I was gifted a Philips 141U chassis in about 1971/2 and had may fun hours and a couple of shocks playing with it until eventually it was dismantled. I never did get it going! At the time I didn't know what the set looked like as the cabinet had been smashed when the owner tripped over his dog and dropped the set onto a flagstone floor! One thing I remember was the set had very distorted sound and the UL41 lit up purple. A replacement UL41 did the same and at the time that was the limit of my abilities hence the chassis bit the dust!
Fast forward 40 odd years and I have another! The set came from a stall at Biggleswade swap meet, it was only a tenner and as the cabinet looked good with no cracks in the Bakelite or the plastic front so I think it was a bargain. I expected the set would not work as it no doubt would be full of the famous Philips 'Tarbombs'. As I was handing over the cash the seller volunteered that the set "worked when it was last tried!" I Joked "Oh really? When was that? 1977?" He replied " No, a year or so ago".
Now, I have bought a few radios in my time and I interpreted that as "It doesn't work" "It's pretty ****ed" 🤣. Lovely ! No fun if it works. For a tenner I don't expect any guarantees!
When I got home I took the back off and had a look inside. Hmm... suspiciously clean, and an empty valve holder! As this was the rectifier I reasoned that it was possible some diodes had been fitted under the valve holder and the dropper adjusted to compensate for the missing heater. The dropper had certainly had some attention!
I plugged it in and switched on. Nothing. I nipped up to the workshop and fetched a UL41. Tried again, Dial lamp lit and heaters lit, yea! That was it though not a peep from the speaker.
Today I put it on the bench and removed the chassis, In true Philips fashion this wasn't completely straightforward, The plastic front has to come off to enable the dial pointer to be threaded through the slot in the case. The dropper has been messed with, one end is open circuit and disconnected. The reason there was no H.T was because the wire connecting the AC to the rectifier Anode was connected to a tag on the sound output transformer... The music really would go around and around if it worked!
I connected the wire to the dropper so it would get some mains this still leaves one section of the dropper open circuit so the HT may be a little high but should do for a test. I switched on again and after a short warm up time there was some spluttering from the test speaker, The UL41 was sparking away merrily! I checked for shorts and after finding none replaced the UL41 with another and tried again. Same spluttering so I replaced the UL41. Still the same. Dark forces have been at work here! I found a circuit in the RTV books and went down to the kitchen and put the kettle on!
Part two to follow after I have put the hammer on charge!
Good little sets. I have one and have had a couple in the past. Remarkably sensitive using the internal frame aerial. If it's a little insensitive, try another IF amp valve. You might find the output transformer is causing the sparking UL41. Check the primary resistance, it's around 300 ohms. They look good when assembled as the whole front grille is illuminated.
You'll need to change those tar bombs! Watch the one across the mains if it hasn't already exploded.....they go with a wallop (and make an awful mess)!
@sideband Thanks, I will check the transformer, I have had a few Philips transformers open circuit primary in the past. I made a mistake with the pictures and have managed to duplicate the cabinet pic and the under chassis pic I can't see a way of deleting one picture without deleting them all. Can this be corrected please? Sorry to be a pain!
Circuit from the RTS book.
have managed to duplicate the cabinet pic and the under chassis pic I can't see a way of deleting one picture without deleting them all. Can this be corrected please?
Yes. See your post.
the cabinet looked good with no cracks in the Bakelite
The company called it 'Philite' and there was a whole division in Eindhoven dedicated to making the stuff. It was also used to make household items unrelated to electronics. They pop up from time to time in the 'Philips made' group on Facebook.
@boater-sam C30 is a real menace for the output transformer, if that’s leaky/short the transformer will be overloaded.
Frank
Would not do the UL41 much good either!@boater-sam C30 is a real menace for the output transformer, if that’s leaky/short the transformer will be overloaded.
Boater Sam
C30 has been replaced previously that is the white capacitor under the chassis. C32 had been disconnected by the previous owner so it looks as if they were also looking for the same fault. I may get a bit more time later today to have another look. I will report back...
I have just realised I made a typo in the first post it was the UY41 rectifier that was missing hence my comment about the diodes. I am going to do some further checks and see if I can find the problem. There are no shorts on the HT line so the problem must be excessive current flow once the valves have warmed up.
It Lives! 😎 That has been an hour of fun! I disconnected the output transformer and tested it for resistance and leak to earth. I disconnected the feed to pin5 of the UL41 leaving the rest of the the HT line and the smoother in circuit. I then had HT on the smoother. Suddenly the voltage dropped, came back and dropped again. Then the UY41 flashed and sparked, lit up purple and before I could switch off the dropper burnt out! Great!
