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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 29th Jun 2022, 5:20 pm   #21
Lucien Nunes
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Default Re: Faulty valves - Scrap or keep?

And unless generously supplied with known faulty valves, might be repurposing usable items in a way that removes them from ever being available for repairs.

Quote:
Keeping dud valves seems deeply odd to me; would you keep broken mugs, worn-out tyres, or blown lamp-bulbs/fuses?
No, maybe and maybe.

Unlike most types of valve, most varieties of mug are still being manufactured and a new mug is likely to be better than a repaired one. Non-operational preserved vehicles can be exhibited with tyres that are no longer suitable for road use, but would look odd with bare rims. Truly life-expired tyres are often perished throughout and could not be used in any way to contribute to future repair / conservation efforts, which is not the same for valve electrode assemblies. I have some n/g lamps that look generally intact but don't work. I can let people handle them without fear of losing something valuable if dropped.

This forum has an emphasis on making things work; sets and parts are seen mainly in the light of whether they are useful towards this aim. This is not universal in the study of historical objects. For example, dinosaur skeletons don't 'work' and they've already been documented and studied, and once upon a time there were thousands of them around. So by some of our metrics are not worth keeping.

People presumably used to throw dead Loewe 3NFs away once the repair service came to an end.
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Old 29th Jun 2022, 7:22 pm   #22
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Default Re: Faulty valves - Scrap or keep?

I might keep worn out tyres if still marginally useful for example to fit to a vehicle in order to tow it away for scrap, much cheaper than a recovery truck.

I would not keep a broken mug unless so rare as to be still interesting even if broken.

I would keep dead light bulbs if rare and interesting but not otherwise.

Cant think of a reason to keep dead fuses, except perhaps very short term as a reminder to purchase new ones. Or in the workplace to give to the store keeper "please order more of these"
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Old 1st Jul 2022, 10:21 am   #23
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Default Re: Faulty valves - Scrap or keep?

So, you have a couple of PX4s apparently dead. Play around with them, re-solder the pins
and whatever else you can think of, still don't work. Did you re-solder them well enough?Is there something wrong with your test gear? Must be duff, might as well bin them....
or keep them, just in case?
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Old 2nd Jul 2022, 9:49 am   #24
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Default Re: Faulty valves - Scrap or keep?

I have a few dead valves , none of which are rare but they are interesting shapes and filaments but i certainly dont keep every dead valve that comes my way.
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Old 2nd Jul 2022, 10:26 am   #25
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Default Re: Faulty valves - Scrap or keep?

Could they be useful as dummies to check for shorts? I have been building a small radio that uses the mini battery types and I had a short which wiped out all three heaters! But in my backtracking and repairing where the shorts were occuring (dirty and shorting trimmer cap and lack of insulation for the base), I used the valves to still test the circuit before putting new functioning ones in that may blow again.

It occurred to me that it's only the heaters that blew, so while non functioning and trash, the rest of the internals will still at least connect to the right places, enabling me to check voltages to an extent. Though one doesn't want to be buried in valves. It also seems sad to throw away something in limited supply, but then if it's broken... What can one do?
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Old 2nd Jul 2022, 10:36 am   #26
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Default Re: Faulty valves - Scrap or keep?

Sadly Spencer,
once the heater or filament is blown the valve does not function, no emissions, so no meaningful measurements can be had by using it...
Alan
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Old 2nd Jul 2022, 11:13 am   #27
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Default Re: Faulty valves - Scrap or keep?

Oh yes, I know the current would be all wrong and actual measurements are off but I mean in the sense that I was able to check in practice that no sparks or shorts were occuring at least in those conditions, which make me comfortable enough to put new valves in. A bit like when you fit stabilisers to a bicycle!

Perhaps it's not a good method. My next project also involves 2x DF91s, so I may keep the dead DF91s I have for that purpose.
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Old 2nd Jul 2022, 1:54 pm   #28
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Default Re: Faulty valves - Scrap or keep?

