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Old 28th Aug 2020, 9:36 am   #1
woodchips
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Default Avo CT160 valve testers in auction

Correct section to list?

If you look at

https://auctions.ramco.uk/auctions/7560/ramco-10236

Ramco.co.uk have three Avo CT160, they call them CT161, valve testers in their auction.

Ot go to Ramci.co.uk and click on auctions then scroll down to the electronics auction.

Wonder where these came from?

Last edited by woodchips; 28th Aug 2020 at 9:44 am. Reason: There are five of the testers
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Old 28th Aug 2020, 9:43 am   #2
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Default Re: Avo CT160 valve testers in auction

Looking more closely they have five of them, called CT160, CT161...CT165 for some reason.
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Old 28th Aug 2020, 11:28 am   #3
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Default Re: Avo CT160 valve testers in auction

Looking at the photos, the first one seems to have a different socket box to the others.

That auction seems to have some rather attractive stuff. The headset testers, pressure testers, sound level meters and the angular position stuff make me think it's a clearout from some military/aerospace outfit.

The HP spectrum analysers E440x are known as the 'Mosquito' project. LCD and more up to date, but designed as the economy family. They work well and have more modern interfaces than earlier families. Of course, to know what's actually in the box, you need to see the listing of fitted options.

The HP 856xE series spectrum analysers are the high performance family of a generation earlier. Well known, quite capable. The E on the end marks them out as having updated processors and a card cage for option boards. Again you need to know the fitted options to know just what you're getting. 6x analysers seem to go for around 2k at Stewart of Reading, but that includes the 22GHz variants. These are portable versions and descendants of the legendary HP8566 "Doomsday Box" project.
These use CRTs and not just that electrostatic scope-type CRTs. Known to dim and defocus with age and absolutely irreplaceable. There are some kits from vendors in the US to do an LCD replacement, but they are very expensive. With an E, you can always suck trace data to a computer and view it there even if there is no functional CRT. (The very last versions of this family did switch to a colour LCD, but they are rather rare)

The distortion meters are classic old-school HP. Lovely inside. Reasonable performance. Rock solid construction and very reliable taut-band movements in the meters (likely platinum).

The most of the HP 5400 series oscilloscopes were subsamplers. Most ran at 20 MS/s and sometimes split that between two channels. They'll only reach their headline MHz on repetitive signals. Very much dated and not as useable as modern ones.

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Old 28th Aug 2020, 12:40 pm   #4
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Default Re: Avo CT160 valve testers in auction

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Originally Posted by Radio Wrangler View Post
Looking at the photos, the first one seems to have a different socket box to the others.
David
I'm not sure that is so. It looks to me as though all of the insulating boxes on the flying-lead and disc-seal connectors are present on all but the first example. Also, the nature of the Loctal (B8B or B8G) socket looks different on some in that most look to have a light colour (ceramic?) and some to have a darker colour (phenolic?).

Since I don't own a CT160 (more's the pity), I may be talking rubbish.

Colin.
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Old 28th Aug 2020, 2:21 pm   #5
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Default Re: Avo CT160 valve testers in auction

All five at 16* Listed as "Test Set Electronic Valve CT160" Couldn't find them by "search" at first being a bit dim [Woodchip says actually 161 as well].

Are the five Universal Avometers at 139* all the same model?

Dave W
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Old 28th Aug 2020, 2:44 pm   #6
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Default Re: Avo CT160 valve testers in auction

I do like the look of the 'battery capacity testers' at the end of the listing. I've got plenty of modern, precise methods of measuring battery capacity, but one of those would look really impressive at the end of the bench!

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Old 28th Aug 2020, 6:43 pm   #7
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Default Re: Avo CT160 valve testers in auction

Those battery capacity testers are good. Bought about a dozen years ago and sold all but two which I still have.

They are very simple, no processors, just big resistors and switches. What is interesting is that they will test a 2V battery by adding 6V to the battery voltage so the load transistors can actually work.

Did trace the circuit, but wonder where that went?

I would point out that they are about a 2' cube and quite a lift!
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Old 28th Aug 2020, 9:10 pm   #8
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Default Re: Avo CT160 valve testers in auction

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Those battery capacity testers are good. Bought about a dozen years ago and sold all but two which I still have.

They are very simple, no processors, just big resistors and switches. What is interesting is that they will test a 2V battery by adding 6V to the battery voltage so the load transistors can actually work.
Interesting. Do you know anything about their maximum voltage/current/battery capacity? Asking for a friend...

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Old 29th Aug 2020, 9:37 am   #9
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Default Re: Avo CT160 valve testers in auction

There are three voltage ranges, 2V, 20V and 40V, so presumably lead acid single, 12V and 24V cells/batteries.

Ammeter scaled to 50A but I would reckon 20A is probably nearer. The 2V setting with the additional 6V boost I seem to remember at being 10A or so.

Have a 60 minute run back timer to measure capacity.