I turned the chassis over and eventually saw the problem, there was solder splash on the valve holder of the UY41 pin 7 to chassis! I removed the splash fitted another UY41 and lashed in a dropper section across the fused one. I then had HT no fireworks. I reconnected pin 5 of the UL41. HT still ok. So I had a good look at the wiring to the transformer. I noticed at this point that the wiring on the bottom of the dropper was untidy and badly joined with bare wire, this was underneath the dropper and very close to the primary tags of the output transformer so I wonder if there was an intermittent short there? I sorted that out and made sure the dropper tags were clear of the transformer reconnected the primary and tried again. Success ! It works! no more killing valves!
I tuned it to Caroline and replaced C30 which had been disconnected previously. I snipped out the mains filter cap as it wasn't a x2 it was an older RS replacement.
The dropper is still a mess from the previous work it has received so I need to have a proper look and tidy that up, I'll replace C29 for obvious reasons and then give the set a longer run under supervision. If it is picking up Caroline without an external aerial things can't be too bad. We will see! This was more difficult than it needed to be, the solder splash probably explains why the UY41 was missing when I got the set! The problems all seem to have been caused by the horrible soldering done to the dropper. I will never know what the original fault was. The chances of finding an original dropper are pretty low I suppose so I will have to make one up, the replacement section will do for now. At least it is solidly fitted and safe!
I'll post some final pictures once it is back in it's box! Thanks for the advice and replies it is encouraging! At least I can fix stuff now that I couldn't when I was 10 or 11... I just can't climb trees anymore!
These sets do work well with their internal frame aerial although I'm not sure why given their simplicity. It must be down to high Q coils. I might have a scrap chassis for one of these. I'll have a look when I'm next in the mancave. I vaguely remember having a butchered chassis which yielded some spares for the one I currently have. I don't remember what the dropper is like though....
It is back in it's case, for the time being anyway... I replaced the grid coupler, fitted a x2 cap on the back of the mains switch and gave the chassis a gentle wipe over with a cloth moistened with WD40, mainly to reduce or hide the scuff marks from a previous cleaning attempt. The dropper section is a bit untidy but better than the previous lash up of bare wires and loose connections. It will do for now. I cleaned the switches and valve pins. The case needed a little clean and polish before I put it back together. Then I took it apart again and fitted the part I had forgot to refit first, the little gear thing that the wave-change knob fits on to. I checked the plug connections and that it has a 3 A fuse which it does and called it 'done for now'
It works well and looks pretty so I am pleased with it especially for the price I paid!
That looks great! I do like the styling of the cabinets on these.
I have a Philips 151U which as far as I can see has the same chassis and almost the same circuit design with the only difference being that it has a ferrite rod instead of a frame aerial. Two sections of the mains dropper were open circuit on mine when I first received it.
Laurence
@lsmith That is interesting, the 151U looks much more modern. I think these Philips droppers are fragile maybe only just adequately rated, so a small overload even if brief results in failure. ISTR the one I had donkey's years ago had some dropper repairs with large wire wound resistors hanging off it!
I do like the design but it has the usual Philips quirks like fiddley grub screws retaining the knobs and the dial cursor threaded through a slot so you have to turn it to one end and then thread it through a second slot in the end of the scale to release, to reassemble you really need three hands to align the chassis hold the cabinet and lift the pointer through, all at the same time!
I have been listening to Caroline for most of the afternoon and evening, so far so good the dropper has held up!
I don't think this is much better than your original. It has two 1k 5 watts in parallel across one section (presumably R4....Philips manufacturers manual). Yours if you want it. I don't know if you will find a good dropper. All the 141s I've ever had had at least one section bridged.
@sideband Many thanks it is better than mine as mine has fallen in half when the second section failed when the Rectifier flashed over. It is really now just a heatproof tag strip for the replacement sections. The downside is that the Voltage Adjuster wouldn't work as it is which is no real problem but it does all look very untidy. If you don't mind I'll take you up on your kind offer if you could send me a PM with how much I owe you total inc postage I can make payment via paypal if that is OK?
Rich.
OK I'll check the other sections first (I just removed it from the butchered chassis). It's FOC and I doubt the postage will be much anyway. PM me your details. If you clean the tags up and tidy up the two parallel resistors it won't look too bad.
@slidertogrid You should have bought that busted-up 141U I had on my stall at Biggleswade for spares...
