hi!  

I have renovated a few old vintage receivers lately 2023. Bought them in early 90's. 

My SA-AX710 - showed Overload message after a few minutes..could sometime restart again automatically ... but then  If I tapped on the case- it went into overload again.. 

Here are the manuals : https://www.hifiengine.com/manual_library/technics/sa-ax710.shtml

After reading all input from blogs about Overload, I came across this posting: 

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UnknownJune 14, 2016 at 11:43 AM

Hello, I find repairing and restoring electronics is as fun as working on old cars. Thank you for sharing your experience. Here is my 2 cents in return.

I recently acquired Technics SA-AX710 with typical intermittent “OVERLOAD” symptoms described in the previous comments. It turns on but has its own mind, run for few minutes then goes into overload shut off, and comes back alive etc. I was also able to trigger the “overload” by slight touch/press on the cooling heat sink on which three power amplifier modules (IC601, 602 and 603) and two medium power regulator transistors (Q701 and Q708) are mounted, then pins are soldered to the PCB.

I was intrigued to read through the frustration on this column, and determined to get to the bottom and share the result. It took several days of reading, testing, wondering and poking through and happy to say I fixed it and understood, I think, the exact causes for my unit as well as for several other cases, may be.

First, the cause for my unit: As Martin correctly points out all along, microscopic bad solder joint on pin 2 and 3 of the IC602 (14 pin RSN36S5A-P power amplifier IC module) was the direct cause. This is probably a case of inadequate long term reliability due to either bad PCB pad design or fault in manufacturing quality. All points to weakest spots due to the long term thermal stress. I also noticed 10 screws holding the main PCB down warped the board just enough to cause further long term stress on the IC pins (imagine thermal cycles the area goes through with both bad soldering and warped tension….it will lead to microscopic disjoint…not visible outside though).

Solution: carefully re-soldered all three power module IC pins (14 pins x2 plus 26 pins).

Result: works perfect and I am 99% sure this is the immediate cure. I say 99% because it could happen again on the same spot or somewhere else that has been in progress. For now, I am happy and predict it will go for years before that happen again.

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So what I did was to follow this advice and resolded  all pins on the mothercard for ic601,ic602 ...26 + 7 , because 7 pins looked ok. 

Result- works as a charm and if I hit the case(tapping) - it still works.  So my conclusion is same as "Unknown" writes-  a manufactoring error , and over time the solding points loose connection due to stress from mainboard ,  Also the FAN now works fine , I could not see that earlier.  

A long time I suspected the speakers input , so I  mounted bananplugs instead. Using bar wire , could cause short cuts , giving overload problems too.  But the bad solding on the mother board is truly the main culprit.  

Also I have a RADIONETTE Soundmaster 75 ,  Samsung SCM-7800 Combo unit  . 

The Radionette works perfect , Bought in 1970!  After some renovation at RetroRadio.se -

but the SCM-7800 , needed new cassette player belts and cleaning of CD, which I managed to fix my self. 

The old CARLSSON speakers  from 70's , which my father built (OA-5)  - are also renovated by  https://www.hifikit.se in Stockholm 

And sound is fantastic.  

https://www.carlssonplanet.com/hogtalare/producerade/sonab-oa-5-typ-1/