modifying an old philips cd160

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Ant
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modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 12:20 pm

I like my Philips cd 160.
Midi sized so it fits in the limited space, 1986 vintage, it has a TDA 1541 DAC in it and sounds rather nice as it is. It can be abit harsh at times, but has something to it that I like.
I've been in conversation with a chap called Mark recently who also likes these and has 2. While discussing these players the subject of mods came up, and I have long thought that the cd player could be improved fairly easily. Swap out the op amps and recap, basic work that would probably make a noticeable difference to the player. There are loads of pages all over the place on modding early cd players, but no consensus anywhere on what to do and what not to do.
Having done some research, it seems that my initial thoughts on recapping and replacing the op amps are what people recommend as a good start.
Mark has sent me one of his spare players to act as a base to compare with once I start, with a view to modding his once I've done what I'm going to do with it if it does improve.
The internals are nicely laid out, the sub board I've moved I presume is the driver board for the display and controls

ImagePhilips cd160 internals by anthony cresswell, on Flickr

That lovely old DAC chip with a collection of caps around it, some that are looking abit bulged on the tops and rather sorry for themselves

ImagePhilips cd160 internals by anthony cresswell, on Flickr

The output stage where again the caps look pretty worse for wear...... and the lm833n op amps that I'm sure can be replaced with a better sounding pair, and I presume the 2 transistors are the muting transistors which apparently is a good idea to take out for some reason that I'm not entirely clear on

ImagePhilips cd160 internals by anthony cresswell, on Flickr

And the power supply section. The large caps look ok, the small ones again look abit bulgy so are probably better off replaced.

ImagePhilips cd160 internals by anthony cresswell, on Flickr

Some folks have also recommended replacing the diodes with shottkys, again, I'm not clear as to why as I've never used them, to me a diode is a diode is a diode. p'raps someone can explain.

The first part of the plan is to replace all the electrolytics with elna simlic 2 or cerafines. Simply because I like the elnas when I've used them on amps before but suggestions are welcome. I need to identify the output caps and their values too and decide what to replace them with, I quite like the TAD paper in oil caps in the valve amps so i'll look into that. Part 2 is to replace the 2 op amps with something better, again suggestions are welcome on the type, and see what that does when compared with Marks standard one. I took a look at the clock which is an 11.2896mhz clock, and there is plenty of free space to put a low jitter replacement clock in it if I want to.

All suggestions are welcome, I've not modded a cd player in years apart from putting some black gates in an arcam black box 3 dac years ago so I'm pretty rusty on all things digital.

cheers ant

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Re: modifying an old philips cd160

Post by Neal » Thu Sep 21, 2017 1:16 pm

Ant, where are the decoupling caps? Underneath the PCB?

Simple things you can do, yes upgrade the decoupling ‘lytics, the o/p opamps and Schottkys diodes (softer switching). Also replace the ‘lytics in the I/V stage.

The TDA responds well to PSU changes and if you want to go the whole hog independent supply feeds for each voltage rail, include the CS8412 in this.

Other stuff to try is to add a 10uF cap between the -5 and -15v pins, oscon or such like and for me a really big one is to make sure the voltage measured between those two pins is exactly 10v….if its out even by a small margin it affects the sound noticeably.

If pin 13 is floating, ground it…

There are other tweaks as well but they escape me for now…..
Only the Sith deal in absolutes.

Ant
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Re: modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 1:38 pm

No not underneath. Ive got hold of the service manual and the last cap before the output socket is a 100uf 10v electrolytic :shock: wasnt expecting that tbh
There also doesnt appear to be any muting transistors I can see anywhere either. The cct shows them but they arent there.........
Edit: found the muting transistors just me being dense

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Nick
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Re: modifying an old philips cd160

Post by Nick » Thu Sep 21, 2017 1:55 pm

Well, somewhere if not underneath, there should be 14 decoupling caps around the 1541.

LME49720 would be my op amp suggestion.
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Ant
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Re: modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 2:01 pm

Under the board there are a load of smt capacitors off the 1541 pins yes, it was the caps on the output stage after the op amp I was looking for, didnt realise it was the dac ones neal meant
Cant tell what value the smt ones are

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Re: modifying an old philips cd160

Post by Neal » Thu Sep 21, 2017 3:00 pm

Yup those are the ones, they are probably ceramic...up to you if you want to change them maybe a bit of a faff though. I'd concentrate on the 'lytics first and the voltage supplies.
Only the Sith deal in absolutes.

