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Tube amps with tv tubes
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Old 16th September 2020, 02:55 PM   #21
duncan2 is online now duncan2  United Kingdom
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The Frame deflection tube associated with the CRT yoke in the late 50,s-60,s was the well known PCL85 I lost count of the number I changed due to that fault .


It was superseded by the "improved " PCL805 , it wasn't till later that I found that the design couldn't cope with dual 405/625 switching in UK TV,s in other words the tube was "under-designed " .


I still have several in my junk box.


As this fault seems to be also present in the USA according to Wg_Ski.
The tube was basically an ECL type series with a heater of 18volts for UK series heater TV,s .
After a multitude of complaints the PCL805 was brought out it wasn't a great deal better , this tube was HOT !!! in a TV circuit even cooked associated resistors -typical blackened PCB .
It was made worse by the dual standard ( switchable ) UK TV of 405/625 lines versions ( I owned several ) .


If you look at what it was asked to do in a TV circuit especially switch on from cold you will understand the load it carried.
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Old 16th September 2020, 06:54 PM   #22
Parafeed813 is offline Parafeed813  Netherlands
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Quote:
Originally Posted by duncan2 View Post
For European viewers US terminology Magnoval is known here as=B9D conforming to the Pro-Electron nomenclature ( Standard,s Body ) I can see the point of Kodabmx,s complaint I was not alone in complaining about the engineering imbalance of a very large tube having small steel pins with the only reinforcement being the glass base ,it got worse with the even heaver later versions used in color TV,s .
Always thought that magnoval was the official socket name, as it is printed on all xL5xx datasheets I have seen.
It's true that the EL/PL509/519 is a bit tall and heavy to be mounted by the socket alone. The Philips and Sylvania datasheets state that 'additional supporting of the tube at the top is required.'
That's something to address with the PL509 amp that I'm planning.
Perhaps combining shielding the topcap connection and supporting the top of the tubes.
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Old 16th September 2020, 08:06 PM   #23
duncan2 is online now duncan2  United Kingdom
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I personally don't know any tech guy into tubes in the UK using the name "Magnoval " but I realise the US has different designations for tube (valve ) bases .
The standard in the UK was used by Mullard /Mazda etc even the UK Wireless World equivalent books which are available on a very good US website for downloading.
If WW/EW used those designations you can bet all UK engineers used them too including government departments as the AVO VCM was used by them( and me ) and the base designations conformed to UK spec.


The last issue of the PL range had a very large valve/tube ,its size made the small pins look unstable --and were .


I once got a shock from the top cap while repairing a CRT television it was worse than a direct mains shock- it was near 800 volts at a high current luckily it wasn't across my heart just my arm which took a week for the throbbing to stop and was stiff for a while after.
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Old 17th September 2020, 01:14 AM   #24
PRR is offline PRR  United States
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Tube amps with tv tubes
> I personally don't know any tech guy into tubes in the UK using the name "Magnoval " but I realise the US

"Giant 9-pin in this dang TV set"

Only their parents used "Magnoval" or "B9D".
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Old 17th September 2020, 11:44 AM   #25
kodabmx is offline kodabmx  Canada
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Tube amps with tv tubes
Apparently, it's a PL24SH if you're Soviet

4x Ceramic NEW SOCKET PL24SH-2K 6KG6 /SK509 /EL509 /6P36S /6P41S /6P42S /6P45S | eBay
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Old 17th September 2020, 06:53 PM   #26
smoking-amp is offline smoking-amp  United States
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My experience has been just the opposite. The big hot octal tubes develop loose bakelite bases when the glue to glass interface fails. So many old octal tubes with adhesive tape wrapped around the base to glass joint. That's why they came up with the octal button bases later, which are more like Compactron bases.

If you have cracked a Compactron, Novar or Magnoval base tube, then you have a bad socket. Lots of old TV sets had cheesy sockets with tin plated socket pins that soldered themselves to the tube pins in the heat. A quality socket doesn't have such problems.

For audio purposes, the lower gm "audio" tubes generally do have a straightforward linearity advantage (if you are not using the extra gm for N Fdbk that is). However, with N Fdbk, even just local N Fdbk, the balance can tip the other way.

This is especially apparent with the latest design developments using TV "Sweep" tubes. Crazy drive has given us constant gm (versus plate current) beam pentodes without even using N Fdbk (feedforward actually).

