PSU designer understanding.

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Paul Barker
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#31 Re: PSU designer understanding.

Post by Paul Barker »

What are you planning to order as a replacement? Any links?

I don’t think many of us want 3000v ac swinging to and fro in our homes these days. I’m more than covered if I did.

Today, compared to the ‘90’s there is very little offered on auction sites with suitable secondary voltages. Its possible to get up to 400v by buying a din rial 400v step down to 230 which you rotate, to get 400v ac at 500mA for < £100 delivered. In old days we could get the ex mil boatanchor power transformers, but they’re all but gone.

As it’s 500 mA capable then maybe a voltage mulitiplier smoothing first then a shunt reg pulling at least the quiescent voltage of the output valve at the end might sound just as good as basically if it’s a valve like a 811a for instance what you mostly hear from power supply is the sound of two powerful transmitting valves running the current through each other, and I doubt that the disadvantages going before that shunt valve would damage the outcome.

The benefit from the shunt valve on any power supply is worth the effort. The capacitorless transistorless power supply I’ve used a number of times has always sounded much better to me than any other power supply. The detail of how it’s dine is all on Stephie’s pages via JAC mirror these days. Ive been using Stephies methods since I firts came into this hobby about 1996. I haven’t found anything Stephie suggested that sound less than expected.

When I firts tried A2 with the sv811-10 the sound was so amaising to my ears compared diretcly to the 300b in class A1. The poor old boring dull 300b was completely outclassed. I mentioned this on the forum in those days that was an email group hwich has sadly long gone. The only replies I got were from Jonathon and Steve Bench ( as Stephie was called at the time.) Johnathon hasn’t ever tried it afaik, but he was like a equivalent stage of new entrant full of enthusiasm as I and we batted all these things to and fro on that group. Stephie replied with copious encouragement and affirmation.

Them were the days.

I saw Stephie at vsac but didn’t realise, as there was a frok jewellery and makeup involved, which didn’t matter a jot, but I didn’t know the person I saw was Steve Bnech. I think it may have been after vsac he made the naouncement. Certainly I didn’t know. I overheard Stephie and naother highly skilled individual. Just wish I’d realised who the person in a frok was I would have thoroughly enjoyed spending more time engaging in conversation. But I didn’t do bad pinning Bruce Edgar down for half a day.
Last edited by Paul Barker on Wed Apr 29, 2020 3:59 pm, edited 1 time in total.
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pre65
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#32 Re: PSU designer understanding.

Post by pre65 »

Paul Barker wrote: Wed Apr 29, 2020 3:31 pm What are you planning to order as a replacement? Any links?
Normally I would use Antek in the USA for toroids. They do a 400VA with two 500v secondarys and two 6.3v secondarys for $57. BUT, shipping and import duties + VAT add quite a lot.

https://www.antekinc.com/as-4t500-400va ... ansformer/

The other day I was looking on Google maps for an old railway station in a rural area and up popped a marker for a toriod manufacturer. I got in contact with them and they offered me a 400VA (on a 500VA core) transformer, 400v + 400v secondarys for £85 each, inc carriage. BUT, I had to send pound notes in a plain envelope.

I need to get back to the man to see if a 500v + 500v would be the same price.

If anyone want to know the manufacturer then PM me as I'd rather not make it public.

*
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#33 Re: PSU designer understanding.

Post by Paul Barker »

Mint Phil. Don’t lose the details for future reference.
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#34 Re: PSU designer understanding.

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Paul Barker wrote: Wed Apr 29, 2020 4:13 pm Mint Phil. Don’t lose the details for future reference.
If theyre making it for you ask them to do the 500v secondary as 1000vct then you can use an valve full wave rectifier rather than a hybrid bridge you are aiming at. It’s not as if theyr’e making any more turns, just adjusting where they connect them, you could do it by stacking them but better to have them connected correctly at manufacture. Nothing else requires more capability because when you valve full wave rectify a centre tapped winding it only ever draws on half the winding at a time. So it’s just the same as a transformer as you described in terms of core square inches (or centimeters if you read modern books) and wire diameter primary and secondary. It’s different if you bridge rectify across the full secondary (by stacking both 500v secondaries yourself), that demands current from the full 1000v at all times, so there is more heat and some of the two main other design criteria may require boosting (core size and wire csa).
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#35 Re: PSU designer understanding.

