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Old 25 January 2010, 21:08   #1
chiark
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CDTV problems - clock shows 3FFF, doesn't recognise

Hello all

I've got a CDTV, which is lovely and intriguing .

It came without CDTV PROMs, as the ex-owner had a devboard and wanted to keep the board. Understandably . Tahoe very (very) kindly sent me some 1.0 PROMs for it, and this has breathed some life into it.

It'll read and play CDTV disks (well the welcome disk that I've got). If I put an audio CD in, it doesn't bring up the "player".

It'll boot off a workbench 1.3 disk, and will mount the Welcome disk. If I put in an audio CD and type "info" from a CLI, I get no output...

So, questions!

- Is there a way to reset the NVRAM? (Or is that even needed?)
- Which chip has the RTC in it? (There's the clock in the CIA of course, but a secondary clock at DC0000-DC7FFF - what chip has that in it?)
- does the drive itself contain firmware, and is there any way to update that firmware? (I wonder if that's what is causing the problems with CDs)
- anyone seen anything like this before (3f ff)

Cheers,
nick.
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Old 25 January 2010, 22:00   #2
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OK, answering my own question from the schematics...
MSM6242B is a realtime clock, at u61.

Bit more of a clue: the clock doesn't save at all. Ever. Using the CDTV prefs screen to change the time, then re-entering the CDTV prefs screen, sees the time return to the default. Language changes do persist...

There's no battery in it, so it seems unlikely that it's leaked
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Old 26 January 2010, 00:05   #3
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It looks like it's broken for good. Send it to me! (I'd like to get my mitts on CDTV, always liked the look of them )
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Old 26 January 2010, 01:12   #4
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Other potential causes (not in any particular order)

X2/U61 (TOD clock IC), U57 (bidirectional transceiver), U60 (buffer), U50 (inverter), U74 (NOR), U80 (AND), U60 (buffer), U73 (OR), U12 (Gary), X4/U62 (clock display IC).
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Old 26 January 2010, 07:42   #5
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Thanks Shadowfire. Not wishing to sound a complete muppet, but is there an easy way to check the functions of those chips out? Looking at the schematics, they're all around the clock chip (I know that much) but I wouldn't know how to validate they're working other than doing the check to see if they get too hot

All connections look good, unfortunately. The variable capacitor looks like it might have leaked?

Last edited by chiark; 26 January 2010 at 15:34.
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Old 26 January 2010, 21:10   #6
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Variable capacitors don't leak!

But they can caught the fumes of a leaking battery.
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Old 27 January 2010, 09:13   #7
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Well, this variable cap had gunk all over it
And there's no battery in a CDTV
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Old 27 January 2010, 13:42   #8
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So, I started tracing. And I found that pin1 of u74 should be connected to Pin 8 of the clock chip (u61).

But it isn't.

There's a via under u75 that looks like this...


I don't think that's helping!
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Old 27 January 2010, 14:26   #9
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OK, I soldered a wire from pin1 U74 to pin8 U61, and the clock works

Now just to work out why the CDTV only plays the Welcome CD... Hmm!
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Old 27 January 2010, 16:49   #10
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Just given the other CD a damn (damn) good clean and it now plays.

I suspect that the laser is very picky on the discs it'll read...
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Old 28 January 2010, 16:59   #11
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Just disassembled it and gave the laser a clean.

WOOHOO! Plays anything!
(Thanks for the suggestion, FOL!)
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