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Old 18th Jan 2018, 8:15 am   #61
Freya
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Default Re: Pye B18T found, how did I do?

Its a bit tricky to advise or comment on your restoration as you don't really update on what is being replaced or worked on at the time. Pictures can help too.
You can't diagnose a faulty line output transformer with a multimeter unless it's to check for open windings, an oscilloscope can be used to ring the windings, more info on this is available online.
The only advice I can give is to go back and check the line oscillator components, check the control slider as these like to fall to bits.
Have you got the negative 35-40 volts line drive on the PL38 grid?
The cathode bypass capacitor C29a (25uF) will need changing, remember to install it the right way around with the positive end going to chassis.
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Last edited by Freya; 18th Jan 2018 at 8:30 am.
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Old 18th Jan 2018, 9:06 am   #62
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Default Re: Pye B18T found, how did I do?

I should have said boost capacitor NOT cathode bypass, that's what happens when your supposed to be taking your child to school and rushing.
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Old 18th Jan 2018, 2:27 pm   #63
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Default Re: Pye B18T found, how did I do?

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Originally Posted by 12jslater View Post
what should the values be on the sets LOPT I have removed it from the chassis as it being a bit picky on whether it want to work or not.
Put it back!! As stated, you can't check a LOPT (or any transformer for that matter) with a multimeter except for open-circuit windings*. The poor line whistle could be caused by the main smoothing capacitor failing and giving low HT with lots of ripple. Try not to jump to conclusions, sort one thing out at a time. Put the LOPT back, replace the main smoothing can (for the moment, disconnect it and use the modern replacements as they are....you can restuff the old can later) and change the EY51. See what you have at that point and go from there.

*a lot of circuits show typical resistance of windings but they are only a guide. One shorted turn is enough to stop a transformer from working but you would never be able to measure the difference in resistance with a testmeter.
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Old 18th Jan 2018, 8:12 pm   #64
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Default Re: Pye B18T found, how did I do?

And it's alive!!! Not by much but there is a faint line on the screen, the LOPT coils wire had broke where it is soldered to the metal tags, it has been reattached and there is a line whistle!! After restuffing the electrolytic can after it increased even more and the line is slightly more visible and there is no speaker hum anymore.
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Old 18th Jan 2018, 9:20 pm   #65
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Default Re: Pye B18T found, how did I do?

OK Jake good news this tells us the line stage is alive and doing something, and that the CRT is potentially a good one. Are you seeing a thin horizontal white line on the screen which responds to the brightness control being operated? If so this will mean frame collapse. Some simple voltage measurements should be taken next in the frame oscillator and timebase. Are you working from a circuit diagram? One of the things I'd also suspect is the continuity of the height control (frame amplitude). Check for volts each side of the slider. This could well be open circuit.
Another thing well worth doing with your B18T at this stage if you haven't done so already is to take each one of those red EF50's out (do one at a time) and carefully clean all the pins and the valveholders up.

Last edited by matspar; 18th Jan 2018 at 9:27 pm.
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Old 18th Jan 2018, 10:07 pm   #66
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Default Re: Pye B18T found, how did I do?

That was a close call with the LOPTX, I'm glad you were able to fix it.

I am tempted to suggest that you now adjust the position of the ion trap magnet on the neck of the CRT sliding it laterally and rotating it slightly adjust for maximum brightness.
but BEWARE:
You currently have a the common classic fault called frame collapse, and that white line can easily burn the phosphor screen giving rise to a black line across the picture when the set is working normally, so whatever you do, keep the brightness very low so the line is just visible until you repair the frame fault.

PS How about some pictures as you progress, I would like to see how you got on restuffing the smoothing block, you would be teaching me something, as I have not yet done one myself.
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Old 18th Jan 2018, 10:24 pm   #67
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Default Re: Pye B18T found, how did I do?

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Originally Posted by rambo1152 View Post
so whatever you do, keep the brightness very low so the line is just visible until you repair the frame fault.
The line is very dim so no worries of that happening, after looking over the service sheet tonight I noticed that two of the caps that have been replaced are wrong values as I had no service sheet, I will correct this tomorrow and I will put the LOPT in its metal can again as it is currently in a clear plastic box outside the chassis as I didn't want to have to have the hassle of removing it again from the chassis if it had indeed been faulty after soldering the wire back on.
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Old 18th Jan 2018, 10:44 pm   #68
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Default Re: Pye B18T found, how did I do?

What tube has it got? I donít recall my B18 having an ion trap.
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Old 18th Jan 2018, 11:08 pm   #69
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Default Re: Pye B18T found, how did I do?

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What tube has it got? I donít recall my B18 having an ion trap.

MW22-14 C.R.T I believe, don't quote me on it though
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Old 18th Jan 2018, 11:13 pm   #70
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Default Re: Pye B18T found, how did I do?

Apologies if it hasn't. I was reading about the one that Courtney Louise restored, but I don't think it was the original tube she ended up with.
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Old 19th Jan 2018, 7:04 pm   #71
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Default Re: Pye B18T found, how did I do?

You probably already know but if the CRT gun is straight and points at the screen it doesn't use an ion trap but if the gun points at an angle towards the CRT neck then it needs a trap.
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Old 22nd Jan 2018, 4:24 pm   #72
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Default Re: Pye B18T found, how did I do?

Very interesting find. I commend you for being able to enter a shabby chic shop, I can definitely understand your distaste. They take beautiful old pieces of furniture, slap some white paint on, then sand the hell out of them. Looks like you saved it. I’m not such a fan of the plain PYE TVs of this era, but I reckon I’d feel compelled to buy it if I saw it in a place like that.

I see there’s now someone younger than me on this forum. Oooh your parents will love you for having this hobby. Just prove them what you’re capable of and they should hopefully relax (slightly) on your room becoming a workshop. Things seem to be going well so far. Hope you manage to get the set working!

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