Thermionic Valves

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flaxcottage
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Thermionic Valves

Post by flaxcottage » Sat Feb 17, 2018 1:11 pm

In another thread I promised to post some photos of my thermionic valve collection so I ventured into my shed and dug out some specimens.
UU3.jpg
UU3: A 1930s full wave rectifier for a radio PSU
UU5.jpg
UU5: A 1930s to 1960s full wave rectifier for a radio PSU. This dates from the 30s
IW3.jpg
IW3: A 1930s high power full wave rectifier.
VMS4.jpg
VMS4: A catkin version of this IF pentode from the 1930s. The outer case is a copper screen (hence the patina). Inside is a copper anode fused to the glass envelope.
ACSG.jpg
AC/SG: A RF tetrode from the early 1930s
PT4.jpg
PT4: A power output pentode from the 1930s. This produced up to 2W of audio power!
EF50.jpg
EF50: A high frequency pentode valve used in huge numbers in WW2 in radios and radar sets. Surplus valves appeared in the early 50s and were used by home constructors in early TVs.
EBC33.jpg
EBC33: A double diode triode used in radios to extract the audio from the amplified IF signal; from the late 30s
12E1.jpg
12E1: A high power pentode valve dating from the early 1950s. They were used in regulated PSUs and could handle 200-300mA at voltages up to 800v.
All these valves with the exception of the EF50 were removed working from original equipment. The EF50 came in a box of 'junk'. The early valves had 4v 1A heaters (this was the standard at the time). The mains transformers were massive, having to supply up to 10A at 4v and 150mA at 350v (I wish I had kept some of them!)

The 12E1 was salvaged from a PSU chassis. There were two in parallel providing about 0.5A at 500v, variable. :shock: Not the sort of power one would use today. Home constructors were a hardy lot BITD. :lol:
- John

Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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Re: Thermionic Valves

Post by martinw » Sat Feb 17, 2018 1:28 pm

Some nice specimens of electronics from yesteryear you’ve got there John =D>

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Re: Thermionic Valves

Post by crj » Sun Feb 18, 2018 2:47 am

Impressive, but what on earth were they thinking when the chose the shape of the enclosure for some of those? I'm looking especially at the UU5.

Does making it a bizarre shape serve any electronic purpose?

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Re: Thermionic Valves

Post by flaxcottage » Sun Feb 18, 2018 8:46 am

When one looks at valves it is noticeable that there are several shapes that are repeated across the decades and across manufacturers. For valves which enjoyed a long production life, they may occur in several different envelope shapes and base configurations. The UU5 was a case in point.

Jump to the present day and we have different package shapes, silicon technology and sizes for the same integrated circuit. Maybe in 90 years time someone will be asking the same question about the humble SN7400. :lol:
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Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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Re: Thermionic Valves

Post by martinw » Sun Feb 18, 2018 10:55 am

crj wrote: Does making it a bizarre shape serve any electronic purpose?
Possibly it’s due to the mechanics of the design, cost, manufacturing process, all these things go hand in hand in any design ...

For example here’s a 486 DX with the size of the chip and the size of the actual bit that does all the hard work, the die (small rectangle of silicon in the middle) ...
647B456C-0E6F-4DB1-BBC8-489ECB90E073.jpeg
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Re: Thermionic Valves

Post by flaxcottage » Sun Feb 18, 2018 12:45 pm

I ventured into the flaxcottage valve vault again. This time I retrieved some television valves and an oddity I collected from a heavy duty stabilised PSU.
20P1.jpg
20P1: A 1950s vintage line output valve.
U801.jpg
U801: This is a beast of a valve, a quad diode rectifier.
These two valves above came from our very first television dating from 1953, a 12" B&W table top EKCO (very similar to the EKCO T161). The U801 was very problematic. It served as both HT mains rectifier and EHT efficiency diode, something it was not designed to do. It regularly broke, often with spectacular effects!
PY33.jpg
PY33: An early 1960s HW rectifier diode. This could handle over 300mA.
One 'feature' of valve TV sets was their live chassis. Because of the huge power demands of these sets, often over 150W, a mains transformer was not used to isolate the mains. Diodes such as the PY33 above were placed in series with the live mains input to provide about 220v HT for the other valves. Wiring the mains plug the wrong way could be fatal! :?
PY500A.jpg
PY500A: A late 60s television efficiency diode
The PY500A was designed to rectify some of the flyback energy from the set's EHT/line output transformer to provide a boosted HT line, often around 800v. It could withstand anode voltages of several thousand volts.
PL504.jpg
PL504: A late 60s line output valve.
PL519.jpg
PL519: A line output valve for large screen colour TVs. This was one of the last of these valves produced. An early 70s example.
The above two valves show the development of the line output valve. The PL504 could dissipate 25W whereas the PL519 handled 35W.
DLS16.jpg
DLS 16: An interesting oddity. This is a thermal delay switch from a stabilised PSU.
DLS16 side.jpg
DLS 16 from the side
The job of this little beauty was to delay the application of the rectified HT to the PSU stabilising circuits until the valves had reached their operating temperature. This, in some measure, protected the external equipment from over-voltage damage. It could handle switching over 500v at 500mA.
- John

Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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Re: Thermionic Valves

Post by Diminished » Sun Feb 18, 2018 5:21 pm

For emotional and historic reasons with which I won't bore you, I have a real fondness for these.

