Test Equipment Anonymous

Ok so I bought the Tek 453 that was floating around for £40. Figured it'd be worth it for parts even if it was completely hosed. But it turned out to be better than it looked.

Naked photo


First obvious problem is the mains lead is TERRIBLE. The plastics have degraded so badly there are bits of wire hanging out. Someone clearly attempted to use it in death trap mode as the cable was covered in tape. This was dismantled and a new cable added from a chopped of IEC lead. Surprisingly the fuse in the original lead was still good (!)

Before - and that was a relatively good bit of cable!

After


The little roll of solder came in handy - looks like no one has repaired anything yet which is good


Anyway that was done, it was put back together and it powers up. The fan is a little noisy but sounds ok. Of course there is no HV at all. Cursory debugging suggests that the HV oscillator is not running at all and some of the oscillator bias is off which suggests something is up in that circuit. It does not however look loaded down, which is nice! I will look at it on the next run at this.

One of the joys of the 453 is the immense amount of information on it out there. There is a full technical and design specification available which describes everything in extreme detail and on top of that plenty of debugging help in Tekscope magazine August 1970. Both available on w140.com

Full size image

Excerpt from Tekscope Aug 1970 with HV debugging steps. Very nicely written and good comment at the bottom.

bd139 wrote: ↑Thu Oct 31, 2024 10:46 am Excerpt from Tekscope Aug 1970 with HV debugging steps. Very nicely written and good comment at the bottom.

(Gorgeous scope, btw! I like.)

Only, as noted in Discord, that the comment at the bottom disqualifies a sizeable portion of humanity from taking part.

The debugging instructions are quite good. Somewhat like the Field Circus manuals for IBM Real Computers. Granted, it's only subassembly (FRU) swap level, but it is done in a very detailed decision tree style. You will have a working computer at the end, and possibly a pile of swapped hardware on the floor.

The Dell case I had the other week, with a b0rkened RAID controller, had a similar flowchart intended, so when they came back with "please run the system bare bones", ICBA, so only ripped out the RAID controller from the otherwise complete machine, and lo and behold, it POSTed fine and went looking in the void for something to boot from. Replied back: "I cheated, this happened." and Dell caved and shipped the needed part.

My very first job at IBM in 1973 was a high powered switch card tester which had a 453 integrated into the tester to verify proper waveform and frequency.

Your acquisition persuaded me to get out it's bigger brother 454 and give it a quick checkout. There's many common parts between the 453/454 and I have a parts unit if you need something unique and unobtanium. If I recall the only parts missing from it are the vertical output transistors which Sean in New Mexico (former blog member) needed to fix his 454.

Ahha thanks for that. I will let you know.

Nice specimen that 454. The vertical amp in that is a piece of artwork!

Is your 453 one of the units that was branded for IBM?