5000x dead channel repair options

donkeychips

Member
Hi folks,

I've been a member of this fine site for a little over a year, lurking and soaking up the knowledge...

I stumbled into a 5000x with a dead channel for $15 last week and decided to take it on as a "practice project" before tackling the restoration of my dad's Pioneer SX-750.

I have been reading up on old threads for the past couple of days, and haven't come across an answer to my particular issue. The unit output is fine through the pre-outs feeding a good amp, but I get loud static that doesn't change with the volume control through the right side when the pre to main jumpers are in place.

My dilemma is this: At some point the left driver board was smoked and the repair looks to have replaced all transistors on the board as well as the outputs. The resistor values (see attached image) were changed, I assume to drive the new transistors properly. The repaired channel sounds good.

The question is do I "follow the leader" and repair the dead side to match, or use the correct cross referenced transistors for replacements and don't touch the other components. I guess a third option would be to replace components on both sides to factory spec.

Opinions???
 

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I'd make sure the values match the schematic, though I wouldn't sweat the style differences at the moment. Check the transistors and other parts- there isn't much of anything in that circuit! Do you know how to check transistors? Check the devices on the heat sink including any bias transistor that might be mounted there. Be sure to check the pots. Find the bad stuff and replace it. Once it works you can contemplate getting matching parts for left and right. Don't put any stock in cross reference lists. Get advice here for suitable modern semis.
 
Thanks for the reply Conrad.

I tested all transistors (removed from circuit) using the diode test function of my DMM. All components on the F-1063 board as well as the output transistors read from 0.5xx to 0.6xx volts so I don't think a bad transistor is the issue.

Could the speaker selector switch or a bad cap be causing the issue? If the problem is not in the driver board or the output trannies I don't know where else to look :scratch2:

I plan on doing a full recap, but was holding off on the order until I get this sorted in case I need to get other parts...
 
Thanks for the reply Conrad.

I tested all transistors (removed from circuit) using the diode test function of my DMM. All components on the F-1063 board as well as the output transistors read from 0.5xx to 0.6xx volts so I don't think a bad transistor is the issue.

Could the speaker selector switch or a bad cap be causing the issue? If the problem is not in the driver board or the output trannies I don't know where else to look :scratch2:

I plan on doing a full recap, but was holding off on the order until I get this sorted in case I need to get other parts...

PM me I am local maybe you can bring it by and we can take a look
 
Thanks for the generous offer of help goat!! :thmbsp:

It is nice to know there are local resources such as yourself who are willing to help an amateur such as myself.

I am waiting for my cap order to arrive, and will go thru the controls once more with deoxit and recap the amp section before throwing in the towel...
 
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