18 volts is too high for the filaments. It should be around 10 volts. The excess might have fused the 1R5. Might be an idea to just check what the power supply is doing, and find out if the extra 8 volts is supposed to be there.

The filament voltage is derived via a 10 watt dropper resistor from 150 volts. If a valve goes OC filament, there is no load so theoretically it will go up to 150 volts.

The only thing that stops it is a 12 volt rated bypass electro. At least that bypass cap will be nicely re-formed!

Rest assured it will be correct when the dead bottle is replaced. I need to check my battery valve stock which is on a high shelf in the garage.

Pretty sure I have a couple of NOS 1R5s - if not I can pull one from a radio.

Back working on the 21-11. As Ian so kindly offered me a replacement 1R5 I put the Titan aside and got stuck back into the 21-11. This time I am determined to start from the power supply and work forward. That said I am struggling to make much progress. I think I have proved the power transformer good. But this bloody 3 way switch has been doing my head in. I have finally worked out what is supposed to happen when the switch is turned to mains power mode (One place to the right). At this point I disconnected the power supply from the rest of the set. There are three wires to take off and my thinking is I need to power up to see whats happening and I don't want to do further damage.
I see that the cathode of the rectifier tube supplies both HT and LT via some resistors in each line to drop the voltage to the required levels. So far so good. The voltage from the cathode of the rectifier looks right at around 130 volts. But then I lose the plot. There is a 2.7K resistor at the input to the 3 way switch which is supposed to drop the voltage from 130 to 90 for the HT supply. I get just a couple of volts drop. I tested that resistor and it was a little high at 2980 ohms but I thought that it was probably not the fault but I changed it anyway. The other input to the switch from the rectifier has two huge 1.3K 5 watt resistors in series. I think they are supposed to drop the voltage to the LT level. I can't find any info on what it should be but I am guessing around 10 volts as the first valve in the filament series string wants 7.8 volts. I get around 60 volts after the resistors. They tested OK but in case they may have been breaking down under load I tried to substitute them. I didn't have any 5 watt resistors so I rigged 5 (1 watt )x 15kohm resistors in parallel and connected them up and did a quick test. Result about the same as before. So I reinstated the old resistors. Clearly I am missing something. Probably blatantly obvious to anyone that reads this.
Am I not seeing the required voltage drops because the power supply is not connected to it's load (the radio)? I am scared to hook it back up and feed 60 odd volts into the LT circuit without consulting you guys first. Actually I think I have done exactly that when I was stumbling around in this set last week. Just to be sure I checked all the filaments of the tubes again. I found two more open circuits. Both the 1T4s are also open circuit across the filaments. Not sure if this is my doing or they were already dead when I got the set. Despit the frustration of the last couple of days I am having great fun trying to learn a bit about trouble shooting these old radios. If there is anyone out there familiar with this circuit I would some guidance.

So sorry guys. I did not see any of your recent posts until just now. I didn't notice that there was a page two and so didn't see page two until I posted my latest misadventure today. So funny. My questions were answered before I even asked them. Sorry to say that 12v cap hasn'[t reformed Ian. I replaced it with a 50 volt electro yesterday but it went pop after a few minutes of running the power supply. The learning curve is steep. I contacted you via email regarding the 1R5s. Not sure if you got that. Cheers Ray.

"I replaced it with a 50 volt electro yesterday but it went pop after a few minutes of running the power supply. "

Yep, that's what would happen, without the intact series string. You gave it over 100 volts!

Will check the garage tomorrow & email you

The learning curve is steep, but a very satisfying one to conquer. Next is a TV!*

*(if you want to!)

Oli

If the filaments are going to be destroyed by over voltage, there needs to be a review of the Power Supply and if it has mistakes?

Thinking aloud I wonder if there is benefit in tying a high wattage Zener across the filament supply to drag down the voltage?

Marcc I did check the power supply and found it to be correct as far as my limited knowledge would allow. I moved the primary to the 250 volt tap as suggested. Then I checked the output side. All I had to go on were the voltages on the rectifier tube and they were all correct. So the rectifier is outputting 130 volts from it's cathode and the two diodes are getting 140 volts each as expected. The low voltage tap is outputting 6.5 volts which I think is correct. I don't know if there is anything else to check. It was nagging at me that after I disconnected the radio from the power supply I may not get the voltages I expect as there would not be any load other than the resistors. From the comments I got but did not see originally it looks like that is correct. The other thing nagging away at me is the role of the three big capacitors in controlling these voltages. I still don't quite grasp how the capacitors affect the DC voltage as my understanding is that capacitors block DC. By the way I did try and test those caps in circuit a few days ago and they all tested high by around 50% above their expected values. I didn't trust my readings as they were all high by roughly the same amount. And I had already caused myself grief previously when I didn't get the expected continuity readings across the transformer windings. I think I should change those caps even though the two biggest ones are really hard to get at without dismantling the power supply (again). Thanks for everyones patience on this. I know it's becoming a bit of a saga but I am very grateful for your directions on how to proceed. My gut feeling is I should replace those caps and put the power supply back in circuit. What do you reckon?
Oli give me a break. As you can see I am wrecking this radio. Imagine what havoc I would cause inside a TV set. But thanks for the encouragement. Cheers Ray.

As you can see I am wrecking this radio.
All part of the experience!
Well, thats how I see it.

