HappyHourStudio
Active member
Does anyone have a recommendation for a power transformer with these specs that’s readily available???
OLD TRANSFORMER SPECS…
- Thread starter HappyHourStudio
- Start date
Help Support GroupDIY Audio Forum:
Does anyone have a recommendation for a power transformer with these specs that’s readily available???
Brian Roth
Well-known member
That's an unusual combination. Relatively low plate voltage and current with a rather high filament current (and CT as well). What sort of packaging is it in....and what device requires those specs?
A quick glance at https://www.hammfg.com/electronics/transformers/power didn't come up with anything, and they have a LOT of choices.
Bri
A quick glance at https://www.hammfg.com/electronics/transformers/power didn't come up with anything, and they have a LOT of choices.
Bri
HappyHourStudio
Active member
Yeah, I’ve had a hard time sourcing anything close.
I’m attaching a schematic of the supply I was trying to build.
I’m open to suggestions on other ways around this!
The final output is 235VDC 30MA/6.3VAC 2.4 AMP
rock soderstrom
Tour de France
These are actually rather rare values, B+ seems to be either very low or a voltage doubler (see @emrr ) is used. If this is the case, you can better look for a transformer with the correct target voltage for a normal rectifier.
HappyHourStudio
Active member
Here’s the schematic if you wanted to take a look! It is a weird one!
HappyHourStudio
Active member
Thank you! You’re totally right. A voltage doubler is used. A selenium rectifier.
rock soderstrom
Tour de France
As expected, a voltage doubler. Your target voltage is 290VDC before filtering. With a bridge rectifier, you will then need approximately a 225VAC secondary winding on your mains transformer. These are relatively easy to obtain...
rock soderstrom
Tour de France
Not really, I have seen similar things in several US schematics. The Altec 436 also has this.
In the end, the target voltages and currents are relevant, how you do it is up to you. I would use a standard 4 diode bridge rectifier, they are a bit more common on my side of the pond,
I would probably add a bit more filtering to the power supply shown and then use the series resistors to adjust the voltage to my conditions.
Elevating the AC heater voltage is a good thing!
Good luck!
merlin
Well-known member
- Joined
- Aug 17, 2011
- Messages
- 342
You could use two separate transformers, one for plate, one for heaters.
But yeah, it might be easier to just change the voltage doubler to an ordinary rectifier and use a 225V-ish tube amp transformer.
scott2000
Well-known member
Heathkit 54-59 over specced a bit.... 54-81 a bit weak.... heater tap can't pull the extra current can it??
may be others....stopped there....
https://reverb.com/item/52225297-gr...t-vintage-power-transformer-tested-6-3-v-1954
may be others....stopped there....
https://reverb.com/item/52225297-gr...t-vintage-power-transformer-tested-6-3-v-1954
HappyHourStudio
Active member
lol. Yerppp
HappyHourStudio
Active member
Might have to just abandon making this exact power supply and look toward something with the same output. I’ve been using a Heathkit Power supply, but I’m worried it won’t be able to power the new rendition of the console I’m building. It worked well with the old version.
HappyHourStudio
Active member
Yeah, I believe that’s the call. Nothing seems to be matching up just right. As I’d mentioned, I used a Heathkit variable power supply which worked well for the 5 channel console I built, but I’m rebuilding it into a 10 channel board with direct outs, two buses, and an echo send. Not sure the Heathkit could handle allllll of that.
Brian Roth
Well-known member
The total heater current for the "new build" should be easy to calculate; just add up the current from each of the tubes. The B+ is trickier....does the Heath have a current meter?
Regardless, for the B+ download the FREE PSU Designer app offered by Duncan Amps. You can "what if" a ton of variables to arrive at a good solution.
Bri
PS, if doing a new build, don't overlook the toroidal transformers from Antek....excellent value.
Regardless, for the B+ download the FREE PSU Designer app offered by Duncan Amps. You can "what if" a ton of variables to arrive at a good solution.
Bri
PS, if doing a new build, don't overlook the toroidal transformers from Antek....excellent value.
HappyHourStudio
Active member
Oh yikes… well… the Heath is an SP-2717A, which is 6.3 VAC @ 4 Amperes… my new build is @ 10.2 Amperes…
So I guess that’s off the table; however, I do believe it could power the VDC side of things…
Each modular unit within the board I’m building is 235V @ 2.5ma… of which there are a total of 34. So looking at 85ma.
The Heath supply (according to the specs):
0 to 100 mA continuous; 125 mA intermittent.
So maybe I should just build or find a separate filament power supply and use the SP-2717A for the high voltage.
-Kyle
rock soderstrom
Tour de France
With such a high current requirement, a good quality switch mode power supply (SMPS) with some additional filtering would be the better option for the filament voltage.
Check this link:
https://groupdiy.com/threads/switching-psu-filtering.80123/
amplexus
Well-known member
Agree. With that much current this is a perfect use case for switch mode. If its a new build you may be able to strap the heaters for 12.6v and use any commonly available 12V smps with the appropriate wattage. Cheap and cheerful, even with extra filtering (which may or may not be necessary for heater strings, but doesn’t hurt).
Then you can just grab a cheap 230VAC Triad WPT series for the b+ and do a standard bridge rect. Arrangement. With that 12v smps and a toroidal trafo for b+ I’d bet your footprint is smaller or around the same than the originally specified unit would have been.
Cqwet Dbdfte
Well-known member
- Joined
- Oct 2, 2023
- Messages
- 551
That 6.3 V is biased up to +34V which an SMPS may not be happy with.
Read the docs.
Read the docs.
