AVO TT169 Transistor Tester

[David Simpson]

Folks, just a post for info. I've read all the "Search" posts. Seemingly a half-decent in-circuit tester. This one however is un-used, completely un-blemished, & the blue plastic wallet is immaculate, and still works. Only cost a quid at an ARS junk sale! A diddy wee addition to my collection of five other types of testers/analysers(CT446 Mk2 to an Atlas DCA55).

Regards, David

[Kevin Hoyland]

Morning David.
Top man a Avo Transistor tester for £1.00 bargain of the year. I will phone you later.

Kevin

[nutteronthebus]

Hi I have one of these testers and paid £11.50 for it so yours is a bargain ( great for in cct testing )


Dave L

[David Simpson]

Thanks for the replies, Kevin & Dave. Yep, a quid for an un-used NOS little tranny tester is a great bargain. My VMARS chum GM8AGM, Martin, got it for me a last week's Aberdeen ARS monthly junk sale. About three years ago, from the same place, he got me a Hartley CT436 Scope, fully working, for a fiver!
Another Tr Tester in my collection is a Kamoden HM-350, (there is a post about it ), which I snaffled myself at the same sale about 2 years ago, for just a few pound coins, but that needed some TLC.
Folk might query why someone needs 5 tr. testers, magpie compulsion maybe ? No - I attempt to use them all several times a year. Especially now that I've acquired an 21st century Atlas DCA 55. Its amazing to see old 50's/60's etc. testers hold their own against micro-electronics latest. And also see how my wee collection of "Crystal Triodes"(very first transistors) compare to more modern junction & FET's etc. Also, back in the 60's, I used to service & repair RAF CT446's. (And CT436's).

Regards, David

[TonyDuell]

You did get a bargain. I think I paid a tenner for mine about 20 years ago. It is a pretty good in-circuit tester (rather better than most). I hope you got the 2 leads (one for small signal transistors with a strange double spike probe on the end, the other for power transistors with a pair of croc-clips) and the (green) probe to connect to the base of the transistor under test.

[Phil G4SPZ]

I've got one of these too, bought at a radio club junk sale for a couple of pounds, and in working order. Since acquiring it I've never needed to use it in anger!

[David Simpson]

Sunning Up - thought I'd do a wee comparison test with more advanced transistor testers, even though the TT169 is merely an in-circuit tester. Used a 2GT182 Ga PNP (OC71 eq.).
1968 Mullard Data Book says expected hFE of 41

1968 AVO Tr. Data Manual says typical beta of 47

1996 TITS says hFE of 30

Results :- CT446 Mk2, beta = 64

1950's Sienens Ediswan Type R2285, alpha dash/beta = 54

1980ish Kamoden HM350, hFE = 30

DAC55, hFE = 48

Chinko/AVO Homebrew tester, hFE = 62

And the TT169 starts to flash at 1.5 on the control knob. Obviously this is just an arbitrary indication.
Both the DAC55 & the CT446 just showed a few tens of uA leakage.

Conclusion - just a handy reliable wee in-circuit go/no-go tester. But the probes are a bit awkward to use.

Regards, David

[Phil G4SPZ]

Crikey, what a wide variation between testers. I wonder why? If five valve testers had yielded such disparate results, there’d have been uproar. It just goes to prove that a man who owns one transistor tester knows the gain of the device he’s measuring. A man who owns 1+n transistor testers isn’t quite so sure...!

Which tester do you think is telling the truth, David?

[David Simpson]

Right enough, Phil, quite a disparity. Firstly - the Siemens is a very early PNP only tester from the 1950's. Works on a "buzzer" principal. Just a go/no-go tester really. The Kamoden is a cheapo basic Jappo tester from round about 1980. Actually called a "Checker" so not expected to be very accurate, but actually matches the TITS expected gain. The DAC55 should be jolly accurate I'd have thought, and in fact gives the same gain as the AVO TDM (47/48). That leaves the faithful CT446, in which I have the most trust, having serviced & repaired them in the RAF back in the late 60's. Its gain of 64 is jolly close to the Chinko/AVO homebrew tester which gave 62. This I also trust(see "Test Equipment Project Quiz" thread raised on 20th Sept.2016). As it has in-built self-test facility utilising transistors thoroughly tested originally by "Pamphonica".
So - just for a quicko test of an unknown transistor - I use the DAC55. For accuracy I use the CT446 or the Chinko/AVO homebrew tester. The others are just for vintage collection purposes.
For valves, well - I try & keep my AVO MK3 up to spec, also my homebrew DC tester. So trust them, particularly after they held their own against Dekatron's Roetest during the 6AQ5 Standardisation Project I ran last year. If I also still had a Taylor 45, then I would consider it just a go/no-go tester, likewise a Mullard HSVT. But even so, those valve testers are pretty decent in their own right.

Regards, David

[Phil G4SPZ]

Thanks for that, David. I can see now that your two ‘best’ testers gave pretty well the same results. It has also just dawned on me why you’ve used the four-letter acronym for Towers, keeping abreast of the situation I’m sure