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Vacuum Tube Experience Anyone?  
User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Posted (7 years 1 month 2 weeks 23 hours ago) and read 3310 times:

Hello,

I'm currently trying my luck in restoring some WW2 British army HF radio transceivers (Wireless set No. 19) to working condition. Does anybody in here have experience working with vacuum tube technology?
Does anybody have a source for an affordable power supply, which would deliver regulated DC voltages up to 550 V at appr. 50mA?

Jan

25 replies: All unread, showing first 25:
 
User currently offlineQueso From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 1 month 2 weeks 22 hours ago) and read 3301 times:

You'll likely have to build one from an old HV transformer (just try the different taps on the secondary till you get something that will give you 550v RMS) and a bridge rectifier or something like a 5Y3 rectifier tube.

User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 2, posted (7 years 1 month 2 weeks 22 hours ago) and read 3297 times:

The tranceivers need three voltages for operation: 12V for the heating, 250 V for the receiver, intercom amplifier and transmitter modulation and ozcillator stages and finally 550 V for the transmitter power amplifier stage.

Jan


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 3, posted (7 years 1 month 2 weeks 22 hours ago) and read 3286 times:

I only fiddled with civilian post-war equipment which mostly ran at 200V... TVs and audio devices were significantly different in design, but at least the latter used linear transformers with 6.3V for heating and 2*200V with a double-diode rectifier (some valve-based, some solid state) and simple electrolytic buffers after that.

They can't have had very high demands on absolute voltage stability when you think about it...  Wink

But it was still enough to give you a very solid whack when accidentally coming in contact with the not-quite-discharged capacitors...  fight 

It should still be possible to improvise a power supply for your needs, but getting your hands on the high-voltage parts might be a bit tricky.


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 4, posted (7 years 1 month 2 weeks 22 hours ago) and read 3273 times:

Quoting MD11Engineer (Thread starter):
Hello,

I'm currently trying my luck in restoring some WW2 British army HF radio transceivers (Wireless set No. 19) to working condition. Does anybody in here have experience working with vacuum tube technology?
Does anybody have a source for an affordable power supply, which would deliver regulated DC voltages up to 550 V at appr. 50mA?

Jan



Quoting MD11Engineer (Reply 2):
The tranceivers need three voltages for operation: 12V for the heating, 250 V for the receiver, intercom amplifier and transmitter modulation and ozcillator stages and finally 550 V for the transmitter power amplifier stage.

Jan

Designing a power supply would be the easy part of it. You're going to have to build it yourself, of course. It would be a good idea to start with figuring out how much you need in the way of current for each circuit. That'll tell you what you need when you go transformer shopping.

I'm assuming that the radios had some sort of motor generator power supply like some of the BC348s had?

I do not know how availability of vintage type electronic components is in Germany, but availability is good here. you may find that you end up using a 120v input transformer set, and then use a stepdown transformer to make your line voltage in Europe do the job.

I've built and repaired a number of tube type guitar amplifiers and some rather simple broadcast band receivers but higher order electronics is really not my strong suit. I would suggest that you invest in a good quality multimeter, a couple of throwaway cheapies (Chinese, they cost about $3 each on special here), and start hanging around with some ham radio type old geezers.

You can expect that you will want to bring the internal voltage up slowly with a variac once you get your power supply built, and you can also expect that electrolytic capacitors will be shot and any paper/oil capacitors will be leaky and any resistors will have changed value.

It would be a good idea to check out this guy and get hooked up.

Best of luck keeping the old boat anchors alive.

http://www.qsl.net/ve3bdb/


User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 5, posted (7 years 1 month 2 weeks 22 hours ago) and read 3273 times:

Quoting Klaus (Reply 3):
It should still be possible to improvise a power supply for your needs, but getting your hands on the high-voltage parts might be a bit tricky.

