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Author Topic: Sansui A-80  (Read 4179 times)

Offline panosliak

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Sansui A-80
« on: February 20, 2016, 02:27:26 AM »
Greetings to all.its my first post.
i have a Sansui A-80 amplifier with issues.
i was trying yesterday to set the bias.i could set only one channel.the other one for some reason couldnt be set.the timpot seemed dead.
i decided to put a fixed resistor.i set the one channel with 1.5 mV,unsoldered the trimpot and measuerd it.it was 171 ohms.
so i took 2 resistors 170+1 and connected in series to the place of the trimpot.i did the same with other channel.
switch on and guess what.big hum,buzz,.to one channel,..not so much to the other.no sound at all.
the buzz hum,..increasing when i increase the volume,.and the opposite.
so i guess i killed it?.i put back the trimmers again.doing the same thing.no sound at all.i tried aux-phono with load and without.same result.
what do you think?.besides my ignorance.can anyone guide me what to do?
Thank you!
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Offline F1nut

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Re: Sansui A-80
« Reply #1 on: February 20, 2016, 04:19:59 AM »
Welcome to the forum and sorry about your misfortunes.

You should try asking at AudioKarma, I'm pretty sure they have a bunch of Sansui people there.
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OldiesButGoodies

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Re: Sansui A-80
« Reply #2 on: February 20, 2016, 10:17:11 AM »
Sounds like what you did is reasonable.  The trim pots Vr01/02 are 150 ohms each,  so it may be that the one you removed was a tad out of spec.  Could you have caused heat damage to a part near the trim pots while replacing?  That has happened to me on occasion.   What voltage are you reading across R87 and R88 now?

OBG
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Offline papabearjew

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Re: Sansui A-80
« Reply #3 on: February 20, 2016, 10:26:47 AM »
Welcome to the nut house!
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Offline panosliak

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Re: Sansui A-80
« Reply #4 on: February 20, 2016, 12:58:56 PM »
i measure  R87,R88 and i see 20,and 31 mV
its double (0.33) resistor.i measure from common(middle) to emitter
i measure the outputs.left channel 03.5mV and right channel 04.5mV
52V to the collectors of the output transistors.
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OldiesButGoodies

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Re: Sansui A-80
« Reply #5 on: February 20, 2016, 01:51:37 PM »
And the power supply caps test ok?  Can you measure them and confirm they are still doing their thing close to 6800 uf?
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Offline panosliak

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Re: Sansui A-80
« Reply #6 on: February 20, 2016, 02:19:36 PM »
well,.i cant measure the caps.no capacitometer.
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OldiesButGoodies

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Re: Sansui A-80
« Reply #7 on: February 20, 2016, 02:25:45 PM »
This may best be handled by a local audio tech. You may have a bad cap somewhere - would be hard to diagnose without a full set of diagnostic tools. 
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Offline MacGeek

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Re: Sansui A-80
« Reply #8 on: February 20, 2016, 08:31:03 PM »
This is an example of the frustration that makes this such a great hobby.  Welcome to the Forum.
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