A handy tip after smashing a little transformer - UK Vintage Radio Repair and Restoration Discussion Forum

shaunhw · 25th Jul 2017, 2:25 pm

Greetings from sunny Rotherham.

On Sunday I got hold of a few valves for my old (working) Bush CTV 167 and thought I'd test them in the set! As bad luck would have it, I'd placed the back cover screws on the top of the cabinet. What a daft thing to do!
Though the set was off, one of them rolled off the top, and landed on the decoder board, and smashed the ferrite top off the reference phase switching transformer, which was laid among the components. I tried to glue the ferrite disk back on the top but there was no colour apart from a strange pink! Removed the disk again but this brought the windings with it due to the superglue. I thought that's it. No chance of getting another. I thought I'd try and wind one myself. Worked out that the two secondary windings were about nine turns each by winding the wires back on to the core, and the primary was about 14 turns. Where to get a similar "Dumbbell" core ? Looked in an old computer switch mode power supply, nothing really suitable, then found an old ADSL broadband filter, in my junk box, and took it to bits. A couple of similar "dumbbell" shaped cores where in there, inside a protective rubber covering, so I thought I'd try one of these. The core was about twice the thickness and much taller. So I got some wire off a transformer in the switch mode supply, and wound the three coils. The secondaries in parallel first and the primary over the top of these. Filed down the old dumbbell, and glued the new one from the filter to it and connected the leads to the pins. Fired up the set. Severe hanover bars so swapped the connections of one of the secondaries. OK but green faces, but the pal switching was obviously working! Swapped the connections around for the primary. Full correct colour restored! In case any folks out there ever have a similar issue, I thought I would pass this tip along! Not like the original, which I'll put back if I ever get lucky enough to find one!

Regards to all, and my gratitude to those here who've helped me in the past
with old sets, and ideas.

Shaun (Ex Radio Rentals service technician and fellow old tech enthusiast!)

slidertogrid · 25th Jul 2017, 2:55 pm

Brilliant repair.

I would have been looking for a scrap panel...
I have had the odd disaster in the workshop, my most recent while working on a record player was to melt the mains lead on my soldering iron. The iron was safely in its stand but the cable managed to wiggle itself down into the spring of the holder and melt. I wouldn't mind but I had only just fitted a replacement.

Rich.

shaunhw · 25th Jul 2017, 3:13 pm

Hi

I was almost in tears when this happened on Sunday. Usually I'm more careful than this, especially on something so old. I'm not sure if there are any scrap panels around for this model any more. There might be a similar Tx in another old design however.

Slightly less recently the line transformer... (which has been rewound at some point by someone else who owned this set before I acquired it in 2009) ...started arching internally, and burned a hole in it. Fortunately I managed to switch it off very quickly. I managed to clean out the charred debris, wash the hole out with IPA, clean again, wash again, and fill then it up with none corrosive silicone sealant, the type available from Maplin. I was staring at the timebase chassis for nearly two weeks wondering if I dare connect it all back up after doing this!

All is well so far...

There's a dearth of old valve based UK colour sets on Ebay - I've not seen one in absolutely ages when I've been looking and the Bush is the only one I have.
No 3000's and the like either - However I think I saw enough of those to last me out... lol!

Regards,
Shaun.

Skywave · 25th Jul 2017, 3:35 pm

A very interesting tale. You are to be congratulated on your persistence, patience, perseverance - and a bit of lateral thinking too, thrown in for good measure!

Well done.

Al.

Philips210 · 25th Jul 2017, 4:02 pm

Hi.

Excellent repair. My worst mishap was when I picked up the soldering iron stand by the spring from the top of our 26" Pye hybrid. The spring unscrewed itself from the base and the latter fell and clocked the tube base board. The ensuing hiss meant a replacement tube, I still get embarrased about that!

PAL decoder faults are generally interesting circuits to repair and they can often give a new fault or challenge. ISTR the Pye hybrid decoder closely followed the recommended circuit published by Mullard so was a quite straightforward design. The Bush decoders including the CTV25, CTV167, A823 etc were somewhat different and I found these to be a little more difficult to service. I miss repairing the old colour TVs and I'm always on the look out for any early colour sets. The oldest colour TV in my possesion is a 20" ITT CVC9 which is working well.

Regards
Symon.

shaunhw · 25th Jul 2017, 4:54 pm

Here's some pictures.

You can see the home made phase switching transformer circled on the Bush decoder board. It's glued onto the old ferrite base of the broken transformer

The other picture is a shot just taken of the set working with this component in circuit with normal colour. Moire patterns are because of the phone camera

Regards from Rotherham,

Shaun.

