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sony str de 475 bad tuner

 
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ivtec



Joined: 19 Nov 2008
Posts: 31
Location: Mass

PostPosted: Wed Nov 19, 2008 10:30 pm    Post subject: sony str de 475 bad tuner Reply with quote

Hi guys;long time no see ; i need your help,
i have here a STR DE 475 sony receiver and it runs good in all inputs and outputs exept the tuner has a rumble hum more in FM and doesn't lock in the stations, when pressing the tuning it keeps serching statins and never stops unless i press the frequency buttom, i can here the station sound but with a hum rumble as a back ground, more on FM, i opened the tuner and i checked one RF ic just next to rf connector with my fluke with diode position and it rings continuity on all 3 legs is this normal or this might be the crupit?


i also notice the green board very smoked black around the UPC2581V
and i checked all the Caps 10uf 100v next to the UPC2581 with my capanalyzer for ESR and don't know if this is normal because of the ICs but all those caps seem dry i mean they even reed nothing.
but the receiver works perfect exept the tuner with that noise i mentioned.

i also need your help on this progect on this receiver,i would like to add a 120voutlet that i can get from a str de 325 and transfere it to the str475, is this possible,the way i see it, is, i would unsolder the 2 pins of the outlet 120v switched 120w 1a max. and i connect one to the fuse pad and the other to the Relay, would this be a good safe connection?
i would be very gratefull if you guys can help me on this.thanks in advance.
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PostPosted: Sat Nov 22, 2008 1:37 am    Post subject: Reply with quote

some came up i suspected the tune but i swapped for a known good oneand the hum and ramle on the FM persists so maybe around the ics 701 702 maybe some picofarads caps what you guys think? minnie any help, thanks.
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sat Nov 22, 2008 6:41 am    Post subject: Reply with quote

Sounds like you may have ideas but based on your description, you are looking at entirely different things here;

Just looked at the diagram and IC701,702(upc2581)are predrivers known to run hot but have nothing to do with the tuner? (apples and oranges here)
As far as the 10mf caps, they should always read 10mf with cap reader and if they don't, should be replaced regardless of any circuit. If in-fact your problem is ONLY with the tuner section and everything else is OK, problem is most likely in the tuner module. As there is no schematic for the actual tuner, are there any electrolytics inside the module? also, you may have a problem with prescaler &/or PLL IC or other component inside the tuner.
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PostPosted: Mon Nov 24, 2008 6:09 pm    Post subject: Reply with quote

thanks, actually swapped the tuner for a known good one and hum in the fm and a litle less in am it was still there so i replaced all the caps in the dark smoked area besides all of them were dead dry, around the ICs UPC2581 and powered and i started to smell some burning and then it went in protect, but i didn't see anything burned,i tested again and all caps i installed new were all good exept a protect ic next to ic 702 upc2581,a c1815,shorted i replaced it and powered again and no avail just in Protect mode, any idias minie thanks
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