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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 6th Mar 2021, 6:48 pm   #1
Linnovice
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Default Revox PR99 display problems

Hi all. I'm in the process of refurbishing my PR99 MkII. It's not a shotgun project, I'm only doing one board at a time and then testing. My knowledge is limited but growing (hopefully) but I've hit a problem.
I started by completely overhauling the transport system. Brakes, motor run caps, and transport control board. All fine. Yesterday I recapped the power supply, it made sense while I had the transport control board out. Put it all back together and tested. All good except I've lost the locator display. All the buttors work ok (well they seem to, I can't guarantee as I can't see the display). Everything else works fine also so, I'm a bit flummuxed. I haven't touched the locator board, other than to take the front panel off which only involves taking out a multipin plug. Is it just a coincidence or am I missing something blindingly obvious? Either way any suggestions would be most welcome.
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Old 6th Mar 2021, 9:03 pm   #2
DMcMahon
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Default Re: Revox PR99 display problems

Not familiar with this at all, it looks a great and complex machine.

Nothing blindingly obvious to me but may not be co-incidence, maybe the act of removing the front panel has disturbed a bad connection at the Locator board.

I assume the Locator board is the "Locator Command" which houses the 7 segment LED displays for the tape counter displays.

If all 6 displays are off then would suggest something common. First thing I would do (if practical to access and monitor) is check the +5V (pin 18), 0V (pin 9) and clock signal (pin 13) at the MC14499 (IC1 & IC2) Decoder/Driver chips for the 7 segment displays.

Looks like these connections are derived from the Locator MPU board.

David
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Old 9th Mar 2021, 5:28 am   #3
Linnovice
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Default Re: Revox PR99 display problems

[QUOTE
Nothing blindingly obvious to me but may not be co-incidence, maybe the act of removing the front panel has disturbed a bad connection at the Locator board.

Looks like these connections are derived from the Locator MPU board.

David[/QUOTE]

Right in one David. The locator board is connected via a multipin plug/socket. The 5V+ pin was loose in the plug and was not making contact.
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Old 9th Mar 2021, 2:39 pm   #4
DMcMahon
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Default Re: Revox PR99 display problems

That is good, well done.

David
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