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Old 24th Aug 2008, 2:17 pm   #1
slidertogrid
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Default Pye VT21C restoration.

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Originally Posted by slidertogrid View Post
Thanks Trevor ,
I have got a Pl83 in the set, apart from the tuner valves, a load of Ef80s, 1 eb91 3 ecc82s and a pcl83 there are no other valves.
Apart from the ones in the line o/p cage!
I have removed the chassis and given it a quick clean, I have checked the caps around the frame stage and none read leaky on my AVO 8 they all give a kick and then return to a very slight reading on the highest range, is it possible that they leak when Ht is applied?
The dropper had been "repaired" and the heaters were a little on the bright side to say the least, I have fitted a temporary resistor and the heaters look better but now I have a lack of width and even less frame scan! Maybe the valves are all clapped due to being overrun? luckily the tube still seems bright.
I have checked the circuit as best I can and the pl83 is definitely the frame output valve, maybe someone has fitted the wrong valve in the past? it must be somewhere near though as I have some scan and no burning resistors!
The pictures show the chassis as removed pre cleaning, the underside showing capacitors ancient and modern!
The final challange when (if ) I get the set working will be the cabinet!
Mods, sorry if this is now not in the correct section, please move if inappropriate If anyone is able to confirm what valve I should have it would be greatly appreciated.

Rich.
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Old 24th Aug 2008, 9:39 pm   #2
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Default Re: Pye VT21C restoration.

Here are the pictures of the chassis anyone know what it is? is it the same a the pre pcb Pye continental?

I have managed to track a pl83 down so I will give it a try tomorrow, this old beast seems to have had a long service life if previous repairs are anything to go by and if possible I would like to squeeze a few more out of it
Rich
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Old 24th Aug 2008, 10:00 pm   #3
murphyv310
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Default Re: Pye VT21C restoration.

Hi Rich.
I'm going to dig out the service info I have on the VT21 tomorrow and have a look, I would say though although your AVO gives a kick and then settles back doesn't always mean the caps are ok, even slight leaks can mean problems especially in a frame stage. My advice is always change the waxies and also those horrid moulded hunts (maroon & black in colour) take your time and check your work every time, dont deviate from the values fitted except for the change in preferred values that took place about 40 years ago (eg 0.05uf now 0.047uf etc) frame stages especially need values as close as possible to the design.
Ill repost as soon as I have more info.
Good Luck.
Trevor
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Old 24th Aug 2008, 10:40 pm   #4
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Default Re: Pye VT21C restoration.

Trevor, thanks for your help, I will change all the original capacitors in the frame stage and try again, if this is going to be the case throughout the set I can see it being a job for the long winter evenings!
Working on the set with the chassis connected, to take voltage readings around the frame stage for instance will present another challenge
If you do have a diagram it would be a great help
Rich.
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Old 24th Aug 2008, 10:52 pm   #5
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Default Re: Pye VT21C restoration.

Quote:
Originally Posted by slidertogrid View Post
I have checked the caps around the frame stage and none read leaky on my AVO 8 they all give a kick and then return to a very slight reading on the highest range, is it possible that they leak when Ht is applied?
Yes! The test with an Avo is no real test at all other than short circuit/open circuit. It only needs a fractional leak to cause problems in a frame output/oscillator stage. The Avo does not test at anywhere near their working voltage nor does it test their value. No point messing about with any of these old waxies...change the lot. I guarantee that they will be off value (sometimes by a very long way) and leaky (even 20 meg is too much). They will also leak more at their working voltage or even break down completely. By all means, change them one at a time if you prefer.

Rich.
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Old 25th Aug 2008, 10:29 am   #6
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Default Re: Pye VT21C restoration.

Quote:
Originally Posted by slidertogrid View Post
If you do have a diagram it would be a great help
Rich.
Hi Rich.
Can you PM me with your E-Mail address and I will send you a copy of the manual (you're correct the frame o/p is a PL83 "odd")
Trevor
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Old 25th Aug 2008, 4:49 pm   #7
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Default Re: Pye VT21C restoration.

Thanks Trevor pm sent.
Rich, thanks for the advice I will change all the caps in the frame stage for a start and see what happens, I have managed to get a PL83 today as well so there is hope!
Right then! cutters, box of caps, solder, iron and lots of patience, I think I might wait until I get the circuit from Trevor

Rich.
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