Another Solartron SR153

[AlanBeckett]

For the first one see - http://golbornevintageradio.co.uk/forum/...p?tid=4760

This one has clearly had a much harder life - corrosion on the Chassis, broken Valve and some Carbon Resistors looking very much the worse for wear. In fact the Resistors raged from 'Maybe 20%' to 'Is that a Resistor?' One disintegrated when touched. 
There aren't many so a wholesale change was made. With a new (Rectifier) Valve fitted and a clean up it works fine.

       

So, what now? I've got two so I can sensibly Test Valves - Anode and Screen. However, this is the Un-regulated version - it just relies on the flatish Pentode Characteristics - and I was pondering on adding some extra Circuitry ro regulate the Output. There is a Regulated version - SR151 - but I've never managed to track down a Schematic or seen one for sale. Come on Lawrence, you're the expert on finding things that don't exist.


  SRS151.pdf (Size: 794.9 KB / Downloads: 21)

Alan

[ppppenguin]

I have both a 151 and a 153. Great bits of kit. The 151 is {censored} heavy. Hope the attached manual helps.

[pwdrive]

Not sure if I understand which one you're after Alan but the SRS 153 schematic can be found on this page (shown as a thumbnail):

http://www.vintage-radio.net/forum/showt...hp?t=26663

Lawrence.

[pwdrive]

Ignore post#3 Alan...It's the heat...

Lawrence.

[AlanBeckett]

I know the feeling Lawrence

Splendid fellow young Jeffrey. Think of all those EL34/37s. If someone gave you one which needed a set of Valves you'd need a new Mortgage to afford it.

I wasn't thinking of a direct copy, just getting some idea of how they went about it.
I was thinking along the lines of generating a stabilised Negative Supply as a Reference to the Pot then comparing the Pot Slider to a sample of the Output. The result of that comparison would be the Control Voltage to the Series Pass Valves. I fear it will have to be SS.
Some Sums called for methinks.

Alan

[pwdrive]

Would bits of the valve circuit shown here be of any use?:

http://www.r-type.org/articles/art-088.htm

Lawrence.

[ppppenguin]

The 153 supply isn't actually stabilised but uses something close to a series regulator to vary the output voltage. ISTR the series pass valves were similar to EL81 line output.

If you want to use valves something like PL81 line output valves might be a good choice for the series pass. Cheap and rugged. Basically anything with high current/power capability that the audiophools haven't latched on to. They know about EL509 (the 6.3V version of the PL509 colour TV line output bottle) but the PL509, the smaller PL504 and Pl36 might still be plausible. The classic 6080 double power triodes, widely used for series pass in professional valve kit, may be too expensive now.

The TL783 often forms part of a solid state high voltage supply. I think it can be floated to give higher voltages than 125V but protecting it from output shorts could get interesting. http://www.ti.com/lit/ds/symlink/tl783.pdf

Very simple circuit here: http://www.eleccircuit.com/the-variable-...ly-0-300v/

This site is reputable: http://sound.westhost.com/project151.htm

I have a feeling that Mark Hennessey has a fair bit of accumulated knowledge on PSU design so it would be worth waiting for his input.

[ppppenguin]

More bumph

[AlanBeckett]

The 153 supply isn't actually stabilised but uses something close to a series regulator to vary the output voltage.

That's what it says in Post #1 above Jeffrey

ISTR the series pass valves were similar to EL81 line output.

If you want to use valves something like PL81 line output valves might be a good choice for the series pass. Cheap and rugged. Basically anything with high current/power capability that the audiophools haven't latched on to. They know about EL509 (the 6.3V version of the PL509 colour TV line output bottle) but the PL509, the smaller PL504 and Pl36 might still be plausible. The classic 6080 double power triodes, widely used for series pass in professional valve kit,  may be too expensive now.

The Pass Valves are CV428s or equivalent which as far as I can tell from the Data Sheet are entirely adequate.


  cv428.pdf (Size: 77.6 KB / Downloads: 5)

The TL783 often forms part of a solid state high voltage supply. I think it can be floated to give higher voltages than 125V but protecting it from output shorts could get interesting. http://www.ti.com/lit/ds/symlink/tl783.pdf

Very simple circuit here: http://www.eleccircuit.com/the-variable-...ly-0-300v/

This site is reputable: http://sound.westhost.com/project151.htm

I have a feeling that Mark Hennessey has a fair bit of accumulated knowledge on PSU design so it would be worth waiting for his input.

They look like interesting Sites but I don't want to rip it to bits, just add some Stabilisation.

Alan

[Mark Hennessy]

I have a feeling that Mark Hennessey has a fair bit of accumulated knowledge on PSU design so it would be worth waiting for his input.

Not at those voltages And what are those funny glass fings

Still, the topologies are familiar enough...

The unregulated supply appears to be a pair of followers fed from a pot that is fed from unregulated supplies. To improve on that, I guess there are two options:

1. Stabilise the voltage across the pot to improve things a little...
2. Go the whole hog and add a bench of negative feedback, etc. Which is what the posher version obviously does.

Guessing Option 1 is the preferred route?

There's 2 references needed - one to fix the voltage across the pot, and another to offset the pot below ground to account for the "Vbe" of the followers. I'm guessing the latter is a relatively small (variable) voltage, and that might well be within the remit of the good old TL431 (that can stretch to 36V). But the high voltage one would worry me most, being a softy when it comes to this sort of thing. What are we talking about - 350V? So attention to detail is obviously needed. A string of zener diodes is the obvious "KISS" solution - I've reasonable confidence in them at higher voltages. Seven 50V jobs would be a start, leaving nothing too worrying over a single component.

Or, how about neons?

Anything more complex or precise is probably wasted given the lack of NFB.