THESE MODIFICATIONS ARE FOR EXPERIENCED PEOPLE ONLY.
DOING IT WRONG MAY CAUSE PHYSICAL HARM TO YOU AND MAY EVEN START A FIRE SO BE EXTRA-EXTRA CAREFUL.
NEITHER MYSELF OR PAUL TAKE ANY RESPONSIBILITY FOR YOUR WORKMANSHIP.
I have been contacted by Paul Kelly in the USA who has been modifying the 500W power supply to improve the overall performance of the DVD player. Paul has been kind enough to let me publish his modifications here. I will let him tell the story:
"Here is a list of the modifications I have done to the power supply of my APEX 500W player to improve it's performance. A lot more could be done to improve performance, but it will take some time & probing. The wiring from the power supply pcb is scandalously inadequately sized, and the bundled harnesses guarantee worst case transmission of nasties; twisted pairs or shielded wires of much heavier gauge should be used here. There should also be a couple of added sub-pcb's next to the other two main boards so that the raw output voltages from the supply pcb could be additionally filtered and regulated much closer to their end use.
Anyway, I finished the first mods to the 500W late last afternoon. The mods to the power supply are:
1- Installed a .01 uF 1KV ceramic cap across the AC line cord just inside the enclosure.
2- Replaced the stock rectifier diodes with 600v 8A HEXFRED soft recovery diodes.
3- Replaced the large caps in the low voltage section of the power supply with 1,500 uF 16v Panasonic HFQ (high frequency, low Electrical Series Resistance (ESR) caps and installed snubbers (.01 uF 50v ceramic cap in series w/8 ohm 1/2 w CC (carbon composition) resistor (R) total of 4 electrolytic caps.
4- Installed a .01 uF 1KV ceramic across the 47 uF 400v electrolytic cap in the hi-voltage section. I would like to replace this with a much larger cap but larger value 400v electrolytics are a bit scarce.
5- Replaced the 1 uF electrolytic cap next to the TO-92 transistor w/a 10 uF HFQ. This is obviously meant to de-couple the DC input to this transistor but is too small for the job.
Switching power supplies have many benefits to the manufacturer due to low parts count/cost, but the user pays for this through the nose in the form of HUGE amounts of noise, ripple, and other garbage, which is why you never see switching power supplies used in audio gear, etc. and also why the power supply in the 500W is 4-5 counties (provinces ?) away from the main circuitry : a poor attempt to modify the noise effects of the switcher supply. Unfortunately, a large amount of the noise generated is impressed upon and thus carried by the DC outputs.
So, what was the result of these mods ? The first thing I noticed upon inserting a DVD was the dramatic improvement in the audio on the lead-in to the main menu of the disc : the music was much more dynamic and its's range very noticeably extended and the bass had greater range, depth. & impact ; in short, much greater realism. Throughout the entire run of the disk (Drowning Mona w/Danny DeVito, Bette Midler) the dialog was much easier to understand, and the stereo effect was noticeably improved. Image quality was also noticeably enhanced and the quality of the color was enhanced i.e. greater depth & saturation, better flesh tones and greater range.
Overall, there was greater improvement in the quality of the audio than the video, which was not surprising since this is where most A/V equipment cuts corners and quality. This is really too bad since for several decades it's been the improvement in audio that has led to the re-vitalization of motion pictures than any other single factor : the increase in 'you are there' reality of the experience. I will never forget the first high quality Home Theater experience I had over a decade ago : Raiders of The Lost Arc with 4 channel surround sound. When the Me-109 is attacking Indiana Jones & his father in their biplane I actually ducked in my chair as the Msesserschmidt banked and came at them in its' second pass from outside the room (it seemed) from the right rear. It was the audio that created the impact of reality."
Many thanks for that in depth explanation Paul! Paul has promised to let me publish any more improvements he makes to his player. Stay tuned!