Vidor My Lady Catherine CN435Z: Questions before attempt to revive

[Simon Gittins]

Originally Posted by Cobaltblue

Someone who has the same model

(which I don't) would be able to help further.

This page shows the Vidor range but no internal pictures. There are also restoration hints.
http://www.portabletubes.co.uk/portables/mycoll.htm

[granazis]

Originally Posted by Station X

What's a "handing cable"? Not a term I've come across before.

Autocorrect blunder "hanging" - connected to nowhere

[Techman]

Have you checked that speaker output transformer primary as advised by at least two people yet, perhaps you have and I've missed it as I skimmed through this thread? Nine out of ten of these Vidor radios that I've seen have got an open circuit output transformer primary, they're known for it. They're a special transformer with a high turns ratio and use very fine wire and there's no spares available, so check it before going too far with this set, as a dud transformer will be a show stopper, unless you want to pay for a professional rewind!

[granazis]

Originally Posted by Techman

Have you checked that speaker output transformer primary as advised by at least two people yet, perhaps you have and I've missed it as I skimmed through this thread? Nine out of ten of these Vidor radios that I've seen have got an open circuit output transformer primary, they're known for it. They're a special transformer with a high turns ratio and use very fine wire and there's no spares available, so check it before going too far with this set, as a dud transformer will be a show stopper, unless you want to pay for a professional rewind!

I haven't as I need first the solution to the issues with the circuit. One thing at a time.

[Techman]

No, sorry, the transformer is the very first thing you check before anything else on one of these sets and it's so easy to do. I don't think you appreciate the seriousness of this part being faulty, as it probably makes the set beyond economical repair.

[Radio Wrangler]

Originally Posted by granazis

I haven't as I need first the solution to the issues with the circuit. One thing at a time.

One thing at a time is fine.

But the right order can avoid an awful lot of disappointment.

Checking that transformer is one, quick, ohms measurement in an obvious place.

In a couple of seconds it tells you whether all the effort you've put in up to that point has been wasted.

David

[Sideband]

Originally Posted by Radio Wrangler

One thing at a time is fine.

But the right order can avoid an awful lot of disappointment.

Absolutely! No point in carrying out repairs to the simple parts only to find it doesn't work (won't work) because of the output transformer. A couple of seconds to check can save hours wasted on the rest of the set. It's up to you of course but its one of the first things I check (in almost any radio) but particularly one of these....

[Ed_Dinning]

Hi Granazis, these transformers can be rewound, but with the fine wire involved it is a pain in the butt. Most will be faulty so not easy to get a spare from a scrap set and it will possibly be likely to fail in short order

Ed

[granazis]

The Transformer doesn't look to be faulty. I have checked it with a multimeter. Both windings have continuity and applying the leads of the multimeter to the input make the speaker produces little sounds, which is what we should expect.
What I would like to resolve is the 2 capacitors (they are capacitors) connected to C5 but going nowhere (see first image, in yellow and red circles the capacitors' both ends, in blue the possible point of connection, also shown in the last image: in red the ends of the capacitors and in blue the possible/probable point of connection).
For the one (100 pF) I believe is the C6 and should be connected to R2 (27K) - there is indeed indication that it was connected to a resistance coloured red-violet-orange - so that must be the one. Both ends to pin 4 of V as I understand. Am I correct?
The other one is colour coded: brown black brown black (fourth image) - so 100 pF and must be C4 going to pin 6 of the V1. However, I am not sure at all. The logical - as I look at it - is to be connected like the other one - both at the same place. The third image gives another perspective.
I also took a photo of the PCB side but the possible connection is on the other side (second image).
Any ideas, anyone, please?

PS. It seems that the 100pF capacitor is the C4 and is connected to R3 - yellow-violet-green - 4.7M - C4, R3, R6 are all connected to pin 6 of the valve (g3) and on the other end R3 goes to L6 (via R7) and the R6 to LT+ according to diagram (which is for chassis based CN434, not my PBC based CN435)

[Cobaltblue]

Its great news that your output transformer is OK.

Thank you for the pictures that helps a lot.

Revisiting the circuit the red capacitor is C4 the red wire going off to TC1 and 2 and the aerial winding in the lid.

In that the case the floating end needs to connect to pin 6 of V1 and it looks as if the brown capacitor is C6 and that needs to connect to the empty pin.

That pin connects to G1 of V1 (pin4)

If you remove V1 from its socket to we get a clearer image of the board around the valve we might be able to see where the red capacitor attaches to the board.

Cheers

Mike T

[granazis]

Originally Posted by Cobaltblue

Its great news that your output transformer is OK.

Thank you for the pictures that helps a lot.

Revisiting the circuit the red capacitor is C4 the red wire going off to TC1 and 2 and the aerial winding in the lid.

