Deer Sir; I have just been given three ENIAC machines to display in a museum but they are currently in Nigeria where they were used for nuclear weapons testing. I can get them and preserve them for the National Museum of Science but I need your help. They won't believe I am a serious collector unless I can show them that I own a working PDP-1. I need you to box up and ship me a working PDP-1 so that I can set it up and show it to them. Then they will send me the three ENIACs by first class air mail. I will keep one, send one to the museum and you can keep one. You will agree that an ENIAC, the first digital computer, is much more valuable than a PDP-1 so you will understand that I must keep the PDP-1 just in case they do a "surprise" inspection. Thank you for your help, it is a good cause. Sincerely, Prof. Peabody. ----------------------------------------------------------- :-)

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Chuck McManis Sent: Wednesday, May 23, 2001 10:07 PM To: classiccmp(a)classiccmp.org Subject: Need help Deer Sir; I have just been given three ENIAC machines to display in a museum but they are currently in Nigeria where they were used for nuclear weapons testing. I can get them and preserve them for the National Museum of Science but I need your help. They won't believe I am a serious collector unless I can show them that I own a working PDP-1. I need you to box up and ship me a working PDP-1 so that I can set it up and show it to them. Then they will send me the three ENIACs by first class air mail. I will keep one, send one to the museum and you can keep one. You will agree that an ENIAC, the first digital computer, is much more valuable than a PDP-1 so you will understand that I must keep the PDP-1 just in case they do a "surprise" inspection. Thank you for your help, it is a good cause. Sincerely, Prof. Peabody. ----------------------------------------------------------- :-)

p.s. I think it is hard to say "XYZ was the first computer". In that time many "first computers" where build by independent people.

Hi, This guy is auctioning a: Vax QBUS KDA50 Disk Ctl (M7165) http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1240600239 What sort of interface is this? It almost looks SMD. Guess it isn't, also rule out SCSI and MFM, by appearances. Standard disflamer: This is Not my auction. John A.

Hi, This guy is auctioning a: Vax QBUS KDA50 Disk Ctl (M7165) http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1240600239 What sort of interface is this? It almost looks SMD. Guess it isn't, also rule out SCSI and MFM, by appearances.

Standard disflamer: This is Not my auction. John A.

SDI?

>p.s. I think it is hard to say "XYZ was the first computer". In that >time many "first computers" where build by independent people.

I agree, but what about the Baby machine at Manhcester? ISTR from reading "Computer" that something was missing from either ENIAC or EDSAC in order to make it a "real" digital computer.

I agree, but what about the Baby machine at Manhcester?

On 24 May, Iggy Drougge wrote:

Baby machine? Do you mean the machines of Charles Babbage? As I know these machines were not programmable.

> I agree, but what about the Baby machine at Manhcester? ISTR from > reading "Computer" that something was missing from either ENIAC or > EDSAC in order to make it a "real" digital computer.

I believe it was the sharing of code space with data.

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Mike Ford Sent: Friday, May 25, 2001 12:16 PM To: classiccmp(a)classiccmp.org Subject: Microwave oven collectors? My 17 year old "microprocessor controlled" microwave oven stopped making food hot the other night. Everything still appears and sounds about the same, just food stays cold, and when it first happened there was a bit of the smell of the gates of capacitor heaven being open. Should I take a swing at fixing it, or yield to the cheap new inverter technology? Victim is a Panasonic Dimension 3 microwave/convection oven (top of the line those many moons ago). Location is SoCal.

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell Sent: Friday, May 25, 2001 1:59 PM To: classiccmp(a)classiccmp.org Subject: Re: Microwave oven collectors? was a bit of FIrstly a word of warning. A microwave oven is by far the most dangerous thing you're ever likely to work on. The power supply can provide about 4kV at a significant fraction of an amp. This will kill you if you touch it. Not 'might kill you', but 'will kill you'. It is a _lot_ more dangerous than the EHT supply in a monitor or TV, for example. And of course there's always the danger of microwave leakage. If I wa going to fix it, I'd start by connecting a mains voltmeter (or test lamp, or something like that) across the primary (mains side) of the high voltage transformer. Try to 'cook' (have a cup of water or similar in the oven as a load). If you get mains at that point, then the controller, interlocks, etc are all working correctly. If not, then the problem is on the mains side, which is somewhat safer to work on. Assuming that you are getting mains to the HV transformer, then there are basically only 4 parts in the microwave generator circuit. Discharge the HV capacitor with a suitable bleeder resistor before touching anything : The HV transformer (check the winding resistance when the unit is turned off and unplugged) The rectifier diode. This has a very high forward voltage drop (10s of volts) and can't be checked with a normal ohmmeter or diode tester The HV capacitor, for which you need a high voltage insulation tester to make any reasonable tests on it. The magnetron. You can check the filament continuity (disconnect it from the transformer), should be very low, and for shorts between the filament and the anode block. The latter is earthed, the filament runs at a high -ve voltage wrt the chassis. There is some more information in the sci.electronics.repair FAQ. I must say, though, that I don't like working on microwave ovens, due to the high voltage, high current PSU. Monitors and TVs don't bother me that much, but the thought of working near a transformer that will supply 4kV at 0.25A or so worries me. If you do decide to open it up, take great care. And as ever I am not responsible for any injury caused if you do attempt to repair it. -tony

> > My 17 year old "microprocessor controlled" microwave oven stopped making > food hot the other night. Everything still appears and sounds about the > same, just food stays cold, and when it first happened there was a bit of > the smell of the gates of capacitor heaven being open. Should I take a > swing at fixing it, or yield to the cheap new inverter technology?

At 10:15 AM 25/05/2001 -0700, you wrote: >My 17 year old "microprocessor controlled" microwave oven stopped making

>the smell of the gates of capacitor heaven being open. Should I take a >swing at fixing it, or yield to the cheap new inverter technology?

Suggest you scare it. The turntable in my Dimension 3 quit, motor not running, and as soon as I brought home another used oven the "3" started up again and is still going.

[Williams tube memory] Are you sure? I thought there was a metal electrode over the front of the CRT, and the signal picked up from that was fed back to refresh the charge image on the CRT face (yes, this is a simplification).

So if you moved the electrode to see the screen, you'd lose the memory contents.

I can well believe having a second CRT coupled up, which had the same deflection signals, and in which the beam intensity was controlled by the amplified singal from the pickup electrode. That would display the memory contents as an array of dots.

And VCR97s [1] were not exactly uncommon, adding a second one would not have been a problem

[1] Valve Cathode Ray 97 IIRC. A very common radar CRT from WW2. Common enough that _I_ have one in the junk box.