Just to follow up, I resolved this problem. The HF (1 MHz steps) VCO was intermittent. It was a subtle problem and, being intermittent, took a while to find. The VCO tuner board runs on +11V and -35V. It outputs about 0 to -20V to the VCO which, in turn, ranges from 1200 to 2199 MHz. My problem was ...

The HF phase lock loop on IFR 1000's seem to have a high failure rate. This is the PLL that moves in 1 MHz steps and lights the left frequency lock light on the front panel. You will often see these IFRs on ebay with that particular light out. Mine is out now and I'm guessing that this is a somewhat...

I'm restoring an IFR-1000A and I need a small knob for it.
Anybody have one?
Thanks.

I did a little searching on the Internet.
It appears a good charging voltage for a 12 volt lead-acid battery is from 12.9 to 14.1 volts.
Less than this won't charge. More than this can cause outgassing.

At what voltage should the IFR 1000A battery charger voltage be set?
The service manual does not appear to specify this adjustment.
It is controlled by variable resistor R5123 on the "Duty Cycle Reg. & Batt Charger" board.

Not sure which battery the IFR 1200S uses but here is the battery for the IFR 1000, 1000A and 1000S:
https://www.osibatteries.com/p-900-hawk ... yrene.aspx

WWV works perfectly because the IFR time base is 10 MHz -- one of the WWV frequencies. I can receive both signals at once, listen to the beat frequency and dial in my oscillator to the exact right frequency.

Some replacement 7404 ICs arrived today so I replaced the suspect 7404 in my OSC/OVEN circuit. With the new chip, the oscillator was working. My scope showed the signal still looked kind of weak so I adjusted the variable capacitor and the signal got strong! Much stronger than before. I put it all t...

That's a good idea I hadn't considered but it would take a little engineering to get it in there. After some more experimenting, I've found that the 7404 driver(/inverter) IC is extremely temperature sensitive. Just a drop or two of freeze spray on that component immediately revives the oscillator. ...

Here is the schematic.

I have an IFR 1000A radio test set that intermittently stops working. When this happens, the PLL lock lights go off. I tracked the problem down to the 10HMz Oven and Osc. unit. I opened the unit up but, inside, it gets a little hairy. The crystal is in a three-transistor circuit which is kept temper...