I think! Just looked at the one I have here but not used it in many years, too useful to dispose of, too large as well.
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Old 7th Sep 2020, 6:15 pm   #10
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Default Re: Avo CT160 valve testers in auction

See that the five CT160's have jumped in price, all around 500 plus 15% plus VAT now.

Lot of other items seem well priced, not for me, can't face the hassle plus you can't collect, has to be posted etc. Seems a bit out of date.
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Old 7th Sep 2020, 6:22 pm   #11
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Default Re: Avo CT160 valve testers in auction

Now the main problem with the CT160 is there is a fair chance that the meter is toasted. The measurement procedure calls for the anode current dials to be set to the AVO book value, the assumption being that will be within a few mA of correct.

But - shove in a KT88 or similar that is shot and has low emission - and the meter pegs and burns out really fast.

So - I'd feel miffed if I had stumped up 500 plus for a non-functional CT160.

Craig
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Old 7th Sep 2020, 6:55 pm   #12
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Default Re: Avo CT160 valve testers in auction

The bidders in auctions for VCMs seem to overlook this large risk. If it's as seen, off power, then assuming the meter is melted, or the irreplaceable pot is shot ought to put a low limit on the price. If you want to sell one of these for the full market price, then you ought to have to put some work into showing that it is worth it.

Someone could be very upset.

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Old 7th Sep 2020, 10:04 pm   #13
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Default Re: Avo CT160 valve testers in auction

Bollox, says me, to "sight unseen" bidding. Maybe a phooked meter, maybe a phooked RV2, maybe a phooked mains transformer. Too risky is my advice. "Caveat Emptor" comes to mind.
Mind you, I bet some starry eyed audiophool puts in a bid, then we all will have to suffer endless (much repeated/much answered) questions on how to fix it.

Regards, David
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Old 7th Sep 2020, 11:22 pm   #14
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Default Re: Avo CT160 valve testers in auction

I bought mine from Gerry Horrox for a hundred quid with a know dead meter. But I found the AVO MkIV test meter (basically a VVM) had physically the same meter - and I was given it free. So I sacrificed it for the meter, swapped scales, and implemented the op-amp fix to compensate for the very different sensitivity meter.

Then I changed a resistor value so the default range is 100mA FSD with the current controls set to zero. So you get a value for the anode current with a specified grid voltage. Plus the opamp limits the voltage on the meter, so it overloads by an absolute maximum of a factor of two even if you get the settings entirely wrong.

So it is pretty bulletproof now and works perfectly.

But usually bidding goes potty for an AVO valve tester. I cannot get my head around the price people are prepared to pay for an operationally unknown tester.

I was lucky to be given my MkIII and MkII valve testers free. The MkIII needed a new Vg pot - fortunately linear in the III. And the MkII had a stuffed meter - but an electrically dead (but living meter) MkIV VVM has yielded yet another compatible movement, currently awaiting an op-amp fix.

Craig
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Old 8th Sep 2020, 11:12 am   #15
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Default Re: Avo CT160 valve testers in auction

Like Craig, I actually acquired, two or three years apart, two CT160's from Gerry Horrox. Having spoken with him on the phone, and received recommendations from a nearby Forum/BVWS chum, I was confident in getting my monies worth.
The first one was fully working, but needed some cosmetic refurbishment, but this was reflected in the cheaper than normal price. The 2nd one, as he honestly told me, had a phooked meter. He had actually sold it previously to a chap who phooked the meter, then phooked the op-amp kit which Gerry supplied afterwards. Gerry took it back, and I got it for half-price including another op-amp. Worked a treat with a MK1's 444uA VCM meter I had spare.I then later acquired a pristine(internally) MK3, but with a tatty exterior for under 150. So then later flogged the two CT160's. One of them went, for more than it cost me for the two initially, on eBay for big bucks.
I'm not telling this tale to boast about acquisition/selling skills, but to encourage folk to seek advice & personal recommendations when it comes to buying the likes of CT160's. Actually seeing one working before you part with any dosh is the best course of action. But, if like me your are several hundred miles away from the Home Counties, then contact Forum/BVWS folk "in the know", and get proper advice.
At the end of the 2nd decade of the 21st century - bite the bullet & build your own DC Valve Tester/Curve Tracer, or a Sussex, or if you are rich - a RoeTest.

Regards, David
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Old 8th Sep 2020, 12:12 pm   #16
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Default Re: Avo CT160 valve testers in auction

Quote:
Originally Posted by David Simpson View Post
At the end of the 2nd decade of the 21st century - bite the bullet & build your own DC Valve Tester/Curve Tracer, or a Sussex, or if you are rich - a RoeTest.
I agree, I have a selection of testers but the only one I fully trust is my Sussex.

Peter
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Old 9th Sep 2020, 10:20 am   #17
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Default Re: Avo CT160 valve testers in auction

I don't really understand the comments about how expensive and risky these CT160's are being bought from auction.

