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> Ft200 Power Supply
kellys_eye
Posted: March 07, 2012 09:49 am
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Whilst I now have the full schemmy of the original PSU for this txcvr, there is no indication of current draw for the relevant lines.

There is a 600V, 300V, 150V and -100V along with 12.6V @6.3A for the tube heaters.

The -100V line is (obviously) very low current. I'm guessing at

150mA for 600V,
350mA for 300V and
100mA for 100V.

If anyone knows otherwise I'd appreciate a head's up. I have to rebuild this PSU and am considering different approaches.

Do you think there's any mileage in knocking out an SMPS version? Say a simple LOPT-type of supply (flyback) for the 600/300/150V/-100 supplies? The transformer version weighs a freekin' ton...... laugh.gif

As far as the rest of the set goes I've had to dismantle and rennovate the tuning dial slo-mo mechanism. Nice and smooth now!


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CWB
Posted: March 07, 2012 03:34 pm
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ehhh ... i'd stick with the original as much as possible .
sure , it has some weight to it ... but it is also very forgiving in the overload department .
besides , how often do you move the supply around ?

i am also thinking that some good design/filtering practices will be needed to keep the hash off of the ac line and so-forth .
another problem might be the HV in a swmps design ... this is being discussed in another thread .

i'll bet that supply is lighter than the one for my old swan 500CX ...
the supply was for 110/220volt and 12volt (i don't think you mentioned if yours was or not) .
even the supply for my kenwood 440-TS is not exactly lightweight .

fb on cleaning up the vernier .


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kellys_eye
Posted: March 07, 2012 05:29 pm
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Yeah I'd jave kept it 'stock' if it had been the original PSU but the one I have is a knocked up version which is very tatty. The transformer isn't original and there is one of the supply chokes missing - the main caps could do with replacing (a matter of course really) and after all 'that' it would be just as easy to start from scratch.

My googling reveal that the original FT200 PSU often went into flames shock.gif when the set was mis-tuned and the HT side overloaded......

The 12V version PSU is a separate item but I don't have that - not really missed but if I went SMPS I could do it at 12V anyway if I felt a need to keep the 'mobility' factor.

Any 'news' on the supply line consumptions?


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CWB
Posted: March 07, 2012 09:42 pm
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hmmm ... a flame-out power supply ... that is actually a visual overload indicator . laugh.gif

any numbers on the replacement transformer ?

i am still digging through the boxes and sorting/stacking stuff .


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kellys_eye
Posted: March 07, 2012 10:00 pm
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Two transformers:

Gardiners GR27443 (which has the secondaries marked for voltage but not current) and
DS:1788/2 (markings just visible so best-guess). This has no other markings and will be tested out-of-circuit to establish the secondaries unless you know???

Other mods done:

changed the original 'mic gain' pot for one with a pull-switch to allow on/off switching of finals heaters. This mod has been documented by other users as necessary to lengthen life of finals as they are permanently on - and HOT!

Set is, (I've noticed) crystalled for all the 28MHz bands too - an option on this model.

Alos working my way through the pdf documents, retyping and re-drawing the schemmy. A bit OTT but I do like to keep full documentation with my 'stuff' as, once embraced it tends to stay with me forever and this little set is growing on me!


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CWB
Posted: March 08, 2012 01:44 pm
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it is surprising how much info on the '200 is available .

information on rebuilding and schematics :
http://stn6732.ip.irlp.net/ft200.html
the site is a little slow loading but has good info .
i downloaded the zip folder containing the 4 pages of schematics ...
i used ifranview to look at the resulting bitmaps ... looks decent .
ifranview performs better than most other programs ... i strongly recommend it .

more info :
http://www.vmarsmanuals.co.uk/new/ft200.htm

a site with a lot of schematics and info about different makes and models of equipment :
http://gmcotton.com/

a cool site with a lot of schematics :
http://grumpy.proboards.com/

it looks like gardeners was bought up by or is a subsidiary of "avon magnetics" .

if push comes to shove , you could always load the secondaries (OOC) to the point where you get a (say) 10% drop in voltage .
from there figuring out the current is straight forward .
of course , large high value resistors are hard to find these days ... not may in the bone pile .


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kellys_eye
Posted: March 08, 2012 08:58 pm
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laugh.gif

been there, done that (on all of them!) - your first link is my fave.

The schemmy I have is identical but I'm still 'cleaning' mine up - I'm sad enough to want to change all the squiggly resistors to 'blocks'..... rolleyes.gif Same with the manuals - whilst they're all readable I still want mine to be 'new' hence the retyping and new images/annotations etc.

One thing missing is a decent set of component location drawings. I'm doing the PCB versions and have photographed the underside for other identification illustrations I'm doing. Should end up with something that SHOULD have been done by the manufacturers (probably was sometime, someplace, somewhere) but I haven't found it yet.

I'll be 'upping' them somewhere for everyone else who wants 'new' documentation when I'm done.

Yeah, I'd considered that route with the transformer but using an electronic load.


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tekwiz
Posted: March 08, 2012 09:16 pm
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You may need a bit more capacity from the +600V line. Most of those rigs typically had ~125W output. Considering the dismally low efficiencies of tube RF amps, you should have a supply capable of delivering 3-4x as much power to the final amp stage.
It's much better to have too much than not enough power capacity.


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kellys_eye
Posted: March 08, 2012 10:01 pm
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Whilst 'power is good' is certainly true, this particular set has 'adjustable' power output by virtue of tappings on the transformer. IIRC you can go as low as 25W.

My own requirement is QRP so even at 25W I'm way over the top - I'm even contemplating changing out the final stage for a completely new one based on lower power finals and easier-to-source (i.e. cheap) tubes. Maybe even drop a solid-state stage in there? Possible sacriledge as I'd prefer to keep the rig 'stock' for whatever reason ('normal' mods acceptable).

Not sure which way I want to go at the moment - open to any suggestions.



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tekwiz
Posted: March 08, 2012 10:11 pm
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What type of finals? Given only 600V on the B+, I'm thinking sweep tubes?


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kellys_eye
Posted: March 08, 2012 10:24 pm
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Finals currently fitted are (hard to obtain) 6JS6A's.

There are mods to change these to 6146's or 6DQ5's (yes, the sweep tubes) but mean a socket change too - at which stage I think I'd contemplate ditching the tube finals altogether.



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tekwiz
Posted: March 08, 2012 10:42 pm
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Aren't the 6JS6s sweep tubes? You'd likely get a bit less power if you converted to 6146s; 600V B+ is a bit low for full output with those.
I can't count the number of 6146s I smashed as a teen. They were a standard output tube in the audio tone control transmitters in the institutional clock systems my father used to service. I had baskets full of them. Had a spud gun specifically built to use them as ammo.
That ought to make a few hollow state addict nutsacks clench in abject horror. tongue.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

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kellys_eye
Posted: March 08, 2012 10:50 pm
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QUOTE (tekwiz @ March 08, 2012 10:42 pm)

That ought to make a few hollow state addict nutsacks clench in abject horror. tongue.gif

Mine too! Aaaargh....... laugh.gif

I used a 5763 and 6146 for my first ever tube transmitter way back in the 70's and LOVED those old 6146's. Not sure where the nostalgia is coming from but the 'toob bug' has hit me hard and I'm 'mad for 'em' laugh.gif

I'm now considering using tubes to make an SDR front-end to use with a PC rolleyes.gif


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tekwiz
Posted: March 08, 2012 11:12 pm
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Then I guess you don't want to hear about my buddy & I dropping entire toob type TV sets out of the back of the car @ 60mph? tongue.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

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kellys_eye
Posted: March 09, 2012 12:25 am
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nah.... toob TV's were dime a dozen when I was a kid and even I was caught by passing motorists lobbing old toobs at the cars! I WAS aged 5-ish though laugh.gif

A family friend used to use our yard to collect old TV's when he was delivering new sets around town.


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CWB
Posted: March 09, 2012 01:51 am
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i believe the reason they used 600V on the plates was to extend the life of the finals .
and in case of going into the "oh hell" mode , you at least had a small chance to shut it down or correct the problem (ie : too much drive) .
flash over becomes a consideration at higher voltages .
of course when that happens , the party is pretty much over .

it looks as though 600 volts is a good trade-off for the 6146 ...
it is in the ballpark of/for the modes/freqs used in the '200 :
http://www.nj7p.org/Tube4.php?tube=6146

my experience with the 6DQ5 was replacement after 3 months .
running them at 100 watts CW extended the life to 6 months or more .
a set of them was only good for one shot of not correctly neutralizing them ... if you were fast on the switch . loosing bias had a similar effect .
even if you caught them in time ... the working life was shortened .


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