So - 1974 turntable - an SL-55. I took out the transformer for 100v (japan) and here it's 220v so I tested in isolation and measure 39v secondary coil. So I guess it's an 18v - and the DC motor is 18v on sticker. So replace with a new transformer. It has a rectifier thing, can't see the diodes but didn't fully dismantle it to understand it all. I'm still new to messing with things I didn't build myself so asking for advice.
Has an old axial 470uF axial cap for smoothing AC i guess. Thats 50 years old - it still has measurable capacitance. Thing works after transformer change out - I'm only an enthusiast who makes amps and power supplies. So tell why I shouldn't do this:
1) solder in parallel a new 470uF (50v) with the existing cap. I figure if the resistance of that goes up it will just mostly use the new cap and bypass old one. Then I don't have to de-solder the old one.
2) if I did change out the old cap why not throw in a 1000uF or higher?
It has a voltage regulator IC that looks pretty much like a modern one, I didn't read the writing on it yet. Any reason I should replace that - would that improve anything being a modern one?
I put a 2amp transformer in - the old one seems, by size to be 0.5 to 1 amp max. Does putting a bigger transformer require any change? Anyway, when I power it on/off (by merely selected it works fine so I guess if things were going to go wrong they would have already.
Next plan is to make a phono pre-amp and put it inside the very spacious area under the bonnet (upside down) of this unit. This thing seems really rare and there is a manual website that has seemingly every manual ever - including turntables. This thing doesn't have a manual on there. This manual seems a lot like what I see in this one https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Technics-SL-23-Service-Manual.pdf if anyone cares. Nice how old manuals have circuit diagrams etc.
Has an old axial 470uF axial cap for smoothing AC i guess. Thats 50 years old - it still has measurable capacitance. Thing works after transformer change out - I'm only an enthusiast who makes amps and power supplies. So tell why I shouldn't do this:
1) solder in parallel a new 470uF (50v) with the existing cap. I figure if the resistance of that goes up it will just mostly use the new cap and bypass old one. Then I don't have to de-solder the old one.
2) if I did change out the old cap why not throw in a 1000uF or higher?
It has a voltage regulator IC that looks pretty much like a modern one, I didn't read the writing on it yet. Any reason I should replace that - would that improve anything being a modern one?
I put a 2amp transformer in - the old one seems, by size to be 0.5 to 1 amp max. Does putting a bigger transformer require any change? Anyway, when I power it on/off (by merely selected it works fine so I guess if things were going to go wrong they would have already.
Next plan is to make a phono pre-amp and put it inside the very spacious area under the bonnet (upside down) of this unit. This thing seems really rare and there is a manual website that has seemingly every manual ever - including turntables. This thing doesn't have a manual on there. This manual seems a lot like what I see in this one https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Technics-SL-23-Service-Manual.pdf if anyone cares. Nice how old manuals have circuit diagrams etc.
