I have had an old Onkyo DX1400 cdp for a few years. I got it cheap, second hand, scratched and knocked around with drink stains on and in one corner. That said, it plays quite well and has very reasonable specs although the 100Hz power supply hum was loud and clear and the DAC hissed like a kettle boiling.
In last few weeks I have been fixing and tweaking a dead Marantz CD52. When I played it after fixing the draw cog and correcting the laser and servo adjustments it was noisy and hissy, but very nice. Demanded a full suite of tweaks with a very satisfying result. Its now a keeper.
Leads inevitably to the restoration of the DX1400 and I thought I would share the process.
That circuit is 'different' and I dont pretend to understand the nuances but at a high level all the standard blocks are there.
So to step 1:
The box opens easily to expose the pcb but the transformer secondaries are hard wired to the board and need to be desoldered to attack the underside. I had a 6 way screw terminal block of the right pitch in stock so thats now in use.
The power supply has +/-5V digital and +/-8V analog regulators fed from the same rectifier + 2200u smoothing caps. The pre and post regulator caps are now 4700u Nichicon HE series - these being the biggest that would fit.
At the supply nodes of the op amp and DACs (there are 2 BurrBrown PCM61P) were 220u/16v are now 470/16, also HEs. Similarly the digital supplies on the decoder and DACs were 100/6.3, now also 470/16. All the electrolytics are bypassed by 1000p disc ceramic which I have left in place for now.
The standard op amp is the NJM5532, now replaced by a socket with an LME49720. It also has the usual 220/50 electrolytic coupling cap on the audio output that I have left in place for now. When I measure the DC offset I will decide what to do.
Massive improvement with these changes. Hum and noise largely gone and both the top and bottom ends of the frequency response can be heard. Quite nice and sort of 'mellow', very pleased.
I have a 16.9344 TCXO on order from Valabs in Taiwan to do the re-clocking (I used one of theirs for the CD52 too). I am looking for a suitable small transformer to supply the 8V rails independently and it happens that I have a bunch of reg103/104's to regulate all the 8V nodes independently along with the 5V nodes around the DACs.
Darker blue caps and the red terminal block are new but plenty of open space for transformers, clocks and regulators.
Cheers
John
In last few weeks I have been fixing and tweaking a dead Marantz CD52. When I played it after fixing the draw cog and correcting the laser and servo adjustments it was noisy and hissy, but very nice. Demanded a full suite of tweaks with a very satisfying result. Its now a keeper.
Leads inevitably to the restoration of the DX1400 and I thought I would share the process.
That circuit is 'different' and I dont pretend to understand the nuances but at a high level all the standard blocks are there.
So to step 1:
The box opens easily to expose the pcb but the transformer secondaries are hard wired to the board and need to be desoldered to attack the underside. I had a 6 way screw terminal block of the right pitch in stock so thats now in use.
The power supply has +/-5V digital and +/-8V analog regulators fed from the same rectifier + 2200u smoothing caps. The pre and post regulator caps are now 4700u Nichicon HE series - these being the biggest that would fit.
At the supply nodes of the op amp and DACs (there are 2 BurrBrown PCM61P) were 220u/16v are now 470/16, also HEs. Similarly the digital supplies on the decoder and DACs were 100/6.3, now also 470/16. All the electrolytics are bypassed by 1000p disc ceramic which I have left in place for now.
The standard op amp is the NJM5532, now replaced by a socket with an LME49720. It also has the usual 220/50 electrolytic coupling cap on the audio output that I have left in place for now. When I measure the DC offset I will decide what to do.
Massive improvement with these changes. Hum and noise largely gone and both the top and bottom ends of the frequency response can be heard. Quite nice and sort of 'mellow', very pleased.
I have a 16.9344 TCXO on order from Valabs in Taiwan to do the re-clocking (I used one of theirs for the CD52 too). I am looking for a suitable small transformer to supply the 8V rails independently and it happens that I have a bunch of reg103/104's to regulate all the 8V nodes independently along with the 5V nodes around the DACs.
Darker blue caps and the red terminal block are new but plenty of open space for transformers, clocks and regulators.
Cheers
John
