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 AWA CHAMPION 4 429 MA question for Brad
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 Return to top of page · Post #: 1 · Written at 10:19:06 PM on 2 April 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

I have successfully recapped this little beauty. I couldn't get full volume with this in my work shop. Either plugged through my variac and dimbulb tester or directly from the power point. However in the kitchen it attains full volume easily . Why is this when it was earthed in the workshop as well.
Could there be a problem with the house wiring?.


 
 Return to top of page · Post #: 2 · Written at 10:29:50 PM on 2 April 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6013

In the workshop, did you have an isolation transformer in circuit?


 
 Return to top of page · Post #: 3 · Written at 10:39:14 PM on 2 April 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

Yes GTC but not when directly plugged into the wall.


 
 Return to top of page · Post #: 4 · Written at 10:45:43 PM on 2 April 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4345

What is the workshop made of? This one in Metal & that makes a Faraday Cage. Mobile phone is on an Aerial.

When we converted the Farm power from Aerials to underground, every bit of wiring was checked and It was amazing what dodgy things a few electricians had done.

Being a water diviner the earth rods have been strategically placed.


 
 Return to top of page · Post #: 5 · Written at 10:48:08 PM on 2 April 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

It's brick veneer with gyprock walls set up to be converted to a granny flat if need be.


 
 Return to top of page · Post #: 6 · Written at 12:17:53 AM on 3 April 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1910

That scenario is quite common.

The mains wiring in the street (or in your case, probably the back lane) picks up radio signals and pipes them into the house. The radio's mains cord pipes them into the radio. This is obviously very inefficient and the effect is subject to addition and cancellation effects due to the layout of the wiring. You probably have one or more mains wiring stubs that are trapping out the signal in some rooms more than others.

For an explanation of stubs see here: Don't worry about the maths, just look at the pictures.

https://chemandy.com/technical-articles/stub-filter/how-does-a-stub-filter-work.htm

The 429 is no ball of fire to put it mildly when it comes to sensitivity so most of the time the AGC can't regulate the volume if the signal is too low.

Does a new IF amp bottle help it?


 
 Return to top of page · Post #: 7 · Written at 12:24:09 AM on 3 April 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1910

Sorry again Brad! I for one just couldn't resist!

That's three of us jumped in to answer for you!


 
 Return to top of page · Post #: 8 · Written at 12:36:10 AM on 3 April 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

Ok Ian I'm sort of understanding ,now to throw something else into the equation. There is a brand new solar system on the roof and the invertor is between the kitchen and the garage which is not seperate to the house.
Plus this issue has only been noticed in the last 6 months.


 
 Return to top of page · Post #: 9 · Written at 12:50:35 AM on 3 April 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1910

Well there's your stub!!

Old stagers might remember the trick we sometimes used in the early days of TV, where Ch2 would in some locations be too strong and cause cross-modulation of other channels, usually Ch7.

You'd cut a length of 300 ohm ribbon and connect it to the antenna terminals in parallel with the TV antenna ribbon. Then snip bits off the other (open) end until you got what you wanted, namely, attenuation of Ch2 without tilting the passband too much and causing ringing in the picture (and sometimes loss of sound!)


 
 Return to top of page · Post #: 10 · Written at 7:37:50 AM on 3 April 2020.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 941

Another trick was a short length of aluminium foil wrapped around the 300 ohm ribbon behind the TV and slid backwards and forwards to find the best signal.

I worked on a Champion a few years ago. Its sensitivity was OK for what is essentially a city radio. Could pick up Sydney stations about 60km as the crow flys, on 3m of wire inside a house, no earth, with an iron roof, no wall sarking. This was despite never figuring out the reason for a slightly low high tension voltage. Let it go in the end because nothing was overheating and the performance was good.

It is now back in my hands with a failed mains switch (two pole) which is on the back of the tone control (0.5MOhm). If anyone has one of these spare I could use it; otherwise may bypass the switch and put a switch in the lead.


 
 Return to top of page · Post #: 11 · Written at 9:07:29 AM on 3 April 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6352

Valve radios are funny things. Next to none of them work in my office at work because it is on the lower ground floor and is surrounded by reinforced concrete - a fairly good faraday cage, even for AM which can pretty much punch through anything.

As others have said, even though AWA was the king of radio in Australia, some of their designs are wanting and other companies such as Astor and Philips made sets with better quality sound.

There's been times when I've even just sat a perfectly working radio on a table and played it with no problem but when the radio is turned in another direction it will stop receiving the signal.

Under most circumstances, a valve radio from the 1940s should work without an earth connection, but there will be times when, for a number of reasons, a radio won't work at all, or it will but with reduced performance.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 12:15:49 PM on 3 April 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1575

I'm convinced there may be a power problem as my variac will hardly push above 200 volts.
Ok I just tested the power point with my multimeter and it's dead on 240 volts .
So this is two problems (1) a faulty variac and (2) something is causing the signal to be low which you have all explained clearly .


 
 Return to top of page · Post #: 13 · Written at 12:45:38 PM on 3 April 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6352

Does it remain at 240V under load? If not, time for a new one. There should be no electronics in a variac apart from that to run a built in digital volt meter - just a big coil of wire with a sweeping contact to vary the voltage.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 14 · Written at 2:37:18 PM on 3 April 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1910

Even so, it'd be worth trying a new IF amp bottle and a touch-up of the IF transformer cores. - tuned to a weak station of course.


 
 Return to top of page · Post #: 15 · Written at 5:25:30 PM on 4 April 2020.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 400

An IF alignment can really bring back sensitivity if it's a bit off.


 
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