Oli

Electrolytics generally have a wide capacitance tolerance, typically -10%, +100%.

In most cases you can't have too much.

As I said, the filament voltage will be correct when there is a load. That is determined by the laws of physics, in particular, Ohm's law!
No need to worry about it.

If a filament should go O/C (and battery valve filaments are quite fragile), the other valves will not be damaged because no current can flow.

To get the correct voltage for the filaments. If they are in series its the sum of the filament voltages (from tube data). I note on one radio I recently serviced there were 40 Ohm resistors across the filaments one burnt through. All were faulty.

Electrolytics & Non polarised caps are different. In both cases, neither can be reliably checked in circuit. Only some plate & grid resistors can reliably be checked in circuit, for value. As I often commercially fix and for a long time, some of my methodology is a bit different. I can, preferably with all tubes out, power the "B" rail from the reformer, if I think there is a problem.

Yes! a non polarised cap should not pass DC. Aged waxed paper caps will and end up in the bin. They have two test and if you test for capacity and it leaks like a sieve it can be wrong. Capacity in the majority, cannot be tested "in a circuit" One end has to be free: Minimum. The second test and the critical one is leakage. Again, one end free, or it totally out. You then use an Insulation Tester that can produce a voltage close to its working voltage, or test voltage.

If the thing shows an ohmic resistance, I scrap it. anything below 200Meg as a coupling cap, can be destructive to a tube.

The common Electrolytic is chemical. It has an oxide layer as an insulator. Left unpowered, that layer deteriorates and the cap can present as a short, and they do. This can be destructive and the reason if you can't test them, you dump the lot.

There is a process called "Reforming". This attempts to recreate the oxide layer, On an aged Red "Ducon" HT filter that is usually a waste of time.

With the reformer: Due to a lack of knowledge of its storage time, plus the reliability of some, it has reached the point where I will put them on the reformer before use to ensure they are good.

Thanks for the help guys. Following this latest batch of advice I decided to take the caps around the power supply out and test them. It proved a bit easier than anticipated as I was just able to wriggle the two big ones out without dismantling the power supply again.Two tested high and one had very little capacitance. So I replaced them. I managed to get a 1R5 tube from the internet and itb arrived yesterday. I should point out that Ian had a look in his stash but the only 1R5 he had was marked U/S. He offered to pull a couple out of his working sets but I could not ask him to do that so I declined. Thanks for the offer anyway Ian. And you were spot on with your advice that the filament voltage supply would come good once I got rid of those caps. While thinking on what to do next I remembered that I had at least one and possibly more 1T4s in a home made tube amp and valve regenerative receiver I built some time ago. A quick check revealed two working 1T4s. I quickly cobbled the set together on the bench and powered up on the dim bulb unit. I had a meter on the L.T tap, ready to kill the power if it went above 10 volts. But just as Ian predicted the voltage slowly came up and levelled out a 8.5 volts and there was audio from the speaker. I tuned around and stations came in loud and well maybe not that clear but the radio was working. After the set warmed up a bit the hum was barely audible but still present. I counted about 8 wax caps still left on the under side so I am assuming they are the cause of the hum but this is a very crowded little chassis and I decided not to go any further with this set for now. I will re visit this one once my cap replacement skills improve a bit. The case needs some work and the tuning knob is busted but I am calling this a success. It was a great feeling when I heard noise from the speaker. So I will have a week off (at least I will try to have a week off) and dig into the box and see what comes out next. There is a Philips radioplayer 101 and a HMV C13-C and a Philips 135B plus a couple more I can't remember. Thanks again to all that responded.

It's good that you figured it out.

I just had a look among the spare bits and pieces and found some parts from the one that I scrapped. There's the front and back of the case, and also the power supply. Haven't found the main chassis though.

Robbert if the other bits from your 21-11 show up and you want to get rid of them I would buy them from you. Especially the knobs and the plastic dial plate. Of course I know that most people on these forums have a hard time parting with any of their stuff. Usually much to the disdain of her indoors. So I don't have any expectations but just in case. The offer is there.
In the meantime I delved into the big cardboard box last night and out came a HMV C13-C. Ooooh I like this one. The case is busted. Mainly the bottom but there is an ugly repair on the top section. It's near the bottom damage and it looks like the radio was dropped at some stage smashing one corner. The good thing is any repairs would not be all that visible as they are at a bottom rear corner. The chassis is very dirty but still sound and the radio looks pretty straightforward in design. It's all there.The only problem I foresee is that I am not familiar with some of the tubes and I'm wondering if they will be hard to get if needed. Still there is plenty of room underneath and it is just a cool looking radio. I think this could be the keeper in the bunch. I will start a new thread detailing my attempt at a resto.

My mistake. The new project is actually a Kriesler 11-20 and not a HMV C13-C. Hahaha I have so many radios to play with I am getting them mixed up.

I know the dial was broken, that was one reason why it was scrapped. The knobs would be on the main chassis, which I don't know if it still exists. I will have a look in the graveyard.

EDIT: I cannot find any sign of the chassis or its knobs. Guess it must have been in very bad shape then.

EDIT 2: I don't have a HMV C13C, good luck with the repair to the case.

The Philips 135B looks quite similar to a radio that I gave to Carl. Mine had concentric knobs, so more functions. It was brown. It's only a 4-valver, so it isn't going to be greatly sensitive.