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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 20th Jan 2021, 6:42 am   #41
DoubleWound
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Default Re: Ultra Model 50 (1937) Restoration

The RF cans came off my set easily for coil rewinding.

The IF cans look similarly easy and you can see the nuts on the image of my finished chassis.

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Old 20th Jan 2021, 5:10 pm   #42
OldTechFan96
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Default Re: Ultra Model 50 (1937) Restoration

I am making good progress with stripping and cleaning the chassis. Once all that is done, I'll focus on neatening up my poor under chassis work.

Removing the can shields was easy but needed to be done carefully.
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Old 27th Jan 2021, 2:00 pm   #43
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Default Re: Ultra Model 50 (1937) Restoration

More progress:

All of the chassis cleaning has been completed and everything has been put back together. I could not believe how shiny the chassis ended up. Most of this work was done with Brasso wadding and finished of with Autosol. The shield cans were cleaned with Fairy and a toothbrush.

The paper transformer covers were tatty so I sprayed them silver.

I did not touch the tuning capacitor as I did not think cleaning would make it look much better. I did not want anything contaminating capacitor.

Two adjustable capacitors have slightly loose screws. I'll have a closer look when it is alignment time.

The next task will be to neaten my under chassis work.
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Old 17th Jun 2021, 6:39 pm   #44
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Default Re: Ultra Model 50 (1937) Restoration

I've switched this radio on for the first time since I reconnected the mains and audio output transformers.

Unfortunately the set is silent and the UU4 rectifier is getting hot. I'll recheck my work and also check if the transformer secondaries test good for continuity.
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Old 18th Jun 2021, 2:57 pm   #45
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Default Re: Ultra Model 50 (1937) Restoration

I've buzzed out the mains transformer, audio output transformer and the three windings associated with the speaker. Everything measures as it should.

The transformers were correctly reconnected. I've double-checked old photographs.

I next checked the resistance between the positive end on each smoothing capacitor to the chassis.

C22: 1K ohm
C23: 6 ohm

These measurements are similar to what was measured across the speaker coils. I'm confused. The speaker is also connected correctly.

The voltage measured on the HT tag of the speaker is 210V. I think it should be 260V.

Does anybody know what is going on?
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Old 18th Jun 2021, 3:21 pm   #46
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Default Re: Ultra Model 50 (1937) Restoration

Step one, find out what is taking the current, I would start by pulling the output valve and and re measuring.
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Old 18th Jun 2021, 3:31 pm   #47
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Default Re: Ultra Model 50 (1937) Restoration

Find out what's causing the 6 Ohm HT short.

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Old 18th Jun 2021, 6:03 pm   #48
OldTechFan96
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Default Re: Ultra Model 50 (1937) Restoration

I've tracked the HT short to one of the IF cans. The braided lead that connects to the top cap of V3 is grounded to the can via a solder lug.

I disconnected the braid from the can and the short disappeared. See the attached photos. Photo three shows how things should be connected, but this was S/C in my case.

I probably should remove the can again and have a look. All of the cans were removed in the past to wash them.

Once the set was powered up, it worked normally.
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Old 21st Jun 2021, 5:21 pm   #49
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Default Re: Ultra Model 50 (1937) Restoration

Since everything was back to normal I decided to realign the set. The tuning mechanism of my E2 decided to give up just before the LW RF adjustment. I was able adjust the IF frequency to 456KHz and perform the MW RF alignment.

I think this has made a large improvement to reception and audio quality.
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