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Old 14th Apr 2017, 11:20 am   #41
bionicmerlin
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

John
Thanks for your message..I'm wondering if I'm better off trying to find someone to look over the set like yourself if someone is offering. I don't want to remove and test countless components to I find the right one. It wouldn't matter on a old set but don't want to muck this one up.
going back to what you and others have said about being faulty from new it's never had a plug top fitted if it had I'm sure there would of been screw marks on the tinned solder on the flex Andy
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Old 14th Apr 2017, 3:56 pm   #42
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

Hi
I agree with John - the capacitors are good quality. I have had a couple of the grey ones fail, but of course that would have been in sets with many years under their belts.
I'd be tempted to give it a long (supervised) soak test and see if any faults either appear or - even better - go away.
I'm of the opinion that this was a prize or present or a 'just in case' set. Possibly the owner worked in a shop and was given it either as a retirement present or because it never sold and was in the way.
Thinking about your fault, the fact it happened suddenly leads me to (again) agee with John. A resistor will usually change value slowly, and a poor electrolytic improve with time as a general rule. I suspect a leaky transistor late in the IF strip. Voltage readings will help here - start with checking the LT voltage is correct. Do you have a service manual or circuit diagram?
Good luck!
Glyn

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Old 14th Apr 2017, 4:34 pm   #43
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

I am still amazed by how simple (how few components are used) a valve based B/W telly is.
 
Old 14th Apr 2017, 5:13 pm   #44
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

...until it goes wrong when there are tiousands!
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Old 14th Apr 2017, 11:30 pm   #45
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

Glyn.
Thanks i do have a service manual . I will try and give it a long test tomorrow night when i got more time thanks for your help Andy
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Old 16th Apr 2017, 2:55 am   #46
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

I have had the set on for about a hour and a half not much change in the picture but i had the sound go off. I could get it back very low by off tuning the set. I think it might be C68 a HT smoving cap as it was very hot .
Picture is at low brightness not pulling but more so on caption so much also unstable most of all if i dont give it a signal and its got poor contrast, i have got a couple pics but not that good if this helps.One at low brightness and one at high. As can be seen ay high brightness its very bad Andy
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Old 16th Apr 2017, 7:54 am   #47
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

It does indeed look as if the electrolytics are reforming. Switching it on for short periods say 5 mins at a time might do the trick. You will probably find that it is C91 4uf that heated up. Given the 5 min treatment it will probably reform and run cool. Some replacements may be required. J.
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Old 16th Apr 2017, 3:08 pm   #48
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

A list of modifications to the 1500 chassis that I came across some time ago, and a manual supplement for the varicap tuner version. The mods probably don't apply to this particular set though, and just by coincidence, the front cover of my 1500 manual!
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Old 17th Apr 2017, 2:19 am   #49
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

John yes it looks like your right the cap that was hot now runs cool also on testing its not far off its value.
Haven't done to much to it tonight but I still got no sound . I think the amp side of things must be OK as touching the volume I got a good hum. I will check my input set up later on the unlikely chance the problems there.
Bill your service sheet has more changes updates than my general thorn sheets but my tv does have the upgrades done as far as I can tell Andy
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Old 23rd Apr 2017, 2:00 am   #50
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

I hope I can get a bit more help from someone who knows more than me. So that should be easy.
Still no sound and bad contrast and unstable pic.
I'm thinking the sound could be faulty transistor VT11 on the service sheet. The test voltage on the collector should be 11.5 volt and it measures 17.2 volt. On the Base it should be .6 volt but it is 1.6 volt.

Also going back to the vision side VT 8 should have 25.2 on the collector but it's 23 volt and on the emitter it should be 5.2 volt and it is only .7
In testing the voltage on some other transistors it's not far out so making me think they could be suspect.
Any help please guys. Andy
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Old 23rd Apr 2017, 7:59 am   #51
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

I think you need to see why you have zero sound. Is the audio amplifier working? If not test the output stage first and then back to the pre amp. This is all within the PCL82 valve.
If this stage is dead I can suggest a fault check procedure.
The intercarrier sound signal is taken off from VT8 collector but I would have thought you would have had at least some poor sound as you have a picture.

I think you have several faults. Check C37 the video coupling cap 64uf [Use 100uf]
Also check the value of the preset contrast control R34. It should be 220 ohm and may have risen considerably. There are a number of possibilities including transistor failure. If you get frustrated and fancy a rescue mission to West Sussex I may be able to help. Regards, John.
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Old 23rd Apr 2017, 6:59 pm   #52
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

In any other example I'd be tempted to replace all the 'lockfit' transistors in the IF strip with modern parts. However that will remove a degree of originality, of course - but may well remove your faults!
Did you mention the sound was poor when you first switched on? Maybe the speaker has died or the output transformers tags have worked loose.
Glyn
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Old 24th Apr 2017, 2:16 am   #53
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

Thanks for your kind offer john I might take you up on that if I don't get anywhere .
Just to recap. The set worked almost perfect to start. I tried it over a few evenings for about 20 mins at a time. Later I left in on for about a hour and the contrast went and upset the sync and pulling at at high brightness.
Sound died not to long after .
If I off tune the station preset I can here very low sound in the back ground.
The main amp is working as I get a nice hum if I touch the volume pot.and as a double check I have fed a audio source to the volume .
If it was a old set I would mess about with it

But with limited knowledge I don't want to muck this set up. I will check the items you said to try later today .
Thanks both of you Andy
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Old 5th May 2017, 2:20 am   #54
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

Just gone back to the set after a short break.
John I have tested r34 and it's ok. C37 tested ok but tried a 100mf in its place only difference is it's more stable at high brightness.
Can I take you up on your offer To have a look I will send you a message Andy
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Old 5th May 2017, 7:52 am   #55
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Default Re: Time Warp Tele (Alba) (Thorn 1500)

Sure Andy. I will be in touch. John.
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