Electronics > Repair

HP 1744A analog storage oscilloscope - repair thread

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c4757p:
I don't have much to post tonight, but I'm off from school tomorrow and will spend some time with this.

Just got an old HP 1744A for repair. Doesn't power on.

Hmm... looks like this one's had a rough life. Filth, rust, and what's this on the inside? Dead spiders, dead insects, and a (thank god!) vacant mouse nest. Bastard chewed a hole in the fan dust cover and crawled right in.

It's been exposed to quite a bit of moisture already, so I cleaned it out in the sink. This washed off some of the Aquadag coat on the exterior of the CRT, but it was already flaking and needs to be reapplied. Not a problem. As far as I can see, the tube hasn't been cracked, though I haven't had it all the way out yet. The mount is broken... will have to find a way to replace it. I doubt epoxy will be strong enough to repair the existing one.

I'll take more, better pictures as I take it apart piece by piece. These storage scopes are getting pretty rare - I am not going to risk powering it on until I've inspected every board.

dr.diesel:
Ahhhh, old equipment porn, be back in 5 minutes....

c4757p:
More like Floridian spider porn... :scared:

This thing was truly horrifying on the inside. Shame people treat their equipment like this...

I'm really hoping the CRT didn't suffer any damage from the broken mount. The ass I bought it from packed it about as well as you'd pack a football... I couldn't figure out how to remove the CRT though, and didn't want to mess with it since they're pretty much irreplaceable. I'll read the service manual before trying to get it out.

I have a slight suspicion that the only reason it wouldn't power up is a slightly misaligned power button.

edpalmer42:
I have a 1744A sitting on my bench that was manufactured in 1983.  Since it just keeps on working, I haven't been able to talk myself into buying a digital scope.  Mind you, the fan is getting a little noisy.........

Ed

Kilroy:
Do be carefull of that storage CRT...it is a very special tube. Too bad the scope looks so neglected because it is a very capable 100Mhz instrument. If it offers you any hope at all, I have seen some scopes that looked like they were thrown out of a moving vehicle and the tubes were fine, amazingly.

Incidently...the 1744A is basically a 1741A, sharing the same 100Mhz bandwidth but having a more sophisticated storage CRT. HP called it an "expansion storage" CRT. It used a small, high presicion storage mesh combined with an electronic lens to magnify and projected the image. And it was really quick...a write speed of 1800cm/uS.


I have a 1727A which has an even faster expansion storage CRT at a write speed of 2000cm/uS. It uses an improved CRT based on the 1744A tube but with added high speed vertical plates to match its high bandwidth 275Mhz amplifiers. This 1727A CRT is a beautiful piece of engineering...using transmission line type deflection plates which, to the vertical amplifier, appear as a resistive rather than a capacitive load.

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