Thorn 1400 an Ultra 6658

[Tazman1966]

Hello All.

Seeing as there seems to be a lot of Thorn/BRC activity of late I thought I'd better add mine to it which had been patiently waiting its turn.

Not much to do to it to get this one going. A quick look over and almost everything seemed to be in order. C107 (0.1uF) was split open though so I replaced that. The original was 300V but I only had 1000V, a bit bigger but I made it fit. On with the power and...nothing. I discovered that R106 the heater supply resistor section on the dropper had gone o/c but I had a handy replacement dropper section - 140R instead of 128R but it would prove a point. With that bit in place time to power up again and after a bit of a lengthy warm up I was greeted with a nice bright raster. I tuned in the set to Mikey405's test card DVD and bingo a nice result. I'm not over happy with the dropper bodge and remembered that Glyn (Welsh Anorak) had some NOS Thorn droppers so I've replied to his thread and wait for an answer. It also works on 405 lines but I'm not sure properly as I haven't got a signal to feed into it yet.

The cabinet was absolutely filthy dirty so I took out the UHF tuner to remove the buttons and get easy access to the bright work and also removed all the other control knobs washed the cabinet and then polished it cleaned up all the knobs and then reassembled it.

On reapplying power as it started to warm up R123 the 100R feed resistor to the system switch solenoid was glowing like a Christmas light. I quickly switched off and disconnected the feed to the solenoid assuming that it had gone s/c maybe.

I had another look today and noticed that when I'd disturbed the wiring to the tuner the insulating sleeve on the back of the VHF tuner where the system switch selector is, the contacts appeared to be touching. I sorted that out and reconnected the solenoid wire but it wasn't working. R123 has been killed. I have'nt got another at the moment as it's a fusible one (that didn't fuse!!!) so that's where I am at the moment and probably where I'll stay for a while as I'm going into hospital for a small operation on Friday and will be out of action for a while.

For now though, here's some pictures of the set working on 625 lines and it must be a good 'un as there's no buzz on the sound

[Focus Diode]

What a beautiful set! More evidence these push through 19" and 23" Mazda tubes are ever lasting!

It's vital R123 is fusible and would disconnect the system switch by cutting the middle (grey) lead at the tuner microswitch until the correct resistor can be found. I'm sure I have one I can send you.

Buzz free 1400s do exist: The 1967 HMV 2640 I used to have gave superb results at UHF, my Ferguson 3655 still troublesome despite schE mods.

Cheers,
Brian

[Focus Diode]

Found a sutiable resistor to replace R123, actually R123 from a scrap 1400 chassis I was given some years ago. I'll pop it in the post for you.

Hope the hospital visit went ok. Look forward to hearing from you again soon.

Cheers,
Brian

[Tazman1966]

Hello Brian et al

I'm getting better and better each day, however one aspect of this set is not.

Seeing as I now had an Aurora http://converter.home.comcast.net/ I thought I'd get out into the garage and try the set on 405 lines.

Now if you remember the resistor that supplies (via the microswitch on the back of the VHF tuner) the solenoid, had gone up in smoke due I thought to the contacts on the aforementioned microswitch being bent together by some clumsy clot (ME) so I was sent a nice new resistor by Brian (Focus Diode). Before I fitted the new one I thought I'd better check the solenoid out. It looked fine with no signs of burning and the DC resistance of the windings was 165R - the manual states 175R - but what's 10R between friends so I assumed that all would be well.

I fitted the new resistor and applied power. Within seconds the new resistor glowed like a light bulb again and died with a puff of smoke. Now am I right in assuming that the solenoid should only be energised for sufficient time to switch systems? Also am I right in assuming that when the micro switch on the back of the tuner (S15) makes the corresponding one connected to the solenoid (S12) breaks when the system switch is actuated so that this happens?

I get the feeling by simply putting this down in words I may have answered my own question but do you guys think that one of these switches may be stuck shut? Bear in mind before I took the set to bits to clean it the system switch worked fine.

With the switch working manually here's a couple of pics of the set working on 405 lines and the resistor that went bang!!!

By the way I had to adjust the local osc core in the VHF tuner as the fine tuning outer ring doesn't work because the raised white plastic collar thing is broken inside.

I look forward to hearing from you soon.

[Welsh Anorak]

Hi Tas
First - still no luck in the dropper quest, but not given up hope yet!
You have answered your own queation - S2A jumps in the other direction to the microswitch - or should! There's nothing else in the circuit. Does the solenoid actually move the switch and does it move freely? You won't have a lot of time to find out! Basically the solenoid is connected across raw mains via your resistor. To test it, I'd feed it with a 100 ohm wirewound, a fuse and some mains (very briefly!) to see whether it actually moves, and that will remove everything else from the circuit. If the slide switch works it must be the solenoid - a faulty microswitch would simply blow the mains fuse.
I might actually have a solenoid - that's if the Thorn 2000 one is the same?

Glyn

[Focus Diode]

I thought these resistors were supposed to be fusible!!! Was there a loudish hum before it blew up? If yes then the system switch itself it suspect for being too "tough", that is in need of lubrication. If all silent it looks as if the solenoid itself has gone s/c as Glyn says.

Yes, I do believe the same solenoid was employed in the 2000 chassis.

Cheers,
Brian

[Tazman1966]

Hello Chaps!

Sorry Brian to have blown up your resistor. I really don't think that it stood a chance to melt the solder it glowed so quick. There was no hum and on removing the solenoid it and the system switch is as free as a bird. As I said earlier the DC reading for both coils in the solenoid are 164R and 165R - the manual states 175R do you think that's okay?

