Bush PB.12 Stray Wire - UK Vintage Radio Repair and Restoration Discussion Forum

BrianAllen · 22nd May 2020, 6:31 pm

Try as I may, I just don't have the experience of wiring diagrams, to identify the orange wire from the soldered lug on the transformer leg/support (there is a black wire on the lug which comes from a tag on the transformer).

Does anyone have any idea where this orange wire should be attached?

Thank you.

P.S. I am still searching for a CL 33 valve; have tried all of the usual places but still no luck!!

Station X · 22nd May 2020, 6:45 pm

As shown in the chassis view in the service sheet, that's the voltage selector.

BrianAllen · 22nd May 2020, 6:59 pm

Hiya, not the one on top with the green plug; the long orange wire below (it has a lug on it that obviously needs to be bolted/attached to somewhere, not obvious to me.

Thank you.

Cobaltblue · 22nd May 2020, 7:08 pm

Bush often use screw terminals on the speaker transformer connections.

Where does the attached connection go.

Cheers

Mike T

BrianAllen · 22nd May 2020, 7:17 pm

This set was part dismantled when it was acquired; hence my query.

There are 2 terminals bolted to the speaker transformer ( one goes to anode on valve 4 and the other to a H.T. line).

All I know is that the orange wire is soldered to that lug which is bolted between the main transformer and the transformer support leg.

Brian

BrianAllen · 22nd May 2020, 7:36 pm

Just a thought; as the orange wire is soldered to a lug that is bolted to the transformer support leg, could it (the orange wire) be a common/earth connection that needs to be bolted somewhere?

Should the speaker/speaker transformer have a common/earth connection?

cathoderay57 · 23rd May 2020, 9:42 am

Re: CL33 - there's nearly a full set of valves for this set on eBay at the moment: https://www.ebay.co.uk/itm/Vintage-R...sAAOSwXederDvs except for the CV1581 which is an ECH35 as opposed to the required CCH35. Sounds as if they might be "pulls" but you might be lucky!

BrianAllen · 23rd May 2020, 9:53 am

I have now obtained a CL 33 but will keep an eye that set of valves.

Thank you for taking the time to post the link.

Brian

Wellington · 23rd May 2020, 6:56 pm

Hi Brian

My suspicion is that the transformer in this set has a electrostatic shield (or screen), and this orange wire should be connected to that.

I'm not 100% sure, but I think an electrostatic shield is a broad, flat, thin piece of copper (effectively tape) which wraps around the primary coil of a transformer to prevent mains-borne interference being transferred to the secondaries. The circuit diagram in the Bush service sheet for the PB12 seems to indicate that an electrostatic shield is present and connected to the radio chassis.

I think I've heard of internal shorts developing to the electrostatic shields in transformers, so there's a chance that the shield in your set was deliberately disconnected. Of course, somebody could've just broken the lug off the transformer accidentally. You could try and reconnect it (after first checking that the shield isn't shorted to any other transformer connections) but I think the set should work OK without it.

BrianAllen · 23rd May 2020, 7:10 pm

Good evening and thank you for your post.

You have just given me an idea; I wonder if it is anything to do with this plate which as you can see from the attached pic is bolted to the component tag board??

Brian

BrianAllen · 23rd May 2020, 7:30 pm

The orange wire is the exact length required (when passed through the chassis) to meet up with the plates first fixing stud/nut.

On closer inspection (with a good magnifying glass) I can see very small traces of blue/green on the orange wire lug; would you agree that this is probably from the plate...…..the plate is only silver because I have cleaned and sprayed it.

Wellington · 23rd May 2020, 8:43 pm

Quote:

Originally Posted by BrianAllen

You have just given me an idea; I wonder if it is anything to do with this plate which as you can see from the attached pic is bolted to the component tag board??

Quote:

Originally Posted by BrianAllen

The orange wire is the exact length required (when passed through the chassis) to meet up with the plates first fixing stud/nut.

Well, it always possible that it could be something to do with that plate, Brian. I would've thought, though, that there was a closer point at which the plate could be connected to chassis (rather than taking a wire all the way out to the main transformer mounting).

Quote:

Originally Posted by BrianAllen

On closer inspection (with a good magnifying glass) I can see very small traces of blue/green on the orange wire lug; would you agree that this is probably from the plate...…..the plate is only silver because I have cleaned and sprayed it.

I thought that plate looked rather shiny and new! Was it blue/green originally? I am skeptical, personally - but as you have the set in front of you, you're the one in the best position to judge! I don't think it would do any harm to use the orange wire to connect the plate to chassis.