I have notice this. Almost all regulated variable power supplies I've seen for sale are only up to something like 30 V DC.
The last of the transceivers I bought on eBay came with a home brew power supply, actually when I tested the set as receiver (I don't have an amateur radio operator's licence yet) it worked fine for a few hours (I received 40 m band commercial transmissions from Canada and possibly Japan as well as CW, morse code, transmissions from radio hams, loud and clear using my 6m CB antenna), but after a while the set suddenly went quiet. I checked the power supply and found it operating at about TWICE the required high voltages, a massive overload. I checked the tube heating circuit using a lab power supply and found all tubes intact.
I assume that I must have shot a capacitor, after all the capacitors in the receiver circuits were rated at appr. 300V and were by now 60+ years old.
After i opened the power supply, which looked fairly professional from the outside, I found out that on the inside it was extreme "Pfusch". With all the loose components (especially the two high voltage capacitors of 50 microfarads each) loose and long unisolated wires hanging around I was lucky I didn't get killed.
The circuit was a simple transformer, 220V net to one winding with 12.6 V 2.5 A and one winding for 260V 200mA, connected to a voltage doubler circuit made up out of four diodes and two capacitors, plus a few resistors.
I might cannibalise this power supply to build something more reliable, but I'd like to have a power supply with which I can slowly rraise the voltage, especially to regenerate the capacitors on old sets whicjh haven't been used for decades.

Jan


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 6, posted (7 years 1 month 2 weeks 22 hours ago) and read 3269 times:

Quoting MD11Engineer (Reply 2):
The tranceivers need three voltages for operation: 12V for the heating, 250 V for the receiver, intercom amplifier and transmitter modulation and ozcillator stages and finally 550 V for the transmitter power amplifier stage.

I'd get in touch with your local radio amateur scene for that... They're probably the only people around who have an interest in and experience with high-powered tube technlogy below high-end industrial stuff nowadays. They may also be helpful in getting a matching power supply or at least finding parts for one.

What you need will most probably be a bit trickier than the supplies I knew back then, since you will not only need high voltage but also significant amounts of current out of it. The simple linear solution may just not suffice there.


User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 7, posted (7 years 1 month 2 weeks 22 hours ago) and read 3254 times:

Thanks for the hint, Klaus.

The original military power supply (of which I have one, but not in working condition so far) used a dynamotor and a vibrator/transformer/rectifier to convert 12 resp. 24 DC (e.g. from a vehicle's battery) to the respective voltages.
Normally the vibrator was used while the set was in "receive" mode to save battery power, but the dynamotor jumped in through a relay as soon as the "transmit/receive" relay went into transmit mode.

Jan


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 8, posted (7 years 1 month 2 weeks 21 hours ago) and read 3250 times:

That sounds like really interesting dinosaur technology...!  bigthumbsup 

User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 9, posted (7 years 1 month 2 weeks 19 hours ago) and read 3223 times:

Quoting Klaus (Reply 8):
That sounds like really interesting dinosaur technology...! bigthumbsup

Correct!

Here is a picture of the rig I was talking about:


Unfortunately the British Army had the built in VHF set removed in the 1950s, so that it only works as HF CW and AM receiver, and as a CW transmitter (2-8 MHz, 15-18 W)

This is a look on the chassis of another set of the same type, which is more original (hasn't been tampered with)from the top:
On the left are the built in VHF set (in the small shielding box) and the sockets for the tubes of the intercom amplifier, the center is the HF transmission PA amplifier tube and tuning capacitor and the audio amplifier of the HF set and to the right the tubes (and under the big box) the tuning capacitor of the HF set.

http://img.photobucket.com/albums/v174/jkrusat/WS19-top-small.jpg

And this are the spaghetti in the chassis (no printed circuits back then, just phenolic strips with eyelets riveted to them as anchor points for the components):

http://img.photobucket.com/albums/v174/jkrusat/WS19-bottom-small.jpg

Here is the data plate and some details from the front cover. The unit was built in Canada by Northern electrics under a British specification. Sets of this type were also given to the Russians as war aid under the lend-lease treaties, thus the cyrillic lettering beneath the English one:

http://img.photobucket.com/albums/v174/jkrusat/WS19-data-plate-small.jpg

This is a shot of the original military power supply without housing. The dynamotor is in the bottom part. The black box seems to be a transformer for the vibrator circuit. Up on top is the relay, which switches the dynamotor on when the set goes into transmit mode:

http://img.photobucket.com/albums/v174/jkrusat/WS19-PSU-LH-small-text.jpg but the unit needs a full overhaul

Here is my oscilloscope, old but it is working Big grin


and here is my electronics work bench:

http://img.photobucket.com/albums/v174/jkrusat/Bench-small.jpg

On the left are two low voltage (up to 15V) power supplies. Then there is the set I mentioned earlier with the military power supply behind it to the left. The round object attached to it's housing is a variometer, a variable inductivity used to match the HF transceiver to the antenna. Behind the upturned set is the other, more original, set, which probably has never been used since 60 years and contains all the parts (VHF transceiver, intercom amplifier) removed from the other sets. This will be my project as soon as the other set is finished. On top of it is a marine long wave to HF receiver from the 1960s. To the right of it is a vehicle mount for a Bundeswehr SEM 35 man portable VHF FM radio transceiver from the 1960s-70s and to the right of it a Bundeswehr SEM 25 FM transeiver from the same period, which was installed in vehicles.

