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Tektronix 180A & 181 Time Marker

July 8, 2011

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:

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  1. Would like to share that I am presently restoring a circa 1958 Type 180A with much success. I’m totally thrilled to find, unadjusted, that the higher frequency time markers are nearly spot on and that’s with testing against a rubidium oscillator for reference in my HP reciprocal counter. For example, the 1uSec marker has a period of 1.000,009 x10-6. Same for the 1mSec marker at 1.000,009 x 10-3. As expected, the slower markers from 5mSec through 1Sec need some adjustment since I replaced the ‘bumble-bee’ paper timing capacitors. I don’t expect adjusting these will be much of a problem.

    What I’d also like to share is, like your unit, I discovered a rare unsoldered joint. The unit was producing a 5Mhz sine wave but no 10Mhz or 50Mhz sine wave. I observed that tube V134 was not heating (lighting) up. Since the circuits are cascaded, it made sense why no 50mhz was coming from V144. That led me to discover that one side of the 6.3v heater supply was not soldered to pin#3 in V134 (the 10Mhz oscillator). This is a long solid bus wire that connects from V173 through the pin#3 tab at V134 and onto pin#3 for V144. While soldered at the ends, the bus was not soldered as it passed V134. Problem solved.

    I’m always inspired by your efforts to recover and document great old test equipment. I think I am not alone is saying that. This is an activity I and many others very much enjoy.

    Best regards,

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  1. Tektronix 181 Time Mark Generator repair | Buttons, Switches, Knobs & Lights

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