Post by pre65 »

Forgive my ignorance Paul, but if you connect the two 500v secondarys together in series is not that the same as 1000v centre tapped ? With a bridge the centre tap is not used.

I usually put the secondarys in series and use a hybrid bridge. I have quantities of 6D22s damper diodes or U19 half wave rectifiers as the valve part to use with suitable diodes.

EDIT.

You added to your post whilst I was compiling mine. :)

+ I obviously didn't read it properly first time. :oops:
Last edited by pre65 on Wed Apr 29, 2020 4:31 pm, edited 1 time in total.
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#36 Re: PSU designer understanding.

Post by Paul Barker »

pre65 wrote: Wed Apr 29, 2020 4:26 pm Forgive my ignorance Paul, but if you connect the two 500v secondarys together in series is not that the same as 1000v centre tapped ? With a bridge the centre tap is not used.

I usually put the secondarys in series and use a hybrid bridge. I have quantities of 6D22s damper diodes or U19 half wave rectifiers as the valve part to use with suitable diodes.

EDIT.

You added to your post whilst I was compiling mine. :)
I always do that! fun ins’t it?


Its always best to have it made to correct method, you can stack two windings but when they make what you ask for it stands more chnace of being safer and better. the two seperate secondaries connected up for 500v means the transformer is rated with margin for safety as a 500v object, when they wind a 1kvct they wind it with the consideration it’s running at 1kv. Just how the old militray transmitting valve power supplies were spec’d. Ive never been comfortable with people stacking voltages or altering the wya they use the winding. i.e. full wave bridge rectifying a 1kvct winding across the 1kv and not connecting to the centre tap, for the reason hidden in what Ive said already. The winding wire core size and insulation qualities are chosen for how the transformer is specified for use. If you do do differnt, you’d have to under rate it and watch out for insulation brekadown.

When winding a ct winding they make it one continuous winding with a central tap off. If they’ll do it, I’d ask.
Last edited by Paul Barker on Wed Apr 29, 2020 4:37 pm, edited 1 time in total.
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#37 Re: PSU designer understanding.

Post by pre65 »

I use this useful data sheet, it's in the stacks section of the forum.Very useful to get the best from transformers one might already have.

http://www.audio-talk.co.uk/archive/5c007.pdf
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#38 Re: PSU designer understanding.

Post by Paul Barker »

pre65 wrote: Wed Apr 29, 2020 4:36 pm I use this useful data sheet, it's in the stacks section of the forum.Very useful to get the best from transformers one might already have.

http://www.audio-talk.co.uk/archive/5c007.pdf
That link is ok but the details ive just given you arent there. I learned those details by tsudying transformer winding. It’s in there, Hammond aren’t telling you everything, if you were studying to actually wind transformers it would be a different matter.

Hence, “ask thme if they can centre tap a 1kv winding for you instead of making it with two 500v windings.”
Last edited by Paul Barker on Wed Apr 29, 2020 4:41 pm, edited 1 time in total.
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#39 Re: PSU designer understanding.

Post by pre65 »

PS.

I usually prefer 6D22s damper diode because of the 30 second warm up and then reasonably smooth ramp up to full voltage. Also I have more in the way of 6.3v transformers to heat them.
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#40 Re: PSU designer understanding.

Post by Paul Barker »

Id just use two mecury or two u19’s on a centre tap, how it’s always been before the modern world. If you wnat the slow start from the damper diode pass the b+ through one before the choke input.

