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At 11:29 12/12/98 -0500, you wrote: Well David, this model will not be too useful in troubleshooting a computer. Looking in my 1966 Tektronix catalog in the specs for the 503 I find that the bandwith (basically, the calibratable frequency response) of the input amplifiers is DC to 450 kHz. Short pulses often found in digital logic may not be seen and a probable logic timing defect would be missed with this scope. The response of this scope's P2 CRT phosphor is a bit slow too and though a pulse could be swept by the electron beam the phosphor may not be bright enough to see it even in a darkened room. This unit would be great for audio work however (0-20 kHz)! Besides, $80 is far too much to pay for this model. If you could get it for around $25-$35 you'd be in the ballpark I think (only IF it works!). You'd have to get adaptors for any modern scope probes you would buy nowadays. The input connectors are known as type PL-259. Unless you found early Tek probes (type P6006 or P6023) at a hamfest you'd need a male PL-259 to female BNC adaptor. Actually, at the frequencies this scope would be useful, you could simply get an old set of VOM probes with uncovered banana plugs and plug them into the center of the PL-259 connector as use them as is. The scope weighs 29 1/2 pounds. For those of us working on older computers (with clock speeds of, say <1 MHz to maybe up to 3 MHz) my feeling is to have a 'scope with a freq. response of at least 20 MHZ so that most short-risetime pulses and glitches can be caught. A 100 MHz scope would be ideal to see most everything. However, one day at work I couldn't solve a logic switching problem in a prototype I was building. Clock speed was 2.0 MHz. I had to drag in my 250 MHz HP 183A scope from home to find it. Our 100 MHz Tektronix missed it. With todays 50 MHZ+ clock freqs even that 250 MHz scope can't see some short pulses on a 486 motherboard I've worked with. This is where a good, fast logic probe is needed or a fancy, expensive very wide bandwidth scope (1 GHz BW and higher). David, if you are interested in that scope yet, ask if you could plug it in and test it. There is a built-in calibrator with two square-wave signal levels available, 500 mV and 5 mV, at somewhere between 300 and 500 Hz. Most HP, Tektronix and other high quality scopes have a built-in calibrator. Take a half meter length of hookup wire along. Strip both ends back a few mm before you leave the house. I assume you would be able to figure out how to setup most of the controls on the scope. If not, ask in private email please. Stick one end of the wire into the center of one of the Vertical Input connectors and the other into one of the two CAL. OUT pin jacks. If setup okay and the scope is interested in working then you should see a square-wave signal somewhere near the CAL. OUT amplitude level on the screen. This advice also applies toward you other somewhat inexperienced folks out there who happen across a scope and would be allowed to do a simple test before buying. I call this a "Classic" oscilloscope being over 30 years old. I don't know the production years of this model though but it was introduced before '66. It would be great tool to use on an IBM 704! If it was closer to me I'd like to add it to my Tektronix collection. Regards, Chris -- -- Christian Fandt, Electronic/Electrical Historian Jamestown, NY USA cfandt(a)netsync.net Member of Antique Wireless Association URL: http://www.ggw.org/freenet/a/awa/