[time-nuts] repairing an HP 5248M crystal oscillator

Dave Brown tractorb at ihug.co.nz
Mon Dec 8 14:23:57 EST 2008

If the oven in the M version of the 5245 and the 5248 is the same then 
I have some notes here re pulling it apart etc. I have a 5245M and had 
to replace a buffer amp transistor in the oven some years ago.  The 
series regulator in the 'always on' power supply failed short and took 
it out - like the good little fast three legged fuse that it was.....
 I recommend that over voltage protection be added and a more rugged 
regulator pass transistor be fitted to the power supply while you have 
it on the bench, just in case. The 5248 supply may have these matters 
attended to- not sure.

DaveB, NZ

----- Original Message ----- 
From: "Dave M" <masondg44 at comcast.net>
To: <time-nuts at febo.com>
Sent: Tuesday, December 09, 2008 6:04 AM
Subject: Re: [time-nuts] repairing an HP 5248M crystal oscillator

> You can get an excellent PDF copy of the 5245M manual from Artek 
> (http://artekmed.startlogic.com/page3.html) for only $10 US.  They 
> do good work there.
> -- 
> Dave M
> Life is like a roll of toilet paper; the closer it gets to the end, 
> the faster it goes.
>  The oven on a 5248M is not working properly. I have the schematics 
> for
>  48L however not the M. Does anyone have a schematic for an M model? 
> The
>  oven light comes on and dims, however the instrument appears to be
>  temperature sensitive. I believe this is a double oven unit.
>  Thanks, Dan
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