Jan


User currently offlineQueso From , joined Dec 1969, posts, RR:
Reply 10, posted (7 years 1 month 2 weeks 19 hours ago) and read 3215 times:

Your first challenge (after you get a power supply set up) is going to be to replace all of those paper capacitors in there. The wax degenerates over time and none of those will have the capacitance they are supposed to have. It looks like some of them have already been replaced with slightly more modern electrolytics so that will help but they probably all need to be checked. Then you'll probably need to disassemble those relay contacts and clean all of them. Lots of hours to be put into that chassis!

Quoting Klaus (Reply 6):
I'd get in touch with your local radio amateur scene for that... They're probably the only people around who have an interest in and experience with high-powered tube technlogy below high-end industrial stuff nowadays.

That's the only reason I know anything about them. My current tube-type toy is a Dentron Clipperton-L with 4 572's in it and it puts out about 1200 watts. I've been playing with tube-type RF amplifiers since 1982, but I have never rebuilt one as old as the transmitter you have in the picture. I've just salvaged those for usable parts- such as the transformers!


User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 11, posted (7 years 1 month 2 weeks 19 hours ago) and read 3202 times:

Actually the rig upended on the bench worked for several hours until I fried it with the excessive voltage. I hope it is just one or a few capacitors which went south. But I'm currently bidding for an affordable AF and RF function generator on eBay, so that, together with a proper power supply, I can go through the set from the audio amp through the detector and mixer stages to the HF amplifier step by step until I have found the faulty component.

Jan


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 12, posted (7 years 1 month 2 weeks 8 hours ago) and read 3129 times:

Quoting Queso (Reply 10):
Your first challenge (after you get a power supply set up) is going to be to replace all of those paper capacitors in there. The wax degenerates over time and none of those will have the capacitance they are supposed to have. It looks like some of them have already been replaced with slightly more modern electrolytics so that will help but they probably all need to be checked. Then you'll probably need to disassemble those relay contacts and clean all of them. Lots of hours to be put into that chassis!

Perhaps what you're seeing there is leakage, m'dear Queso. Wax paper capacitors ultimately fail because they are evacuated/dried out in manufacture but moisture gets in.

The average Fluke multimeter with a 'capacitance test' merely puts the capacitor under test into an r/c timing circuit. If it leaks, it takes longer to recharge and thus the reading is off. Alan Douglas has some great information about this and other subjects in his book Tube Testers and Other Classic Electronic Test Equipment-including a schematic for building a capacitor leakage tester.

Of course if you have a good test rig that will test them under load you can figure out leakage. I've got a Sprague TelOhmike that's the tits for leak checks and reforming old electrolytics-which never works very well, by the way.


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 13, posted (7 years 1 month 2 weeks 8 hours ago) and read 3124 times:

Quoting MD11Engineer (Reply 9):
Here is a picture of the rig I was talking about:

Ahhh... the memories...! Big grin

Cool (or rather hot) gear!

The mobile units were obviously quite a bit "messier" than the stationary ones I usually had dealt with... sort of high integration in the steam age...

I know that you you're used to operating potentially dangerous machinery, but please be extra careful - that anode supply can kill, and we still have use for you!


User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 14, posted (7 years 1 month 2 weeks 6 hours ago) and read 3082 times:

Quoting Klaus (Reply 13):
sort of high integration in the steam age...

Some of the tubes are in reality two in one, e.g. one pentode and one triode or two diodes in one housing.

Quoting Klaus (Reply 13):
I know that you you're used to operating potentially dangerous machinery, but please be extra careful - that anode supply can kill, and we still have use for you!

I know the basic rule about "one hand in the pocket" while measuring on live circuits.  Wink

Jan


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 15, posted (7 years 1 month 2 weeks 1 hour ago) and read 3039 times:

Quoting MD11Engineer (Reply 14):
Some of the tubes are in reality two in one, e.g. one pentode and one triode or two diodes in one housing.

Or even four:
1952 EABC 80, eine neue Röhre für AM/FM-Empfänger ( EABC80 )

The EABC80 was in pretty widespread use in valve-based radios, basically as a kind of valve IC...

