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pioneer a-307r rebuild

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tpk

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Hi Folks,
I am working at the moment with Pioneer a-307r. My amp microcomputer PD5443A fail. So I decide remove microcomputer. This IC controls Input selection, Direct, Loudness function, speaker Protection function . I dont need this. I need only speaker Protection function. Does anyone can build my wiring diagram for speaker protection? Please look picture. I believe it needed only 1 transistor and few resistors to get it work.
Thanks.

Services manual here.
http://www.kallhovde.com/pioneer/tricomp/Audio/A/A-207R_307R_RRV1912.pdf
 

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unclejed613

Well-Known Member
Most Helpful Member
it looks as if you are trying to bypass the protection completely. grounding the collector lines from the overcurrent detectors will disable the protection circuit. that's not a good idea. what is wrong with the CPU chip that makes you think you should remove it?
 

tpk

New Member
cpu is faulty. No Mate I need figure out how add some parts to get it work protection. Amp at the moment rebuilded sounds great but protection missing. I need pro level theory advice. On these 2 lines green & blue add some parts.
 

unclejed613

Well-Known Member
Most Helpful Member
looks like you need a pullup (470 ohms) to +5V for the wire marked in green, and an NPN transistor with the base connected to the green line, the emitter connected to ground. and the collector connected to the wire marked in blue. the blue wire should also have a 470 ohm pullup to +5V. this will operate the protection relays, but will not provide any time delays that the CPU would have provided. you could use a time delay on the base of the added transistor, but it would need to be strictly a positive edge delay of about 5 seconds (in other words, the speaker relays need a turn-on delay of about 5 seconds to allow the amps to settle after power-on, as well as waiting 5 seconds to turn the speaker relays after a protection trip). in order to protect the output transistors properly there must be no time delay on the falling edge.
 

tpk

New Member
thanks I will do. I figure out with time delay long time ago:) U just need add resistor with cap (switching after 5s) protection relay wont turn ON if speaker A/B line dont switch mosfet q333; q335
 

unclejed613

Well-Known Member
Most Helpful Member
a simple RC time delay won't work because it will delay the turn-off of the relay when the protection trips. the kit nigel mentioned should work, and although the kit only detects DC offset as-is, i think it's possible to add inputs to it from the existing overcurrent detectors in the amp (the two red lines in your drawing).
 
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