[TechAssist] Re: Aiwa ADV58u amplifier-tuner , no sound

  • From: becyn <becyn@xxxxxxxxxx>
  • To: techassist@xxxxxxxxxxxxx
  • Date: Mon, 29 Nov 2004 19:30:58 -0500

the relay has nothing to do with the voltages seen  on the amp board. it 
only disconnects/connects  the  the amp output to the speaker terminals. 
( By the way you dont need any loads hooked up to start the process) DO 
NOT UNDER ANY CIRCUMSTANCES  ENGAGE THE PROTECT RELAY IF LOADS ARE 
ATTACTCHED!!!!! This will damgage the loads and do furher damage (ie; 
smoke, flame) to the amp

I dont understand what you mean by "no voltage on the junctions". You 
mean that literally? As in  no Vcc or Vee or just no offset at the 
emitter swamping resistors? (low ohm ceramics)?
Perhaps it's as simple as open fuses in the power supply?
You need to be very precise in describing the voltages otherwise I can't 
make head nor tails of it.
A normal fail mode is : 1) unit powers up, but no audio out
                                   2) all voltages present at amp and 
everywhere else, but  a DC offset of 1volt or more can be measured at 
the power amp's output  connection. (you must measure it at the pcb)
You might have something else, especially if you really don't see ANY 
voltages at the amp, but you're gonna have to do some 
troubleshooting...or send it to ME for repair!! ;-)
By the way, whats your company name and address?  I'm surprised that 
Jeff didn't get on you about this!

Jim McVey
McVey Alltronix   
327 Broadway
Newburgh N.Y. 12550

Factory authorized
service for over 20
major brands.
845 561 8383

larry wrote:

>thank you for the advice.
>I do mostly tv repair but fix a few audio, now and then.
>most the time i can check the collectors and find a short or 
>see burnt resistors.
>but this time none of the 5 output transistors have a short 
>and no burnt resistors.
>i have no voltage on the junctions of the transistors, where 
>the outputs are connected.
>but i doubt i would, because the relay never closes.
>the power supply has normal voltage to the relay.
>i am afraid to manually close the relay.
>what is my next step?
>Thank you,
>Larry
>
>
>
>
>becyn wrote:
>  
>
>>Are amps new to you?
>>IF you have voltages and no output, the thing is in protect mode which 
>>kicks in if a dc voltage is dectected on the amp out node. Otherwise, 
>>the speaker would burst into flames-(not good ;-)
>>
>>No doubt one (or more)  of the amps have a dc offset caused by shorted 
>>output transistor, drivers or problem with the differential amp. happy 
>>hunting...
>>
>>Jim McVey
>>McVey Alltronix   
>>327 Broadway
>>Newburgh N.Y. 12550
>>
>>Factory authorized
>>service for over 20
>>major brands.
>>845 561 8383
>>
>>larry wrote:
>>
>>
>>    
>>
>>>the readout lites, tunes stations, but no sound.
>>>please , any clues where to start?
>>>I have plus and minus 45 volts and also 23 volt + and -.
>>>Larry
>>>
>>>
>>>
>>>      
>>>
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>
>  
>

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