Quoting MD11Engineer (Reply 14):
I know the basic rule about "one hand in the pocket" while measuring on live circuits.

Yeah... and they often take quite a while to discharge...!


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 1 month 2 weeks ago) and read 3034 times:

Quoting Klaus (Reply 15):
Quoting MD11Engineer (Reply 14):
I know the basic rule about "one hand in the pocket" while measuring on live circuits.

Yeah... and they often take quite a while to discharge...!

Take a test lead with a 100k resistor built into it. Attach it to the plate of the first tube and clip it to the chassis. Go have a smoke or a cup of coffee. That'll discharge all the electrolytics through the resistance string. Leave it wheile you're working on the presumably cold chassis. Electrolytics have a sort of memory.

But yeah, they can punch your lights out....the brown Concert hit me with the full whack of 5 or 6 20 uf/500v capacitors running at a plate voltage measured at 504v. I never did that again.


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 17, posted (7 years 1 month 2 weeks ago) and read 3026 times:

Quoting Dougloid (Reply 16):
Take a test lead with a 100k resistor built into it. Attach it to the plate of the first tube and clip it to the chassis. Go have a smoke or a cup of coffee. That'll discharge all the electrolytics through the resistance string. Leave it wheile you're working on the presumably cold chassis. Electrolytics have a sort of memory.

Indeed... and it gets even more vitally important when dealing with cathode ray tubes. Either know what you're doing and be severely paranoid and extremely cautious or don't bother opening the TV or monitor in the first place!

Quoting Dougloid (Reply 16):
But yeah, they can punch your lights out....the brown Concert hit me with the full whack of 5 or 6 20 uf/500v capacitors running at a plate voltage measured at 504v. I never did that again.

I only got acquainted with a measly 200V, but it was enough "fun" for a lifetime!  fight 


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 1 month 2 weeks ago) and read 3017 times:

Quoting Klaus (Reply 15):
Or even four:
1952 EABC 80, eine neue Röhre für AM/FM-Empfänger ( EABC80 )

You mean like this?
Big version: Width: 640 Height: 480 File size: 78kb
EABC80


Quoting Klaus (Reply 17):
I only got acquainted with a measly 200V, but it was enough "fun" for a lifetime!

Well I was tweaking the power tube bias voltage after I'd retubed it and replaced some critical parts-including the electrolytics.

The amp was face down on the floor and the chassis was sitting there connected to the speaker load with the innards exposed with everything powered up. It was a summer day, I was a little sweaty and wearing a tee shirt and maybe being a wee bit careless, yes?

My right arm brushed across the chassis and kaPOW! It felt like being pitched naked into a snowdrift, only real fast. Put a pretty good burn on my arm too. I remember inhaling real hard, like ooooooooooooohhhhh! No more home made electroshock therapy thanks I'll take the store bought variety.

I got bit by a Fender Champ one time too but that was not my fault....it was in a barn and it had been raining...nothing makes a better ground than standing on top of generations of damp animal piss in soggy shoes.


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 19, posted (7 years 1 month 2 weeks ago) and read 3013 times:

Quoting Dougloid (Reply 18):
You mean like this?

Yeah., that looks like it.

I've had quite a few opportunities to "taste" main power at 230V/50Hz, but the one time 200V DC felt much, much worse. I'm not really unhappy about modern electronics generally playing in the low voltage range nowadays...


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 20, posted (7 years 1 month 1 week 6 days 22 hours ago) and read 3001 times:

Quoting Klaus (Reply 19):
Yeah., that looks like it.

I've had quite a few opportunities to "taste" main power at 230V/50Hz, but the one time 200V DC felt much, much worse. I'm not really unhappy about modern electronics generally playing in the low voltage range nowadays...

I avoid vintage television like the plague because I am scared about the kind of voltage that's seen in some of them-the pulse voltage can be 1.6 kv and the insulation was crappy to begin with.

I like your Tek scope there, MD11 Engineer. You can't go wrong with Tektronix or HP test equipment for that matter. I'm wondering how it ended up in Deutschland unless it was some military surplus hardware. Some day I shall take a picture of some of my test equipment. I'm uncommonly fond of anything that has a nixie tube display, and I have a Fluke 8100 and a Systron Donner multimeter with nixie tubes.

I have a periodic romance with vintage test equipment, some of which can be picked up cheap. Back in the eighties the multimeter that Garrett said you just gotta have to do inflight checkouts on Garrett TPE331-8s was a Valhalla Scientific multimeter-counter that cost several thousand bucks back then. I got a new air force surplus one off of fleaBay last year for $15.....how times do change.

