As regrds bandwidth, for digital repairs, a good rule of thumb is that the bandwidth should be at least 3 times the master clock rate, probably more. A 100MHz scope is adequate for just about any classic computer work. You can get away with a lot less (even 10Mhz only) if you know what you are doing, and know how the instrument behaves. If you get a 'scope that takes plug-ins, you'll have many enjoyable hours at hamfests trackign them down :-). More seriously, make sure it comes with the appropriate number of general-purpose plug-ins (a 2-trace Y amplifier, timebase, etc). Certainly for Tektronix 'scopes there were soem very special-purpose plug-ins that, while interesting and fun, are not what you're looking for at this point. Don't get me wrong, I love my old Tekky 555, but I really don't think this sort of instrument is good for a beginner who doesn't want to learn how to repair valve circuitry and 'scopes in general. They are very maintainable, and the manuals are excellent, but since they're over 40 years old, you are going to have to do some work on them. It's not hard to do your own calibration. You need the proper manual for the 'scope, of course (HP and Tekky provided excellent manuals, I beleive there are companies that sell copies). As regards 'standards', remember you can't read a 'scope to better than 1% anyway (and that's pushing it). A reasonable crystal oscillator will do as a time standard, a bandgap references as a voltage standard. Most of the time you don't need high accuracy when using a 'scope anyway. IMHO, Tektronix are the best all-round 'scopes (if you get one of their general-purpose models). LeCroy made some lovelly stuff, but it was all very high-end and expensive when new, I am not sure how often it turns up at hamfests). I have never really liked HP 'scopes (and the user interface on their DSOs of about 10 years ago is horrible!). -tony

Yeah, I'd rather not have a PDP11 sized scope, but thanks for the suggestion, I'm sure they're wonderful devices. -----Original Message----- From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Christian Corti Sent: Friday, June 09, 2006 3:14 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: Need pointers on Oscilloscopes On Fri, 9 Jun 2006, Tony Duell wrote: My experiences with a 555 are *very* good. Found one on a scrap heap three years ago, and someone picked the power valves (and the funny diode 2AS15-A) and their sockets out of the power supply (and cut the wires). It took me some time to get replacement valves and rewire the power supply around the sockets, but in the end, the scope worked like a charm! The traces (it's a real dual beam, not dual trace) are sharper and finer than everything else I've seen so far (mostly "modern" equipment like Hamegs or HPs). We use it here e.g. to adjust the heads on RK05 drives or to measure the signals on our LGP-30s (we have two working now!). (Some pictures are on http://computermuseum-stuttgart.de/dev/tek555, you can click on the pictures to see more) Christian

On Fri, 9 Jun 2006, Jim Beacon wrote: :-)) It's a RIM Oszillette. RIM was a shop/seller in Munich that was widely known to sell interesting kits, mainly in the 60s/70s. They sold electronic parts, amplifiers, power supply etc. and many things as a kit. One of the kits was the Oszillette, a small scope with a tiny Valvo scope tube and only 4 or 5 other valves. We have it on the picture to show the difference: tiny 5 valve scope compared to huge over 100 valve scope (plus external power supply), as much as in our LGP-30! The Oszillette has no trigger, it's free running with sync and frequency adjustments via front knobs, and only 1:1 and 1:10 signal inputs. Christian

On Saturday 10 June 2006 10:23 am, Chuck Guzis wrote: Yes! They even had a dual-trace version, as I recall, from the ads. I always wanted to get a hold of one of those to try and use, but never did. I ran across one guy who had one, and he wasn't that thrilled with it, but spent his time doing bench work and no field service at all so it wasn't that big of a deal for him to put it aside. Me, I had a big old Tek 524AD at the time, not the sort of thing you wanted to move at all if you didn't have to, and surely not something you'd want to carry around doing field service. But the Tek I have now is a whole lot smaller and ligher... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Somewhere I have the issue of Practical Television magazine which gives construction details for a 1 valve + CRT scope. OK, there are some semiconductor rectifiiers in the PSU too. The valve is for the timebase, the Y input goes straight to the CRT plates. But it was useable for the signals in vavle TVs of the time, and a lot better than nothing. Woudln't we all :-) -tony

Roy J. Tellason wrote: Well now days you could use a voltage multiplier. Did they every have a DIY for B&W TV like they had for radios the begining years of development?

