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The Yorkshire Rediffusion MK1 CU2213

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Wed Oct 14, 2015 6:16 pm

The cap in question lies at the top of the pcb next to the 220k, if in doubt snip one end off.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Wed Oct 14, 2015 6:32 pm

The cap in question lies at the top of the pcb next to the 220k

Yep, that's the one.
if in doubt snip one end off

Is it OK to run the set up with the cap snipped or do you mean just to measure ?

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by Alistair D » Wed Oct 14, 2015 9:51 pm

The problem occurred after you replaced the open circuit 680k resistor. Lift one end of the replacement to see if the new fault has gone.

Al

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Wed Oct 14, 2015 9:56 pm

Update on the replacement 1K on the base of PL509, it's burnt up.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Wed Oct 14, 2015 10:17 pm

Alistair D wrote:The problem occurred after you replaced the open circuit 680k resistor. Lift one end of the replacement to see if the new fault has gone.

Al

Hi Al,
I shall do that tomorrow but I'll replace the now burnt out 1K first.

Hi Malc.
bcl pre-set rv303 was rusted up so replaced but no change.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Thu Oct 15, 2015 12:16 am

If the 1k has burnt up then the trip is o/c on both sections. The 1k, 2 x BC148 bcl transistors and the 1k bcl pot will be u/s. The .01mfd from the 220k to deck can be left out for testing as it only gives a shadow to the left of the raster if out of cct. If the 680k is left out of cct the the A1 volts will be unadjustable, Malc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Thu Oct 15, 2015 12:36 am

Hi Malc,

Once again thanks for the info.
I shall have to order some BC148 transistors before I can go any further and I guess a new trip too.

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Thu Oct 15, 2015 12:39 am

Almost any general purpose npn transistors will be ok.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Thu Oct 15, 2015 12:45 am

malcscott wrote:Almost any general purpose npn transistors will be ok.

Still have to order some though, three legged beasties are something I don't have in stock :ccb

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by Cathovisor » Thu Oct 15, 2015 11:12 am

Get some BC547s and BC557s Marc - good general purpose NPN and PNP devices with a reasonable voltage rating.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Thu Oct 15, 2015 11:37 am

Cathovisor wrote:Get some BC547s and BC557s Marc - good general purpose NPN and PNP devices with a reasonable voltage rating.

Thanks for that Catho. :aad

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by Mark Hennessy » Sun Oct 18, 2015 12:49 pm

Beware of any transistor that looks like a BC148 - those "Lockfits" are notorious for causing trouble. As said, BC547/557s are good.

The silicon in a BC148 is identical to the BC108 and BC548. Likewise for the BC147 and BC149. The BCxx8 devices are the general-purpose variants; the BCxx7 have a higher voltage rating, and the BCxx9 are selected for low noise.

There's even a Wikipedia page: https://en.wikipedia.org/wiki/BC108_family

Lockfit BF19x are equally troublesome, but can be harder to substitute.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Sun Oct 18, 2015 1:08 pm

Mark Hennessy wrote:Beware of any transistor that looks like a BC148 - those "Lockfits" are notorious for causing trouble.

Thanks very much for that, being new to "transistor" technology it's good to be armed with information from those in the know.
As it turns out the Lockfits have already been ousted on the rgb panel in the sets past :aaq

Cheers,
Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 12:18 pm

malcscott wrote:If the 1k has burnt up then the trip is o/c on both sections. The 1k, 2 x BC148 bcl transistors and the 1k bcl pot will be u/s. The .01mfd from the 220k to deck can be left out for testing as it only gives a shadow to the left of the raster if out of cct. If the 680k is left out of cct the the A1 volts will be unadjustable, Malc.

Hi Malc & all,

The replacement transistors (BC547) have arrived today so I'll pop them in this afternoon. I have already replaced the pot on the RGB panel, replaced the 1K that burnt on the base of PL509, re-fitted 680K for A1 volts and the .01 is still out of circuit on the LOPT board. Is it OK to re-apply power now or should I be looking else where first for other potential faults ?

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Mon Oct 19, 2015 12:45 pm

Check the trip for o/c on the bcl section. This is the usual cause of this problem. It will be ok to short it out until one is obtained, later sets did away with the trip and an 18 ohm fusible resistor was incorporated within the psu. I cant remember the details of this mod, Malc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 2:03 pm

Hi Malc,

You were right about the BCL section of the cut out being O/C.
The coil is detached from inside the cut out, It's not obvious where it was originally connected to but I guess it should go to chassis as the other end of the coil is to PL509 via R505.

Marc.
DSCF3487.JPG
Spot the wire floating around at bottom of the cut out

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 2:41 pm

Hi all,

The trip is now repaired and back in the set.
Powering up again it still gives a very dark picture but at least there's no smoke any more from the 1K.

Marc.
DSCF3489 forum.jpg

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Mon Oct 19, 2015 2:44 pm

Does the bcl pot have an effect? Check A1 volts, Malc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 3:01 pm

malcscott wrote:Does the bcl pot have an effect? Check A1 volts, Malc.

BLC pot no effect, A1 voltages are 515, 450, 500

Marc.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Mon Oct 19, 2015 3:12 pm

Try adjusting rv405 pre-set brill pot on t/b panel.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 3:21 pm

malcscott wrote:Try adjusting rv405 pre-set brill pot on t/b panel.

Adjusting rv405 does improve the picture but not by a lot, at maximum adjustment shown on photo.

Marc.
DSCF3492 forum.jpg

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Mon Oct 19, 2015 4:40 pm

Check PL509 cathode volts as indicated in manual. With the colour turned off is it possible to get a grey scale?

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 5:02 pm

malcscott wrote:Check PL509 cathode volts as indicated in manual. With the colour turned off is it possible to get a grey scale?

Cathode voltage is 3.3 (should be 2.7)
As photo with colour turned off.

Marc.
DSCF3494 forum.jpg

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by malcscott » Mon Oct 19, 2015 6:03 pm

Check ht volts to decoder pcb, also D407/D405 on t/b panel go leaky.

 
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Re: The Yorkshire Rediffusion MK1 CU2213

Post by marc » Mon Oct 19, 2015 6:47 pm

malcscott wrote:Check ht volts to decoder pcb, also D407/D405 on t/b panel go leaky.

Hi Malc,
22.3v to decoder (should be 23v)
Checked D407 & D405 and they seem fine.

Marc.

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