The old electro will have red on the positive end and bare metal on the negative end. You must connect electros the right way around otherwise they can go short circuit or even explode.

Now that you've connected them backwards they may well have been damaged.

If you're not sure, use a voltmeter to find out which way they should go. Don't just guess, that's how things get destroyed.

As for the hum, the fact that it goes away when the volume is turned down indicates the problem is in the tuner section, rather than the main power supply and audio stages.

I notice the wires to the volume control are not shielded. Was it always like that?

A 6V4 can have up to 40μF on its cathode terminal. After the resistor you can have even larger sizes, 100μF or more. As to why they only used 8/16μF, I cannot say.

As pointed out during the War & after one version had about 26 variations. Three turned up at a radio club "fixit day" and despite the numbering and same cabinet, they were three variations.

Do beware of 50K and 500K resistors especially on output tube grids and that is across the board with all radios of that era. And if 6AD8 follows others/ The plate resistor may be high.

This set is shown as back biased so C17 is negative to CT and C16 goes to ground via R9.

I would use medical "Micropore" on the speaker cracks as it can be moulded. I used to coat it with a Selleys Acrylic glue, however, it seems to have vanished. Do not use rigid glue like PVA as it can cause tears: It should be a flexible adhesive, like a rubberised type. Currently I am experimenting with a Heiniger "Shearers Adhesive" which is Latex & for sticking cloth grinding pads to the comb sharpening disks.

Transformer is a "Shielded" type: Those I will make a point of earthing the chassis.

If it is a model 11-20 then it may be a 11-20X, 11-20Y, 11-20Z or 11-20AA.

The later 11-20 models gradually moved from octal to 9 pin Noval valves, with the last 4 being completely Noval.

Next is to work out which one of the 4 variants it is.

Thanks for the advice guys. I will do my best to act on all of it. The wiring of the set has not been altered by me except for when I replaced the wax capacitors. All those red wires were as they are now. I will start looking in the tuner section just as soon as I work out where that is. Hahaha just kidding. Sort of. I should never have changed those electrolytics around but the schematic (11-38) seemed to indicate they were in back to front. I was thrown by the thick black lines on the dual cap symbol which I thought indicated negative. Anyway I didn't run the set like that for long. As soon as the caps started to get warm I knew I had stuffed up and shut it down.
Just to be clear. If the model and tube compliment is stamped on the chassis. Not the cabinet. Does that mean I actually have a variant of the 11-20 or could it still be an 11-38? I will ground the chassis before I power it up again. I am finding it hard to check resistors as I don't know for sure if I have the right schematic and so do not know what value they should be. The colour codes are worn away to the point I can't use them as a guide. I am scared to change anything without knowing the correct values. I would love to get to the point of knowing for sure what model and variant I have.

What is patently obvious is that it is actually a recycled chassis. Chassis stamping & re-tooling was not cheap. You will note that the tubes are sitting in holes punched for octal tubes with specially made sockets for the miniature tube riveted in them.

It is therefore, going to follow the circuit for the miniature tubes. Remember always, the centre tap of the power transformer HT winding is always the most negative point. In a "Back Bias" configuration, relative to only the voltage across the back bias resistance. Any electrolytic centre tap to chassis, will be positive to chassis. Very common in Philips sets. Reversing electrolytic caps can destroy them.

Resistors can be checked "best as" per previous irrespective of there being a circuit and I usually do that as I change caps to avoid, time wasting and the risks of re-work, later on.(Commercial fixer)

With Kriesler, if its got green paint on the joints, its original.

I believe the 11-20 and 11-38 chassis have the same or similar footprint. The 11-38 appears to be an updated version of 11-20 in a different style cabinet.

I’ll send a pdf of a list of all the 11-20 variants which shows all the changes. From there you may be able to work out which version you have.

Hi Marcc. Thanks for continuing to try and help me despite your words not sinking in. Remember I am very much a beginner. When I read your replies I know there is very useful information in them. But I just don't have the fundamental knowledge to decipher what you are telling me. For instance. " In a "Back Bias" configuration, relative to only the voltage across the back bias resistance. Any electrolytic centre tap to chassis, will be positive to chassis.". I have no idea what that means. I am trying to picture a centre tapped electrolytic cap but I have not heard of such a thing. So I start to doubt myself. Have I wired the electrolytic to ground (C13 0n the 11-38) backwards? I know there is gold in your explanations but I struggle hugely to decipher them with my limited knowledge. Is there any way you could dumb down your answers so I can understand them? When you say " It is therefore, going to follow the circuit for the miniature tubes.". Does that mean you are still of the opinion that I have the 11-38? That is the schematic I am continuing to work from until proven otherwise. Also "Resistors can be checked "best as" per previous irrespective of there being a circuit ". Not sure at all what you mean by that one. I hope I do not come across as being critical Marcc. I am sure everyone else on here understands perfectly what you are telling me. But sadly I don't. I am not the sharpest tool in the shed but I am trying hard to learn. So I hope I am not testing your and everyone elses patience too much. Cheers Ray.
P.S. Thanks Mono. I look forward to having a look at what you have sent via email.

I would have replied sooner But on both computers site locked up and I had to wait until it condescended to actually re-load: Common; two different OS & browsers.

Looking at the 11-38 circuit R8 & R5 are back bias. Back bias is a cost cutting way of setting the fixed negative tube grid bias, without the expense of cathode resistors & caps needed for self bias of the individua tubes. It is not uncommon in Philips, Kriesler, Astor, AWA and others.

All of the cathode current goes back to the CT via R6 & R8 and when everything draws the right current, you get the -7V, which is also the grid bias for the 6M5.

C13 8μF is across the back bias. The CT is the most negative, therefore it is positive to chassis. Reversing it will destroy it and the back bias. Its metal jacket must not touch the chassis.

C13 is also why C12 negative is also -7V above ground and goes to the Centre tap. Its metal jacket, should also not touch ground. Mess that up & you get hum especially with C13. The higher the cap on the cathode the higher the voltage. +/- 20% is considered normal. If you have more than that on the heaters, move the primary tap to 260V

As I have commercially fixed for nearly 60 years & they still arrive, my techniques may vary substantially from hobby fixing. Much to the chagrin of many. I do not use a dim bulb. Startups are done from a modified isolation transformer with downrated fusing & a kill switch.