There can be shades of grey when it comes to some valves being 'faulty'.

One such example is the 6BM8, which I'd suggest is the most 'pulled' noval power pentode in Australia - in that anyone involved with servicing valve equipment would likely have pulled them, given the variety of radio's and radiograms etc that this valve was used in.

A few years ago I won a box of 83 such pulled valves for I recall $2. As an exercise in frugality I tested each one in a typical cathode biased test circuit for nominal anode voltages, and for grid leakage of the triode as well as the pentode, and then tested good like valves for matched pairs in a PA amp. I ended up with 17 matched pairs, and an additional 34 ok pentodes (the triode grid was leaky). I didn't test the 'ok pentodes' to see how many could be used as matched pairs, but likely to be a few. Based on that batch, my general comment would be that in Australia there are likely quite a few 'faulty' valves that could happily live a useful life.

Furthermore, one option is to use just the pentode portion of the 6BM8 if it is still ok, especially when the valve has been pulled due to a leaky triode input grid. Obviously not for existing applications that actually need a 6BM8, but certainly ok for those just wanting a noval power pentode (with probably more than a 7W anode dissipation limit now).
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Old 2nd Jul 2022, 1:59 pm   #29
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Default Re: Faulty valves - Scrap or keep?

I don't keep old, duff valves in large numbers, but I do hang on to a couple, for example a low emission SD4 in the hope that one day it is possible to revive it. I don't hold much hope mind, but the couple that I keep don't take up any room. Not just that, but one day I may acquire a set that uses (say) an SD4 and I can fit it if only for the visual aspect in a 'vision' only radio.
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Old 3rd Jul 2022, 8:53 am   #30
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Default Re: Faulty valves - Scrap or keep?

I bet most of the valves I have aquired over the years, stored in boxes here and there are probably dud.
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Old 3rd Jul 2022, 9:03 am   #31
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Default Re: Faulty valves - Scrap or keep?

Quote:
Originally Posted by Pilot Mariner View Post
I bet most of the valves I have aquired over the years, stored in boxes here and there are probably dud.
You're welcome to use my Mullard valve tester Mark!
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Old 3rd Jul 2022, 9:10 am   #32
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Default Re: Faulty valves - Scrap or keep?

Thanks Steve, must bring those PX4s over one day !
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Old 3rd Jul 2022, 5:18 pm   #33
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Default Re: Faulty valves - Scrap or keep?

Quote:
Originally Posted by G6Tanuki View Post
I am very much of the hoarder-in-reverse 'if in doubt throw them out' school; I hate clutter and have [voluntarily] restricted myself to a limited storage-space!

Keeping dud valves seems deeply odd to me; would you keep broken mugs, worn-out tyres, or blown lamp-bulbs/fuses?

[Though my late mother used to put old lamp-bulbs back in the carton the replacement came in, then inevitably these dud-bulbs-in-a-new-box would find their way back into the cupboard-in-the-utility-room where new bulbs were kept, leading to much frustration/time-wasted-fault-finding when a bulb failed and a 'new' one failed to restore illumination. I also worked briefly with a guy who would take a replacement fuse/panel-bulb fron our spares, and put the failed one back in the packet with the new ones; when we discovered what he had been doing I got the entire spares-holding written-off and reprovisioned; the offender left our employment at the same time].

In my youth I used to salvage the octal bases from valves, but having accrued a collection of a few dozen and never having used one, they went to the skip during one of my student-era house moves.

These days I 'crack' failed fuses, and snip a few pins off dud valves to make sure they don't [either inadvertently or through deception] re-enter the supply-chain. In times-past I would 'pop' valves to destroy the vacuum but in recent times, having become aware of the potential risks of some of the materials inside, I just snip a few pins off and they go to WEEE along with failed lightbulbs (whether LED or CFL).

Quite a lot of the supposed "NOS" boxed valves I see advertised are, I suspect, 'pulls' from equipment where a technician has put the failed valve back in the carton the replacement came in, and these have found their way back into the supply-chain.
Indeed, I recently purchased a PCL85/05 that was supposedly NOS. It wasn't; it was definitely a pull, which had been returned to a new carton!