Then the "new" series Schade local N Fdbk (UnSET, CED) can produce Triodes from "Sweeps" that rival, if not exceed, the best DHT triodes. (no plate curve rollover from mis-match between grid1 and plate or grid2 characteristics, greatly reduced distortion.)

Finally, Crazy Fdbk, combined with the "new" series Schade scheme (UnSET, CED) has now given us "Triodes" with constant gm and straight line plate curves. A Load Invariant constant gm lack of distortion. This is the proverbial "wire with gain". This has long been the mythical Holy Grail of tube design (or any amplifying device). Like Alchemists turning Lead into Gold. It's for real now. These are exciting times for those in the know. I would even say an historic moment.

One can exceed the quality of the best DHT tubes now without having to use extreme HV B+ or high primary Z OTs. One can make a cheap 211 or 212 Amp equivalent for a few hundred $. Without hazardous HV or compromised OT frequency response, and with low output Z. Maybe no flashy big transmitter tube look or heater illumination, but it's now a practical DIY project for everyone. Where is Heathkit when we need them?

a) Crazy drive
b) "new" series Schade (UnSET, CED)
c) Crazy Fdbk with the "new" series Schade drive

d) some $1 TV tubes don't even need any circuit tricks.

just for comparison:

e) 26LX6 native beam pentode mode
f) 26LX6 Crazy drive mode

g) 211 DHT triode

Unfortunately, many of the once low cost TV Sweeps are approaching about 1/2 the price of "audio" tubes now. With demand will come new production eventually, hopefully, like the cap-less PL509.
Attached Images
File Type: jpg rsz_38he7_g2_g1_7vs_74v.jpg (60.6 KB, 134 views)
File Type: jpg 21HB5A_Corr_Schade.jpg (641.7 KB, 133 views)
File Type: jpg Crazy_FDBK_Cath_drive_21HB5.jpg (671.9 KB, 135 views)
File Type: jpg TFH_in_triode.jpg (97.9 KB, 131 views)
File Type: jpg 26LX6_grid1_drive.jpg (51.4 KB, 110 views)
File Type: jpg 26LX6_Crazy_drive.jpg (71.9 KB, 15 views)
File Type: jpg 211_datasheet-curves.jpg (329.2 KB, 17 views)

Last edited by smoking-amp; 17th September 2020 at 07:02 PM.
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Old 17th September 2020, 07:27 PM   #27
Kay Pirinha is offline Kay Pirinha  Germany
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The capless EL509 was produced by Svetlana under the moniker EL509II but is now out of production as Svetlana has ceased their production of glass tubes. J/J still produces another one called EL509S.
Unfortunately they both are Octal tubes and share the EL34 pinout with the plate pin 3 next to the heater pin 2.
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Old 17th September 2020, 08:19 PM   #28
duncan2 is online now duncan2  United Kingdom
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The UK produced a EL506 Pentode in the 60,s suitable for audio using the UK standard --B9D base ,this valve/tube was much better designed with the anode/plate on pin 9 with pin 8 as a N/C .
As a matter of fact Mazda /Brimar UK valve/tube factories both produced it and Thorn/EMI a British company produced an audio amplifier circuit for it .


Click the image to open in full size.



By the way early design UK/USA valves /tubes of the 20,s/30,s ended up with old school insulating tape round the bases as the methods used to hold them steady were very low grade , so much so if they were moved a few times the internal wiring snapped off near the glass tube section .


I was able to cut the Bakelite out , file down the glass and resolder some of the very old exotic (expensive ) radio types .
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Old 18th September 2020, 03:28 AM   #29
smoking-amp is offline smoking-amp  United States
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If you like EL506 ($ 600 Ebay), take a look at the 10JA5 Vertical Sweep ($3 Vacuumtubes.net)

Other than 1/3 the screen V, nearly the same tube.

7868 and 7591 are similar too. (and same screen V)

Last edited by smoking-amp; 18th September 2020 at 03:39 AM.
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Old 18th September 2020, 04:10 AM   #30
wg_ski is offline wg_ski  United States
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A vertical sweep with a full 19 watt dissipation rating? In-tereseting.... looks like it likes a really low class B-ish bias in push pull too.
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