🚀 go-pugleaf

In article <8901011415.AA07578@MATH.Tau.Ac.IL> <finkel%TAURUS.BITNET@CUNYVM.CUNY.EDU> writes:
> Help!
> 
> The clock module of my A501 has stopped functioning.
...
> Battery Backed up clock not found
....
> I tried using the 'setclock opt reset' but it didn't help.
> 
> I opened my A501 unit. The Battery output is 4.12V, and according to
> the schematics it should to be 4.5V. Is this the problem?
> According to the schematics, the battery is also supposed to be NiCad.
> Is it charging while the machine is on? Also, The RAM on the module
> works OK. Only the clock stopped working. What can I do?
> What output should I expect on the test point TP3 on the A501 board?
> I'm an EE student, and I'd like to try and fix it by myself. What is the
> cost of a new 6242 chip? ( If this is the problem )

The voltage you mention is probably OK if measured at the clock chip,
it's a little bit suspect if measured at the battery.  You should check
that the battery is charging when the machine is powered up - it is
trickle charged through a resistor.

The test point is connected to the test pulse pin on the clock chip.
You get out different signals depending on how the output has been
programmed.  If is really intended for setting the frequency.

The place I would look is on the leads of the crystal, with a scope
you should see a 32 KHz waveform on both of them, though it may decay
when you hit it with the scope probe.  If you don't see that, and there
is power at the chip, then either the crystal is broken internally or
the chip is bad.

I guess it would also be possible to have a problem with the main board
such that the clock read/write commands are not getting to the clock/
memory board.  Maybe the first thing to check would be that whether your
A501 works in somebody elses system and whether yours works elsewhere.



-- 
George Robbins - now working for,	uucp: {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@uunet.uu.net
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)