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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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."

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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.).

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IIRC, EPROMs (i.e. the chips that can be erased with UV light) don't require battery backup. RAM will, though.
Why weren't EEPROMs or flash memory used? They would have been available when the things were designed (in the 1990s/early 2000s)...
Recently, I picked up one of these radios (GPR4401A) fairly cheaply at a radio rally. A fellow enthusiast in the vicinity remembered using them when working for Motorola, and told me that it was well worth what I paid for it.
We discovered that there was still charge in the battery - noise poured from the speaker when the set was switched, on indicating that - at the very least - the demodulator, amp and transducer were functioning. He told me that the charger was connected
via the 15-pin D-Sub connector. An odd choice, given that the connector was designed for signals rather than power! Pinouts and charger details would be most welcome (I don't have a manual, and the Wayback Machine gives me the impression that Chase never
got round to setting up a website!)
The most significant problem, though, is a blank LCD - somewhat inconvenient, as the radio is menu-driven. I gather this wasn't an uncommon issue. Any ideas here, as to a fix? The unavailability of schematics (I doubt they didn't exist, at least
internally, for such a complex product) or a service manual didn't help.
As regards the possibility of corrupted memory, might it be possible to read the data from the chip (if it's in a set that still works) and stored as a 'backup file'?

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At the factory we ran a calibration program. This stepped the receiver every few mega hertz in sync with an accurate sig gen. The receivers internal broadband noise source way turned on every time the receiver was stepped and the resultant receiver
output was measured. Any descrepency with the sig gen level at each frequency was stored in rom so it could be added or subtracted to the sig level measurement. I think it is the rom info that gets corrupted over time as the receivers tend to work in
all other respects. Bit of a bugger. If I had known people would be using them for home use I would have included a manual cal bypass switch.

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Any details, as to the charger requirements and connector pinout, would be most welcome!

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