Oscilloscopes

[jdhurst]

I wanted to branch this out of "Stuff that lasts".

I have the following working oscilloscopes:
1. A Tektronix 455A2B2 50Mhz dual trace "portable" scope that I purchased new in 1978. Still works fine.
2. A Tektronix 7704A 200Mhz 4-bay bench scope that I purchased used on eBay in 2001. It needed a repair in 2002 that I had done by Sphere Electronics in B.C. It has 7A26, 7A24, 7B85, 7B80 and 7B92A plugins along with a 7A13 differential comparator and two 7A15A plugins that can make the 7704A an X-Y machine.
3. A Tektronix 7104 1GHz 4-bay bench scope that I just purchased on eBay. It has 7A29 (1GHz), 7A19, 7B15 (200ps) and 7B10 plugins. This scope works great and was about the fastest analogue scope built.

The 7704A developed a faulty horizontal mode switch, so I purchased a junker 7704A frame on eBay for next to nothing. I recovered a good horizontal mode switch and repaired my own 7704A.

The junker machine is filthy (years of grime). I am dismantling it and cleaning it for parts. I took out the main power supply, and cleaned it. When I fire it up (no loads), it clicks. That is usually a sign of overload and PS won't start.

There are a couple of scope owners in here. Any thoughts about the clicking?

Thanks, ... JD Hurst

Edit: It is the +54V supply (30 volts). The other three basics (-54V, +17V and -17V) are OK. So something is loading that supply, and I am just tracing through the supply circuit diagram.

[jdhurst]

The junker 7704 is a goner. The aluminum rails and panels were all rough and dark brown or green. So I got it all apart, the CRT out (burnt) and the circuit boards, knobs and misc. parts retained. The power supply is in trouble. There is a incoming power board, rectifier board and regulator board, then on to the rest of the machine. I disconnected the regulator from all the supply points and the power supply is still overloading, so there is a bad component in the first two boards. Very difficult to get at because of the construction, but I have a manual, so I shall pick away at it. The rest is scrap. ... JD Hurst

[JHEM]

You have to learn to turn away from these personal challenges John!

Reminds me of my surgical adventures years ago inside an old tube amped Teac open reel tape deck. I ultimately defeated the monster, but only by performing a heart transplant from a solid-state donor.

Regards,

James

[jdhurst]

If the company in B.C. can repair the power supply, I might just do it. It is a drop-in replacement for my good 7704A, should it ever need it. ... JDH