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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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6th Sep 2018, 11:31 pm | #21 | |
Dekatron
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Re: Valve Tester Prices?
Quote:
The basic tracer though will provide 350V at 1A, and 1500V at 200mA (all variable) in pulsed operation (which you need to do with the PL519 anyway to demonstrate) so will easily cope with the valves you mention. Craig |
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7th Sep 2018, 10:48 am | #22 |
Nonode
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Re: Valve Tester Prices?
For those folk who doubt their ability to attempt to build a full sized DC tester rather than buy an AVO VCM, or Mullard, or Taylor etc. - I say - firstly build the CV455/491(ECC valves) basic standardising circuitry which AVO recommend in their VCM & CT160 Manuals. Just as Les did. His linking it to a transistor curve tracer is a great idea. Once you're happy with your rig - add a B7A, or an IO base, & an extra HT screen supply, then have a shot at a few wee pentodes. Then you are well on your way to a full-blown DC valve tester. Maybe it'll take you a year or more to acquire all you need from Forum sales, BVWS swapmeets, auctions, gumtree, ARS junk sales, etc. But Jesus - you'll save yourself a fortune, and be jolly proud of your achievements.
Hey Paul & Moderators - couldn't all these Valve & Valve Testing threads, which now span several sub-forum sections - get put into one big "Sticky " section ? Just like the AVO8 & Mullard Cards threads. Or indeed - get a dedicated extra sub-forum ? Regards, David |
15th Sep 2018, 11:51 am | #23 |
Heptode
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Re: Valve Tester Prices?
You would think given the 2nd hand prices that someone in China would suddenly start producing new copies of older simpler machines. I have a Taylor 45C, Avo (the old admirality type), and three others - one of which is from the US (has step down transformer) and is the first one I go to as it's relatively simple to use and set up. One of the things I've always wanted to find is those testers which plugged into the radio valve socket itself with an adapter (into which the valve was plugged) - you could measure voltages directly on them apparently. Never come across one.
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15th Sep 2018, 8:19 pm | #24 |
Dekatron
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Re: Valve Tester Prices?
Hi these plug in units were often called set analysers and allowed voltage and current measurements to be taken on a valve as it operated in the set.
They could, however, create havoc with the set's operating conditions due to stray capacity. They were sometimes supplied as special "multi testers" in a nice case to repair shops that had more money than sense, but it would impress the customers. I must admit they look quite good and I have a couple of examples here, not that I've ever tried to use them. Ed |
15th Sep 2018, 9:12 pm | #25 |
Nonode
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Re: Valve Tester Prices?
As a professional amplifier repair person, I find the Sussex I built a few years ago is perfectly suitable for checking that any given valve is performing according to spec. It’s also suitable for matching output valves.
I’m not really interested in the esoteric qualities of AVO testers and the Mullard that I gave away was too bulky.
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15th Sep 2018, 10:28 pm | #26 |
Octode
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Re: Valve Tester Prices?
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16th Sep 2018, 1:40 pm | #27 |
Octode
Join Date: May 2009
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Re: Valve Tester Prices?
If someone, the Chinese or anyone else, suddenly would manufacture a valve tester that would become the modern standard for valve testing the valve manufacturers would suddenly have to back their claims when they sell valves and that would upset the current sales I guess.
Comparable and repeatable test results is still a problem as we don't have a standard-valve to compare against that shows repeatable measurements over time, nor do we have anyone offering calibrations of valve testers nor calibrations of a standard-valve - at least to my knowledge, I could have missed some though, please correct me if I am wrong as I would gladly get in contact with them.
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16th Sep 2018, 6:09 pm | #28 |
Nonode
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Re: Valve Tester Prices?
I think that amongst this Forum fraternity & the BVWS, and VMARS, there is a broad spectrum of enthusiastic valve testing folk, who own, or have built several models of VCM's/ testers, & modern DC types. Long may it continue.
