[time-nuts] Noisy Sulzer 2.5 - Suggestions?

[Ed Palmer]

On 2016-08-18 10:00 AM, paul swed <paulswedb at gmail.com> wrote:
> Ed,
> Thats quite the challenge and yes the carbon resistors must be about 50
> years old now. So questioning them is reasonable. I have a c so take my
> next comment with caution.
> The oscillator is a small circuit and then it runs to buffers and
> multipliers and stuff.

That's one of the differences between the 2.5 and the 2.5x models. The 
2.5 only has 2.5 MHz and lower outputs so no multipliers. Hopefully, the 
other circuit blocks are more or less the same.

> Lots of parts of every type. Maybe it makes sense to isolate and measure
> just the oscillator circuit to see how it behaves without all of the other
> stuff. Also there were various regulators in that can.

Yes, noise on the internal voltage regulator would affect everything.  I 
might replace all the Ta capacitors 'just because', but beyond that, 
divide and conquer makes a lot of sense.

Ed

> Lots of possibilities for trouble. But also worth the effort to figure it out.
> Great old oscillators.
> Regards
> Paul
> WB8TSL
>
>
> On Wed, Aug 17, 2016 at 4:25 PM, Ed Palmer<ed_palmer at sasktel.net>  wrote:
>
>> >I picked up a Sulzer 2.5 (not 2.5A or 2.5B or 2.5C) oscillator and 5P
>> >power supply.  It's working, but the AlDev at low tau is poor. After a few
>> >days of operation the AlDev @ 1sec. is only 1e-10.  It's not the power
>> >supply.  I'm running under 'AC fail' conditions with a lab power supply
>> >standing in for the batteries.  This bypasses almost everything in the
>> >power supply.  Eventually, I plan to replace the batteries with lead-acid
>> >and replace the circuit board with an improved circuit.
>> >
>> >So, I'll be opening up the oscillator to see what's what.  My first 'usual
>> >suspect' will be the Ta capacitors, but I'm wondering about all those
>> >carbon composition resistors.  Should I be looking at a wholesale
>> >replacement with metal film?  Maybe just in the oscillator and AVC areas?
>> >Are there any other known trouble spots with these oscillators?
>> >
>> >I haven't been able to find any info on the 2.5.  The manuals and
>> >schematics for the 5A and the 2.5B/C are some help, but the 2.5 is very
>> >different from the 2.5B/C.  Any info would be greatly appreciated.
>> >
>> >Thanks,
>> >
>> >Ed