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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 6th Mar 2019, 4:32 pm   #1
G6Tanuki
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Default R209Mk.2 PSU

I fear the vibrator-transformer on my R209 has developed a shorted-turn: the radio's drawing something near 3A when it should be half that, the HT is only about 70V (so the voltage-regulator tube doesn't strike) and the transformer gets smellily-hot after about ten minutes. I've changed the various suppression components around the vibrator but that hasn't made any difference.

It's a rather 'hot', well-performing R209 - I recently reworked it replacing all the leaky grey-rubber-covered decoupling capacitors in the plug-in modules [this being one of the best bits of the R209 design - so easy to work on!] and a bunch of resistors that had gone out-of-spec, along with giving it a complete set of NOS made-for-the-US-Military-by-Sylvania-and-Tung-Sol valves and it then performed better than it ever had in the previous 35 years I've owned it.

So to keep it going I plan to convert it to mains-only. My idea is to use a 15V 1.5A transformer feeding a bridge-rect with something like a LM317 to provide the 600ish mA for the heaters, then another small 30V transformer wired 'backwards' across the 12VAC from the first transformer to provide the 100-or-so-Volts of HT.

Just wondering if anyone else has done similar?
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Old 6th Mar 2019, 7:16 pm   #2
ex seismic
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Default Re: R209Mk.2 PSU

How about keeping it 12vdc and getting HT from one of the dc-dc modules readily available eBay? There's one that will go up to 340v I think with more than enough mA for a 209. I use one in a WS31 and it doesn't seem to kick out any noticeable RF. Might be different for an HF set of course but for only a few pounds it is worth a go.
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Old 6th Mar 2019, 8:35 pm   #3
G6Tanuki
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Default Re: R209Mk.2 PSU

An interesting option - I may have a play with this. Seems that people have used similar modules to provide the few-milliamps-at-100-or-so-volts for NixieŽ-tubes etc so the idea is definitely worthy of consideration. Brute-force suppression shouldn't be a problem - I've got a bunch of 1000pF Erie bolt-in feedthroughs to throw at it if needed.

Though going to a 240V-input supply would make life easier - quieter for a start - and mean I didn't need to run the big Diamond 12V PSU just to power a little radio.
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Old 6th Mar 2019, 10:27 pm   #4
ex seismic
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Default Re: R209Mk.2 PSU

I have one of the Nixie units in a WS38 supply, again seems RF quiet. Much more restricted in terms of output though than the ebay modules, I can't remember what voltage the 209 needs so cannot say if they would be suitable.
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Old 7th Mar 2019, 7:32 am   #5
Ed_Dinning
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Default Re: R209Mk.2 PSU

Hi, the vibrator transformers lead a hard life insulation wise, especially if the snubber capacitors are dying.
The transformers themselves are easily rewound.

Ed
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Old 7th Mar 2019, 10:01 am   #6
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Default Re: R209Mk.2 PSU

Hi
I have an R209 mk2 that was converted to mains by a previous owner. I will have to open it up to remind myself exactly how it was done. From memory it was an appropriate HV transformer with a regulated supply for the filaments.

It works well on AM but the CW tone sounds more like a buzzer and there is some drift in that mode. Not sure if it is the BFO or VFO.

I have considered converting it back to 12V but i guess the vibrator transformer is unobtainable and I don't have an original to get rewound.

Don m5aky
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Old 7th Mar 2019, 10:55 am   #7
G3VKM_Roger
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Default Re: R209Mk.2 PSU

Hello Don, etc

Yesterday I received the following from a member of the TCS-Radios group on Groups.io.

"They seem to have improved those little yellow
High-Voltage DC-DC converters, sourcing enough power to make
them more useful. You can find'em on Ebay and Amazon
for 8 or 10 bucks, like this one:

https://www.ebay.com/itm/183717171988

They spec them for 20 Watts continuous. Recently
got a couple and decided to try one on a newly-
revived TCS receiver. Set the output for 190V.
At that B+ the TCS draws about 70 mills at full
volume, about 13 Watts. Ran it for
a couple of hours and the FET never got beyond
comfortably warm to a fingertip and the
heatsink remained cool."

I see they do bigger modules up to 450V too.

73

Roger/G3VKM
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Old 15th Mar 2019, 6:19 pm   #8
G6Tanuki
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Default Re: R209Mk.2 PSU

Investigating my junkpile, I've sourced the bits needed to do my initial 12V-regulator-and-back-to-back transformer-for-the-HT scheme, a bunch of boards salvaged last year from a client's scrapped 500-page-per-minute A3 colour-printer yielded a couple of suitable transformers and loads of LM340-12 regulators, good-quality electrolytics and sensible bridge-rectifiers.

I'm preferring to go this path because firstly it's zero-cost and secondly it avoids the issue of RFI from inverter-oscillators.

The R209 will work again!
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Old 19th Mar 2019, 8:56 am   #9
trh01uk
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Default Re: R209Mk.2 PSU

Quote:
Originally Posted by G3VKM_Roger View Post

"They seem to have improved those little yellow
High-Voltage DC-DC converters, sourcing enough power to make
them more useful. You can find'em on Ebay and Amazon
for 8 or 10 bucks, like this one:

https://www.ebay.com/itm/183717171988

They spec them for 20 Watts continuous. Recently
got a couple and decided to try one on a newly-
revived TCS receiver. Set the output for 190V.
At that B+ the TCS draws about 70 mills at full
volume, about 13 Watts. Ran it for
a couple of hours and the FET never got beyond
comfortably warm to a fingertip and the
heatsink remained cool."

I see they do bigger modules up to 450V too.

