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

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Old 14th May 2024, 7:21 pm   #1
Robsradio
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Default Valve radio help please

Evening
I’m sure I know the answer, but valve sets are a bit alien to me, transistors any day for me.
I’ve bought an Ever Ready Sky Baronet battery valve set, which had an mis aligned tuner gang, it now move true and short free, but still no audio output, well a tiny signal with ear next to speaker, band switch cleaned etc.
AF coupling cap good, all Cs and Rs around ok and good audio level from output stage when tested.
I think the DAF96 pre amp valve may be suspect as when i connect pin 5 and 6 of V3 with a few Meg resistance I get audio at a reasonable level, although the heater is ok and it’s detecting, would the valve savvy on here agree, or am I wrong?
I’ve included a snippet of diagram.
Thanks as always for your inputs.
Rob
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Old 14th May 2024, 8:28 pm   #2
60 oldjohn
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Default Re: Valve radio help please

Bad heater connection in valve base? use ammeter in LT lead and move the valve. Could be other pins of course.

John.
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Old 14th May 2024, 8:59 pm   #3
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Default Re: Valve radio help please

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Originally Posted by 60 oldjohn View Post
Bad heater connection in valve base? use ammeter in LT lead and move the valve. Could be other pins of course.

John.
Seems to be drawing current, I’ve cleaned pins and socket but still no go sadly.
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Old 14th May 2024, 9:12 pm   #4
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Default Re: Valve radio help please

As always check the voltages on the output valve pins and compare the readings with those in the service sheet.
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Old 14th May 2024, 9:33 pm   #5
kalee20
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Default Re: Valve radio help please

If the DAF96 had a bad filament connection, you wouldn't get any output at all because there'd be nothing to detect the IF signal (the detector is also in the same bottle).

My money would be on the anode load resistor (to Pin 5) or the screen-grid feed (to Pin 4) - or the bypass capacitor from Pin 4 to 0V.
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Old 14th May 2024, 9:59 pm   #6
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Default Re: Valve radio help please

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Originally Posted by kalee20 View Post
If the DAF96 had a bad filament connection, you wouldn't get any output at all because there'd be nothing to detect the IF signal (the detector is also in the same bottle).

My money would be on the anode load resistor (to Pin 5) or the screen-grid feed (to Pin 4) - or the bypass capacitor from Pin 4 to 0V.
Just seen your message, your money was well placed, just got back in from work room with a smile, the bypass cap C22, it tested fine on the bridge, but thought what the heck, swapped it out and hey presto, it works! Cap still tests ok, must be breaking down.
Thanks all.
I have to say it sounds wonderful, no background hiss, static and seems to resist SMPS noise too, shame there’s not much to listen to.
Rob
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Old 14th May 2024, 10:16 pm   #7
kalee20
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Default Re: Valve radio help please

Super! and thanks for the feedback!

It doesn't take much leakage in that capacitor for the screen-grid voltage to be dragged down significantly. And that's like turning off a tap - the valve will cease to perform.

Really glad you've got your little set working, this type of 4-valve superhet can give really good results which is why it was so popular. It's just the expense of batteries which killed it off, once tr*ns*st*rs were capable of working at the requisite frequencies.
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Old 14th May 2024, 10:28 pm   #8
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Default Re: Valve radio help please

Many thanks, I really do need to get to know valves, I grew up with 70s transistor sets and never strayed too far.
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Old 15th May 2024, 7:20 pm   #9
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Default Re: Valve radio help please

Hi Rob, even if working correctly it is worth checking any other paper caps, especially those that decouple the AVC line and any high valve resistors. These will not normally do any damage but will reduce the set's sensitivity.

Ed
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Old 17th May 2024, 9:39 pm   #10
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Default Re: Valve radio help please

Thanks Ed, I might give them a look at as it sounds great, but I’m only picking up the couple of main uk stations, after dark not many more, so you may be right about lacking sensitivity.
Thanks
Rob
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