Philips PM9690 xtal oven schematic/manual? - UK Vintage Radio Repair and Restoration Discussion Forum

dinkydi · 28th Nov 2011, 4:35 am

Does anyone know of the whereabouts of a schematic or manual for the Philips PM9690 "ovenised" 10MHz crystal. This crystal reference was a common option with many Philips frequency meters/counters.

I have repaired a number of these references using a rough circuit I have drawn out (the most common fault is, surprise surprise, blown tantalums) but I now have a unit with a more complex fault - the oscillation amplitude is unstable and after 10 minutes oscillation stops altogether.

A schematic/manual would be of great help because it would minimise my time poking around in the fragile circuitry of the oven "inner sanctum".

Peter

WME_bill · 28th Nov 2011, 9:27 pm

Philips PM9690 oven reference oscillator. For PM6611 to PM6615 timers/counters. The attached, taken from the Timer counter manual may give you some ideas. Presumably the fault lies with the oscillator itself. If the oven control, then that would presumably cause a slower cycling effect, affecting the stability, but not the ability to oscillate. Have you tried it with without the oven in use. I suppose the power transistor mounted on the case controls the heater, or is the heater. You will note the challenging comment - PM9690 is factory repair only. Let us know how you get on with the challenge. Bill m0wpn

dinkydi · 29th Nov 2011, 9:07 am

Thanks Bill for your thoughts and pdf posting. The other counters that offer the PM9690 option have similar oscillator write-ups in their manuals. However, the design of the PM9690 actually changed over time.

In Bill's pdf the photograph shows a PM9690 with components on a board external to the oven box housing. In later designs the housing is bigger and encloses all components, including the board - this is the type I am presently working on.

One has to question whether enclosing tantalums in a box that operates at considerably elevated temperature can be good for reliable long-term performance.

The PM9690 part number in Bill's pdf is 9446 096 900.1, while my unit has a part number 9446 096 90011 and I would not be surprised if there were other designs and part numbers in existence.

Peter

28th Nov 2011, 4:35 am	#1
dinkydi Retired Dormant Member Join Date: Feb 2011 Location: Sydney, Australia Posts: 277	Philips PM9690 xtal oven schematic/manual? Does anyone know of the whereabouts of a schematic or manual for the Philips PM9690 "ovenised" 10MHz crystal. This crystal reference was a common option with many Philips frequency meters/counters. I have repaired a number of these references using a rough circuit I have drawn out (the most common fault is, surprise surprise, blown tantalums) but I now have a unit with a more complex fault - the oscillation amplitude is unstable and after 10 minutes oscillation stops altogether. A schematic/manual would be of great help because it would minimise my time poking around in the fragile circuitry of the oven "inner sanctum". Peter

29th Nov 2011, 9:07 am	#3
dinkydi Retired Dormant Member Join Date: Feb 2011 Location: Sydney, Australia Posts: 277	Re: Philips PM9690 xtal oven schematic/manual? Thanks Bill for your thoughts and pdf posting. The other counters that offer the PM9690 option have similar oscillator write-ups in their manuals. However, the design of the PM9690 actually changed over time. In Bill's pdf the photograph shows a PM9690 with components on a board external to the oven box housing. In later designs the housing is bigger and encloses all components, including the board - this is the type I am presently working on. One has to question whether enclosing tantalums in a box that operates at considerably elevated temperature can be good for reliable long-term performance. The PM9690 part number in Bill's pdf is 9446 096 900.1, while my unit has a part number 9446 096 90011 and I would not be surprised if there were other designs and part numbers in existence. Peter