[time-nuts] SRS PRS10 repair

Mike Cook michael.cook at sfr.fr
Sat Aug 22 12:38:28 EDT 2015


> Le 22 août 2015 à 03:40, Bob Camp <kb8tq at n1k.org> a écrit :
> 
> Hi
> 
> On any microprocessor based gizmo, getting the micro running (again) is 
> generally priority number one. It sets everything up and gives you the diagnostic 
> info you need to go further. Garbled serial is better than none at all. It suggests
> something short of a total MCU death spiral …
> 
> Bob
> 
>> On Aug 21, 2015, at 7:26 PM, Brian M <brayniac at gmail.com> wrote:
>> 
>> Dear list -
>> 
>> I have come into possession of a for parts prs 10. I'd like to try to
>> repair this device. What I've noticed so far. Serial is garbled. (Even at
>> varying baud rates).

 You don’t say how you are connecting to the Rb. The manual states:
"RS-232 data is sent to the host on pin 4, received from the host on pin 7. The baud rate is
fixed at 9600 baud, 8 bits, no parity, with 1 start and 1 stop bit. No DTR or CTS controls are
used; rather, the XON/XOFF protocol has been implemented. The transmit drive level is 0
and 5 V, not the +/-12 V normally associated with RS-232. These levels are compatible with
most RS-232 line receivers, but does not require their use (a TTL inverter may be used
instead), hence simplifies the interface when used inside an instrument at the sacrifice of
degraded noise immunity over long lines."

So make sure that you adhere to that.


>> Lamp isn't lit.

What’s the date code. Early versions may be reaching EOL, though 20yrs id quoted. 

>> Doesn't look great. I'd like to know
>> if anybody else has wandered down this path. What are common failure modes?
>> Anything match up with what I describe? Voltages to check would be helpful.
>> The 10MHz out looked okay on a scope. Haven't gone further yet. I suspect
>> the crystal is fine.
>> 
>> Thanks in advance. Happy hacking!
>> - Brian
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