In that the case the floating end needs to connect to pin 6 of V1 and it looks as if the brown capacitor is C6 and that needs to connect to the empty pin.

That pin connects to G1 of V1 (pin4)

If you remove V1 from its socket to we get a clearer image of the board around the valve we might be able to see where the red capacitor attaches to the board.

Cheers

Mike T

Thank you, I have removed the V1 and there is indeed a point of connection visible. But about the capasitors:
The red one is 100pF (clearly written on it) and that makes it C4 or C6 according to the CN434 diagram I have, and the brown should be also either C4 or C6 - although as they are both 100pF it wouldn't matter much would it? Where they go matters.
From what i see though you are most likely right.
So from what I understand so far - the red 100pF (C4) goes to the R3 (yellow-violet-green) and pin 4 (g1) while the brown one (C6) - also 100 pF - goes to R2 - orange-violet-blue and pin 6 (g3) - it only the position of the cables that makes me think it could be vice versa.
There are two "orphan" connections, one for the R2 that has (with remains of solder on it) and one for the R3 without remains of solder. And there are two floating ends, the red one C4 with remains of solder (that logically will go to the connection without remains R3) and one without remains (brown C6) without remains that will logically go to the R2 that has remains. Only that will require to kind of cross the two.
Thank you very much. I will remove the valve and comeback with some pics before soldering anything.

[Cobaltblue]

I initially thought that the red capacitor went to the tab and that the silver mica was more likely in the oscillator side of the circuit.

However it does matter because the tuning capacitor "Feeds through" on the fixed vanes and there are components connected to the other side.

Also I suspect the red wire goes to the frame aerial making the red capacitor C4 as its part of the preselector coupling to the frequency changer.

However trying to work with pictures and not being easily able to spin it around in your hands as it were its easy to get it wrong.

Cheers

Mike T

[granazis]

Please see here my final assessment:
an image as an overview
another image without the valve is showing where the floating capacitor legs go:
Brown goes to the upper lump of solder, near the printed number "5"
Red goes down near the green-blue-green resistance.
and another image shows the same from some distance.

Any comments?

[Cobaltblue]

The resistor is 5.6Mohm which is R6 (grid bias) on the circuit which does go to pin 6 of V1.

So this looks like its the right place for C4 the puzzle is why both of these capacitors were disconnected in the first place.

Cheers

Mike T

[granazis]

Originally Posted by Cobaltblue

The resistor is 5.6Mohm which is R6 (grid bias) on the circuit which does go to pin 6 of V1.

So this looks like its the right place for C4 the puzzle is why both of these capacitors were disconnected in the first place.

Cheers

Mike T

That's easy, from its looks they were not disconnected intentionally but are due to bad solder or soldering. They look like cold solder joints. The solder remains in both cases intact and round and full indicating no attempt to disconnect them.

[granazis]

Originally Posted by Cobaltblue

The resistor is 5.6Mohm which is R6 (grid bias) on the circuit which does go to pin 6 of V1.

So this looks like its the right place for C4 the puzzle is why both of these capacitors were disconnected in the first place.

Cheers

Mike T

This morning I soldered the floating legs of the capacitors to the most likely connections.
THEN
I fed 1.38v to the LT connection and 86.4v to the HT (used a mix of new and used 9v batteries to get under 90v as the brand new were giving me 98v. I don't know if the valves can stand that.
Then flipped the over open switching the radio on
I tick sound indicated it was turned on.
Within a minute the MW/AM stations where coming loud and clear.
It works!
Thank you all for your help and advice!
Later today will try LW.

[Simon Gittins]

That's great!
Do at least check C21, the audio coupling capacitor, as if it allows any significant positive voltage to get to the grid of the output valve the output transformer could fail.

[Cobaltblue]

Originally Posted by granazis

This morning I soldered the floating legs of the capacitors to the most likely connections.
THEN
I fed 1.38v to the LT connection and 86.4v to the HT (used a mix of new and used 9v batteries to get under 90v as the brand new were giving me 98v. I don't know if the valves can stand that.
Then flipped the over open switching the radio on
I tick sound indicated it was turned on.
Within a minute the MW/AM stations where coming loud and clear.
It works!
Thank you all for your help and advice!
Later today will try LW.

Nice one I have a bit of a thing for these little portables so it's always good to hear of someone going the extra mile to get a result.

Cheers

Mike T

[Station X]

Well done. We like happy endings here. Your methodical approach has paid dividends.

[granazis]

Originally Posted by Simon Gittins

That's great!
Do at least check C21, the audio coupling capacitor, as if it allows any significant positive voltage to get to the grid of the output valve the output transformer could fail.

I have looked for it but could not identify it on the PCB, It's not where the photos of the non-PCB models show.
On the PCB many capacitors are labeled: C16, C17, C18, C19... but no C20 or 21 I could see.