Shortly before Christmas I re-valved my guitar amplifier as I had a gig to play. One of the original valves had gone microphonic (a big problem at stage volumes) so I bought gorgeous new sets of ECC83s and EL84s:
IMG_20170823_132553434_HDR.jpg
I think the thing I learned from this is that a valve can quite easily go out of spec while still operating. A friend of mine recently got in touch with me about a Vox AC30 which was routinely blowing a fuse at power-on, and my guess is that he just has a dodgy valve in it which is sucking marginally too much juice through its heater when cold, but functions just fine in all other aspects.

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Re: Thermionic Valves

Post by flaxcottage » Sun Feb 18, 2018 5:33 pm

Nice.

It is a shame that Mullard is no longer making valves. I loved the Mullard logo BITD.

I used an EL84 and an ECC83 to make my first audio amp with an EZ81 as the rectifier. :D My mate used a 6V6 as the output and I was jealous 'cos it sounded better. :(

Somewhere I have some UL84s that were used in portable record players. To get the right heater voltage an auto-transformer was used along with a UY85 rectifier. For some reason the UL84 does not have the same power output as the EL84. :?
- John

Why do I keep collecting Acorn gear? I'm going to need a considerably bigger man-cave. :?

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Re: Thermionic Valves

Post by Diminished » Sun Feb 18, 2018 7:06 pm

I vaguely remember Mullard valves. New-old-stock Mullards are still sought after by guitarists.

I think the reason I like these little baubles so much is because I was exactly the right age to be captivated by them. There is a documented phenomenon of children being enraptured more by slightly antiquated technology than by modern technology, and this was definitely true for me growing up. Everything new was already solid state by the time I was born, but there were still bits of old valve gear kicking around the house, and I was fascinated by the fact that they had to warm up before they could be used.

I do worry about the supply of these things. I believe there are something like four companies worldwide still making them. Oddly, the company that made the devices I bought was IIRC established sometime in the mid 90s, which seems a very strange time to set up a firm making thermionics, but they seem to be doing all right. Still, some days I feel like stockpiling a couple of spare sets. I did get a shock when I wanted to replace a broken-down old 19" CRT monitor a few years back and discovered that in the intervening few years, every single company had stopped making CRTs. Flat panels have improved a lot since, but in the earlier days it seemed to me that monitor manufacturers had made a cartel-style decision that as an industry they were simply going to switch to selling products that were in many ways inferior, just because it was convenient.

Still, I should be glad that the humble guitar amplifier was the one consumer product that resisted the solid state revolution, otherwise you really wouldn't be able to get these at all any more, and we would all have to use horrid digital modelling amplifiers instead.

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Re: Thermionic Valves

Post by Coeus » Sun Feb 18, 2018 9:15 pm

Diminished wrote:...I do worry about the supply of these things. I believe there are something like four companies worldwide still making them. Oddly, the company that made the devices I bought was IIRC established sometime in the mid 90s, which seems a very strange time to set up a firm making thermionics, but they seem to be doing all right...
Clearly there is a market for them as you have just bought some. I think valve-based amps are still popular with guitarists and there are also niche markets in expensive audiophile HiFi amps and pre-amps for audio recording. Some studio condenser mics have a valve inside the housing. All condenser mics need an a small pre-amp/impedance converter as the capsule must see a high impedance while the cabling back to a mixing desk will be low impedance (and usually balanced) to avoid noise pickup but more modern designs will tend to be FET-based.

I wonder what other markets still exist. I read a few years ago now that high-powered RF applications, for example TV transmitters, tended to be valve based and that was long after just about everything else was transistorised or even IC-based. I don't know if that is still the case.

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Re: Thermionic Valves

Post by Diminished » Sun Feb 18, 2018 9:24 pm

Coeus wrote:I wonder what other markets still exist. I read a few years ago now that high-powered RF applications, for example TV transmitters, tended to be valve based and that was long after just about everything else was transistorised or even IC-based. I don't know if that is still the case.
I assume domestic microwaves still use magnetrons, although those are a very specialised type of valve.

Maybe radar still uses them too.

