Technics Receiver Overload

My first piece of "serious" audio property was Technics SA-EX 300 that I bought in 1997.
After starting receiving overload messages when cranking volume up, I opened it up and saw pristine electronic elements performing without glitch.

Although not opened or cleaned for 11 years:

• there was very little dust inside
• capacitors cool after hours of work, original shape, no distortions
• cooling fan noiselessly gets on and off, depending on internal case temperature
• huge cooler in the middle of the case was not overheating, just felt warm
• all soldering intact, connectors firm

It was only after I readjusted clumsy wire connectors at the back of the case, that fixed the problem.

Pulling every individual speaker connection in & out, making sure that it felt connected, I restored firm connection, and receiver started blasting without overload interruptions.

I feel that receiver's back panel is the only weak spot of this piece of art.

Never paying to much attention on speaker cables, I used most common ones, twisting their connector end with hand, without soldering them. Inevitably, they lose their grip in time, and cause overload when system draws maximum output power.
In my case, that is 5x100w.
The two front speakers, two surround and one passive sub-woofer, each bearing power of 100W.

 

Update 2 months later:
After performing fantastic for awhile, it went back to the original state.
If volume is left on maximum, when unit is powered, starts to choke right away.
Than, after 4-5 minutes, an error goes away, but the receiver must not be used at 100%.
At this point, I think that the problem is in wires I use to connect speakers with the receiver.
They are of lowest quality. However, the price difference is substantial, so I will give another update when I manage to buy the grounded, shielded speakers' wires.

Update:
It's not the wires. The receiver goes to error without wires connected, so it's logical that the speaker's wires have nothing to do with the problem.

Update Aug2011
I have notices that after disconnecting all the speaker wires from the back of the receiver, and then a couple of hours later connecting them back, the sound system works on loudest without a glitch, and not reporting error for a couple of weeks.
The bass sound , even without the amplifier, is especially impressive.
Then it is back all over again. I am still dwelling on buying expensive shielded audio cables.

Update Sept2011
Still doing unplug-connect back trick.

Update Nov2012
Disconnected the unit and hoping to find some cash to have it repaired by a professional.

Update April2013
Gave it to an experienced electronics repairman, he claimed that output amplifier passed the test, and suspect that a CPU is to blame. Which in this case translates to "dump the thing". I am not giving up yet.

Update January2015.
Gave up on it and bought another used unit online (somewhat better version - SA EX510).
If not permanently cooled with external cooling fans, audio gets interrupted with the same message again. At this time, I am fairly convinced that the all Technics receivers from that era have serious cooling issues.