Pioneer Tuner question

sixt8mopar

Well-Known Member
I have a pioneer sx-850 with a bad tuner, the FM goes bad after a few minutes of operation.I have heard that this series is somewhat known for tuners crapping out.

So I have a 650 donor unit so I was wondering if the tuner from a 650 would be the same.I was thinking it may be an easy swap.Any thoughts?.......Jeff
 
Why not repair the existing problem?

Jeff:

Why not repair the problem instead of creating all the extra work of looking for and swapping tuners? As long as parts are still available your 850 tuner is repairable. I might be able to give you some direction if you can more accurately define "the FM goes bad after a few minutes".

Sincerely,

Ken Bernacky
President, Stereo Surgeons, Inc.
http://www.stereosurgeons.com
 
Well it basically sounds good for a minute or two then it starts to sound distorted like.It doesn't go away.When I am using any of the inputs (tape/cd)it sounds great.Switches and controls are clean.
 
Last edited:
Hi,
Sound like either the tuner needs alignment, or bad component in the tuner path. When you say it sounded distorted, does it sound like it is off tuned? Same when you switch to mono?
Replace the whole tuner is almost immpossible because it involves changing one or more pcbs, furthermore, you need to realign the tuner after installation too!
Mc
 
I thought the xx50 series had the better tuners anyway. I know in the xx80 series, if the tuner chip blows, your SOL on getting a new one. Thats why people like the smaller models for there tuner chips.
 
likely cause

Check The tuner section voltage regulator transistor. Probably a d313. You should see 13.5 volts on it's emitter. these often open up after getting hot. The emitter voltage will go lower and lower as it gets warm. The collector will be above 20 volts when working and failing.
 
The OnSemi TIP31 is a great replacement for the D313 if that's the problem. I've used it several times and now routinely replace the D313 with the TIP31 when I see it.
 
Not Criticical

Most any NPN power tab transistor can sub for the d313. Not critical at all Just a pass transistor.
 
Could someone please post a picture of the tuner board and the transistor to check out.I don't have any schematics so if somebody could please..........
 
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