Pioneer sx-980 First steps

[reely]

Hello,

I am repairing a SX-980 for a friend. I have had it on my bench for two years and replaced the four main power transistors then (Q102,102). Now I have taken on the task again I have found a few other components fried on the power amp assembly ( R25,26 4.7 1W and Q6,Q7, R19 and VR1) on one side only. The components on the protection circuit all check fine.The unit did have signals on the preamp out 2 years ago. My question is once these components on the power amp are replaced is it safe to power up the unit to check the voltages or should I be wary and check elsewhere to avoid damage.

Thanks in advance

 

[glen65]

Hello,

I am repairing a SX-980 for a friend. I have had it on my bench for two years and replaced the four main power transistors then (Q102,102).

Hello,
You said all four, did "both" channels blow?
The manufacturer of the output transistors for that unit stopped making them decades ago. What exactly did you replace them with?

Now I have taken on the task again I have found a few other components fried on the power amp assembly ( R25,26 4.7 1W and Q6,Q7, R19 and VR1) on one side only. The components on the protection circuit all check fine.The unit did have signals on the preamp out 2 years ago. My question is once these components on the power amp are replaced is it safe to power up the unit to check the voltages or should I be wary and check elsewhere to avoid damage.

Not necessarily, given the circumstances it would be wise to go through and check all of the components on the amp board. All resistors transistors diodes etc.,
double check the outputs as well. All it takes is one missed component and it could blow the whole works all over again.

 

[zebulon1]

You do know about the use of a Dim Bulb Tester? Seems I've been harping on that this week.