To think that a Chinese thingy is going to appear and destine all our equipment to the skip - is an anathema to serious vintage RR&R folk. From the free standardised valve project I ran last year, some of us got jolly close to Martin's Roetest's results, 6AU5GT-wise, and many others were close enough, % - wise. If you've got the dosh - then buy a Roetest or a AVO163, or a Tek. If you're handy at building projects - then build a Sussex or a self-designed DC Tester. If you've only got a few quid - look out for a cheapo Taylor 45 & do it up. ( I acquired really grotty one a couple of years back for £60, and sold it several month's later for £160(to a satisfied vintage guy)). Regards, David |
23rd Sep 2018, 10:56 pm | #29 |
Dekatron
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Re: Valve Tester Prices?
Clearing out the loft (a serious big job involving 8 carloads of squirreled junk to the dump) I found an AVO price list from 1980. Among other gems was the price at that time of a VCM163, at £795 plus VAT. Translating that forward in time to now, and adding current VAT comes to £4,100.
Which makes the average price on eBay of ~£1k a bit of a bargain, even though well out of the league of most pockets. I'll scan the list and post it. Craig |
24th Sep 2018, 12:06 am | #30 |
Dekatron
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Re: Valve Tester Prices?
I do wonder how many new valve testers were actually being bought in 1980- though I'm prepared to be surprised! I can certainly imagine that there was a fair amount of military legacy support still going on (after all, Port Stanley runway was bombed on H2S, and Shackletons combed the skies with 1944-vintage radar until 1991....) but the Services surely had had most of the valve testers that they needed by then, with a small replacement trickle. It was noticeable that the price of the AVO8 eventually exponentiated into extinction, perhaps this was going on with the VCM163 as demand went down and price went up in a vicious spiral of production diminution. It would be interesting to know the price in the heyday- say the mid '60s.
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24th Sep 2018, 12:21 am | #31 |
Dekatron
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Re: Valve Tester Prices?
I've now changed my mind. When I was casually looking at the prices of such things a while ago, I had noticed that the prices being achieved (not what folk were asking) had bottomed out compared with when I'd looked probably several years previously. However, out of interest I've just had another quick look and I see that prices are up again, although there's quite a variation for what on the face of it looks like the same pieces of kit. I suppose it depends a lot on who's on the lookout at a particular time, so if someone wants one and pays over the odds at a particular time, then another one comes on the market a short while after, then that same person is unlikely to want to buy another. The other person who may have been interested in the original tester may then be able to buy the second one for less than half the price of the first one if no one else is interested at the time - just an observation.
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24th Sep 2018, 12:33 am | #32 |
Dekatron
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Re: Valve Tester Prices?
If the sporadically reported practice of using valve testers to "burn in" valves of appreciable power capability is at all widespread, then there really will be a diminishing stock and escalating price. It reminds me of the apocryphal tales from the 17th century of black tulip bulbs being hunted out and stamped on to inflate the value of the survivors.
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24th Sep 2018, 12:48 am | #33 |
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Re: Valve Tester Prices?
Alternatively, see it as a source of cheap, burned-out valve testers.
A non-original meter with an opamp and a floating PSU for said opamp or maybe a rewind from Ed ought to do the trick, else you're re-winding cards for grid volts pots David
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24th Sep 2018, 8:46 am | #34 |
Dekatron
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Re: Valve Tester Prices?
Like most electronics, and particularly for valve testers, the majority of the parts cost are:
Casework Transformers Switches and knobs Now in any AVO valve tester there are at least two transformers (and in some models three) with multiple taps. The heater transformer in the VCM163 had 18 primary taps and 3 secondary windings of 10 taps each, plus a shield. Such a transformer is labour-intensive even if you are building it in-house. A quick sum - one secondary winding provided taps at 0.1V increments. If each increment is a single turn, that suggests that the primary winding has to have at least 2,400 turns - which is a lot of turns for a mains transformer primary. And then they are all hand wired and lacing cord loomed. Candidly I'm astonished that they manufactured them and made a profit for the equivalent of four grand. Craig |
24th Sep 2018, 10:59 am | #35 |
Nonode
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Re: Valve Tester Prices?
Another old equipment used by the Vulcans on Port Stanley was STR18 - HF AM Tx/Rx, I was once told. Even though it had been made redundant by Collins 618, RAF-wise, by the '70's. As for the Shackletons, their AEW Radar was a beast of a thing,(ex US WW2 Neptune's ?, & RNAS Gannet's)) I remember from my days on 8 Sqdn.
