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Old 6th Feb 2012, 10:56 pm   #181
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Default Re: Bush AC34, no sound.

The tuning capacitor is made up of 3 sections of vanes with a brass rod from the tuning wheel through the vanes to the back of the cap. There is a forked shaped springy piece soldered to the frame and sitting in the groove of each section. Would it help if I cleaned the tips of the forks where they touch the frame
Bill
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Old 6th Feb 2012, 11:24 pm   #182
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Default Re: Bush AC34, no sound.

It won't do any harm.
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Old 7th Feb 2012, 8:41 pm   #183
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Default Re: Bush AC34, no sound.

Hi lads,
attached voltage readings from UCH42 through 3 wavwbands

Cleaned valve seats, cleaned wiper on tuning capacitor and waveband switch.
Reasonable reception on SW if only we could hold the station.
E.G.Tuned in radio romania and was listening ok when station vanished,retuned again and same happened...this time a slight tap on the tuning cap brought it back. but it will not hold. It is the same for anything on SW
Slight improvement on MW but with same issues as Sw. MW seems to receive only one end of the waveband.
Nothing on LW
For some reason the set will not stay on a waveband ,it needs a tap or two to get the band e.g. switch set to SW but nothing heard, a slight tap on the tuner and the waveband appears, I can then move up and down the band but it keeps dropping!
Bill
Attached Files
File Type: pdf uch voltages on 3 bands.pdf (207.6 KB, 49 views)
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Old 7th Feb 2012, 8:58 pm   #184
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Default Re: Bush AC34, no sound.

Does reception cut at at exactly the same position of the tuning capacitor on all wave bands? If so the chances are the vanes are touching.

Check the tuning capacitor shaft for radial and axial play. there's generally an adjustable bearing at the rear end. Adjust for minimum play without stiffness.
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Old 7th Feb 2012, 9:28 pm   #185
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Default Re: Bush AC34, no sound.

Hi graham,
Couldn't be 100%sure it's in the same spot. I will need to look further. There is a nut on the end of the shaft......I can loosen that and adjust the shaft?
Thanks
Bill
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Old 7th Feb 2012, 9:42 pm   #186
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Default Re: Bush AC34, no sound.

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There is a nut on the end of the shaft......I can loosen that and adjust the shaft?
I'm not familiar with the tuning capacitor in this set. There's generally a lock nut on an adjusting screw at the end remote from the pulley.
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Old 7th Feb 2012, 10:01 pm   #187
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Default Re: Bush AC34, no sound.

Are you sure the tuning capacitor vanes can mesh together without making contact with each other?

Looking at the photos in post #22 the tuning capacitor vanes are open and hanging over the edge of this chassis. This put them in a very vulnerable position and it's possible that one or more of the vanes have been bent, while removing or working on the chassis
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Old 8th Feb 2012, 9:55 am   #188
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Default Re: Bush AC34, no sound.

Hi Dave,
Yes the vanes are very close together,I can just about slide a piece of paper between them.
I have looked very closely at them and can't reall see them touching anywhere. They do mesh together without any difficulty
Thanks
Bill
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Old 9th Feb 2012, 3:51 pm   #189
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Default Re: Bush AC34, no sound.

Hi Lads,
checked the vanes, removed the small bearing at the rear,there was a little dirt, cleaned and replaced it adjusted the shaft so there is no play.
On SW there is reception through the full cycle of the vanes, on MW reception through about 1/2 the cycle of the vanes, on LW nothing.
There is still the problem with not holding station, and with a gentle tap on the chassis station returns but not always.....sometimes it takes going through the tuning cycle to find it again.
Is the capacitor knackered??
thanks
Bill
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Old 9th Feb 2012, 4:11 pm   #190
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Default Re: Bush AC34, no sound.

Quote:
with a gentle tap on the chassis station returns
You obviously have a problem with a dodgy connection somewhere. Could be the waveband switch, a valve pin not making contact with its holder, or a badly soldered connection.

With the fault present wriggle valves gently in their holders, rotate the wavechange switch slightly, but without clicking to the next position and try tapping components and connections with an insulated tool such as a plastic knitting needle. This should help you localise the fault.
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