First of all - what are suitable replacements for the defunct Fairchild J1943-O and J5200-O Transistors?
(There were also R-Types that seem to have distributed less power).
Russ was so kind to send me replacements 10 years ago, this weekend I had to use them.
The reason: The precise multi-turn trimmers were/are still too coarse to set the shunted current.
I accidentally turned the wrong ones. About two turns ramped the current up to 400mA which blew one trannie.
As it was R-Types I replaced all four.
And frankly, this board is not for repairs. Desoldering parts
of pushing a leg through a smaller hole makes the traces peel off.
But something must have changed during the swap of the trannies of the Placids.
I have two vintage CD-Players to compare, both running with ordinary 78xx/79xx regulators.
I also use a test CD (Sony YEDS-18) to play "digital silence" so that the relays do not mute.
Anyway, just by playing the silent track an ramping the volume of the amp
all the way up , the results are stunning:
- A vintage Sony CDP-X5000 shows hiss, which might be due to the 1-bit DAC
that has a lot of noise above the audio spectrum.
- A BuffaloII DAC driven by Placids, Single (I think 2.0.1) and BP (2.1.2) - reveals transformer/Mains hum!
- A vintage Philips CD-304MKII, driven with 78xx/79xx voltage regulators - is dead silent!
Even so silent you can hear the swing arm kicking, could be the servo signal bleeding into the audio circuit
or even be mechanical induction.
Interestingly something must have happened - in 2017 I wrote with the same test, the Placids were dead silent
and surpassing the Philips and Sony!
(There were also R-Types that seem to have distributed less power).
Russ was so kind to send me replacements 10 years ago, this weekend I had to use them.
The reason: The precise multi-turn trimmers were/are still too coarse to set the shunted current.
I accidentally turned the wrong ones. About two turns ramped the current up to 400mA which blew one trannie.
As it was R-Types I replaced all four.
And frankly, this board is not for repairs. Desoldering parts
of pushing a leg through a smaller hole makes the traces peel off.
But something must have changed during the swap of the trannies of the Placids.
I have two vintage CD-Players to compare, both running with ordinary 78xx/79xx regulators.
I also use a test CD (Sony YEDS-18) to play "digital silence" so that the relays do not mute.
Anyway, just by playing the silent track an ramping the volume of the amp
all the way up , the results are stunning:
- A vintage Sony CDP-X5000 shows hiss, which might be due to the 1-bit DAC
that has a lot of noise above the audio spectrum.
- A BuffaloII DAC driven by Placids, Single (I think 2.0.1) and BP (2.1.2) - reveals transformer/Mains hum!
- A vintage Philips CD-304MKII, driven with 78xx/79xx voltage regulators - is dead silent!
Even so silent you can hear the swing arm kicking, could be the servo signal bleeding into the audio circuit
or even be mechanical induction.
Interestingly something must have happened - in 2017 I wrote with the same test, the Placids were dead silent
and surpassing the Philips and Sony!
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No advises from experiences lasting more than a decade?
Short recap:
What are the replacements of the J1943 and J5200 transistors?
Originally it was advised not to connect the Placids / Buffallo II / IVY III to chassis
ground, which I did. They are also running on their own transformers and
input is galvanically isolated from the source.
If I wanted to connect them to the chassis, which point of the combo should be tapped?
All the best, Salar
Short recap:
What are the replacements of the J1943 and J5200 transistors?
Originally it was advised not to connect the Placids / Buffallo II / IVY III to chassis
ground, which I did. They are also running on their own transformers and
input is galvanically isolated from the source.
If I wanted to connect them to the chassis, which point of the combo should be tapped?
All the best, Salar