EEVblog #693 - AVO Transistor Analyser Teardown

Dave tears down a 1962 vintage AVO Transistor Analyser.

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[alancordwell]

Hi Dave, this was obviously originally made for the military, the Z4/ZDA number is an army stores reference. On the lid, the 6625-99-xxx-xxxx is its NATO stock number (NSN). The other giveaway is on the schematic, where the transistors have their military equivalent given - the CV number. Now in British army terminology, CV stood for 'common valve' and valves all had a CVnnnn reference. Now when transistors came along, the military didn't know what to do with them and the guy that made the decisions was on leave. So they took the option 1 (do nothing) path and called them CV as well.

The 'bodge' you see on the wirewound resistors is easily explained- and it isn't a bodge. Those are precision resistors, and they will have been made with a 'tail' of an inch or so of surplus resistance wire hanging out. During factory calibration, the soldered joint will have been moved up or down the tail to bring it into cal- and we are talking a tiny fraction of an ohm, serious precision! So credit where its due.... bodge indeed!!

[harveytwyman]

In the video @ 15:45 it shows hand wound resistors.
The insulation is described in its tongue-twister name as "Double Cotton Covered Copper Wire". I use to work at AVO in the late 60s and it was my job to wind those. They were then painted with a lacquer to stop them unwinding.

[FranLab]

Vacuum Tube shield + little metal tab = battery compartment.  Gear!

[TheCondoInRedondo]

Dave, I'm an engineer from the early 1970s. Testers like that one were used to match transistors for push-pull circuits. There were easier ways to find bad transistors. But fancy testers like that were for matching parameters, often with thermal influences. In the 1970s, the industry moved to Tektronix oscilloscope-style transistor testers with built-in sawtooth generators for displaying the gain curves automatically.

Also, the Texas Instruments 7400-series logic I/Cs were not 1962-ish. Think more late 1960s. CMOS 4000-series were even later, circa 1972-ish if my memory serves. Transistors reigned supreme in the 1960s. Even inside Iron Man's suit. In the comics of the 1960s, everything in his suit was "transistor-powered". I'm sure Tony Stark would have had a tester like your Avocet.

[bratb]

I was crying like a baby when you show this device. Such a beautiful piece of history...

[benadams]

I know it's an old video, but if you still got this vintage transistor tester you should send it to Mr Carlson's Lab, he will have it working better than new in no time.

[IvanIvan]

23:14 these are diodes IR2E1 (International Rectifier) Type 2E1.
See service manual page 28, item no. 43

[msylvain]

It is incredible to see that the rubber straps are still good ! I believe the yellow discs may be early diodes for International Rectifier.

[FireballXL]

Hi I started my apprenticeship in 1973 at a REME works and we had to do all wire looms with lacing cord. if you look closely you should not see any start or end knots. The start you can wind over itself and the end you form a loop and pull the end through the multiple wraps.

[waew]

That thing was built the same year that I was "built"!  I guess I'm old too...

[mikeselectricstuff]

The arrow on the serial no. label indicates it was supplied to the military

[Snufflumpagus]

Best birthday gift ever. An EEVBlog video :D Didn't get to watch it on my birthday sadly but hey, I still enjoy it either way :) I also vote to have you power that baby up and see how it does after 50+ years. Thanks for everything you do for us Dave. Been catching up on videos from the beginning, every day after work I watch a little more. Been waiting on my approval into the forum for ages though D: but watching your videos makes it worth the wait haha.

[mikeselectricstuff]

Those battery holders look like valve shield/retainers

[serialdata]

Thanks for the video it is certainly well built.
The 2 small capacitors are meter protection diodes and the plugs in the battery compartment are held in place by bumpers on the main chassis 

[Technical_Audio]

Lovely bit of kit. I have an AVO VCM163 tube (“valve”) analyzer, probably from the 70s. ACO was most famous for their tube analyzers. While the VCM163 tests vacuum tubes, it uses solid-state active parts inside. I think it’s the best of the service tube testers ever made.

[tomwade]

I love it!  built the same year I grauated from school.

Keep up these antique teardowns.

[markpirateuk]

Great bit of kit, Avo build quality is second to none.
I love the battery holders, they are actually screening cans for signal valves!
Please replace those leaky caps and fire it up, would bet it will work fine.

[powder-phun]

Beautiful thing! I really wish to thank someone who 50 years ago pulled the batteries out. What a mess it would be without that!

[BuysDB]

Great tear down, absolute beauty!  Definitely fix those caps and bring this majestic brick back to life.

[hdmalpas]

That brought back some memories, Love to see it up and running. Thanks Dave, merry Christmas to you and your family.