I'm begining to think that I have a hunch why the resistor went pop. I cannot be sure but when I first put the new resistor in I may well have had the VHF selector set to one system but the system switch itself manually set to another with the result that the power was permanently flowing to the solenoid which of course the resistor could not keep up with. The only other thing that I can think of is that when I did some resistance checks on the system switch at S12, the solenoid supply, I found that in one position the contact doesn't make very well and varies from 30R to 130R meaning that the solenoid might not operate in one direction properly if at all again leaving the supply on. I will give it a good old clean up and squirt with Servisol and then try to get hold of another resistor. Are these weird three legged things still made and if so where on earth can they be got?

Any ideas?

Best wishes and yes Dave they are nice sets. Maybe I need to change my Avatar

[Welsh Anorak]

Hi
The switch should bang over on switch-on if that's the case - that often used to make me jump when servicing them! I think your slide switch is to blame, especially as you say it worked before. Check for tracking and physical damage. I'd use a normal resistor plus fuse for testing as the genuine ones are not easy to get any more.
Glyn

[Tazman1966]

Thanks Glyn.

It really helps when someone else has a more logical approach. Of course you're right about it banging over to the other system if it's set on the alternative system before power is applied. Why I forgot this I don't know because I used to have a 19" Marconi version when I was about 12 and I'm sure I remember it doing this as it managed to frighten my younger sister when she sneaked into my bedroom to watch my telly when I "boobie trapped" it

I would therefore assume from what you say that the relatively high and varying resistance shown on SW12 to earth when in one position is the clue. It means that current flows when SW15 on the back of the tuner is in the "A" position but SW12 doesn't connect properly in the "A" position so the solenoid won't move the switch and it stays energised. I think I've got that right - please correct me if not.

Amazingly I cannot find my Servisol. Would WD40 do the trick?

Thanks

[Welsh Anorak]

Tas - step away from that WD40 NOW!!
Seriously, it has a habit of coating anything it touches and that isn't conducive to conduction (!).
I think you could be right - not enough current flows to energise the solenoid, but enough will flow to blow the resistor. If you weren't distracted by the almighty explosion of the resistor, you would probably see some arcing at the switch contacts.
Clean is the key - meths or ispropyl, followed by re-tensioning of the fingers, then some servisol or similar. Only apply mains when it's as close to zero as possible!
Good luck - hope you find another fusible!
Logical? Moi??

Glyn

[Focus Diode]

I agree with Glyn, although I confess to using WD40 in the past in stubbon cases in the past but wouldn't do so now!

The point S2A closest to the solenoid does sound to be defective. I know my Ferguson 3655 suffered from the problem of switching to one system but not back to the other. I simply cut the middle (grey) lead at the system switch to avoid problems then attached the end to well insulated wire, enabling me to change systems manually (piece of plastic coated metal sticking out of the right when looking at the front). Luckilly I was able to get a selector from a scrap chassis (where that resistor came from!) which cured the problem.

As Glyn says the solenoid should be instant, if jammed or misaligned even for that extra moment power would be maintained with horrible consequences. The fusible resistor should open up of course to prevent this.

If you're lucky it just could be a poor contact, possibly tarnished or burned away through use. Although perhaps interfearing with originality a little one can connect a p/b mains switch from the middle (grey) lead of the solenoid to allow it to work or not. This can be fitted to the back of the set. This was useful in my DXTV days as, with Tag 43 to Tag 44 (marked 625 VHF) I could view 405 or 625 VHF and 625 UHF with this arrangement.


I might have another resistor when I get to the spares box. Just incase I would be inclined to open it up then lightly solder it back into posistion. As to why they should blow up without actually opening up is a mystery and certainly worrying! Indeed if my 3655 requires future servicing work I'll do this automatically!

I may have another resistor which I'll have a look for.

Cheers,
Brian

[Mikey405]

Hi everyone.

A most enjoyable day was had visiting Tas down South fixing this old Ultra TV. But, oh dear, the two primary tools used for servicing the set... (Attached.) I think the soldering iron was a 155 Watt dual-fuel model. If the electricity failed you could poke it in the gas cooker flame for 15 minutes to achieve the same temperature.

From Mike.

[Tazman1966]

Hi Mikey.

I knew I was in for a ribbing after my little soldering iron failed and I had to use this nightmare. Speaking of nightmares, the picture of me holding the WD40 is to frighten Glyn (Welsh Anorak). (Well it frightened me - blimey I'm lookin' old these days!!!)

Anyway the solenoid is now working a treat after cleaning its supply contacts on the system switch and carefully using the end of a stick dipped in WD40 NOT I repeat NOT spraying it to lube it and the contacts. I had to fabricate the third leg of the fusible resistor - no mean feat when you're having to use a soldering iron like that and having Mikey laughing at you as well. Anyway, it's all working and Mike also reassured me that the replacement dropper section that I wired in to replace the heater section of the original dropper was okay so it's now boxed up and awaiting promotion to the sideboard for a long soak test.

Thanks again Mike (and all) from,

[Focus Diode]

Excellent indeed! As for using WD40 for lubrication I don't see any problems with that, I've done similar without ill effects. I was once mad enough to spray inside a UHF tuner with disasterous results! We live and learn....

Cheers,
Brian

[ntscuser]

I loved seeing this set again, thanks

We had one of these as a loan set in the early 1970s while our Bush was away for repair. It was an indifferent performer compared to the Bush but was great fun to use.

The one in the picture looks a bit posher than the one we had but that's probably because it's been looked after much better.

It was a remarkably compact set despite having a 23" tube.