Bell and Howell cinema amp output transformer - UK Vintage Radio Repair and Restoration Discussion Forum

Refugee · 11th Apr 2012, 1:09 am

This item had been run as a HI Fi setup for a year or so and got a bit distorted. It always used to sound slightly better than most other valve amps but I put it down to the solid three part cast case and chassis.

I had resigned myself to having to get a rewind done and had even got in contact with someone whom could do this for me at a reasonable price. I removed the transformer and examined it in order to establish it was not the tar filled type as this may have resulted in a revised quote. When I got it out I noticed a wire that was looking a little bit odd. It turned out to be loose and came away. It was the end of the final turn of the primary winding that appeared to have shorted turns. I did another check on the resistance only to find there was no longer a short.

As I examined why this might be so I realized that what had happened during manufacture is that the wire had come out from under the final layer of paper and in order to avoid having to do it again the operative had stuffed it down the gap where the link between the two parts of that half of the winding linked from below to above the secondary.

No rewind needed now just a little squirt of varnish down the gap just in case there has been any arcing, a bit of heat-shrink and a cable tie.
All I have got to do now is screw it up, put it back in and power it up.

A lot less trouble than I was expecting!

Refugee · 11th Apr 2012, 5:18 pm

The transformer is back in and we are now in perfect working order. Just a bit of cleaning and we are done.

Nickthedentist · 11th Apr 2012, 7:45 pm

You did well to resurrect that. It looks a nicely made transformer and would no doubt have been expensive to rewind.

Nick.

Refugee · 12th Apr 2012, 1:52 am

It was just as well I had a look inside.
It turned out to be a fairly quick job once I got the transformer out.

Neil Purling · 12th Apr 2012, 6:49 am

What's the rated output of that beast?

Refugee · 12th Apr 2012, 3:35 pm

The transformer says 25 Watts on the secondary and 30 watts on the primary.
I will treat you to a little bit of viewing as there is some on the computer here.

11th Apr 2012, 1:09 am	#1
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Bell and Howell cinema amp output transformer This item had been run as a HI Fi setup for a year or so and got a bit distorted. It always used to sound slightly better than most other valve amps but I put it down to the solid three part cast case and chassis. I had resigned myself to having to get a rewind done and had even got in contact with someone whom could do this for me at a reasonable price. I removed the transformer and examined it in order to establish it was not the tar filled type as this may have resulted in a revised quote. When I got it out I noticed a wire that was looking a little bit odd. It turned out to be loose and came away. It was the end of the final turn of the primary winding that appeared to have shorted turns. I did another check on the resistance only to find there was no longer a short. As I examined why this might be so I realized that what had happened during manufacture is that the wire had come out from under the final layer of paper and in order to avoid having to do it again the operative had stuffed it down the gap where the link between the two parts of that half of the winding linked from below to above the secondary. No rewind needed now just a little squirt of varnish down the gap just in case there has been any arcing, a bit of heat-shrink and a cable tie. All I have got to do now is screw it up, put it back in and power it up. A lot less trouble than I was expecting! Attached Thumbnails

11th Apr 2012, 5:18 pm	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Bell and Howell cinema amp output transformer The transformer is back in and we are now in perfect working order. Just a bit of cleaning and we are done.

11th Apr 2012, 7:45 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	Re: Bell and Howell cinema amp output transformer You did well to resurrect that. It looks a nicely made transformer and would no doubt have been expensive to rewind. Nick.

12th Apr 2012, 1:52 am	#4
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Bell and Howell cinema amp output transformer It was just as well I had a look inside. It turned out to be a fairly quick job once I got the transformer out.

12th Apr 2012, 6:49 am	#5
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,085	Re: Bell and Howell cinema amp output transformer What's the rated output of that beast?

12th Apr 2012, 3:35 pm	#6
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Bell and Howell cinema amp output transformer The transformer says 25 Watts on the secondary and 30 watts on the primary. I will treat you to a little bit of viewing as there is some on the computer here. Attached Thumbnails