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Old 17th Oct 2019, 6:42 pm   #21
John10b
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Default Re: Bush AC11 - Newbie Project

The Trader Service Sheet 951 values and your measured values agree, I donít know about the Bush service sheet. From your pictures, plus your readings, I would suggest the transformer is ok.
Enjoy your restoration project.
Cheers
John
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Old 17th Oct 2019, 7:07 pm   #22
Sideband
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Default Re: Bush AC11 - Newbie Project

Don't worry too much about mains transformer (or any transformer for that matter) DC resistances. The values given are only a guide but if you think about it, you only need one turn to go short circuit and it wouldn't make any difference to the reading you get BUT the transformer would not work....it would overheat rapidly and probably fail spectacularly if not disconnected pretty quickly. If the radio is working, the transformer is OK. Replacing the leaky old waxies will reduce HT current possibly by quite a few milliamps and will certainly help to prolong the life of the mains and output transformers.

If the DC reading is wildly out then obviously that would be cause for concern but 10 or even 20 ohms or more doesn't mean there is a fault.
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Old 17th Oct 2019, 9:11 pm   #23
cathoderay57
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Default Re: Bush AC11 - Newbie Project

Thanks for the close-ups of the transformer. Photo #3 doesn't look good, with evidence of charring and so it's obviously been very hot at some point. It is quite possible that you might have some shorted turns. If so it will start to smoke again soon after you apply power. Try powering up without the rectifier fitted and do some voltage checks on the secondary windings. If the transformer is getting hot off-load you will soon smell it. Cheers, Jerry
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Old 18th Oct 2019, 4:15 pm   #24
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

So, taking out V5 (Trader Sheet) leaves just the mains comming into the set connecting to the transformer and everything else out of circuit. A nice easy test. Presumably I can measure the AC voltages at the secondary side (being careful) to see what kind of range they are in.
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Old 18th Oct 2019, 4:37 pm   #25
cathoderay57
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Default Re: Bush AC11 - Newbie Project

That's right. You'll need a multimeter on the AC volts range capable of at least 250v. If the max secondary voltage is around 200v AC that's a good sign but keep a lookout (and sniff out) for transformer burning. If you see or smell smoke then turn off power immediately. Don't leave it running for any length of time unattended.

If, as I suspect, there is a winding short then option 1 is you'll need a replacement transformer. These sets are fairly common so if you post a request in the parts wanted section you might find somebody with a scrap set willing to salvage the mains transformer for you. Second option is to get it rewound and Ed Dinning on this Forum can probably do it for you for a fee. However, let's do the power test first.

Be careful removing the rectifier (and any of the other valves). Some have a metal skirt which isn't a problem but the ones with a moulded glass base are held in place by a small glass pip that slips behind a metal wire spring on the valveholder. If you yank out the valve it is easy to shear off the glass pip and the valve then loses vacuum and is useless. Take care and release the wire spring first if poss.
Cheers,
Jerry

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Old 18th Oct 2019, 8:18 pm   #26
John10b
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Default Re: Bush AC11 - Newbie Project

In your first post #1 you said when you first switched on it worked for a short time before fading and only a buzz, did you detect a suspicious smell or any smoke? Did you notice any wax near the Mains transformer or in the cabinet, when you were taking the pictures?
Cheers
John
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Old 1st Nov 2019, 2:06 pm   #27
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

Managed to find some time to play radios again...

When I switched it on previously there were no burning smells.

I've removed recifier valve - moving the retaining spring out of the way first.

I switched the set and on and kept a close eye on the transformer - no smoke or anything else I'm pleased to say (though I still don't like the look of the transformer).

I've measured the AC Voltage at the taps on the secondary side of the mains transformer - see attached. Voltage comapres quite well to Bush service sheets (no load):
Scale 10V - Mine 10V
Heater 130 - Mine 127V
HT 285 - Mine 270V
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Old 1st Nov 2019, 3:43 pm   #28
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Default Re: Bush AC11 - Newbie Project

I'm guessing the wheel in the attached photo is some kind of flywheel. It currently is loose on the tuning shaft despite there being two screws that could secure it. Am I right in thinking that this has become loose and I should just tighten the screws?
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Old 1st Nov 2019, 4:25 pm   #29
Herald1360
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Default Re: Bush AC11 - Newbie Project

Yes, the two screws to lock it to the shaft can just be tightened.


The flywheel is simply there to give a nice feel to the tuning and it also allows for quick "spin and freewheel" end to end tuning, though it's not a good idea to get too enthusiastic and let things run hard into the endstops!
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Old 1st Nov 2019, 4:28 pm   #30
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

Thanks, screws tightened now
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Old 3rd Nov 2019, 8:19 pm   #31
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

Knobs Cleaned & felt spacers washed.

New bulbs fitted for tunning dial

Refitted the rectifier valve & started her up heaters glowed and after a short while I managed to get Absolute Radio (I've learnt something;-) ). Sound is a bit poppy and cracakly but its kind of working. Dial glowing nicely. No burning or smells from the transformer (though it still looks a bit sad).

I think there is more work to do here but at least there is progress...
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Old 4th Nov 2019, 11:21 am   #32
John10b
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Default Re: Bush AC11 - Newbie Project

Glad you making progress, I was wondering what aerial are you using?
Cheers
John
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Old 4th Nov 2019, 7:48 pm   #33
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

Stock internal loop aerial only.

I remember you said you could run it outside of the cabinet it you made your own and used and extension lead ofr the o/p tx. I was wondering how you get the plugs/sockets to make an extension lead ?
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Old 4th Nov 2019, 8:32 pm   #34
John10b
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Default Re: Bush AC11 - Newbie Project

I had some from an old scrap chassis, AC34, so I removed all the useful parts, the cabinet was badly damaged and full of woodworm so I binned it.
Cheers
John
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Old 5th Nov 2019, 9:39 pm   #35
RetroGuy527
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Default Re: Bush AC11 - Newbie Project

Quote:
Originally Posted by John10b View Post
I had some from an old scrap chassis, AC34, so I removed all the useful parts, the cabinet was badly damaged and full of woodworm so I binned it.
Cheers
John
Ah right - that makes a lot of sense
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