I went up north of here a few years ago and bought a tube caddy that was jam packed with Valvo, Lorenz, Siemens and Gold Lion glassware plus a nice B&K FET multimeter. From $75, I made over $1,200. The EABC 80 is part of what's left.


User currently offlineKlaus From Germany, joined exactly 13 years ago today! , 21385 posts, RR: 54
Reply 21, posted (7 years 1 month 1 week 6 days 22 hours ago) and read 2997 times:

Quoting Dougloid (Reply 20):
I avoid vintage television like the plague because I am scared about the kind of voltage that's seen in some of them-the pulse voltage can be 1.6 kv and the insulation was crappy to begin with.

Yeah... the instinct is well placed. My just recently retired CRT monitor used up to 25KV. Nothing to be trifled with for sure!


User currently offlineSuperfly From Thailand, joined May 2000, 39659 posts, RR: 75
Reply 22, posted (7 years 1 month 1 week 6 days 22 hours ago) and read 2988 times:

MD11Engineer:
Best of luck with your project. I have no experience with vacuum tubes other than replacing tubes on a guitar and bass amplifier. I used to have an early 1960s vintage Scott receiver that was vacuum tube. I wish I had hung on to it. I traded it for two Kenwood KR-9340 quadraphonic receivers. One to use and the other for parts.
It's too bad that the only vacuum tube audio receivers left on the market are extremely high-end and very expensive. My dream is to have two McIntosh vacuum tube amps and use my Marantz 4400 quadraphonic receiver as a pre-amp, as it has two pre-amp line outs for front & rear.

Nice oscilloscope.  bigthumbsup 



Bring back the Concorde
User currently offlineMD11Engineer From Germany, joined Oct 2003, 13940 posts, RR: 63
Reply 23, posted (7 years 1 month 1 week 6 days 18 hours ago) and read 2969 times:

Quoting Dougloid (Reply 20):
I like your Tek scope there, MD11 Engineer. You can't go wrong with Tektronix or HP test equipment for that matter. I'm wondering how it ended up in Deutschland unless it was some military surplus hardware. Some day I shall take a picture of some of my test equipment. I'm uncommonly fond of anything that has a nixie tube display, and I have a Fluke 8100 and a Systron Donner multimeter with nixie tubes.

actually Tektronics is quite wellknown in professional circles. I got mine surplus from the physics department of the Technische Universitaet Berlin, same as the puls counter on top of the rack (which btw. contains a display full of Nixie tubes) and the pulse generator below the scope.

I just got myself a test signal generator (made by Marconi in the UK, ex British military 1962, 20MHz to 250 MHz carrier plus an adjustable AM modulation signal) off eBay.

Jan


User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 24, posted (7 years 1 month 1 week 6 days 8 hours ago) and read 2941 times:

Quoting MD11Engineer (Reply 23):
actually Tektronics is quite wellknown in professional circles. I got mine surplus from the physics department of the Technische Universitaet Berlin, same as the puls counter on top of the rack (which btw. contains a display full of Nixie tubes) and the pulse generator below the scope.

I just got myself a test signal generator (made by Marconi in the UK, ex British military 1962, 20MHz to 250 MHz carrier plus an adjustable AM modulation signal) off eBay.

Tek is good stuff, and even old units like your 545 demand top prices here when they become available-which is rarely. I do not understand scopes at all and I do not own one.

My best piece of equipment is a HP412 VTVM. It uses two clockwork motors and four small light bulbs and photocells for the bridge circuit. It came from Texas Tech surplus, not working.

If you ever get one, all you need to do is open it up, power it up and tunk the clockwork motors until they start turning, then let it run for a couple of days. They get sticky from sitting. The best tool for this is a pencil with a soft rubber eraser on the end.

I also have a couple military VTVMs and three TS352 analog multimeters. They are wonderful equipment of the highest quality and they get sold at ridiculously cheap prices. One TS352 is brand new and one of the others came straight out of military overhaul. None cost over $15.


User currently offlineBigOrange From United States of America, joined Apr 2004, 2364 posts, RR: 3
Reply 25, posted (7 years 1 month 1 week 6 days 6 hours ago) and read 2923 times:

Try sending a letter to one of the specialist radio magazines (CQ Amateur Radio or Monitoring Times) they usually can print your letter and email address and you will get help and advice from others in the same hobby.

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