David.
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Old 3rd Jul 2022, 5:50 pm   #34
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Default Re: Faulty valves - Scrap or keep?

I have a few dud valves which I keep for messing around with on a rainy day. I made a couple of those valve component displays that Mullard made with the grids, cathode ECT. carefully glued to a back board.

I have a NOS EABC80 which the pip got broken off after an unlucky accident I intend to do the same with sometime

I did a nasty experiment to an EF80 that was a well baked pull from an old telly just to see what a small signal valve could take. With the heater lit correctly I connected a big high voltage power supply between anode and cathode without any current limiting I think I got nearly 500mA at over 400 volts before the cathode strip parted from the cathode. Just before it expired the anode was glowing bright yellow!!

Christopher Capener
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Old 4th Jul 2022, 6:23 pm   #35
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Default Re: Faulty valves - Scrap or keep?

I made a duff VU111 valve into a clock for someone who had worked in radar.......he loved it!


Cheers....

Simon.
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Old 4th Jul 2022, 7:13 pm   #36
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Default Re: Faulty valves - Scrap or keep?

That is amazing!
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Old 4th Jul 2022, 7:45 pm   #37
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Default Re: Faulty valves - Scrap or keep?

Interesting thread. I am actually doing a big sort out of valves acquired over the years.
Some are definitely NOS (unless somebody has gone to the extent of preparing a factory level tissue paper wrap and tuck job) but many are an unknown and will lie in wait until I actually need to find out if they are good or not. Known duff are mainly 're-atmosphered' and the internal workings studied. Sometimes just get put in the glass/metal household waste bin (it's all eminently recyclable). But never packed away back into the carton to disappoint somebody in another half-century's time.

Which got me thinking... Has anybody ever come across valve boxes where the engineer had helpfully filled out the printed table "Customer..... Model..... Date removed...."., etc ?

Did you, as a service guy, actually fill out that table ??
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Old 5th Jul 2022, 5:35 am   #38
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Default Re: Faulty valves - Scrap or keep?

Quote:
Originally Posted by stevehertz View Post
That is amazing!


Thank you!
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Old 6th Jul 2022, 5:10 pm   #39
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Default Re: Faulty valves - Scrap or keep?

Quote:
Originally Posted by alfatangowhisky View Post
Which got me thinking... Has anybody ever come across valve boxes where the engineer had helpfully filled out the printed table "Customer..... Model..... Date removed...."., etc ?

Did you, as a service guy, actually fill out that table ??
I never really was involved in 'consumer' valve electronics; but in times-past I filled in plenty of "Factory return" forms for Eitel-McCulloch [Eimac] 4CX350 valves that had been run for 1000 hours 'sweat testing' with a two-tone SSB test at maximum rated limits; this was part of my QA procedure on the HF linear-amops I was producing, and I'd label the return-forms something like "This is not a failure, just tell me how healthy these tubes are?"

They invariably came back with a report saying "these are still within original production tolerance" which was reassuring.
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Old 9th Jul 2022, 6:55 am   #40
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Default Re: Faulty valves - Scrap or keep?

I have a substantial box of "dead" valves/tubes. Mainly the large base 4,5,6,& 7 pin tubes.
It has proven a godsend when having to build extension cables to work on radios, etc.
not to mention helping out my ham buddies.
I also use them as bases for HB coil forms.
Typically, I toss the wire pin tubes that are bad and the octals that are missing any base pins.
I tossed literally 4 35 gallon garbage cans of bad tubes out (I sold tubes at Hamfairs and would only sell tested, good ones) a few decades back. My trash man was not happy with me either, because of the weight.
Anymore, I toss any tube unless it has the odd shape to make Steampunk stuff with. I had a local artist and gifted him with several shopping bags of "duds" to make Steampunk stuff with. He did a good business selling them on Etsy a few years back.
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