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Old 26th Feb 2009, 5:34 pm   #21
Steve_P
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Default Re: Jonell radio problem.

The heaters on the ACE set are not fed through the big cap. They are LT, the HT is the 250v or so rail.

If the LT is low, then it's probably the transformer setting for mains. Is the mains setting right?

For the HT, try a new rectifier.

Cheers,

Steve P.
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Old 26th Feb 2009, 6:13 pm   #22
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Default Re: Jonell radio problem.

As far as I can tell,the mains setting is Ok.the 3 way plug has been set up so that only one setting is possible.The two wires from the mains TRX have been snipped off.If either of these were used then volts would drop,surely.
I think I will have the valves tested although 3 of them were replaced 2 years ago,but not the rectifier.
Do the DC volts on Cap seem about right?
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Old 26th Feb 2009, 8:30 pm   #23
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Default Re: Jonell radio problem.

Well on the ACE circuit it seems low. But it's more likely to be the valve (rectifier) than the caps. Just put another one in, don't bother with testing the valve.

If it's that, keep the old one. It's still got some life, so it might be OK in another set.

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Old 28th Feb 2009, 5:54 pm   #24
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Default Re: Jonell radio problem.(similar to Ace A50 )

A small amount of progress...I have changed the 0.01 MF cap to the output valve with a new one.The 3 voltages at the Electrolytic smoother have all gone up(258dc to 300,234 to 272,170 to 212) and so has the rectifier voltages(I haven't got a spare yet)238ac to 330 and 259dc to 266.(see aprevious thread)Does this make sense?Can anyone xplain it to me?
I also measured the Resistance of a 47 OHM,half watt? Resistor to Anode .This measured 63R cold when isolated.It is a 20% typo(ie no tol.marks).Will this matter?It has been replaced sometime in the past,I can see.
I managed to remove the aerial coil,reverse slug ,retune but no change on LW.
Obviously ,the LW problem is in the inaccessible coil,RF section which is a self -contained unit which is underneath and attached to the wave change switch .It is different from the ACe A50.Again,has anyone got one of these for comparison?Or ever had one?
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Old 28th Feb 2009, 6:20 pm   #25
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Default Re: Jonell radio problem.

It could be that the capacitor you change was leaky. This may have put a positive voltage on the output valve grid increasing the current consumption. With this extra load the HT voltages would be reduced. It might affect the sound quality also. I can't see that this would explain the big performance difference between MW and LW
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Old 28th Feb 2009, 10:37 pm   #26
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Default Re: Jonell radio problem.

I thought you would have changed that! That cap goes leaky and puts the HT (or at least some of it) onto the grid of the O/P valve. This pulls the HT down. Always measure the volts on the O/P valve grid and then change this cap. Otherwise bad things can happen...

Change the caps on the AGC line if you haven't done already.

You might need to get that LW section I'm afraid. Change the caps round the Mixer/Oscillator valve and if that does not help, you'll have to get to that section.

Cheers,

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Old 2nd Mar 2009, 4:11 pm   #27
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Default Re: Jonell radio problem.

I did not mention that I did measure the heater voltages with all the valves out and bulbs.I got 6.1V and as I replaced the valves ,the voltages went down by 0.1 v till back to 5.7v.i am happy with this
I am going to have my meter checked soon against an AVOmeter.
I did measure the votage at the O/P valve and it was 0.01V dc relative to chassis.It still is
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Old 9th Mar 2009, 5:41 pm   #28
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Default Re: Jonell radio problem.

I seem to have solved the LW problem by replacing a 3300PF 1% cap(Aerial feed) with an old but unused Domino type labelled 3000 pf2%.This was rather dog eared and the foil exposed on one corner,which could have been shorting.It was awkward to get to.The result is better LW which now works from short aerial but the RFalignment has changed particularly on SW.I will retune it and put it back in its box.Where can I get a new cap?
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Old 9th Mar 2009, 6:00 pm   #29
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Default Re: Jonell radio problem.

Try these resin dipped ceramics.

http://www.maplin.co.uk/Module.aspx?ModuleNo=297

Cheers,

Steve P.
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