Back to Valve Testers - in the 60's & 70's, the CT160 reined supreme in the RAF, but it was never designed for "burning in" valves. Neither were MK1's to Mk4's VCM's. If folk wish to burn in or "soak test" o/p valves, then the only option is to build a DC rig which can replicate the HT's & Ia's experienced in P - P Amps, Quads,Tx o/p stages, or whatever. Refurbish a big old Amp chassis, buy or scrounge an old o/p T/F. If necessary, get Ed to rewind one, and so on. Its been said, time & time again, spares for vintage valve testers & VCM's are becoming more & more expensive. Folk could probably build a decent & sturdy DC rig for less than the cost of a CT160's 30uA meter! Regards, David |
24th Sep 2018, 12:35 pm | #36 |
Dekatron
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Re: Valve Tester Prices?
The horrible abuse of using valve-testers for "burn-in" is probably engendered by those with cold-eyed vested interest- someone with financial interest in acquiring testers from surplus sources and selling them on at appreciable mark-up could go on audiophile forums with a load of spiel about how much enjoyment they derive from their ££££££ system, and a casual aside as to how their AVO MkIV is instrumental in selecting valves with "three-dimensional air" and "tangible focus". A load of enthusiasts with casually acquired and under-used valve testers chime in, and the OP responds enthusiastically,
"You do know that KT88s need to be burned in on a tester for several hours before they really sing- in fact, it's best done overnight so that the heated anode doesn't suffer from heliophotonic contamination. You also need to burn-in matched valves simultaneously for exactly the same time on the same tester, otherwise the matching goes out the window- I can supply 2-to-1 parallel adaptors for any valve base for only £799 plus VAT." |
24th Sep 2018, 1:10 pm | #37 |
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Re: Valve Tester Prices?
Of course, people with really good hearing can tell instantly if valves have been burnt-in on lesser models of valve tester. "AVO Tested" gives a 75.13% uplift in price. 113.82% if accompanied by a photo.
They can also hear whether or not the original cardboard box for a valve is within a furlong of the valve. David
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24th Sep 2018, 4:53 pm | #38 |
Nonode
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Re: Valve Tester Prices?
On odd occasions in recent times, I've successfully sold big O/P valves on eBay, and via this Forum. All accompanied by a hand-drawn graph from either my DC tester &/or my Mk3. Non of the valves are left to linger on max Ia for more than the few seconds it takes to read Ia & Vg meters, whilst monitoring & maintaining Va & Vs at correct HT's. In fact my DC tester applies VA & Vs together via a two pole hd relay which in turn is only operated by a spring-loaded toggle switch. Vg starts out at max -ve, then reduced gradually step by step, thus Ia increases. At no time does Ia get left on for "burning-in" or "soaking". If audio geeks & phools &/or internet valve speculators make claims about such use of AVO VCM's or Testers - then challenge them to produce a graph of Ia/Vg. Just quoting "AVO Tested" and some figure for Gm doesn't fully relate to an o/p valve's broad working capabilities.
Me doing thing the old analogue/hand drawing way can take 1/2hr to 3/4hr per valve. Those lucky folk with a Roetest, Tek, or other means of digital software testing - can probably knock out a graph in 5 or 10 minutes. That will be the future, I reckon, for testing valves. What you do get with an AVO, HSVT, Taylor, Hickok, etc.(all approaching pensionable age) is a quick & reasonably good continuity/electrode insulation/gas/etc. test, prior to establishing a reasonably good idea of a valve's Gm with a valve working in the lower regions of its max Ia/Vg characteristic. Regards, David |
25th Sep 2018, 7:51 am | #39 |
Heptode
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Re: Valve Tester Prices?
What would happen to valve tester prices if “DC tested” became the ‘must-have’ for the audio fraternity rather than “AVO tested”?
Stuart |
25th Sep 2018, 8:04 am | #40 |
Dekatron
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Re: Valve Tester Prices?
Tektronix used to burn in valves for typically 200 hours in massive racks designed specifically for the purpose. This was both to allow characteristics to stabilise, and to weed out any infant mortality.
I'll try to find the reference. Craig |