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Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

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Old 8th Jun 2019, 4:14 pm   #1
davidgem1406
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Default Ultra Troubador U7961

I have an Ultra U7961 I started to refurbish but found the output transformer to be O/C.

Can anybody help with a replacement?
The transformer primary is 180R + 15R, secondary for a 3R speaker.

Thanks,
Dave.
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Old 8th Jun 2019, 4:17 pm   #2
Ed_Dinning
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Default Re: Ultra Troubador U7961

Hi Dave, what is the part number, an OC16?

Ed
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Old 8th Jun 2019, 4:40 pm   #3
davidgem1406
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Default Re: Ultra Troubador U7961

Hello Ed, I have no idea there are no part numbers given in the service data.
The transformer is all black and waxed up from years of dirt and heat not much chance of that having the part number.

Dave.
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Old 8th Jun 2019, 5:11 pm   #4
westcliff
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Default Re: Ultra Troubador U7961

The transformer ratio is 42:1 if that helps.

Gus.
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Old 8th Jun 2019, 7:31 pm   #5
Ed_Dinning
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Default Re: Ultra Troubador U7961

It should be possible to reverse engineer it OK

Ed
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Old 8th Jun 2019, 8:26 pm   #6
davidgem1406
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Default Re: Ultra Troubador U7961

Hi Gus, thanks for that information, I will note it, but I can't see how that helps me at the moment.


Thanks Ed, I may be able to strip it down and hopefully count the turns, and measure the wire size. However rewinding it is another matter.

Thanks,
Dave
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Old 9th Jun 2019, 9:13 am   #7
Ed_Dinning
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Default Re: Ultra Troubador U7961

Hi Dave, the small humbucking section is typically 5 to 10% of the total turns.
Note on dismantling that the paper shim in the lamination airgap is important.

Ed
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Old 9th Jun 2019, 4:02 pm   #8
Ian - G4JQT
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Default Re: Ultra Troubador U7961

Look out for the Hunts capacitors! I had one of these sets before I knew how notorious these capacitors are. It always seemed a bit deaf even after proper alignment and new, tested valves.

Ten years later I acquired another Ultra U7961, removed all the Hunts caps, realigned and this one was much better.

Upon investigating the original, a grid decoupling cap had gone from 0.04uF to about 100pF! Not enough to cause a clearly traceable fault to someone not familiar with the performance, but enough to significantly degrade performance.

Apart from that, the sets are unremarkable, but function very satisfactorily.

Ian
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Old 9th Jun 2019, 9:26 pm   #9
davidgem1406
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Default Re: Ultra Troubador U7961

Hi Ian, yes I do know about these Hunts capacitors, I replace them all on sight.
I just did a Bush VHF-41, that was loaded with them, most of the moulding had dropped away or was badly cracked. As soon as it was disturbed it just crumbled.

Thanks Ed, I will look out for that if I decide to do it. The set requires a lot of work and a full set of valves as well as the usual capacitors. Also the case is damaged, and paint missing from the tuning scale. Plus a few other bits. It could all be done but is it worth it?

Dave.
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