Paraset power supply please. - UK Vintage Radio Repair and Restoration Discussion Forum

peter.sables · 14th Dec 2007, 11:36 pm

hi.

Yes I;ve built a nice Parset and it runs very nice .. from the mains. what im looking for for it to run from 12v. Any ideas please.

TA.

PETE

OErjan_S · 15th Dec 2007, 1:46 am

I use a vibrator supply with RCLC smoothing filter for a two tube 6K7 Regenerative receiver*.
I also use a "solid state vibrator" that works along similar lines.
http://www.vmarsmanuals.co.uk/newsle...s/vibrator.pdf
I mention it on another posting in tihs forum.
https://www.vintage-radio.net/forum/...ad.php?t=23197

Personally I would use 6V batteries for a paraset, easier to get those 6.3V filaments running for one.
I guess a 12-0-12V transformer with added winding for 6V would also work.
make 10 turns of wire and see how many volts you get, then calculate how many you need for 5.5-6.5V and add them (would prefer to be lower on filamentvoltage rather than higher), just be aware that you make the transformer work harder and loose watts to among others heat, and thereby get lower weight/runtime ratio compared to usining 6V from start.

* the 6SK7 and 6K7 are fairly similar, just pinout differ.
other than connecting wires to other pins and add bandswitching I copied circuit from the paraset.
For bandswitching I used a 3-18pF cap and added a 12 position rotary switch to switch in a chain of 9 x 10pF caps. position 1 is no extra capacitance and pos 10 is114pF total (11 and 12 are not used).

Hmm in that in that postig I also mention a quick and dirty variant I tried.
BUX85 transistors and transformer from a 6V/12V charger, it has two 6V windings that I connect to make a "centertapped" 6-0-6V with 240V secondary (was primary).
12/24V used in same fachion with added 6V winding would perhaps work ok for you I guess.
there MIGHT be enough room on the core from such a charger transformer to manage a 6V 1A winding, I have seen quite a few and many, but far from all would...

peter.sables · 15th Dec 2007, 5:48 pm

thankyou for that. Some studying to do now...

Peter G4MRU

peter.sables · 22nd Dec 2007, 4:17 pm

hi Yes built it.. runs well too. for the 6v I used a 7805 with 3 diodes to jack it up into a 2n3055.. Think it should run OK! . Problem as I see it the 3n3055 is rated at 4 amp and the set runs at I think 5. So big heat sink... Anyway we shall see.

Thanks all.

Pete

OErjan_S · 23rd Dec 2007, 1:39 am

hmm, my sheet makes the 2N3055 as 60V 15A 115W, so well within safe area imho.
The Paraset can use about 8W IN as TX and as receiver is MUCH lower,
driving a pair of 2K phones at confort level and keeping filaments alive is not too heavy.
and as CW is not exactly 100% duty...

If it was 4A, and everything was perfect that would be 4amp times 6V=24W.
In real life, that would be say roughly 8-10W out, still enough for a paraset.
oh, and as we use 2 transistors the duty cycle is reduced to bit above 50%.
just to see I have just run a 15W bulb from my "charger PSU" using pair of
2N3055's (just swaped them for the BUX85's) without heatsink, only for
just over 10min but... they got hot but not too bad (no sizzling when I put wet sponge form my soldering station on one).
those transistors are likely ok for looong time, and if not, fairly cheap, box of 100 cost 146€.

peter.sables · 23rd Dec 2007, 12:43 pm

hi

That's interesting... even better. I can put the 2n3055 inside the box then. I did not really want to use a big heat sink as it did not fit in with the look of the thing. I have fitted some RF filter/caps so nothing gets into the 7805 and mess it up. Only need a Jackson plug then I can try it...

It turned out to be a good project .

