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f.pelosa 30th March 2011 05:00 PM

salvaged pwr supply for Leach Amp
I just salvaged a Technics SU VX-700 and I would like to use its power supply for a work-in-progress Leach Amp.

Do you suggest that I use the whole power supply (transformer, rectifier, capacitors) or just the transformer?
It's quite an old system, probably from the beginning of the 90s', and my worry is that the components could be ruined because of the age.

This is the description of the components:
transformer: "Technics Power Transformer OFC -open free copper- RTP1QSE005-W 12 142TK"
capacitors: "Technics XX pro 10000uF".

The power supply outputs 4 wires: +55,-55,GND,GND. Note that the original Leach Amp schematics ask for +58,0,-58 and 12000uF capacitors.

Any suggestion or comments on the components are very welcome.

Also, what other components do you think I should recycle from the Technics?

Thanks a lot for your precious help

WithTarragon 30th March 2011 05:38 PM

I assume the voltages from the transformer are appropriate (I assumed you checked). IIRC, they should be in the low 40VAC for the Leach. I would not hang on to the old PS capacitors. Go ahead and get new ones. The rectifiers are not that expensive, go ahead and get new ones.

Keep in mind that if you now use larger caps in the PS, this may be hard on the switch (and the rectifiers).

Good Luck

jaycee 30th March 2011 05:41 PM

The transformer and rectifier should be OK, but well, the capacitors may indeed be past their prime. The only way to know for sure would be to test them.

The 55v supplies will work fine on the Leach amp. 10,000uF would also be fine. What I would try and do is work out the VA rating of the transformer. The primary fuse or supply wattage rating would give a clue here.

I'd personally replace that nasty figure-8 power socket with an IEC one :)

jaycee 30th March 2011 05:58 PM

Hm, have now found a picture of the amp's insides. That transformer doesn't look like it's more than 200-250VA. The rectifier is just some discrete diodes on a PCB. So, the transformer would run a Leach amp, but you wouldn't get max power output on both channels when driven hard. Might be OK for regular audio use.

200 OK

f.pelosa 30th March 2011 06:48 PM

In the rear panel of the amplifier it says "..230/240V 690W", and the primary fuse is a
T3 15A 250V. What could the VA rating be?

I do agree about the power sacket :)

I admit I'm quite a beginner, but what do you mean by "The rectifier is just some discrete diodes on a PCB"? Is there another way for building a rectifier?

Thanks again

jaycee 30th March 2011 08:07 PM

Yes, for example see here:

f.pelosa 30th March 2011 08:20 PM

how nice, I didn't know about this. Thanks!

What do you say about the VA rating? Have you got any clue about what it could be?

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