No doubt they will supply the volts and the power. They will also supply vast amount of RFI, which will make them unusable as-is within any receiver. A serious amount of engineering will be required to get the interference down to a level where the receiver actually receives anything - other than crud out of the psu.

By "serious engineering" I am thinking of a double set of screening boxes, with every lead in/out being heavily filtered - such as you get in many professional signal generators. The connection between the two boxes will need to be carefully thought about too, to ensure there aren't heavy circulating currents in the boxes themselves.


Richard
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Old 19th Mar 2019, 8:57 am   #10
trh01uk
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Default Re: R209Mk.2 PSU

Why isn't the simple solution here to just replace the transformer from a junk R209? There's no shortage of them.


Richard
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Old 20th Mar 2019, 7:25 pm   #11
G6Tanuki
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Default Re: R209Mk.2 PSU

Alas I don't have a new 'original' replacement R209 vibrator-transformer to hand! And I guess such a beast is as rare as Unicorn-droppings.

A used replacement - I'd be deeply concerned that it might soon go the same way as the failed one I need to replace (I'm always wary of using used parts). I have a philosophy of 'continuous improvement' - a repaired device should work better/be more-reliable than the original.
My mains-transformers approach seems to be working well as a bench lash-up; there's a good 115VDC available and the voltage-stabiliser ignites nicely. There's also none of the old annoying roughness of the BFO-note when listening to CW/SSB. Now to package it up and fit it back into the chassis.

Oh, and I need to source a suitable mains-connector. The R209Mk3 - which was mains/battery - appears to use a 6-pin aluminium shell Plessey-type connector.
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Old 21st Mar 2019, 7:08 pm   #12
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Default Re: R209Mk.2 PSU

Well, scrap R209s are fairly common - particularly the Mk.2 variety. I have one, and I will take a look and see whether it has the transformer still in it. And if it has, I will see if the transformer is in a reasonable state. And then let you know about it.

The R209 was only earmarked for breaking for spares anyway. This might urge me to get on with it!

Richard
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Old 21st Mar 2019, 8:19 pm   #13
G4_Pete
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Default Re: R209Mk.2 PSU

Hi Richard,
Strangly I have just started to re-build one of these , mine is the AC mains/DC version. Not sure what works yet but I might be interested in making you an offer for some spares like an IF can or audio transformer or headphones if you have them. I have not started on it yet as it smelt so strong of old electronics when I opened it that I have left it in the shed for a bit!!!

Pete
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Old 24th Mar 2019, 8:12 pm   #14
bill knox
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Default Re: R209Mk.2 PSU

Hi

I don't know if it is similar, but I have broken down a vibrator power supply from a PCR2.

I have the transformer and the vibrator, which if I remember correctly is a 4 pin unit plus every thing else that came out of the PSU apart from the bulb-holder and the power switch. I can possibly find the circuit for the PSU just in case you are not sure of the circuitry.

if you could make use of the bits, it's yours for the postage.

Regards

Bill
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Old 14th Apr 2019, 9:41 am   #15
trh01uk
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Default Re: R209Mk.2 PSU

Quote:
Originally Posted by trh01uk View Post
Well, scrap R209s are fairly common - particularly the Mk.2 variety. I have one, and I will take a look and see whether it has the transformer still in it. And if it has, I will see if the transformer is in a reasonable state. And then let you know about it.

The R209 was only earmarked for breaking for spares anyway. This might urge me to get on with it!

Richard

I finally found my scrap R209. Sadly its missing the power unit......so, sorry I can't help with spares for the one in this thread.

It may well be that the transformers burn out, following the failure of the vibrator capacitor. I've had one of those caps fail (an awkward 8200pF as I recall) and smoke was pouring out of the set, so something was getting mighty hot!

Richard
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Old 14th Apr 2019, 10:07 am   #16
M0FYA Andy
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Default Re: R209Mk.2 PSU

My vote would be to get the original transformer rewound if you can't source a replacement part.

Andy
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Old 14th Apr 2019, 10:13 pm   #17
trh01uk
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Default Re: R209Mk.2 PSU

Quote:
Originally Posted by M0FYA Andy View Post
My vote would be to get the original transformer rewound if you can't source a replacement part.

Andy
Andy

this is a popular solution often put forward. But its been pointed out by experts that any transformer which is potted in either varnish (or that equivalent "black stuff") is impossible to take apart - to the point where laminations are clean enough for re-use. Maybe if anyone knows an effective solvent this could be done, but I've not heard of anyone successfully doing it.

Simpler - but expensive - to wind a new transformer from new materials. The specs should be in the relevant EMER for the R209.

But given how common the R209 is, I still think the cheapest option is going to be to find a scrap set which can donate a transformer.

Richard
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Old 15th Apr 2019, 9:15 am   #18
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Default Re: R209Mk.2 PSU

One thing it pays to remember that for any decent looking square or rectangular wave, the rise and fall times can be over 21 times the fundamental with many lower odd order harmonics.

For a 120 Hz supply, if the switching via transistors, or vibrator contacts (with the correct snubber caps) your interference, for the most part, is below the radio frequency spectrum (even if the leakage reactance of the vibrator transformer and winding capacity causes some annoying buzz).

So what I'm saying here, is you can have an RF quiet DC,DC converter, if it runs at a low fundamental frequency. But the 75kHz switching supply suggested in post #7 will splatter RF hash across the radio frequency bands an be impossible (nearly) to shield.

Have a look at the low frequency DC,DC converter in this article (called the Omega Device) that generates no detectable RF over 200kHz (because of the low fundamental). Otherwise, the only way to do it is to go for a pure sine wave supply.

http://worldphaco.com/uploads/WORLDFETRON.pdf
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