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8751A Test 20 1st IF offset oscillator test failed

Question asked by bembel on Aug 10, 2011
Latest reply on Jan 8, 2014 by goingplaces
Hi Everyone, I'm new to this forum.
The recent ownership of a 8751A VNA (and his lack of documentation) brought me here, especially after the reading of EB5AGV & Dr_joel's topic!
I had several problems on my unit, strarting by a dead vertical deflection IC in the dispay module, this IC has gone obsolete and I had to replace it by its cousin (a different TDA). Now it's OK and the display is a bit stretched (can't tweak this) but everything is sitting fine after 2 minutes warmup.
As a DIYer without money, I made myself (out of tin, connectors and resistors) a poor man's splitter, coupler and cal kit, in pursuit of a bargain official test set ...
Everything looks fine for now (I'm still learning to use this fabulous instrument) But during the internal self tests (after failed tests #21 RF osc freq & #40 output attenuator had gone after a whole cleanup)

I still get the error:
Test #20 1st IF offset oscillator test failed (6.27MHz)
Most probable cause of fail
assembly: A3 ref osc
conf: 100%

The A3 board seem in good shape, as do the connectors ... I am in the same situation as EB5AGV with his 8753 cousin, fearing in writing EEPROMS as I have no procedure to backup actual data. As I ain't got no servicing procedures at all! CAN A WISE MAN TELL ME WHY THE 8751A DOCUMENTATION IS SO SCARCE ??? only a maintenance manual and no service manual, no schematics, no nothing !?!

Then my first questions are:
Is there a way to backup the actual eeprom data ?
Does anyone (DR_Joel are you here?) know a procedure to recalibrate the 1st IF offset oscillator please!
Does a service manual exists ? (is the option 915 the service or the maintenance manual?)

Thanks and best regards,


PS: Excuse my poor english please, I'm a batrachian...