Hello,
I've a NAD 6155 C-cassette player dated back to 1986, with a power transformer which I fried few days ago (too hot hereabout for its primary winding...). And as one may guess finding spare parts seems to be quite a problem. Based on the schematics (or rather the voltage ratings of the ripple capacitors) I've guessed that it has a 2-winding secondary with outputs of 12V-0V and 24V-0V-24V. My question is that if there happens to be accurate voltage readings for this transformer, if it's a common type (PTX- 263E) or taylor-made for NAD , and what if it's replaced by eg.t wo toroid trafos, one cnter tapped 24V-0V-24V, and another 0V-24V. Based on the fuses, 500mA only, these are pretty small and fit well in the original sheet metal box. It seems that multi-tapped transformers are quite difficult to find nowadays.
I've a NAD 6155 C-cassette player dated back to 1986, with a power transformer which I fried few days ago (too hot hereabout for its primary winding...). And as one may guess finding spare parts seems to be quite a problem. Based on the schematics (or rather the voltage ratings of the ripple capacitors) I've guessed that it has a 2-winding secondary with outputs of 12V-0V and 24V-0V-24V. My question is that if there happens to be accurate voltage readings for this transformer, if it's a common type (PTX- 263E) or taylor-made for NAD , and what if it's replaced by eg.t wo toroid trafos, one cnter tapped 24V-0V-24V, and another 0V-24V. Based on the fuses, 500mA only, these are pretty small and fit well in the original sheet metal box. It seems that multi-tapped transformers are quite difficult to find nowadays.
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The top section of the transformer appears to generate -/+15 volt DC regulated supplies and so you need at least -/+20 volts DC input to the regulators. That means a transformer of at least 15-0-15 volt AC
I would guess the other winding produces an unregulated 12 volt DC (going off 16v caps and that it supplies the motor) and so that implies a voltage of 9 volts AC.
Check the data sheet for IC601 and look what its max supply voltage is. That chip is fed off this rail. It is possible it could be 9v DC rather than 12 volt DC.
I would guess the other winding produces an unregulated 12 volt DC (going off 16v caps and that it supplies the motor) and so that implies a voltage of 9 volts AC.
Check the data sheet for IC601 and look what its max supply voltage is. That chip is fed off this rail. It is possible it could be 9v DC rather than 12 volt DC.
Thanks a lot for your immediate reply! I checked the chip and it can take 10...16V DC, and it's only a VUmter. So, I'd go for 2 little toroids; 9V AC & 15V-0V-15V AC, worth some 40EUR here. If I'll burn it then there's always a trash bin option...
Buy good ones, slightly higher current, as you live in a hot area, larger transformers will not run fully loaded.
Less chance of over heating.
Soak in varnish if humming.
Less chance of over heating.
Soak in varnish if humming.
Well that should work.
Also, I wonder whether the lower supply could be derived from the top one. Both are ground referenced. A 7812 regulator, a slightly larger reservoir cap for C318, I can't just see anything against that from what I see in the part of the circuit posted.
No guarantees, it would be one to experiment with.
Done, 2 toroids 2x9V & 2x18V. A diy-developement which apparently works; lights on & wheels rolling, and the money lost some 50EUR. Whether this makes any sense is another question...
Thanks for encouragement 🙂
Thanks for encouragement 🙂
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Tell us how it sounds after testing
Spray the contacts, lubricate the motor, generally a bush type motor is used, and check the belts and so on.
Spray the contacts, lubricate the motor, generally a bush type motor is used, and check the belts and so on.
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well done.Belts changed a year back, a new diy-transformer package installed, the thing connected to NAD7140, and The Eagles sounds pretty much the same as +20years ago. Well, may be a bit biased opinion by a hobbyist, but quite ok for now.
Next steps, my NAD5120 is no longer "semiautomatic", but fully manual, no auto-stops neither soft starts. This might more challenging than the cassette deck.
Next steps, my NAD5120 is no longer "semiautomatic", but fully manual, no auto-stops neither soft starts. This might more challenging than the cassette deck.
