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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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3rd Sep 2020, 4:04 pm | #41 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,383
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Re: Help with Invicta valve set
OK. How do you propose to check the alignment? The instructions in the Trader Sheet are usually helpful, but I'm wondering if you have a signal generator? Cheers, Jerry
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3rd Sep 2020, 8:06 pm | #42 |
Octode
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,639
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Re: Help with Invicta valve set
He has a signal generator Jerry, see post 21.
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3rd Sep 2020, 8:53 pm | #43 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,567
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Re: Help with Invicta valve set
Quote:
Just use your signal generator to go through the set starting with the last IF transformer and the generator adjusted to the IF frequency (usually 470Khz but might be 465Khz). Follow the alignment instructions keeping the output of the generator as low as possible (with the volume of the radio set near max). As the IF's peak up, reduce the output of the generator (this avoids AGC action). When it comes to RF alignment, there are usually data marks on the back of the tuning scale that you align the tuning pointer to and then adjust the signal generator to the required frequency in the alignment instructions and then adjust the oscillator coil until you hear the tone from the generator. You might need to increase the output of the generator to start with but again as the tuned circuits come into line, you reduce the output of the generator to as low as possible. It really is quite easy but you need to be familiar with the generator. Going back to the use of a scope, the only time a scope would be used is possibly in the alignment of a top-range receiver where a wobbulator would be used with it to assist in getting the IF bandwidth perfect. A scope on it's own is of no real use other than perhaps for checking that the oscillator is actually working. You only need a signal generator for a standard domestic AM receiver. Some people also like to connect an analogue meter switched to a low voltage AC range across the loudspeaker to measure the audio tone 'peak' during alignment.
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3rd Sep 2020, 9:45 pm | #44 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Help with Invicta valve set
A 'scope is the better peak indicator when aligning, a meter would be second, human hearing's ok to get you in the ball park but isn't very good for the fine final.
Lawrence. |