Are you using a service sheet whilst working on this set? The Bush one has photos of the chassis that may be helpful to you. Curiously, that plate doesn't appear, and I wonder if it was a later addition.

BrianAllen · 23rd May 2020, 9:05 pm

Not exactly blue/green but one of the only parts with no signs of rust on it.

Yes, I have the service sheet but no sign of the plate in the under chassis view.

It may have been a later addition as they did change the location and mounting position of the transformer on later models.

22nd May 2020, 6:31 pm	#1
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Bush PB.12 Stray Wire Try as I may, I just don't have the experience of wiring diagrams, to identify the orange wire from the soldered lug on the transformer leg/support (there is a black wire on the lug which comes from a tag on the transformer). Does anyone have any idea where this orange wire should be attached? Thank you. P.S. I am still searching for a CL 33 valve; have tried all of the usual places but still no luck!! Attached Thumbnails

22nd May 2020, 6:45 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush PB.12 Stray Wire As shown in the chassis view in the service sheet, that's the voltage selector. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

22nd May 2020, 6:59 pm	#3
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire Hiya, not the one on top with the green plug; the long orange wire below (it has a lug on it that obviously needs to be bolted/attached to somewhere, not obvious to me. Thank you.

22nd May 2020, 7:08 pm	#4
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,865	Re: Bush PB.12 Stray Wire Bush often use screw terminals on the speaker transformer connections. Where does the attached connection go. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

22nd May 2020, 7:17 pm	#5
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire This set was part dismantled when it was acquired; hence my query. There are 2 terminals bolted to the speaker transformer ( one goes to anode on valve 4 and the other to a H.T. line). All I know is that the orange wire is soldered to that lug which is bolted between the main transformer and the transformer support leg. Brian

22nd May 2020, 7:36 pm	#6
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire Just a thought; as the orange wire is soldered to a lug that is bolted to the transformer support leg, could it (the orange wire) be a common/earth connection that needs to be bolted somewhere? Should the speaker/speaker transformer have a common/earth connection?

23rd May 2020, 9:42 am	#7
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Bush PB.12 Stray Wire Re: CL33 - there's nearly a full set of valves for this set on eBay at the moment: https://www.ebay.co.uk/itm/Vintage-R...sAAOSwXederDvs except for the CV1581 which is an ECH35 as opposed to the required CCH35. Sounds as if they might be "pulls" but you might be lucky!

23rd May 2020, 9:53 am	#8
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire I have now obtained a CL 33 but will keep an eye that set of valves. Thank you for taking the time to post the link. Brian

23rd May 2020, 6:56 pm	#9
Wellington Hexode Join Date: Jun 2009 Location: Cheshire, UK. Posts: 363	Re: Bush PB.12 Stray Wire Hi Brian My suspicion is that the transformer in this set has a electrostatic shield (or screen), and this orange wire should be connected to that. I'm not 100% sure, but I think an electrostatic shield is a broad, flat, thin piece of copper (effectively tape) which wraps around the primary coil of a transformer to prevent mains-borne interference being transferred to the secondaries. The circuit diagram in the Bush service sheet for the PB12 seems to indicate that an electrostatic shield is present and connected to the radio chassis. I think I've heard of internal shorts developing to the electrostatic shields in transformers, so there's a chance that the shield in your set was deliberately disconnected. Of course, somebody could've just broken the lug off the transformer accidentally. You could try and reconnect it (after first checking that the shield isn't shorted to any other transformer connections) but I think the set should work OK without it. Attached Thumbnails

23rd May 2020, 7:10 pm	#10
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire Good evening and thank you for your post. You have just given me an idea; I wonder if it is anything to do with this plate which as you can see from the attached pic is bolted to the component tag board?? Brian Attached Thumbnails

23rd May 2020, 7:30 pm	#11
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire The orange wire is the exact length required (when passed through the chassis) to meet up with the plates first fixing stud/nut. On closer inspection (with a good magnifying glass) I can see very small traces of blue/green on the orange wire lug; would you agree that this is probably from the plate...…..the plate is only silver because I have cleaned and sprayed it.

23rd May 2020, 9:05 pm	#13
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB.12 Stray Wire Not exactly blue/green but one of the only parts with no signs of rust on it. Yes, I have the service sheet but no sign of the plate in the under chassis view. It may have been a later addition as they did change the location and mounting position of the transformer on later models.