25th Jul 2017, 2:25 pm	#1
shaunhw Retired Dormant Member Join Date: May 2006 Location: Wickersley, Rotherham, South Yorkshire, UK. Posts: 17	A handy tip after smashing a little transformer Greetings from sunny Rotherham. On Sunday I got hold of a few valves for my old (working) Bush CTV 167 and thought I'd test them in the set! As bad luck would have it, I'd placed the back cover screws on the top of the cabinet. What a daft thing to do! Though the set was off, one of them rolled off the top, and landed on the decoder board, and smashed the ferrite top off the reference phase switching transformer, which was laid among the components. I tried to glue the ferrite disk back on the top but there was no colour apart from a strange pink! Removed the disk again but this brought the windings with it due to the superglue. I thought that's it. No chance of getting another. I thought I'd try and wind one myself. Worked out that the two secondary windings were about nine turns each by winding the wires back on to the core, and the primary was about 14 turns. Where to get a similar "Dumbbell" core ? Looked in an old computer switch mode power supply, nothing really suitable, then found an old ADSL broadband filter, in my junk box, and took it to bits. A couple of similar "dumbbell" shaped cores where in there, inside a protective rubber covering, so I thought I'd try one of these. The core was about twice the thickness and much taller. So I got some wire off a transformer in the switch mode supply, and wound the three coils. The secondaries in parallel first and the primary over the top of these. Filed down the old dumbbell, and glued the new one from the filter to it and connected the leads to the pins. Fired up the set. Severe hanover bars so swapped the connections of one of the secondaries. OK but green faces, but the pal switching was obviously working! Swapped the connections around for the primary. Full correct colour restored! In case any folks out there ever have a similar issue, I thought I would pass this tip along! Not like the original, which I'll put back if I ever get lucky enough to find one! Regards to all, and my gratitude to those here who've helped me in the past with old sets, and ideas. Shaun (Ex Radio Rentals service technician and fellow old tech enthusiast!)

25th Jul 2017, 2:55 pm	#2
slidertogrid Octode Join Date: Apr 2005 Location: Peterborough, Cambridgeshire, UK. Posts: 1,898	Re: A handy tip after smashing a little transformer Brilliant repair. I would have been looking for a scrap panel... I have had the odd disaster in the workshop, my most recent while working on a record player was to melt the mains lead on my soldering iron. The iron was safely in its stand but the cable managed to wiggle itself down into the spring of the holder and melt. I wouldn't mind but I had only just fitted a replacement. Rich. __________________ The rotation of the earth really makes my day...

25th Jul 2017, 3:13 pm	#3
shaunhw Retired Dormant Member Join Date: May 2006 Location: Wickersley, Rotherham, South Yorkshire, UK. Posts: 17	Re: A handy tip after smashing a little transformer Hi I was almost in tears when this happened on Sunday. Usually I'm more careful than this, especially on something so old. I'm not sure if there are any scrap panels around for this model any more. There might be a similar Tx in another old design however. Slightly less recently the line transformer... (which has been rewound at some point by someone else who owned this set before I acquired it in 2009) ...started arching internally, and burned a hole in it. Fortunately I managed to switch it off very quickly. I managed to clean out the charred debris, wash the hole out with IPA, clean again, wash again, and fill then it up with none corrosive silicone sealant, the type available from Maplin. I was staring at the timebase chassis for nearly two weeks wondering if I dare connect it all back up after doing this! All is well so far... There's a dearth of old valve based UK colour sets on Ebay - I've not seen one in absolutely ages when I've been looking and the Bush is the only one I have. No 3000's and the like either - However I think I saw enough of those to last me out... lol! Regards, Shaun.

25th Jul 2017, 3:35 pm	#4
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: A handy tip after smashing a little transformer A very interesting tale. You are to be congratulated on your persistence, patience, perseverance - and a bit of lateral thinking too, thrown in for good measure! Well done. Al.

25th Jul 2017, 4:02 pm	#5
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: A handy tip after smashing a little transformer Hi. Excellent repair. My worst mishap was when I picked up the soldering iron stand by the spring from the top of our 26" Pye hybrid. The spring unscrewed itself from the base and the latter fell and clocked the tube base board. The ensuing hiss meant a replacement tube, I still get embarrased about that! PAL decoder faults are generally interesting circuits to repair and they can often give a new fault or challenge. ISTR the Pye hybrid decoder closely followed the recommended circuit published by Mullard so was a quite straightforward design. The Bush decoders including the CTV25, CTV167, A823 etc were somewhat different and I found these to be a little more difficult to service. I miss repairing the old colour TVs and I'm always on the look out for any early colour sets. The oldest colour TV in my possesion is a 20" ITT CVC9 which is working well. Regards Symon.

25th Jul 2017, 4:54 pm	#6
shaunhw Retired Dormant Member Join Date: May 2006 Location: Wickersley, Rotherham, South Yorkshire, UK. Posts: 17	Re: A handy tip after smashing a little transformer Here's some pictures. You can see the home made phase switching transformer circled on the Bush decoder board. It's glued onto the old ferrite base of the broken transformer The other picture is a shot just taken of the set working with this component in circuit with normal colour. Moire patterns are because of the phone camera Regards from Rotherham, Shaun. Attached Thumbnails