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teac receiver- protect mode, all output transistors are ok.

 
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s_carter



Joined: 16 Feb 2010
Posts: 1
Location: Portland, OR

PostPosted: Tue Feb 16, 2010 9:21 am    Post subject: teac receiver- protect mode, all output transistors are ok. Reply with quote

like the title says, TEAC AG-V8500, I cant seem to figure out why this receiver is going into protect... I have checked the output transistors and they all check out fine, I removed all of them from the circuit before checking. I have also checked the emitter resistors and they are fine as well. I'm still new to repairing these kinds of things, and I'm not sure what the next step would be??? I know that I need to branch out through either side of the outputs but I cant seem to understand this manual very well. I'm not used to reading this style of schematic. For some reason all of the 4.7 ohm 2 watt resistors are showing 0 ohms when on the board.

Here's a link to the service manual if you can point me towards a likely suspect.

http://rs519.rapidshare.com/files/310769851/TEAC_AGV8060_AGV8500.pdf

update: now the receiver is blowing fuse f704 but does not show protect. also the speaker relays kick on and off when i switch the speakers between a and b. didn't do that before. Hmm.... no sound though, obviously. preamp outputs work fine. I checked to see if the collectors on any of the output transistors were shorting through the heat sink but they are not.
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Tue Feb 16, 2010 10:28 pm    Post subject: Reply with quote

If blowing F704, there is a load on either one of your +- 63 volt rails.
It normally points to the shorted outputs but you mentioned they check ok? It is possible that they may be shorted now? Unplug unit & check the resistance from either line to ground to see where the short is? Remove or at least desolder the collector of the output(s)

If you have any power amp issue, especially no bias control or leaky drivers etc, you need to have a way to bring up the mains slowly (by means of a variac) or else you will likely fry the outputs as soon as the power is applied.


Last edited by vtech on Sat Oct 05, 2019 6:08 am; edited 1 time in total
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gaspipe2
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PostPosted: Sat Apr 28, 2012 1:06 pm    Post subject: TEAC AG-V8500, Protect Mode Reply with quote

TEAC AG-V8500, I can't seem to figure out why this receiver is going into protect.

Is there a fast and true answer to this issue? Perhaps a suggestion of a repair facility in or near Auroa, IL
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jts1957



Joined: 24 Nov 2008
Posts: 2473
Location: Far, Far Away

PostPosted: Sat Apr 28, 2012 7:18 pm    Post subject: Reply with quote

That's Aurora, IL.
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