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

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Old 12th Jul 2020, 4:24 am   #1
petervk2mlg
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Default Annoying low audio level

Hi everybody,
I'm servicing a radio (an Australian Peter Pan GKJ ) and have come across an annoying problem. When turned on the radio's audio output is low. After a while the audio will suddenly jump higher only to display the same low level the next time it's turned on. Also, if I turn the radio off while the audio is low, the level will increase just as I turn off. Furthermore, if I try to measure the HT voltage while the audio level is at the faulty low level, as soon as my meter probe touches the HT point (for example, the screen of the 6V6G output tube) the audio jumps to the proper acceptable level.

Looking for ideas to find the fault.

Peter
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Old 12th Jul 2020, 8:22 am   #2
Nuvistor
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Default Re: Annoying low audio level

If you have a couple of meters, hook them up and leave connected to different points. Observe any change with the set working and faulty. Hopefully having them permanently connected will not shock the fault into disappearing.
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Old 12th Jul 2020, 10:08 am   #3
paulsherwin
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Default Re: Annoying low audio level

Audio valve faults can sometimes cause these symptoms. It's worth quickly trying replacements if you have spares to hand (you may be able to borrow them from another radio).
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Old 16th Jul 2020, 7:35 am   #4
petervk2mlg
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Default Re: Annoying low audio level

Many thanks for the helpful responses.
Actually, I think I’ve tracked the problem down to a loose PU/Radio shorting link on the chassis. I’d noticed all along that the chassis was a bit touchy if I bumped it even slightly.. Touching the circuit anywhere with my meter probe was causing a slight movement.

I needed to see if it was an RF or audio issue so took out the radio link and connected up a Bluetooth receiver to the audio circuit and there was no problem. On reinserting the radio link I noticed it was a bit loose and making poor contact, reproducing the drop in audio.
Thanks again to everyone.
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