Ant
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Re: modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 4:15 pm

Got the values of the decoupling caps off the cct as being 220nf.
It appears that the 100uf cap is the last cap in the signal path with a 4k7 resistor to ground, then muting transistors drop off the signal track to ground with their associated circuitry after it. I assume that the value is fairly high to prevent the op amp oscillating?
Presumably I could just bypass them when I replace the cap by taking one leg of the 100uf cap ( or whatever value I choose) out and instead of connecting back into the pcb when replaced, take the other side of the cap straight to the socket with an appropriate resistor to ground? I'll be putting some new sockets on the back anyway, the plastic board mounted socket is pretty brittle now
Or am I better off removing them completely?

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Nick
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Re: modifying an old philips cd160

Post by Nick » Thu Sep 21, 2017 5:17 pm

I assume that the value is fairly high to prevent the op amp oscillating?
Not sure what you mean there WRT oscilation. The 220uf cap (if that's the one you are saying is high) is that value to give extended LF response, 220uf into 4k7 has a -3dB point of 0.15Hz
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Ant
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Re: modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 5:36 pm

Its 100uf that one, the oscillation remark was in relation to something I read about keeping the op amp stable, that I may have got the wrong end of the stick about
I'll re read it

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Re: modifying an old philips cd160

Post by Mike H » Thu Sep 21, 2017 5:58 pm

Image

Watching.



I'm thinking mucho scope for cocking things up so simple stuff first; one thing at a time, personally I wouldn't fancy messing with the SMT's but YMMV.
 
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Ant
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Re: modifying an old philips cd160

Post by Ant » Thu Sep 21, 2017 6:06 pm

I've just ordered the electrolytics for now, I'm not messing with the smt stuff for now although the 220nf ones under the dac are pretty easy to get at in this case. Thats for another time......
I'll see what replacing the lytics does first, then the op amps if I haven't broken it in the process :D T'was only a fiver in the first place....

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Nick
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Re: modifying an old philips cd160

Post by Nick » Thu Sep 21, 2017 6:07 pm

Ant wrote:
Thu Sep 21, 2017 5:36 pm
Its 100uf that one, the oscillation remark was in relation to something I read about keeping the op amp stable, that I may have got the wrong end of the stick about
I'll re read it
Well, most op amps will start to be less stable driving into a capacitive load, but a 100uf coupling cap will not create a capacitive load, the load the amp will see if the 4k7 resistor. So -3dB for 100uf then is 0.3Hz seems ok given they don't know what it will be driving into.
Resistance isn't futile it's V / I.

Neal
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Re: modifying an old philips cd160

Post by Neal » Thu Sep 21, 2017 7:42 pm

Ah seems my memory is not what it was ;)

Pin 13 refers to the CS8412!

One additional tweak is to decouple the -5 and -15 rails by placing two .1uf caps in series between the 1541 pins and taking the centre point to Agnd....also those ceramic caps, when/if you come to replace them use .47uf instead of .22

Just ideas that helped my 1541 DAC
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Ant
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Re: modifying an old philips cd160

Post by Ant » Sat Sep 23, 2017 5:20 pm

Ok, so I've done the first mod to the player. Ive replaced all the electrolytics in the unit for new nichicon gold fw's. All apart from the 6800uf psu cap as H M Components were out of stock of that value, so i just got an unbranded one.
Took about an hour and a half to replace them all, checking and checking again, and making sure they were all the right way round.
Put it back together then did an A-B with the standard player that Mark D has sent up to be the control.
Same cables, f5 warmed up both on standard mains rather than the balanced power, just switching between them.

ImagePhilips cd 160 modifications by anthony cresswell, on Flickr

It responds quicker to the fascia buttons, reads the toc on the disc faster and starts to play faster now too.
here is the board with its new bits

ImagePhilips cd 160 modifications by anthony cresswell, on Flickr

doing the a-b shows that the player is quite abit better. Ive had a couple of cds on, maybe about 3 hours worth now and its getting better as the new caps sort themselves out.

Essentially, I reckon its probably back to what it would have sounded like originally, maybe abit better due to the higher grade caps in the signal path, now everything is back to spec. All the caps I've taken out were 31 years old so probably well past the sell by date and way out of spec.

Comparing with the standard one, bass is cleaner, tighter and deeper, mid is abit more forward, not sure thats necessarily a good thing. Maybe that will sort itself out with a few more hours on it. Top is cleaner and not so sharp, simple minds glittering prize hasn't made me wince yet. Imaging is not much different, maybe a little wider but instrument separation seems better. The thing is more solid sounding, less amorphous.

A good start, I reckon we replace the axials next and leave the smt ones alone

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Re: modifying an old philips cd160

Post by IslandPink » Sat Sep 23, 2017 9:25 pm

Sound good , could be a keeper. Musical is the key. My brother in law lent me a Technics player from the same era, the midrange tone was great and it was rhythmic and 'musical' and very listenable.
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