advantest r3131a master oscilator calibration

[cncjerry]

I have had the subject spectrum analyzer for a year, works well, came with the tracking generator, but my WWV testing confirms the master oscillator is off 180hz at 10Mhz.  I've tested it against other sources as well.  I isolated the WWV carrier with a crystal filter then measured it with the analyzer's counter.  I also brought the resulting signal out using the tracking generator while the unit wasn't triggered and measured it with a known counter.  In both cases the delta was 182hz.  I have a way to feed it an accurate 10Mhz signal in the back, so I can get around the problem, but it annoys me.  I also used an A/B function in a Tektronix counter and that gave me the same delta.  The offset is less as the measured signal drops.

I tried pulling it apart, was able to get the back cover off, but there must be a trick to disassembling it further.  I thought if I got it apart I would find the 30Mhz master oscillator and give it a tweak but can't even get that far.  Sounds like I must be pretty lame but I can assure you I am good at puzzles. Taking the back cover off just exposes a ton of sheet metal;  the front bezel comes right off but there I am stuck.  It seems like the wrap-around casing should slide off the front maybe but it won't budge.

Anyway, if someone has experiences with this unit, please pass along the secret.
 
Thanks.

Jerry   

[HighVoltage]

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