Very low audio on rotel 220

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Avenger
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Very low audio on rotel 220

Postby Avenger » 08 Jan 2017, 19:06

The old rotel 220 got recently seems to have an audio issue,you can just about here people with the volume full up. I've checked a few things like mic,wiring + speaker and also swapping the audio ic from a scrapper but no change. I haven't used the radio as yet but rx seems normal on the meter just not on the audio
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Re: Very low audio on rotel 220

Postby Avenger » 08 Jan 2017, 21:31

And just tested the rig and got no tx modulation so wondering if my salvaged audio ic was also faulty
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Re: Very low audio on rotel 220

Postby dt307 » 08 Jan 2017, 21:55

A bad audio chip can kill tx as well
To check the chip ... Don't laugh

Wet your finger and rub it over the solder pins of the audio ic with the volume cranked up
It's a quick way to see if the ic is bad. Not fool proof as the input /output could be going to ground
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Re: Very low audio on rotel 220

Postby dt307 » 08 Jan 2017, 22:12

further fault finding what i do if chip is ok and voltages to it are good (ta7205p)
if i can be bothered i will get the af gen out for the input and scope the output but if you dont have test gear hillbilly it
lift pin 6 inject audio or wet finger (holding a small metal screwdriver in your hand and touching the pin is a personal fav of mine to get a nice loud buzz
lift pin 10 connect a speaker to pin 10 with a cap in series and the other side of speaker to ground
you will easy be able to see which side is bad and i can walk you through once i know

unless a guru wants to chime in with common problems known on this chassis as i rare see a strait 40
Could be the cap on the output
163dt307-chris




“I fear the day that technology will surpass our human interaction. The world will have a generation of idiots.”
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Re: Very low audio on rotel 220

Postby Avenger » 09 Jan 2017, 09:47

:thumbup: Thanks for that,i'll look at it again tonight and try a few of those tests on the audio ic
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Re: Very low audio on rotel 220

Postby Black Spirit » 09 Jan 2017, 17:55

I had a cybernet with same issue and it was a bad electrolytic C94 which had gone dead short, It is located near the audio amp [front] its a large [ish] cap, It might be worth checking.

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Re: Very low audio on rotel 220

Postby Avenger » 09 Jan 2017, 21:11

I've tried the buzz test which does work and then tried swapping the audio ic with one from a wrking rig but with no luck. Still the same issue but i'll have a look at the cap you mention Nick
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Re: Very low audio on rotel 220

Postby dt307 » 09 Jan 2017, 23:09

sorry m8 guess i wasnt clear if you pass the buzz test its not the chip but you found that out
as nick says that cap is the next to look at and i would expect that to be bad
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Re: Very low audio on rotel 220

Postby Avenger » 10 Jan 2017, 18:19

Thanks dt307 as the testing the audio chip info was interesting and worth remembering for next time, I've just changed the cap and she's back up to normal audio again so also big thanks to Nick blackspirit for that one.
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Re: Very low audio on rotel 220

Postby dt307 » 10 Jan 2017, 19:42

love a happy ending
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“I fear the day that technology will surpass our human interaction. The world will have a generation of idiots.”
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