Pete

14th Dec 2007, 11:36 pm	#1
peter.sables Rest in Peace Join Date: Dec 2007 Location: Doncaster, South Yorkshire, UK. Posts: 385	Paraset power supply please. hi. Yes I;ve built a nice Parset and it runs very nice .. from the mains. what im looking for for it to run from 12v. Any ideas please. TA. PETE

15th Dec 2007, 1:46 am	#2
OErjan_S Retired Dormant Member Join Date: Mar 2007 Location: Skelleftea, Sweden Posts: 250	Re: Paraser supply please I use a vibrator supply with RCLC smoothing filter for a two tube 6K7 Regenerative receiver. I also use a "solid state vibrator" that works along similar lines. http://www.vmarsmanuals.co.uk/newsle...s/vibrator.pdf I mention it on another posting in tihs forum. https://www.vintage-radio.net/forum/...ad.php?t=23197 Personally I would use 6V batteries for a paraset, easier to get those 6.3V filaments running for one. I guess a 12-0-12V transformer with added winding for 6V would also work. make 10 turns of wire and see how many volts you get, then calculate how many you need for 5.5-6.5V and add them (would prefer to be lower on filamentvoltage rather than higher), just be aware that you make the transformer work harder and loose watts to among others heat, and thereby get lower weight/runtime ratio compared to usining 6V from start. the 6SK7 and 6K7 are fairly similar, just pinout differ. other than connecting wires to other pins and add bandswitching I copied circuit from the paraset. For bandswitching I used a 3-18pF cap and added a 12 position rotary switch to switch in a chain of 9 x 10pF caps. position 1 is no extra capacitance and pos 10 is114pF total (11 and 12 are not used). Hmm in that in that postig I also mention a quick and dirty variant I tried. BUX85 transistors and transformer from a 6V/12V charger, it has two 6V windings that I connect to make a "centertapped" 6-0-6V with 240V secondary (was primary). 12/24V used in same fachion with added 6V winding would perhaps work ok for you I guess. there MIGHT be enough room on the core from such a charger transformer to manage a 6V 1A winding, I have seen quite a few and many, but far from all would...

15th Dec 2007, 5:48 pm	#3
peter.sables Rest in Peace Join Date: Dec 2007 Location: Doncaster, South Yorkshire, UK. Posts: 385	Re: Paraset power supply please. thankyou for that. Some studying to do now... Peter G4MRU

22nd Dec 2007, 4:17 pm	#4
peter.sables Rest in Peace Join Date: Dec 2007 Location: Doncaster, South Yorkshire, UK. Posts: 385	Re: Paraset power supply please. hi Yes built it.. runs well too. for the 6v I used a 7805 with 3 diodes to jack it up into a 2n3055.. Think it should run OK! . Problem as I see it the 3n3055 is rated at 4 amp and the set runs at I think 5. So big heat sink... Anyway we shall see. Thanks all. Pete

23rd Dec 2007, 1:39 am	#5
OErjan_S Retired Dormant Member Join Date: Mar 2007 Location: Skelleftea, Sweden Posts: 250	Re: Paraset power supply please. hmm, my sheet makes the 2N3055 as 60V 15A 115W, so well within safe area imho. The Paraset can use about 8W IN as TX and as receiver is MUCH lower, driving a pair of 2K phones at confort level and keeping filaments alive is not too heavy. and as CW is not exactly 100% duty... If it was 4A, and everything was perfect that would be 4amp times 6V=24W. In real life, that would be say roughly 8-10W out, still enough for a paraset. oh, and as we use 2 transistors the duty cycle is reduced to bit above 50%. just to see I have just run a 15W bulb from my "charger PSU" using pair of 2N3055's (just swaped them for the BUX85's) without heatsink, only for just over 10min but... they got hot but not too bad (no sizzling when I put wet sponge form my soldering station on one). those transistors are likely ok for looong time, and if not, fairly cheap, box of 100 cost 146€.

23rd Dec 2007, 12:43 pm	#6
peter.sables Rest in Peace Join Date: Dec 2007 Location: Doncaster, South Yorkshire, UK. Posts: 385	Re: Paraset power supply please. hi That's interesting... even better. I can put the 2n3055 inside the box then. I did not really want to use a big heat sink as it did not fit in with the look of the thing. I have fitted some RF filter/caps so nothing gets into the 7805 and mess it up. Only need a Jackson plug then I can try it... It turned out to be a good project . Pete