the v9.7 EPROMs to update this board. I have compared the 494 and 495 memory boards visually and via the parts lists and circuit diagrams in the service manuals and see no meaningful difference. I have moved the v9.7 EPROMs from a good A54 board to the 494 board and installed this in the non-working 495P and it works as expected.



Power supply: As far as I have investigated to date, the power supplies in both 495Ps are working as they should. IOW, I am able to step through the initial checkout section of the service manual and get the results specified in the manual. The capacitors have apparently not yet failed, or may have been replaced by previous owners. Since this has not been an issue yet, I haven't looked carefully to see if these might have been replaced. I see no anomalies in operation which would suggest a power supply problem, but I am still early in the checkout/repair process.


Fan: Not sure yet how to determine if the fan is working properly. For sure, It is turning and moving air. The top of the case gets mildly warm to the touch after several hours of operation, but this doesn't doesn't seem excessive given how much is going on inside this jam packed case. Is there a way to determine if the fan is working as designed? I know it is turning but don't know if it is moving the amount of air it was designed to do. The fan runs quietly, so no apparent mechanical issues.

Thanks,

Rick
K8EZB

On Wed, 25 Jul 2018, Rick Boswell wrote:

[Edited Message Follows]

Sergey,

Thanks for your detailed post. I am new to SA's in general and to the 495P
specifically but am learning. I have spent considerable time with the
two-volume service manual (700+ pages) as well as reviewing various online
resources such John Miles notes, the KO4BB website, and others. Some
responses & questions re your comments:

Firmware: I am familiar with the physical distribution of the firmware on
the A54 memory board, GPIB board, and front panel. Thanks for your offer
to provide images to allow me to program the EPROMs I am looking for. At
present, I don't have the devices or programmer to do this, and since my
need is almost certain to be a one-time need, I'd like to avoid
programming my own EPROMs if I can purchase what I need. I am also

I can program and send you those 2 chips, no problems. Just send me your
address off list to ksi at koi8 dot net.

No need to pay anything assuming you are in the US so it would make it with
domestic First Class package. I have lot of 27256 chips here and it takes
just couple of minutes to program 2 chips.

---
*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*

Wow! You da man! Thanks!

RB