Hi Ray,
Ok, that's the problem. RO, RON, LON are all reading 2.5, LO is 0. However I can trace continuity from the LO input back to the dac output pin. Does this mean the DAC has failed or is there something on the board which could cause it?
Regards
Pete
Any idea what might have caused it, it's odd that just one part of the output has gone?
Yep, gone it is...
The defect may be caused by a short, or an over-voltage. I don't know how resistant those outputs are to such events. But it's unlikely it's caused by the DOS' passive filter because it's, well... passive
. The first part the output sees is a 2k4 resistor, so anything behind that would be pretty harmless. You can check the inputs of the DOS-board against ground, just to be sure. All four should measure about 4k w.r.t. GND.
Replacing the DAC-chip is not very difficult if your soldering skills are nice and neat. The chip shouldn't be too hard to get.
Regards,
Ray
The defect may be caused by a short, or an over-voltage. I don't know how resistant those outputs are to such events. But it's unlikely it's caused by the DOS' passive filter because it's, well... passive
. The first part the output sees is a 2k4 resistor, so anything behind that would be pretty harmless. You can check the inputs of the DOS-board against ground, just to be sure. All four should measure about 4k w.r.t. GND.Replacing the DAC-chip is not very difficult if your soldering skills are nice and neat. The chip shouldn't be too hard to get.
Regards,
Ray
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I've actually got a spare 67 so the final option would be to transfer all the bits to the new board (which might be best long term as there's a lot of raised traces on the current one). I've seen the chips for sale on ebay though so I guess there's nothing to lose by trying to remove the old chip first and seeing if I can do it without any further damage.
Thanks for the help and advice!
Regards
Pete
Thanks for the help and advice!
Regards
Pete
I usually slide a wire under the pins between the PCB and chip itself then as you heat the pins, pull the wire outwards and slightly upwards (upwards to lift the pin off the PCB). You will need to anchor one end of the wire to something near the chip to stop it pulling out the same way you threaded it in.
Ray, when will you have the CFP boards for sale??
Ray, when will you have the CFP boards for sale??
That method works very well indeed. I have a gas-iron that I can use as a hot-air gun, that also works great.
The new boards will be on sale some time this week. In fact, I just received them yesterday. I'm building the first prototype as we speak!
It's just for testing purposes, to see if the board is working correctly, but i'm pretty confident it will. I will post some pics tonight when i'm home.
I managed to keep the price the same, it's still 12 euro's. It has the new CFP-circuit in the input stage with revised current sink, an extra current sink in the output stage, space for box-type MKP or PS capacitors and two new mounting holes.
Regards,
Ray
The new boards will be on sale some time this week. In fact, I just received them yesterday. I'm building the first prototype as we speak!
It's just for testing purposes, to see if the board is working correctly, but i'm pretty confident it will. I will post some pics tonight when i'm home.
I managed to keep the price the same, it's still 12 euro's. It has the new CFP-circuit in the input stage with revised current sink, an extra current sink in the output stage, space for box-type MKP or PS capacitors and two new mounting holes.
Regards,
Ray
I'm a bit worried about cold solders. What effect would a cold solder have on the PSU filter caps? Could that cause the harsh highs Ive been experiencing for some time?
The Bessel filter mod is next, so we'll see...
Btw what does CFP stand for? Where does the board go? I'm very interested in one of those boards.
The Bessel filter mod is next, so we'll see...
Btw what does CFP stand for? Where does the board go? I'm very interested in one of those boards.
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Do you have a parts list for it, Ray?
I tried to put one of those LM317-based regs on pin 16 of my DAC last night, but it didn't work out so well. I removed RD04 and replaced CD07 with the output from the reg. I wired the 12v from C813, which I'm guessing may not be correct - it made the LEDs light up OK but the CD started moving strangely and I got incredibly loud noise for a split second when I turned the volume up, which cut out immediately (I'm guessing because of op-amp protection circuitry).
I built 4 of those regs in one little unit ready to do the DAC supplies, and they all put out 4.9v from a 9v battery so I think they're good.
Is it obvious to anyone what I did wrong?
I tried to put one of those LM317-based regs on pin 16 of my DAC last night, but it didn't work out so well. I removed RD04 and replaced CD07 with the output from the reg. I wired the 12v from C813, which I'm guessing may not be correct - it made the LEDs light up OK but the CD started moving strangely and I got incredibly loud noise for a split second when I turned the volume up, which cut out immediately (I'm guessing because of op-amp protection circuitry).
I built 4 of those regs in one little unit ready to do the DAC supplies, and they all put out 4.9v from a 9v battery so I think they're good.
Is it obvious to anyone what I did wrong?
I've been listening for half an hour after bypassing the DC blocking caps and I'm very happy with the result.
Also, what kind of soldering iron does everyone use? I've had two cases of damaging the copper rings at the pinholes, so I had to resort to using a wire to make the connection. I'm pretty sure my soldering iron is too hot...
Also, what kind of soldering iron does everyone use? I've had two cases of damaging the copper rings at the pinholes, so I had to resort to using a wire to make the connection. I'm pretty sure my soldering iron is too hot...
