Golborne Vintage Radio

I've had this for about a year but never used it in anger, simply checked that it did give a reasonable Output and that the insides looked clean and undamaged.

[attachment=12210][attachment=12211][attachment=12212]

It's just as well I didn't really need it beacause a quick test with my new Load showed that it was way short of the supposed Output.

This is the Little Brother of the SR151. It's not regulated and has quite a simple Circuit.

[attachment=12213]

As far as I can tell from several possibly unreliable Sources it should be good for 350 Volts at 100mA, 400 Volts at 50mA and nothing at 450 Volts - in my day that was called 'Derating'.

I hooked it up to my new Load with the following Results:-

O/C 400v
60k 340v
40k 320v
20k 280v
10k 220v
5k  160v

Clearly not good. However, it came with some Spare Valves so the obvious candidates for substitution were the Series Pass Valves - CV428.
In a nutshell they made not one iota of difference.
So, what about the Rectifiers? Put simply V1 was very Dead, so it was only Half Wave rectifying.

[attachment=12214][attachment=12215]

With the two spare Rectifiers installed the Output was much more impressive.
O/C > 450v
3k5 at 350 Volts (100mA) no problem.
8k at 400 Volts (50mA) no problem

In fact the Results were much the same with the old CV428s installed, perhaps needing the O/P Voltage to be turned up a bit more, but generally fine, so I've left them in.

I'll get a couple of new Rectifiers to be on the safe side but I suspect the current ones will see me out.

By the way, the Load was fine.

Alan

I see the problem, the heaters to far away from the cathode  

Lawrence.

Indeed, with a bit of added Air.
The problem was that the Super Top Cap made it completely invisible until I removed it.

Alan

That rectifier has broken in a very strange way right through the thickest part of the glass.
I would be a little bit concerned by the HT+ terminal post. It looks a little bit "nippy" in the photo.

Nicely made though aren't they Alan with all top quality components and oil filled caps. Mine is model SRS 153S

Maybe if I find the time I will get better valves for mine.

Useful now and again.

Gary

Yes, I agree, it is/was a bit odd where it failed. I did wonder if it had been a bit damp at some stage.

Indeed Gary, it's very well made, and should see me out, particularly with a few spare Valves.

Alan

what about this circuit SRS153 3 ?[attachment=21334]

Here's everything I've got about the Solartron SRS153.

Regualtion is never superb. It's not a regulated PSU.

PS: I think the photo of the underside of the chassis isn't a SRS153 but a SRS152. Please ignore. The PDF and schematic are correct.

I see no great problem in replacing the CV2235 (=EY84) rectifiers with suitably rated silicon. A pair of 1000V parts such as 1N5408 in series, with 10M equalising resistors across each diode will be OK. Suggest 47R 10W resistors in series with each pair of diodes. The choke input filter ensures there won't be any high repetitive surge currents.

I fitted a switch in series with the HT+ output. This means I can let the PSU warm up properly before switching on the load.