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Old 27th May 2019, 7:16 pm   #1
electronicskip
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Default Eddystone 770R Mk2 gone (quiet)

Was using my Eddystone 770R Mk2 today when I noticed it was getting quieter and quieter.
Turned it right up but made no difference , the receiver was still working fine but at a greatly reduced volume.

On turning it off and on again a few times there is always a loud spike and the sound comes back again for a couple of seconds then goes back to being quiet again.

Any pointers I should be looking at? as ive no real experience with repairing these beasts.

Thanks in advance.
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Old 27th May 2019, 7:39 pm   #2
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Default Re: Eddystone 770r Mk2 gone (quiet)

Do you mean low volume or lack of performance station wise?
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Old 27th May 2019, 8:01 pm   #3
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Default Re: Eddystone 770r Mk2 gone (quiet)

Quote:
Originally Posted by HamishBoxer View Post
Do you mean low volume or lack of performance station wise?
Sorry should have said low volume.
Station performance is still fine.
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Old 27th May 2019, 8:56 pm   #4
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Default Re: Eddystone 770r Mk2 gone (quiet)

Start with the output stage(audio) check voltages, maybe even the grid coupling cap and bias cap res has not been changed?
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Old 27th May 2019, 9:06 pm   #5
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Default Re: Eddystone 770r Mk2 gone (quiet)

Yup! I'd say start by checking the LT and HT voltages, then check the valve voltages working backwards from the output valve towards the aerial socket.
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Old 30th May 2019, 6:21 am   #6
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Default Re: Eddystone 770R Mk2 gone (quiet)

This set uses a push pull audio output so there are two audio output paths
There could be a problem with one side of the output stage so it may be worth pulling one of the output valves (EL91) in turn to see if there is any change and to try swapping round the ECC82s however they are both in the audio path (phase splitter, audio preamp and muting control) and to check the headphone socket which is connected to the anode of one the output valves and breaks the earth return of the speaker to mute it when head phones are connected
It may also be worth connecting an audio source to the sockets at the rear to see if the problem is an audio/psu one or if it is earlier in the signal path
These sets can be a bit of a challenge to repair as parts of the under chassis layout is very cramped. Eddystone does state in the maintenance manual that sets that require repair should be returned to the factory - obviously not an option
There is a maintenance manual available on line if you do not have one
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