Pioneer SX-5 Receiver - No FM - diyAudio
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Old 16th December 2012, 05:22 AM   #1
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Default Pioneer SX-5 Receiver - No FM

Good Evening,
Have a receiver here that I had since new. Lost one channel, obtained schematic, traced to bad solder joints on power transistors. Repaired bad solder joints. Now on AM stations, speakers are clear and even. On FM, nothing but static, can't pick up any stations whatsoever. Any ideas as to where to start checking. Understand lots of electrical, schematics etc, but repairing receivers new to this guy. Thank you in advance for any help.
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Old 18th December 2012, 06:01 PM   #2
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make sure all voltage is present
recap the all auxiliary power supply
recap the all tuner
don't mess up with any trimmers

kind regards
sakis
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Old 18th December 2012, 06:20 PM   #3
DF96 is offline DF96  England
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Don't recap the RF/IF section unless you know what you are doing.
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Old 18th December 2012, 06:30 PM   #4
JMFahey is offline JMFahey  Argentina
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I wouldn't touch the FM section to begin with.
First would check incoming connections, clean switches and contacts, etc.
Lots of white noise means it's basically working, but maybe it has nothing to work with.
Did you connect an antenna to the proper terminals?
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Old 19th December 2012, 08:43 AM   #5
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there is absolutely nothing wrong with recaping the tuner as i said though do not try to fix the problem by fooling around with trimmers and capacitors of the tuner ..it will result to destruction of the tuning and that will require knowledge and pro equipment to tune back .

Kind regards
sakis
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Old 19th December 2012, 09:03 AM   #6
DF96 is offline DF96  England
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Generally, when an item has developed a fault the best way to get it working again is to find and fix the fault. Once fixed, you could then think about 'upgrading'.
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Old 20th December 2012, 06:32 AM   #7
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Quote:
Originally Posted by DF96 View Post
Generally, when an item has developed a fault the best way to get it working again is to find and fix the fault. Once fixed, you could then think about 'upgrading'.

the specific approach is wrong when you talk about vintage amplifier ...with the experience of repairing an average of 400 per year i can verify that .

trying to locate if any of the caps is leaky will consume time and one way or another the rest of the caps will eventually need to be replaced .

you cannot expect 25-30years old caps to work properly and even if they do there is no guaranty that they will continue to work for many years to come .

So replacing them all with no questions asked is the way to go and this has nothing to do with upgrade since its a standard service procedure .
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Old 20th December 2012, 10:13 AM   #8
DF96 is offline DF96  England
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It may be a 'standard service procedure' for an experienced repairer, but DIY efforts to 'change all the caps' often seem to end with a dead unit because of newly introduced faults. Then remote fault tracing has to begin on the forum, or a more expensive repair paid for, or the unit gets binned.

Remote fault tracing is easier if it is likely that there is only one major fault. We already started this thread with a number of solder joints 'redone', which fixed one fault and introduced another (solder bridge somewhere?). Recapping is likely to make things worse. It seems to be the modern version of 'swap all the valves until it works' which some TV repairmen used to do instead of fault tracing.

Last edited by DF96; 20th December 2012 at 10:14 AM. Reason: typo
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Old 24th May 2014, 12:21 AM   #9
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I'm back. Hope you guys are still around. So this unit has a mind of it's own and it started working again and has worked for a couple of years now. So here is what is going on. I turn this on and all I get is static. I may pull in one channel on a scan. I can't pull in the local FM channel. If I turn the volume up, both speakers increase in volume evenly. Does this sound like an antenna problem? All I have right now is a piece of wire shaped in a circle that came with the unit back in the dark ages. Let's start fresh and see what happens. I have a DVOM, an oscilloscope (PICOSCOPE on laptop) and a desktop unit which is 20 years old. You may need to show me where to put the leads and settings but I can find my way around the schematic fairly well so don't be afraid to teach me new things.
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Old 24th May 2014, 01:53 PM   #10
DF96 is offline DF96  England
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First check is DC conditions.

Second check is to use a second FM receiver to see if the local oscillator (LO) in the first one is working. Tune the second receiver to 10.7MHz above or below (it could be either) what the first receiver is tuned to. You should hear the LO as a silent carrier. If you thump the first receiver you may hear ringing in the second one.
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