Tektronix 180A & 181 Time Marker

I acquired this 180A time mark generator new-old-stock. In fact, it was not working and through careful examination, I located a joint that had never been soldered. I imagine that when it was new, the joint conducted well and so it would have passed the factory acceptance testing. An unsoldered joint is extremely atypical for Tektronix. Here it is showing 10 & 50μS markers.

It uses an oven stabilised crystal oscillator providing sine outputs at  50, 10 & 5 MHz and markers in half-decade ranges of 1μS through 5S, also trigger impulses in decades from 10μS (100kHz) to 1S (1Hz), useful for accurately triggering pretty much anything.

It is a crystal palace, 52 valves, all NOS. Again and as always, hands OFF audiophiles.

It is extremely useful to me in re-calibrating my scope collection. Here, I have attempted to capture the glow….

Here is a much older time marker, the 181;

Not quite so many valves as the 180A! This one does not have the crystal oven option. I inverted the image so that the valve legends are the right way up:

The reason the 6X4 rectifier is missing is that it was near the end of it’s life and sometimes the B+ would come up too far ahead of the bias supply resulting in the B+ rectifier arcing and a blown fuse. I simply replaced the bias rectifier with two UF 4007s, end of problem. In equipment I design, I always use silicon for the bias supplies to ensure that the bias is present before the B+.

If you look closely, you may spot that amongst other things, the 100μS divider capacitor is new. The 100μS divider would fail a few minutes after switch on, taking all the slower dividers with it and would not lock into time reliably in any case. I often find leaky silver mica caps in trigger and timing multi-vibrators, they tend to be intermittent and can be a pain to find so if you have a time base that runs intermittently or a trigger that is not solid, check the silver mica cap.

And here they are displayed, the 181 at 100μS/div and the 180A at 500μS.div: