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Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Hi,
i need a 200v 50ma supply to power my 80m CW transmitter... (i know this forum isnt about amateur radio xD) the problem is i want it to be small and free of mains hum, lol , not using a big heavy mains transformer, i was thinking maybe a CCFL inverter , any idea what the O/P voltage & current of those is?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
There are plenty of hams here including myself.
I'd recommend some sort of circuit based on a ZVS driving the transformer from an ATX power supply backwards. I built one that could supply something like 100W of HT power. That's somewhat more than you need, but the ready made transformer is convenient.
CCFL inverters have too high output voltage and too low current.
Edit: You never specified whether you want it to run off 12V or mains voltage. If it's mains, I've seen those electronic halogen transformers rewound to provide HT for tube circuits.
All switch mode circuits will spew QRM. It is possible to run a HF receiver off a SMPS with careful filtering. But maybe the easiest solution is to disable the power supply in receive mode.
Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Steve Conner wrote ...
There are plenty of hams here including myself.
I'd recommend some sort of circuit based on a ZVS driving the transformer from an ATX power supply backwards. I built one that could supply something like 100W of HT power. That's somewhat more than you need, but the ready made transformer is convenient.
CCFL inverters have too high output voltage and too low current.
Edit: You never specified whether you want it to run off 12V or mains voltage. If it's mains, I've seen those electronic halogen transformers rewound to provide HT for tube circuits.
All switch mode circuits will spew QRM. It is possible to run a HF receiver off a SMPS with careful filtering. But maybe the easiest solution is to disable the power supply in receive mode.
ahh cool i didnt know that haha.
hmm okay... bipolar transistors can be used in a zvs circuit?
ah,
well ideally mains, but if the circuit is designed for 12v i could just step mains V down to 12v to power it :P
yeah, the circuit im using is this one ftw :) i'll try to find out more about the halogen transformer thing :)
Registered Member #4081
Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139
One way to do it without creating interference would be to use a step down transformer, then feed that output into the secondary of another transformer. I.E 110V > 12V transformer into a 110 > 16.6V and get 200VAC out.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Hi Alf, and Steve :
You and Steve not are not the only one Hams in this thread...
Reading the Alf thread I guess that he need a very simple supply to his rig...
And this means 280 volts for the plate of the EL84. AND 6,3V at 0.3A TO THE HEATERS (oops, almost we forget the heater supply !) Im saying 280V for the plate, because the power supply shown in the schematic specify a 200 - 0 - 200 Vac power transformer feeding a full wave rectifier ckt.
Cheking the EL84 tube data sheet, the working plate voltage is 350V or more, that means that you may built your power supply to deliver 300V.
A transformer rated 110 + 110 / 6.3V is very easy to be found and cheap too. Thes kind of transformer is used to be connected in the 110Vac outlet (with the 2 primaries in parallel) or in 220V (with the two primaries in series). In your case, just one primary is connected in the line, and other primary is supplying 110Vac to a full wave doubler rectifier that will provide 300Vdc for EL84 plate... And the 6,3Vac secondary will supply the EL84 heather. Easy, not is ?
Despite the the heater load is only 0.3 ampere, I have specified 6.3volts@3amper, in order to have the primaries sized to provide the plate current of 50mA ...
I, PY2DZI, shall disclose that I had built very similar rig in the 50ths, operating in the 40m band. It was a 6V6 (6L6 lather) tube with 450V plate voltage... I have got very nice QSOs...
Regars
Newton
P.S - Well, I took a quickly look in your diagram, and I would like make some comments, next time.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Alf ;
Here more info:
Im affraid the "large red led" blow up with the 50mA plate current ... A 25~~30 ohm resistor in parallel with the led, as a shunt, will avoid the led damage .. The 6V 0.5A lamp may be connected in series with the 4 turns and the antena.. This will alow you tune the antenna TOGETHER the output tank ..DO NOT FORGET THE ground that is the conterpoise of the antenna...
Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Steve Conner wrote ...
There are plenty of hams here including myself.
I'd recommend some sort of circuit based on a ZVS driving the transformer from an ATX power supply backwards. I built one that could supply something like 100W of HT power. That's somewhat more than you need, but the ready made transformer is convenient.
CCFL inverters have too high output voltage and too low current.
Edit: You never specified whether you want it to run off 12V or mains voltage. If it's mains, I've seen those electronic halogen transformers rewound to provide HT for tube circuits.
All switch mode circuits will spew QRM. It is possible to run a HF receiver off a SMPS with careful filtering. But maybe the easiest solution is to disable the power supply in receive mode.
hey,
well i tried what you suggested with the halogen lighting transformer, and it works, thank-you for the suggestion! :P only problem is that it requires a minimum power draw for the circuit to work, i just hope the filaments+ the B+ will draw enough current and heres another problem incase ur interested xD
i rewound the transformer, and rectified it, and it powers a mains bulb, but when i added a smoothing cap, the circuit stopped working, so i replaced the 47uf cap with a 100nf one, and it worked this time, however it only smooths the high-frequency part, not the 50hz waveform, so i connected a smoothing cap across the input of the circuit, just after the mains supply is rectified, and its working OK now.
Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
Newton Brawn wrote ...
Hi Alf, and Steve :
You and Steve not are not the only one Hams in this thread...
Reading the Alf thread I guess that he need a very simple supply to his rig...
And this means 280 volts for the plate of the EL84. AND 6,3V at 0.3A TO THE HEATERS (oops, almost we forget the heater supply !) Im saying 280V for the plate, because the power supply shown in the schematic specify a 200 - 0 - 200 Vac power transformer feeding a full wave rectifier ckt.
Cheking the EL84 tube data sheet, the working plate voltage is 350V or more, that means that you may built your power supply to deliver 300V.
A transformer rated 110 + 110 / 6.3V is very easy to be found and cheap too. Thes kind of transformer is used to be connected in the 110Vac outlet (with the 2 primaries in parallel) or in 220V (with the two primaries in series). In your case, just one primary is connected in the line, and other primary is supplying 110Vac to a full wave doubler rectifier that will provide 300Vdc for EL84 plate... And the 6,3Vac secondary will supply the EL84 heather. Easy, not is ?
Despite the the heater load is only 0.3 ampere, I have specified 6.3volts@3amper, in order to have the primaries sized to provide the plate current of 50mA ...
I, PY2DZI, shall disclose that I had built very similar rig in the 50ths, operating in the 40m band. It was a 6V6 (6L6 lather) tube with 450V plate voltage... I have got very nice QSOs...
Regars
Newton
P.S - Well, I took a quickly look in your diagram, and I would like make some comments, next time.
hey,
haha cool :)
ohhh thats the first time i noticed that.. i'd assumed that the required supply voltage was 200V but if its 280V, i can use the tube transformer i have, it supplys around 300v when rectified, and it supplies the filament too.
ahh cool, ive asked the guy who made that circuit to specify the correct B+ voltage xD
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
I would think a smps, especially a home built one is the last thing you want running in your shack, grounded to buss. Even good supplies now supply a noise tuning adjustment on front panel lest a harmonic of the switch lands square on the frequency you are trying to dig out of the mud.
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small 200v 50ma supply?
