Looks like these threads are years old so this will probably never be read! I designed the receiver. There is no service manual, unless one was done after I left the company. The receiver was calibrated automatically by computer over the rs 232 port before the units were shipped. The calibration points were stored in eprom. Depending on the year of manufacture there was a backup battery or 1 farad cap as backup. As the original spec was 10 years receiver life most receivers have now probably died. The cal software ran on a BBC micro. Any programming info is long gone.

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For full context, visit https://www.electrondepot.com/repair/chase-gpr4403-laboratory-receiver-service-manual-please-29513-.htm

On 2023/07/06 2:30 p.m., Tony wrote:
> Looks like these threads are years old so this will probably never be
> read! I designed the receiver. There is no service manual, unless one
> was done after I left the company. The receiver was calibrated
> automatically by computer over the rs 232 port before the units were
> shipped. The calibration points were stored in eprom. Depending on the
> year of manufacture there was a backup battery or 1 farad cap as backup.
> As the original spec was 10 years receiver life most receivers have now
> probably died. The cal software ran on a BBC micro. Any programming info
> is long gone.
>

Talk about planned obsolescence!

So the receiver calibration might change over time and there is
absolutely no way to fix this as there is no calibration program left
anywhere. I/m assuming if anything was changed in the receiver that it
would then need calibration...

And people wonder why I like fixing electronic toys prior to the 2000s!
Stuff after 2000 is not nearly as fixable - too many one-off or customer
parts.

Then there is the question of who owns the device they bought. As an
example one brand of pinball games shuts the game down if it is operated
on 50 or 60 Hertz and that is different than the line frequency
(60/50Hz) that the game was originally set up for.

John :-#(#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Thursday, July 6, 2023 at 7:05:47 PM UTC-4, John Robertson wrote:
> On 2023/07/06 2:30 p.m., Tony wrote:
> > Looks like these threads are years old so this will probably never be
> > read! I designed the receiver. There is no service manual, unless one
> > was done after I left the company. The receiver was calibrated
> > automatically by computer over the rs 232 port before the units were
> > shipped. The calibration points were stored in eprom. Depending on the
> > year of manufacture there was a backup battery or 1 farad cap as backup..
> > As the original spec was 10 years receiver life most receivers have now
> > probably died. The cal software ran on a BBC micro. Any programming info
> > is long gone.
> >
> Talk about planned obsolescence!
>
> So the receiver calibration might change over time and there is
> absolutely no way to fix this as there is no calibration program left
> anywhere. I/m assuming if anything was changed in the receiver that it
> would then need calibration...
>
> And people wonder why I like fixing electronic toys prior to the 2000s!
> Stuff after 2000 is not nearly as fixable - too many one-off or customer
> parts.
>
> Then there is the question of who owns the device they bought. As an
> example one brand of pinball games shuts the game down if it is operated
> on 50 or 60 Hertz and that is different than the line frequency
> (60/50Hz) that the game was originally set up for.
>
> John :-#(#
> --
> (Please post followups or tech inquiries to the USENET newsgroup)
> John's Jukes Ltd.
> #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
> (604)872-5757 (Pinballs, Jukes, Video Games)
> www.flippers.com
> "Old pinballers never die, they just flip out."

This makes me wonder if this end state of calibration data vanishing after xx years was a design requirement (specified by who?) or a byproduct of the design approach taken (to increase machine flexibility? reduce parts count? etc.).