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Re: Thermionic Valves

Post by MartinB » Sun Feb 18, 2018 11:20 pm

Modern mechanically-scanned radars use a 'valve' called a Travelling Wave Tube (TWT) but the latest generation of 'no moving parts' systems are electronically scanned and use clusters of Transmit/Receive Modules (TRMs) - small low-power solid-state RF transmitters which, when employed in numbers, form high power transmitters.

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Re: Thermionic Valves

Post by Andy1979 » Wed Feb 21, 2018 9:58 am

Interesting stuff. As a child of the 80s I missed out on valve gear, but always been aware of it from a general interest in hifi - and from my degree masters supervisor being very proud of his massive thyratron :lol: .

Prices for Mullard valves on eBay are crazy these days.

A few years back my (now) wife and I stayed in a trendy Berlin hotel which had equipped every room with a Pye Black Box record player. She said she wanted one so, eager to impress, I managed to find one for sale locally for a bargain price, only to discover that the power transformer had melted itself, coating most of the components with wax. With help from the invaluable Vintage Radio Forum I managed to rebuild the amp, replacing pretty much everything apart from the output transformer. The biggest problem was finding an equivalent power transformer, but a very helpful chap on the forum was able to supply me with one that was close enough in specification, albeit twice the size. Somehow managed not to kill myself with the high voltages and it's still going strong today. The one concession to modernity was adding a line-input to the amp, so it can also be used for streaming music. Stocked up on spare valves in case of a disaster (not Mullards though!)

Was very tempting to install an eBay solid state amplifier module, but I'm glad I persisted, and it's far more satisfying to listen to than one of the plastic Crossley turntables beloved by hipsters. Now have an itch to build or purchase a stereo valve amp, but have managed to resist so far.

My wife's more recent purchase of a big 1980s ghetto blaster is considerably less impressive on the inside - amazing how much quality was lost in a short space of time.

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Re: Thermionic Valves

Post by martinw » Wed Feb 21, 2018 10:04 am

Andy1979 wrote:As a child of the 80s I missed out on valve gear
Me too, they seem to be making a bit of a comeback though.

https://thevinylfactory.com/features/th ... ipped-off/

Martin

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Re: Thermionic Valves

Post by daveejhitchins » Wed Feb 21, 2018 10:36 am

Sort of a valve - the venerable Nixie tube brought back to life here, but Very expensive. Interesting story, though!

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Re: Thermionic Valves

Post by Lardo Boffin » Wed Feb 21, 2018 10:59 am

On a slightly related note I have one of these for my iPod dock:-
408E84DE-9711-4992-B204-944514609345.jpeg
Stock photo - mine is in a box
I enjoy watching the valves warm up and glow and the one at the back changing based on the music going through it. The more recent version of mine is shown in Martin’s link by the looks of it.
Last edited by Lardo Boffin on Wed Feb 21, 2018 11:01 am, edited 1 time in total.
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Re: Thermionic Valves

Post by martinw » Wed Feb 21, 2018 11:00 am

daveejhitchins wrote:Sort of a valve - the venerable Nixie tube brought back to life here, but Very expensive. Interesting story, though!

Dave H :D
Very interesting =D>

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Re: Thermionic Valves

Post by martinw » Wed Feb 21, 2018 11:01 am

Lardo Boffin wrote:On a slightly related note I have one of these for my iPod dock:-

408E84DE-9711-4992-B204-944514609345.jpeg

I enjoy watching the valves warm up and glow and the one at the back changing based on the music going through it. The more recent version of mine is shown in Martin’s link by the looks of it.
Nice :)

Martin

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Re: Thermionic Valves

Post by BigEd » Wed Feb 21, 2018 11:40 am

> nixie tubes

If we're talking about not-quite-valves, the dekatron-based WITCH computer might be of interest! It's on display and is running most days at The National Museum of Computing on Bletchley Park. It has some relays too so it makes a nice ticketty-clunking sound as it computes.

https://www.youtube.com/watch?v=vVgc8ksstyg

http://www.tnmoc.org/news/news-releases ... e-year-old

Edit: see also the wonderful video Hand Made Vacuum Tubes by Claude Paillard

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Re: Thermionic Valves

Post by martinw » Wed Feb 21, 2018 2:44 pm

=D>

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Re: Thermionic Valves

Post by Diminished » Wed Feb 21, 2018 4:11 pm

BigEd wrote:Edit: see also the wonderful video Hand Made Vacuum Tubes by Claude Paillard
Very cool.

With the Doomsday Clock currently set to 30 seconds before midnight, this knowledge will surely come in handy when the EMP strikes. Bring on the steampunk future! :twisted:

Matched sets might be a little tricky, though.