They are stone age technology, if the meter is toast then it is now a trivial problem to replace with an amplified less sensitive meter, similarly the setting pot, it is a mechanical thing after all. It is far more dangerous to buy a signal generator or spectrum analyser because if they are toast then can't fix it at all. Anything Chinese and you take your life into your hands, there are no service manuals or any information. In fact other than the large manufacturers like Philips anything made by European manufacturers never comes with any servicing info. Anything by HP etc in the last 30 years has lots of custom chips, try and buy spares for them.

An auction is for regulars, not one off purchasers looking for a bargain. If you continually buy from auction then the good and the bad average out. In my experience the stuff is ok, but you do need to know your auctioneers to know if they can be trusted, also their little foibles. As anyone who tried to use Equipnet last year will know only too well.

If Jacmusic are selling MkIV testers for, I think, 1500 euro, then 600 looks a bargain for something pretty similar.

And, no, they are not mine, I am not bidding, not interested. Got my CT160 from Ramco 10-15 years ago, can't remember. My guess is that these are from someone like me who has been slowly buying from Ramco over the years and is now cashing in.
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Old 9th Sep 2020, 11:09 am   #18
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Default Re: Avo CT160 valve testers in auction

Trouble is, its not usually the mechanical "telephone dial" mechanism for RV2 which goes wrong. Its the x3 linear resistance segmentation which gets phooked.Further trouble is - exorbitant mercenary prices being asked for genuine AVO replacements for RV2 & the 30uA meter. Cough up 600 for a CT160, get it home & either both are phooked, or some exitable wally phooks them - then the cost rises to 1K. Just not worth it. Better building a Sussex or a homebrew DC Tester. Far cheaper & more reliable than AVO's range of 1950's VCM's(60 - 70 years old !).
I'm lucky in having carried out repair & maintainance on RAF CT160's, back in the 60's/70's. I also know that several Forum folk have similar work experiences back in their younger years. And, there are two or three Forum/BVWS folk who are highly recommendable for repair & calibration(down south) of AVO's complete range.
CT160's, are to me, like working Labrador gun dogs - the owners need to learn from the dog, rather than the other way round.

Regards, David
Quote:
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I don't really understand the comments about how expensive and risky these CT160's are being bought from auction.

They are stone age technology, if the meter is toast then it is now a trivial problem to replace with an amplified less sensitive meter, similarly the setting pot, it is a mechanical thing after all. It is far more dangerous to buy a signal generator or spectrum analyser because if they are toast then can't fix it at all. Anything Chinese and you take your life into your hands, there are no service manuals or any information. In fact other than the large manufacturers like Philips anything made by European manufacturers never comes with any servicing info. Anything by HP etc in the last 30 years has lots of custom chips, try and buy spares for them.

An auction is for regulars, not one off purchasers looking for a bargain. If you continually buy from auction then the good and the bad average out. In my experience the stuff is ok, but you do need to know your auctioneers to know if they can be trusted, also their little foibles. As anyone who tried to use Equipnet last year will know only too well.

If Jacmusic are selling MkIV testers for, I think, 1500 euro, then 600 looks a bargain for something pretty similar.

And, no, they are not mine, I am not bidding, not interested. Got my CT160 from Ramco 10-15 years ago, can't remember. My guess is that these are from someone like me who has been slowly buying from Ramco over the years and is now cashing in.
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Old 9th Sep 2020, 11:42 am   #19
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Default Re: Avo CT160 valve testers in auction

The other excellent valve curve tracer that costs a whole lot less than a roetester is https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
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Old 9th Sep 2020, 1:23 pm   #20
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Default Re: Avo CT160 valve testers in auction

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I don't really understand the comments about how expensive and risky these CT160's are being bought from auction
The risk is simply financial.

The price of these instruments is hyped up far above the current values shown by other types of instruments of comparable complexity and quality because they are imbued with some sort of mystical aura. It also pumps up the auction prices of CT160s MkIVs and VCM163 in unverified condition.

OK, so you buy one, and it's duff. No problemo. Whip up another meter and print a scale for it. Add an opamp and psu to fix the sensitivity and bob's your aunty Alice. You can now test valves to your heart's delight.

Where you come unstuck is if you decide to sell it. Without the original meter it is obviously non-original, and the magic premium has evaporated. You'd likely get more for it as a non-worker untouched, and hey, at auction, off power, unchecked, it might get close to the price of a worker!

If non-originality doesn't bother you and you can see straight through magic auras, skip the silly prices, avoid the uncertainty, and build a Sussex. That won't have much resale value either, but the valves it tests will be just as tested.


Custom chips in HP and Tek gear are real risks. I get around them by buying several pieces of the equipment at trivial prices by being in the right place at the right time. Then, I've got spares and I can keep sme marvellous test gear going for quite some time. It's software issues that bug me.

David
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