[time-nuts] 10811 warmup (Jason Rabel)
Jason Rabel
jason at extremeoverclocking.com
Sun Jan 21 21:35:56 UTC 2007
Thanks Bruce,
I think we have gotten a little off-subject here... My issue is not with the
oven, but the oscillator circuit itself. I'm not getting any signal on pin
1.
I removed the assembly from the insulation easy enough, I haven't gotten any
further yet, been troubleshooting my shera board today. I don't hear
anything rattling inside so I don't think the crystal is physically broken
like Chris mentioned.
Jason
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Dr Bruce Griffiths
Sent: Sunday, January 21, 2007 3:28 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 10811 warmup (Jason Rabel)
Jason
As long as the thermistor is still within the oven mass and the
temperature regulation circuit is functioning OK, the oven should
actually be OK.
However the temperature control loop may oscillate as the thermal time
constant for which it has been compensated has been drastically
decreased by removing the insulation from the oven mass.
If the oscillation amplitude is sufficient it is conceivable that some
damage due to excessive temperature may occur.
However, the dissipation of the oven heater transistors is limited by
the control circuit so the temperatures reached may not be high enough
to damage components.
The turn on current limit circuit limits the heater transistor emitter
current to about 0.52A with a 24V heater supply, limiting the maximum
dissipation in the heater transistors to about 12.5W with a 24V heater
supply, which is probably insufficient for the inner oven mass to get
very hot once the insulation is removed.
The principal problem is personal burn injury .
Bruce
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