When you had Q02 out, it came out of protect
If DC offset was an issue, it would have stayed in protect.
And when measured collector of Q103 and Q104 was 39V - if fault there I’d expect much lower voltage at collector....
Which leaves the hold circuit (Q301/302 and associated cap and resistors) -
Only other thing to look at is the pull down circuit.. (D301 R305 C302 R304)
It operated with Q302 out, so diode should be ok.
Check R305 C302 R304 are in spec
And pull up (for power off) R307 - is it in spec
If DC offset was an issue, it would have stayed in protect.
And when measured collector of Q103 and Q104 was 39V - if fault there I’d expect much lower voltage at collector....
Which leaves the hold circuit (Q301/302 and associated cap and resistors) -
Only other thing to look at is the pull down circuit.. (D301 R305 C302 R304)
It operated with Q302 out, so diode should be ok.
Check R305 C302 R304 are in spec
And pull up (for power off) R307 - is it in spec
Transistors arrived and will fit and report back over the weekend.
As the relay pins were bent together when I bought the amp it is a bit damaged and the mechanism falls out when you have the amp on its side to get to the circuit board. (No removeable back)
Any suggestions for a modern repalcement relay that fits (SSY69) is the original but is quite large and I am struggling to find an OMRON equivalent)? This is assuming I get the rest of the amp working properly! There is a German ebay seller that sells a replacement but it is pretty expensive (£16 with delivery) and I am assuming they are selling a generic relay - just don't know what it is! This is bearing in mind that relays are £2 - £3 from RS components.
As the relay pins were bent together when I bought the amp it is a bit damaged and the mechanism falls out when you have the amp on its side to get to the circuit board. (No removeable back)
Any suggestions for a modern repalcement relay that fits (SSY69) is the original but is quite large and I am struggling to find an OMRON equivalent)? This is assuming I get the rest of the amp working properly! There is a German ebay seller that sells a replacement but it is pretty expensive (£16 with delivery) and I am assuming they are selling a generic relay - just don't know what it is! This is bearing in mind that relays are £2 - £3 from RS components.
Good news. Repalced Q301and Q302 after a couple of glasses of wine. Just had to!. It worked. It came out of protect, relay clicked on. Will put it all back together and test further in the morning - (don't want to push my luck) before declaring any sought of victory (all credit to SVI2004A as I was just doing what I was told but learnt a bit more about diagnosing electronics).
Will report back.
Will report back.
Yeah got the remote unit as well, built with the same exceptionally thick aluminium face plates as the amp and pre amp but no remote! To be honest probably would not use the remote anyway.
Next project on these is that there is no fm stereo on one of the preamps (I have 2 units) and the other one has fm once it has warmed up.
I repaired another Technics tuner and it turned out to be the power supply caps. Adjusting VCO and T101 made no difference. You can see it in the picture (switched off). The display also brightened up significantly as well after changing the caps.
Technics FM Tuner switches from stereo to mono to beat of music!
I will have a go and report back on a different thread!
Next project on these is that there is no fm stereo on one of the preamps (I have 2 units) and the other one has fm once it has warmed up.
I repaired another Technics tuner and it turned out to be the power supply caps. Adjusting VCO and T101 made no difference. You can see it in the picture (switched off). The display also brightened up significantly as well after changing the caps.
Technics FM Tuner switches from stereo to mono to beat of music!
I will have a go and report back on a different thread!
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