On Wednesday 14 June 2006 12:00 am, woodelf wrote: I don't think I've ever seen one, though I must admit to having thoughts in that general direction way back when... :-) -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

From: "Tony Duell" <ard at p850ug1.demon.co.uk> There were, as Tony says, a number of kits and self build designs available in the years just before and just after WW2. I have a design for a Radar tube based set on my bench at the moment, as I'm planning to modify it into a multi standard monitor (240, 405, 441, 625) for use with a PC based standards converter experiment (we already have it producing video at 240, 405, 525 and 625 line standards, and should be able to push it to 819 lines as well). The design is for the video and timebase sections only, using a VCR97 as the display, with all other valves being EF50 (SP41 or SP61 are the recommended alternatives, all common as government surplus in the 50's), except the video clamp, which is EA90. In the original, the RF stages were taken from a "GEE" receiver (it had a 45Mc/s IF strip which became a TRF video receiver), and one of the plug-in GEE RF units was converted to a TRF sound receiver. Going back further, the Baird 30 line mechanical system became popular after the "Daily Express" newspaper produced and distributed "televisor" kits - somewhere I have a picture of them loading railway trucks with the kits. There were also other suppliers of kits and specialist components, like Nipkow discs, or mirror screws. Cossor produced a kit for a 405 line set, and there were others. Caseless chassis, with and without CRT and valves were also offered in the 50's, and I believe at least one homebuild colour set was based around a readily available chroma panel from a commercial set. Jim.

From: "Tony Duell" <ard at p850ug1.demon.co.uk> available into Yes, the VCR97 is a 6" electrostaic deflection and focus CRT after kits - A very lucky find! I recently got hold of some "television and shortwave" magazines from 1935 to 1939, which cover the late mechanical and early electronic systems (the Baird 240 / EMI 405 competition and such like. There is also a lot of information on the development of the Scophony mechanicaly scanned 405 line receiver (I have one of the few remaining parts of a Scophony set, http://www.g1jbg.co.uk/tv1.htm) Jim.

At the museum here we have Gernsback's ( yes the same Hugo G. the Hugo sf award is named after)radio and television news, prior to that it was separate issues called 'radio news' and 'television news'. The dedicated 'television news' issues had the most wonderful covers. Early Radio and Television history is interesting to study! if you need to get hold of me use the mailbox at www.smecc.org I seldom use this qwest address any more and may not answer ed sharpe archivist for smecc ----- Original Message ----- From: "Tony Duell" <ard at p850ug1.demon.co.uk> To: <cctalk at classiccmp.org> Sent: Monday, June 19, 2006 2:15 PM Subject: Re: TV kits was Re: Tek 555 was Re: Need pointers on Oscilloscopes

On 6/13/2006 at 8:25 PM Roy J. Tellason wrote: My 1942 Radio Handbook shows how to build two CRT-based devices. One is a basic scope, using a 2501A3 CRT (3"), an 80 as a B+ recitifer and another 80 as the rectifier for the anode voltage. The power transformer is a rather odd one with 2 5v insulated windings for the 80's and a 350-0-350v winding for the B+ and a 450v winding that's hooked to one side of the 350-0-350, so the anode rectifier receives 800 vac RMS. Horizontal and vertical amps were both 6C6's and the horizontal sweep was generated by an 885 gas triode (sync supplied through the grid). Total valve count = 5, exclusive of CRT. The second is a simple modulation monitor which uses a very small 913 1" CRT and a 5Z4 for the anode supply. Since the RF and AF signals are applied directly to the 913's deflection electrodes, nothing more is needed. BTW, "UHF" back then meant that you were operating on the 56 or 112 MHz bands--and FM was very hot on the 2 1/2 meter band. "Microwave" was defined as 1 Meter (300 MHz) and down. Exotic strategies to get these frequencies included magnetrons, Kozanowski and Barkhausen oscillators and the WE 316A "doorknob" tube. A brief mention is made of the RCA 825 "inductive output amplifier", which bears a remarkable similarity to an klystron. Although not mentioned, the Varian brothers were the minds behind it. Cheers, Chuck

