[time-nuts] Restoration of a 5065A - Continued

Ulf Kylenfall ulf_r_k at yahoo.com
Wed Sep 13 16:03:24 EDT 2017

The second scrapped 5065 that I manage to acquire could perhaps be braughtback to life. I already have a supply of electrolytic capacitors but I have my doubtsabout the 1.33K resistor that is used in the RV TX assy. It maintains the original value, but the protective surface is gone.
Digi-Key sells a 1/2W 1K33; CMF1.33KHFCT-ND, but I suspect that this 1/2 W ratingis at 25C. The resistor used in the RV TX pcb is considerably larger.
Can someone tell me where to get them? Corby Dawson was kind enoughto supply me with "47 Ohms" of kanthal wire and a 1.33K resistor, but sinceI have "sort of started to collect 5065's", I cannot ask for such favors over and over...
The second question is about the RV Receiver in the unit that has beenrestored . The 2nd Harmonic level is so lowthat the repaired original instrument seems unable to maintain a lock. In the beginning of thelong-time test, the reading was steady at 30, and I was able to adjust theRV synthesizer/Magnetic field so that I had an absolute 0.0 degree phase shiftover more than 30 seconds when comparing the 5 MHz to one of our H-Masersusing a vector voltmeter.
The 709's in the A7 AC-Amplifier has been replaced with 741's (removed the frequency compensation networks) but added a 1nF capacitor between(+) and (-) input on the first amplifier, thus reducing some noise and instabilityon the output signal. The unit was then calibrated and it has beenadjusted according to HP service manual.
After re-insertion, the test instrument readings are about the same as beforethis modification. PhotoCurrent at 30, and 2nd Harmonic starting at about 10,increasing slowly during the on-time hours and is now 15
The unit lost the lock at about that level last week

The 137 Hz generator is at 136.87 Hz (varying by perhaps 0.25 Hz)
The PhotoCell was "formatted" using a hair dryer according to instructions.
Can I expect the 2nd Harmonic level to increase until the unit acheives lock or shall I remove the RV Photocell and put it in a temperature chamber?We have one at my work that can keep temperature quite accurately.
Or should I leave the instrument turned on and let it "sweat it out"?
Ulf Kylenfall

More information about the time-nuts mailing list