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Old 11th Feb 2024, 6:52 pm   #1
kirstyd
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Default Pioneer LX 550

Hi all
while listening to Jonny Walker this after noon the pioneer just went silent .It had been on for about an hour when i went to the kitchen to check on the oven .When i came back it had stopped working. I turned it off and on and then turned up the volume and i could hear radio 2 but very faint . Usually when switching on there's a couple of seconds delay before anything happens then you hear what sounds like a relay click in could it be that ?any suggestions very welcome.
thanks
K
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Old 11th Feb 2024, 6:55 pm   #2
paulsherwin
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Default Re: Pioneer LX 550

Are both channels affected?

It's possible you have a protection relay fault, but that wouldn't normally affect both channels equally.
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Old 11th Feb 2024, 7:36 pm   #3
kirstyd
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Default Re: Pioneer LX 550

Hi Paul
yes both channels are affected .I switched it on about ten mins ago and it came on for a few seconds and then went off again
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Old 11th Feb 2024, 8:38 pm   #4
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Default Re: Pioneer LX 550

Could still be the protection relay driver circuit, or even a genuine DC offset fault and therefore a valid cause of protection. Offset on any one channel disables both outputs but doesn't easily fit the very quiet sound.

Lids off, check all power supply rails, check output voltages of both power amps before the protection relay.

There isn't much else common to both channels. Do CD/Tape/Gram work both channels?

David
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Old 11th Feb 2024, 8:42 pm   #5
paulsherwin
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Default Re: Pioneer LX 550

Obviously the first thing to do is check for dry joints around the protection relay.

You may have a more serious fault which is tripping it though.
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Old 11th Feb 2024, 9:39 pm   #6
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Default Re: Pioneer LX 550

I acquired a vintage Aiwa receiver recently and the sound was dodgy and intermittent on both channels. I removed the start up relay, cleaned the contacts with a slither of card laced with switch cleaner, now all is fine.
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Old 11th Feb 2024, 10:10 pm   #7
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Default Re: Pioneer LX 550

Will have a look at it tomorrow [it's a major operation just disconnecting everything and getting it down off its shelf].

Thanks guys.Will let you know how I get on
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Old 11th Feb 2024, 10:13 pm   #8
kirstyd
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Default Re: Pioneer LX 550

Quote:
Originally Posted by Radio Wrangler View Post
Could still be the protection relay driver circuit, or even a genuine DC offset fault and therefore a valid cause of protection. Offset on any one channel disables both outputs but doesn't easily fit the very quiet sound.

Lids off, check all power supply rails, check output voltages of both power amps before the protection relay.

There isn't much else common to both channels. Do CD/Tape/Gram work both channels?

David
yes everything works Cd /tape /AUX and the radio
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Old 13th Feb 2024, 3:34 pm   #9
kirstyd
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Default Re: Pioneer LX 550

I have decided not to mess with this myself and have someone who knows what their doing put it right . Its now some 45 years old so i could just buy something new but my friends in the know tell me not to bother as the Pioneer is well worth fixing and better quality than new stuff [ it does sound nice when its working] so if there's anyone willing to take it on please contact me
Regards
K
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Old 13th Feb 2024, 6:35 pm   #10
Edward Huggins
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Default Re: Pioneer LX 550

What classic styling this has. It looks so solid and well made. I hope this will sound as good as it looks.
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Old 14th Feb 2024, 11:09 am   #11
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Default Re: Pioneer LX 550

Do the dial lights work?
I think this is similar to an SX550 that I have and it does not have a protection relay as such but just a muting circuit.
It uses the dial light power supply to initiate the power on delay.
Mine had a failed bulb and fuse for this line giving the same problem.
I guess the bulb went 'short' before dying and blew the fuse.
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Old 14th Feb 2024, 8:44 pm   #12
kirstyd
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Default Re: Pioneer LX 550

Quote:
Originally Posted by cjwhoishe View Post
Do the dial lights work?
I think this is similar to an SX550 that I have and it does not have a protection relay as such but just a muting circuit.
It uses the dial light power supply to initiate the power on delay.
Mine had a failed bulb and fuse for this line giving the same problem.
I guess the bulb went 'short' before dying and blew the fuse.
Yes it has the muting circuit. The dial lights have gone out but none of the fuses have blown.
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Old 14th Feb 2024, 8:48 pm   #13
kirstyd
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Default Re: Pioneer LX 550

Quote:
Originally Posted by Edward Huggins View Post
What classic styling this has. It looks so solid and well made. I hope this will sound as good as it looks.
it is very heavy and as for its performance its far better than you think it would be .Only 25 watts per channel but with a good pair of speakers it sounds very good and the added bonus is its pre digital so no fancy gismos to get in the way
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Old 14th Feb 2024, 8:49 pm   #14
kirstyd
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Default Re: Pioneer LX 550

Quote:
Originally Posted by kirstyd View Post
Quote:
Originally Posted by cjwhoishe View Post
Do the dial lights work?
I think this is similar to an SX550 that I have and it does not have a protection relay as such but just a muting circuit.
It uses the dial light power supply to initiate the power on delay.
Mine had a failed bulb and fuse for this line giving the same problem.
I guess the bulb went 'short' before dying and blew the fuse.
yes it has the muting circuit .The dail lights have gone out but none of the fuses have blown
the only difference between the LX and the SX is the two push buttons next to the tuning dial
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Old 14th Feb 2024, 9:02 pm   #15
stevehertz
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Default Re: Pioneer LX 550

Quote:
Originally Posted by kirstyd View Post
Quote:
Originally Posted by kirstyd View Post
Quote:
Originally Posted by cjwhoishe View Post
Do the dial lights work?
I think this is similar to an SX550 that I have and it does not have a protection relay as such but just a muting circuit.
It uses the dial light power supply to initiate the power on delay.
Mine had a failed bulb and fuse for this line giving the same problem.
I guess the bulb went 'short' before dying and blew the fuse.
yes it has the muting circuit .The dail lights have gone out but none of the fuses have blown
the only difference between the LX and the SX is the two push buttons next to the tuning dial
What function do the pushbuttons perform though?
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Old 14th Feb 2024, 9:08 pm   #16
PaulE27
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Default Re: Pioneer LX 550

The more common SX-550 has a MW/FM tuner. The LX-550 has LW too, so not material to the fault. Actually not material at all in a few weeks when Droitwich closes down.
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Old 14th Feb 2024, 9:22 pm   #17
kirstyd
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Default Re: Pioneer LX 550

Quote:
Originally Posted by stevehertz View Post
Quote:
Originally Posted by kirstyd View Post
Quote:
Originally Posted by kirstyd View Post

yes it has the muting circuit .The dail lights have gone out but none of the fuses have blown
the only difference between the LX and the SX is the two push buttons next to the tuning dial[/QU
What function do the pushbuttons perform though?
the bottom button switches between Medium and long wave .the top one switches between internal and external antenna
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Old 15th Feb 2024, 11:27 am   #18
cjwhoishe
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Default Re: Pioneer LX 550

I bought the SX550 new in 1977 (I think from Laskys) and at the time did not know of the LX550.
It has been a good 'workhorse' and when last tried still worked.

Did the dial lights go out when the problem occured, and is the power indicator also out(everything on the 8V AC line not working)?
Is there the 8V A/C supply present on both pins of fuse FU 5.
If there is not then it is worrying that the 8V winding of the transformer could be faulty.

Looking more closely at the schematic (snippit from SX550 attached), the A/C for the dial lights being removed initiates an immediate mute of the audio, so I think it is acting as a power off mute (to eliminate spurious effects on shutdown).
So with this not present it is always in the power off mute mode.
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