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Pioneer sx-727 FM problem

Hi, I have a Pioneer sx-727. I'm the original owner over 40 years. Recently developed fm problem. Loud crackling sound on fm station and then station drifts. No noise at all between stations. AM reception also not good, background buzz, humm between stations on AM only. Unit works perfectly with CD and other inputs. Any ideas what my problem might be? This all started a couple of weeks ago, when I noticed that signal strength meter was not illuminated, I assumed just bulb burned out. Tuning center meter still works. Any help would be appreciated. Thanks.

Reply to
tony
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What about a dead LO or mixer?

If you have a 100MHz 'scope, you should be able to trace through the front end and IF.

Reply to
William Sommerwerck

If there's no noise between stations with the muting off it's probably oscillating. That would maybe indicate filters or bypass caps. If the frequency actually drifts, assuming it has ONE fault which is usual, look around the FM oscillator or mixer stages.

I think buzz between AM stations is just about normal these days, unless you specifically noticed a difference at the same time the FM fault showed up.

Actually RF is not really my strong suit, but it's still electronics. If that reciever uses discrete transistors for the FM, it might be a bit hard to find someone who really remembers how to work on it. That reciever is old enough for a pension, but by all means try to keep it alive.

J
Reply to
Jeff Urban

Thanks for the info. I looked at the AWR-011, Power supply unit board. Anyone know what the tolerance should be on these voltages. For the AWR-011, Power Supply unit board the schematic says pin 2,5,6,7 12.5v, 30v, 30v, 36v I'm measuring pin 2,5,6,7 10.5v, 27.5v, 27.5v, 33v

Is this within tolerance?

Also anyone know what the output of the big transformer (ATT-050)should be Nothing listed on the schematics. I'm measuring pins 13, 12, 10, 3 26vAC, 25.5vAC, 35v AC, 0 (AWR-011 board).

Thanks.

Reply to
tony

Thanks for the info. Anyone know what the tolerance should be on these voltages. For the AWR-011, Power Supply unit board the schematic says pin 2,5,6,7 12.5v, 30v, 30v, 36v I'm measuring pin 2,5,6,7 10.5v, 27.5v, 27.5v, 33v

Is this within tolerance?

Also anyone know what the output of the big transformer (ATT-050)should be Nothing listed on the schematics. I'm measuring pins 13, 12, 10, 3 26vAC, 25.5vAC, 35v AC, 0 (AWR-011 board).

Reply to
tony

Hi Tony,

If you can hear the stations at all and they're randomly drifting try squirting some tuner shower/contact cleaner into the tuning gang where the rotating shaft contacts the bearings. There should be two or three bearings. Then, move the tuning dial quickly from 88 to 108 back and forth several times. You might have to spray several times to get the most benefit from the cleaning. Did that help?

--
David Farber
Los Osos, CA
Reply to
David Farber

Tony,

Have a look at the soldering on the regulator transistors on the power supply board, and elsewhere. While its been a while since I've seen one of these, I remember soldering on the pass transistors getting really awful. Look for overheated, crystallized looking connections. if you find some, desolder and re-solder them.

Regards, Tim Schwartz Bristol Electronics

Reply to
Tim Schwartz

on the power

e
u

Thanks for the info. I'll look at soldering on the regulators. The outputs on the power supply board are withing spec but on the low side. AWR-011, the schematic says pin 2,5,6,7 12.5v, 30v, 30v, 36v I'm measuring pin 2,5,6,7 10.5v, 27.5v, 27.5v, 33v

However the collector of Q3 schematic says 36v, I measure ~20v. I'm not sure if that's a problem. This is on the power supply board AWR-011. Thanks.

Reply to
tony

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