Cold solder = bad contact. So I guess this would make the ripple on the power line worse for rectifier caps. But I don't think harsh highs are caused by it. The local decoupling caps near the IC's are more likely to be responsible for that.
The problem with these players is that once you start tweaking them, you have to go all the way. They will first give more detail and soundstage, but it still sounds a bit harsh. Like the good stuff is there, but it just doesn't come out yet properly.
CFP stands for Complementary Feedback Pair. It's a tweak for the DOS, which stands for Discrete Output Stage. It's a board that comes between the DAC-chip and the output sockets and replaces the entire opamp output stage and analog filter. It's a very good upgrade, you can read all about it here on my website.
I use a soldering station instead of a fixed iron. It has an adjustable temperature and regulates that pretty well. It's a much better tool compared to, say a fixed 15W iron that burns at max. power all the time. You can tell if your iron is too hot if the flux burns very quickly (short puff of smoke) and the solder turns dull very fast if you put some on the tip.
Ray
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Do you have a parts list for it, Ray?
I tried to put one of those LM317-based regs on pin 16 of my DAC last night, but it didn't work out so well. I removed RD04 and replaced CD07 with the output from the reg. I wired the 12v from C813, which I'm guessing may not be correct - it made the LEDs light up OK but the CD started moving strangely and I got incredibly loud noise for a split second when I turned the volume up, which cut out immediately (I'm guessing because of op-amp protection circuitry).
I built 4 of those regs in one little unit ready to do the DAC supplies, and they all put out 4.9v from a 9v battery so I think they're good.
Is it obvious to anyone what I did wrong?
Yes, a partslist and new schematics are underway. Sorry, no time for pictures yet tonight. Maybe tomorrow...
Did you measure the output of the regulator while it was connected to the DAC? C813 is fine for taking power, so that's not the problem.
Is there a new output cap present at the LM317? As you removed CD07, there needs to be an other cap to take it's place. Otherwise the LM317 could be oscillating.
Ray
It's not quite harsh, the highs are just so much pronounced that it cuts into my ears. So it sounds harsh to my ears. I just did the Bessel filter mods 10 minutes ago but didn't replace L601/602 (don't have the parts). So far it seems slightly better.
Could any cold solders go unnoticed, yet damage the system?
I'm afraid I'll have to stop where I am now. I've done the PSU, opamp and output mods as described in the PDF in the opening post and I've disabled the headphone and muting circuits. Now I've done the Bessel filter mod and that's where it ends. I don't have the knowledge or experience to do any of the other mods. I don't even know how to add decoupling caps, so I've skipped that too.
Very interesting. I might still think about doing this. I'm not sure if I want to take any more risks though. If I screw this up, I lose a very decent CD player and I can't afford another one.
The flux does burn very quickly and I do get a short puff of smoke... Since I've used an iron that's too hot for all the mods I've done, it will probably affect its life?
Hey Stabby, I had very harsh treble a couple of months ago and now it sounds smooth again. I wish I could tell you exactly what fixed it - I have changed a lot of components since then - but I have a feeling it was due to bad contacts. I remember finding and fixing some soldered joints that had developed tiny hairline fractures as a result of the PCB flexing. Also, did you put all the back plate screws back in?
I haven't, but I'll do that now
How did you find the bad contacts? I don't really know how to test for that.
The usual suspects for me are the components that stand high off the board with rigid pins like the regulators, or ones that get a lot of mechanical stress during assembly like the RCA sockets. You can usually see the break if you look at the solder close enough, and confirm by gently touching the component looking for movement.
Don't forget to put the three screws back in on the underside of the back plate, and all the connectors - audio out, remote control, optical out - these actually ground the PCB to the chassis. I find it's important to have them in for good bass response.
Don't forget to put the three screws back in on the underside of the back plate, and all the connectors - audio out, remote control, optical out - these actually ground the PCB to the chassis. I find it's important to have them in for good bass response.
Ah... yes, there is a cap because I followed NAD's stripboard layout of Martin Clark's schematic, but I'll tell you what I did do... it looks as though I made a mistake and put 100uF where I was supposed to use 10uF... and I've done that four times!
Would that be at the ADJ pin? That shouldn't be so bad. If the regulator puts out 5V under load, then it should work fine in the player.
Hee the new DOSCFP, time to subscribe to this threat.
Groetjes, Erik.
Ik zal straks even een paar fotootjes maken
I will take a few pictures later today
The Bessel mod slightly rolls off the highs. I did that too when I was first tweaking this player and indeed it sounded better. But after a while, when I tweaked the player further, I went back to the standard filter because I started to miss the little 'bite' in the sound. It sounded too smooth to me.
Well, you can always ask us 'howto' ;-). That's where we are here for! Your player has so much more potential, it would be a pity if that is left untouched. It will benefit a lot from a good clock, that is one of the must-do mods I think. A Discrete Output Stage will improve things as well, it will get rid of the opamps and filter in one go.
A better iron or station will get you better solder joints and less lifted pads. It will make the tweaking a lot easier with less chance of damage. You have to be very careful with the board anyway, because it's not very solid. A cheap-and-dirty fix for you iron could be an in-line light-dimmer. You know, the ones you use to put between the cord of a lamp in your living room. That way you can adjust the power and tune it back a little.
Regards,
Ray