I juts use two power switches, turn heaters on firts then HT. But it’s only me that turns my amps on. Not that I gte it right every time. Very common for anyone using my method to turn ht on first then filament. Doesn’t usually do nay harm. Depends on youre circuit design. You don’t wnat a lod of direct coupling going on if you turn ht on firts by accident. direct coupled valves only last a few seconds more than sand devices when you do that, but thye more likely to survive though rather shagged out. I know because Ive done it so often! Evrything I recommend Ive learned to recommend because I have the shagged out expensive valves to prove it.
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#41 Re: PSU designer understanding.

Post by pre65 »

Paul Barker wrote: Wed Apr 29, 2020 4:42 pm Everything I recommend I've learned to recommend because I have the shagged out expensive valves to prove it.
That's real (if expensive) experience Paul. :)
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#42 Re: PSU designer understanding.

Post by izzy wizzy »

Majestic transformers are great suppliers if you want high voltage stuff; transformers and chokes. All runs quiet and cool. My amp has 2.1kv ct into choke input supply. In a silent room there's a faint buzz just screwed to wood when nearby when both amps on. I use their stuff in all my equipment.

RS do cheap 6.3v transformers to power up rectifiers such as damper diodes. Even if two are required ; one per damper, it's still good vfm.
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#43 Re: PSU designer understanding.

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izzy wizzy wrote: Wed Apr 29, 2020 6:15 pm Majestic transformers are great suppliers if you want high voltage stuff; transformers and chokes. All runs quiet and cool. My amp has 2.1kv ct into choke input supply. In a silent room there's a faint buzz just screwed to wood when nearby when both amps on. I use their stuff in all my equipment.

RS do cheap 6.3v transformers to power up rectifiers such as damper diodes. Even if two are required ; one per damper, it's still good vfm.
Thanks
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#44 Re: PSU designer understanding.

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pre65 wrote: Wed Apr 29, 2020 5:00 pm
Paul Barker wrote: Wed Apr 29, 2020 4:42 pm Everything I recommend I've learned to recommend because I have the shagged out expensive valves to prove it.
That's real (if expensive) experience Paul. :)
Not over a grand’s worth at cost but well over 20 grands worth at replacement cost today a few baloon px25’s a few V1505’s, one person’s carpet et al. Fried a few high voltage components, chokes, caps’ including two Black Gates the top version power caps in their range. Power transformers valve bases. You name it, it died here in spectacular fashion.

Only on e had a dc shock, 400v felt really unwell after, but was working nights as a nurse so home from work to bed, up from bed, to work. Never looked in mirror, firts day off nights, about 3 days after the shock first time I looked at self in mirror, my hair was still sticking straight up on end like Homer Simpson. Noone at work had mentioned it.

Had a multileed herat trace done and no lasting damage evident. Phew!
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#45 Re: PSU designer understanding.

Post by Paul Barker »

Paul Barker wrote: Wed Apr 29, 2020 8:15 pm
pre65 wrote: Wed Apr 29, 2020 5:00 pm
Paul Barker wrote: Wed Apr 29, 2020 4:42 pm Everything I recommend I've learned to recommend because I have the shagged out expensive valves to prove it.
That's real (if expensive) experience Paul. :)
Not over a grand’s worth at cost but well over 20 grands worth at replacement cost today a few baloon px25’s a few V1505’s, one person’s carpet et al. Fried a few high voltage components, chokes, caps’ including two Black Gates the top version power caps in their range. Power transformers valve bases. You name it, it died here in spectacular fashion.

Only on e had a dc shock, 400v felt really unwell after, but was working nights as a nurse so home from work to bed, up from bed, to work. Never looked in mirror, firts day off nights, about 3 days after the shock first time I looked at self in mirror, my hair was still sticking straight up on end like Homer Simpson. Noone at work had mentioned it.

Had a multileed herat trace done and no lasting damage evident. Phew!
Would I entertain a component not rated by manufacturer for use I put it to? NO, I value my life more than thta!
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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