As some of you may know, I recently received a box of valve manuals and so on. Included was a Dick Smith 200 MHz frequency counter, that looks like it might have been a kit from EA. It wasn't working, so I thought I'd see if it could be easily repaired.

There was no activity at all, so the best place to start is the power supply. The fuse was intact, as was the A&R transformer and the diode bridge. But there was nothing after the 7805 voltage regulator. I removed this, and as I did so I thought I saw a bad joint on the 12 volt side. I put the regulator under a load test and it could only make 4.75 volts. With a 100 ohm resistor as a load it was down to 4.5 volts.

I dug out a LM340T5 to use as a replacement - with the 100 ohm resistor it produced 5.03 volts. Much better. So I installed it, and replaced the puny little heatsink with one twice the size.

Power on - the digits all lit up showing 0, with an occasional flicker to other numbers. I didn't have a frequency source handy, but it looks like it might be working now.

Easy job using basic principles.

Good job.

I didn't have a frequency source handy

50 Hz?

Hi Robbbert,

My Counter had a 'blown' input circuit ... check the input sensitivity eg min 10mV, max 1V. Good idea to put a couple of diodes across the input if possible to clamp the input voltages.
You could use a couple of turns of wire to inductively couple to one of your radio oscillator or IF frequencies etc ... but be careful not to make any direct connections. Mains 50Hz maybe too low; the Counter specs should include the Range of frequencies.
If no Specs sheet, then a Signal or Function Generator can be used to determine both the Input sensitivity and Frequency range.
.... you probably know this already ...

Cheers, Ian

If that's the one from the late 70's? Buried in my chaos system is the manual. That early one has serious issues on the HF range.

If you have a Coms radio you have a frequency reference. WWVH, & WWV, are still operating.

https://tf.nist.gov/stations/wwvh.htm

You need to know how to "zero beat" aka Heterodyne and you need to hook the counter to the sig gen capable of generating a listed frequency.

You zero beat against their frequency & set the counter to it & realise how some Signal Generator are. Do note modulation on the Sig Gen should be off. This should be more than adequate to set old radios.

If you grew up in BW TV days where some goose synchronised them to the mains. Synchronisation and Frequency was at the mercy of the Alternators, which wandered by lead & lag as the load changed. Causing the picture to roll.

Marc