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Re: Thermionic Valves

Post by martinw » Thu Feb 22, 2018 6:38 pm

A Philips Mullard PM4 valve received today, which I think is from the mid 1920s 8)
28DCE64E-98DC-46A5-B01C-1E44ABBA7129.jpeg
51403EFE-FAC4-4DC3-9861-6F4DCBB0D2DA.jpeg
52FF2C86-4998-447C-90BC-CF02BA161762.jpeg
4684421D-2B15-435E-944A-63EBA87F49CD.jpeg
317E447E-961D-4A82-8A0A-EAF86087E3A9.jpeg
103EAC78-D2EF-4673-AE1C-37E095DD283E.jpeg
25CBC04A-1945-49C3-9E0D-4D86FF3F1DEC.jpeg
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Re: Thermionic Valves

Post by flaxcottage » Thu Feb 22, 2018 9:23 pm

That is a lovely valve. Looks to be from 1925/26. A triode output valve and probably from a battery operated radio. :mrgreen:
- John

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Re: Thermionic Valves

Post by markjw » Thu Feb 22, 2018 10:11 pm

I still have my grandfather's Leak Stereo 50 - EL34 and ECC83 valves in it - I replaced some that had failed in the 80's and think some of them are Mullard ones. Also have the Leak Point One preamp, Leak FM Tuner, Garrard 301 turntable and a Brenell Mk5 reel-to-reel tape desk (a grey mono version), all dating from around the early to mid 60s

Unfortunately none of these have been powered up in 30 years and think it would not be safe for me to do so unless they are looked at by someone who knows all about them.

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Re: Thermionic Valves

Post by martinw » Fri Feb 23, 2018 9:06 am

flaxcottage wrote:That is a lovely valve. Looks to be from 1925/26. A triode output valve and probably from a battery operated radio. :mrgreen:
Thanks John that’s very interesting :)

Martin

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Re: Thermionic Valves

Post by 1024MAK » Fri Feb 23, 2018 11:29 am

markjw wrote:I still have my grandfather's Leak Stereo 50 - EL34 and ECC83 valves in it - I replaced some that had failed in the 80's and think some of them are Mullard ones. Also have the Leak Point One preamp, Leak FM Tuner, Garrard 301 turntable and a Brenell Mk5 reel-to-reel tape desk (a grey mono version), all dating from around the early to mid 60s

Unfortunately none of these have been powered up in 30 years and think it would not be safe for me to do so unless they are looked at by someone who knows all about them.
As I understand it, there may be two issues.

Some of the resistors (especially high value resistors that drop a high voltage) may have drifted in value.

The bigger problem is the capacitors. If there are any electrolytic types used, these need "reforming". That is, the thin insulation layer inside needs time to reform as the voltage is raised slowly, so that the leakage current is not allowed to rise quickly. This is best done out of circuit. Also the leakage current should be limited by the reforming circuit. Then the capacitor should be held at just below it's rated voltage until the leakage current has levelled off (within acceptable limits).

The second capacitor problem is just that of checking the condition of the other capacitor types for any damage.

But I'm far from an expert on valve systems... so may have forgotten about other problems...

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Re: Thermionic Valves

Post by martinw » Sat Feb 24, 2018 9:01 am

I’ve been looking into the Mullard company (the main/biggest factory was in Blackburn - Lancashire) due to them being one of the biggest valve manufacturers in the UK (there are some brilliant videos on YouTube of the manufacturing process (lots of click clacking machines 8)) in the factory by the way) ...

https://m.youtube.com/watch?v=GDvF89Bh27Y

... and it turns out (due to the Philips connection) that they produced some of the laser disks for the Domesday project!

http://www.bbc.co.uk/history/domesday/d ... 00/page/10

Everything is so interwoven in these hobbies of ours :D

Martin

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Re: Thermionic Valves

Post by martinw » Sat Mar 03, 2018 3:09 pm

A few more valves to add to my collection arrived from Bulgaria today. Although I had to go collect them from the local sorting office due to the snow. Part of the fun of living in the countryside I suppose ...
039B91F8-DD12-4DDB-A3EF-BEBBBF801F85.jpeg
... :)

A couple of red Philips Miniwatt EH2.
A gold Valvo UF6.
And a Mazda DZ908.
All in original boxes =D>
EF8837D9-C9C5-4C7C-B849-1B893CD4F1CE.jpeg
Two shelves in this cabinet are now looking very f’ing cool 8)
40E3400D-0E58-4069-B624-A1382A507D5D.jpeg
Even if I do say so myself :lol:

Martin

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Re: Thermionic Valves

Post by daveejhitchins » Sat Mar 03, 2018 4:27 pm

martinw wrote:Two shelves in this cabinet are now looking very f’ing cool
So . . . When are you open for visitors :roll:

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Re: Thermionic Valves

Post by martinw » Sat Mar 03, 2018 4:30 pm

daveejhitchins wrote:
martinw wrote:Two shelves in this cabinet are now looking very f’ing cool
So . . . When are you open for visitors :roll:

Dave H :D
Now :)

Martin

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