I recently picked up a very old (~1962) HP 104AR oscillator. After replacing three bad Tantalum capacitors, it's working fine. The frequency is a few PPM low, but I'll leave it for a month or two before I try to adjust it. ADEV is measuring < 5e-11 from 2 to > 2000 sec. as compared to an "RMS Deviation" spec of 5e-11 for 1 and 10 seconds. After less than a day of operation there's really no point in talking about aging, but it looks like the 5e-10/day spec isn't out of reach.

Of course, I have questions.....

1. Does anyone have a soft copy of the manual for the 104AR? I have the 103AR manual so I'm not flying totally blind. I know that there's a copy on the auction site, but the price is ridiculous.

2. During warmup, the readings for both ovens on the Circuit Check meter 'hunt' up and down with a period of ~126 seconds. Initially, the Outer Oven hunts over half of the meter scale! The oscillation slowly fades away over a few hours. Is this normal? I've checked all the capacitors on the oven controller board for value and ESR and replaced three. I also checked all the resistors for value and all were okay. Once everything settles down, all the readings are in the acceptable range.

3. All the photos I've been able to find for the 103AR and the 104AR show a grey faceplate with black lettering. Mine has a black faceplate with white lettering. Is there any significance to the color?


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