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Old 25th Nov 2023, 6:45 pm   #1
bristle66
Triode
 
Join Date: Apr 2022
Location: Edinburgh, Scotland, UK.
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Default Hacker RV14 front end problems

I'm currently overhauling an RV14. I've replaced all of the old electrolytics and a number of out of spec resistors. The selenium rectifier was replaced with diodes before it came to me. The valves all test good. So it should be good to go. Trouble is - it ain't. The audio stage is fine. Feed Spotify in through the gram input and it sings like a wee bird. No hum or anything. But the radio is a different story. The EM84 closes up but the volume is faint and there is considerable hum. Advice please.

Last edited by bristle66; 25th Nov 2023 at 7:00 pm.
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Old 25th Nov 2023, 7:47 pm   #2
Silicon
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Default Re: Hacker RV14 front end problems

The fact that the EM84 magic eye closes up suggests that the discriminator is demodulating a strong signal.

Do you have a spare EB91? It may have heater cathode breakdown.

Is the hum altered by tuning across the waveband or by adjusting the tone control?
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Old 25th Nov 2023, 9:41 pm   #3
bristle66
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Default Re: Hacker RV14 front end problems

I've tried changing the EB91. No improvement.

Tuning across the waveband or adjusting the tone control does not affect the hum.

The signal is not that strong. I may have misled you when I said the EM84 closes up.
It opens and closes in the usual way as you tune across the waveband. The set's picking up the usual channels but they're very faint. Almost inaudible against the hum.
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Old 26th Nov 2023, 12:12 am   #4
Gabe001
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Default Re: Hacker RV14 front end problems

I seem to recall that others have had issues with grounding points on these sets. Could explain the hum. Does anything need tightening up?
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Old 26th Nov 2023, 12:36 am   #5
Silicon
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Default Re: Hacker RV14 front end problems

Do you leave any cables plugged into the audio socket and have you installed bluetooth?
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Old 26th Nov 2023, 9:09 am   #6
bristle66
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Join Date: Apr 2022
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Default Re: Hacker RV14 front end problems

I'm aware of the grounding issues. I've been round and tightened up everything I can but I'll do another check.

I don't leave cables plugged in. I haven't installed bluetooth, nor do I intend to.
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Old 2nd Dec 2023, 7:55 am   #7
bristle66
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Join Date: Apr 2022
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Default Re: Hacker RV14 front end problems

Problem sorted. The offender was the gram input. It was effectively frozen in the line-in position. Withdrawing the long reach phono plug did not restore the radio signal. And what I had taken to be a very weak signal was in fact crosstalk. Pretty obvious when you think about it. Whatever, I’ve replaced the gram input and now have a fully functioning RV14 - with which I am well pleased. It’s a lovely little radio and one I intend to keep.

In the near future, I will probably alter the existing phono setup to one which allows me to switch quickly between radio and line input. I’ve had enough of fiddling around with long reach plugs. I need something simpler and less likely to break.

I’m indebted to Mark Hennessy, Hacker guru – who diagnosed the fault – and the estimable George Christofi – who provided the means to correct it. Many thanks, guys. I owe you one.
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