On Sat, 10 Jun 2006, Jim Beacon wrote: I, too, have several large scopes in our museum here. Originally we didn't want to start collecting such items, but being radio/tube enthusiats (me and Klemens) we couldn't let them to the junk. You just can't imagine what can still be found at our university (and others probably too). So now we have a 536 incl. several plugins, a 535A, 547, 502, 555 and 549. BTW I found four big Tek carts, too, which aren't easy to find today. If that's the storage scope then we have it (and it works!) :-)) It came with several plugins inclusive two sampling units. To come back to computers, here's what we tried one day not long ago: There's a (DECUS?) program for the PDP-8 that emulates a Tek 4014 terminal. It requires two serial ports, one to the host system and one to the console terminal, and then a VC8e. It is intended to work with some large screen storage scope but I simply hooked up the Tek 549. The host was a Unix system (Sun 4/260) running GnuPlot (tek40xx). Now guess how it worked... The screen on the scope is too small to read text, but graphics are fine. Christian Jim: Aren't you also a list member on vintage-radio.net? I've subscribed to the list several weeks ago, too, in the need for some idea to get my french HDTV set (819 lines, 11 MHz bandwidth) working again (with a PC, Kat's RGB combiner and a modulator).

Oh, my expereinces are excellent too (and with other Tektronix 500 series). My point is that these 'scopes are 40 years old, and while they're very well made, and will keep going a lot longer, they are going to need some maintenance. Fine if you like doing that (I do), but perhaps not the best choice for a beginner. Suppose some non-technical person was looking for a computer to do simple word procesing on. Would you recoemnd a PERQ, and get them to learn 3PROSE? It'll do the job, it's an excellent machine, but it'll need a bit of looking after. I must have told the story of the time that we got a new Tektronix at the place where I was working. I couldn't get the trace sharp (IMHO), so I phoned Tektronix. They asked what I was comparing it against, and of course I said my old 555 at home. They said that was probably the sharpest CRT ever, and that nothing modern (not even Tektronix) was as good in that respect. Hmmm -tony

Tektronix scopes are always the best. But just got a V1100A Hitachi 4 channel-8 trace-digital-readout scope on ebay for $160. Like new condition and with a pair of 150MHz tek 10x probes. The best scope I ever had, even best than my loved Tek 455 and 465. Highly recomended. Philips are good also, and easy to find info. BTW, anyone with a spare copy of the V1100A instructions' manual? Thanks Alexandre

woodelf wrote: unless you get a digital scope that holds calibration well, you will probably be wise to pick up a frequency reference, and voltage refreence to calibrate them with, unless you have access to such somewhere outside your home shop, such as at work. If you have a standalone operation, being able to check the voltage and triggering on your scope and recalibrate them is desirable too. a lot of bargain scopes will put up a nice square wave, especially tektronics showing the internal test square wave, and wont trigger on the crap you really see in your old computers worth a crap. triggering and reliable probes will probably be the the top two things you will not think of unless you keep them in mind in advance, and it will be hard to judge how good a scope is unless you know the vendors, and trust their description, and that they might let you return a dog of a scope. also, getting a good maintainence and calibration manual will help the above, you wont be doing that wo one. Dont go for some weird and wonderful bargain scope that you cant find a manual for. jim