I got the DAC off my old CD67 last night using UV101's trick of sliding some wire behind the pins and heating them one by one as I pulled on it. Worked a treat!
Sliding it off whilst heating multiple pins would not have worked in this case because the chip was glued in place. Even with all pins desoldered, I had to pop it off with a flat-bladed screwdriver and it was stuck quite well.
I just wish I could be certain it WAS the DAC. It's certainly nothing in the analogue section, and the S/PDIF is unaffected, which all points to the DAC really. I am baffled that it randomly affects one channel or the other and is cured by a reset.
I did notice that the clock gate on the DAC draws so little power that this rail falls away much more slowly than the others. Maybe this is what has damaged the DAC. I could put a resistor across the load so it falls away quickly, or maybe anti-parallel diodes between the DAC power pins so they stay reasonably close when the power's removed.
I'm just worried that the replacement DAC will fail in the same way (if indeed it has failed).
Sliding it off whilst heating multiple pins would not have worked in this case because the chip was glued in place. Even with all pins desoldered, I had to pop it off with a flat-bladed screwdriver and it was stuck quite well.
I just wish I could be certain it WAS the DAC. It's certainly nothing in the analogue section, and the S/PDIF is unaffected, which all points to the DAC really. I am baffled that it randomly affects one channel or the other and is cured by a reset.
I did notice that the clock gate on the DAC draws so little power that this rail falls away much more slowly than the others. Maybe this is what has damaged the DAC. I could put a resistor across the load so it falls away quickly, or maybe anti-parallel diodes between the DAC power pins so they stay reasonably close when the power's removed.
I'm just worried that the replacement DAC will fail in the same way (if indeed it has failed).
Thank you Simon and Brent
Your tech seems very good to me, I did not think of it before but now it seems very easy.
My method is a little different... I heat one pin at the time and suck the solder with a teflon (rigid point) pump.
After removing the solder, I press the pins one by one until they are all loose.... then the chip falls by itself.
I take a lot of time so I do not stress the chip by overheating.
I would like to have a soft tip pump....
Ricardo
PS: yesterday I swaped the LM4562 by a metal can LME49720 I got from a USA supplier (bargain) on the Meridian 101b output stage and the results are incredible.... Everything came into place !
Your tech seems very good to me, I did not think of it before but now it seems very easy.
My method is a little different... I heat one pin at the time and suck the solder with a teflon (rigid point) pump.
After removing the solder, I press the pins one by one until they are all loose.... then the chip falls by itself.
I take a lot of time so I do not stress the chip by overheating.
I would like to have a soft tip pump....
Ricardo
PS: yesterday I swaped the LM4562 by a metal can LME49720 I got from a USA supplier (bargain) on the Meridian 101b output stage and the results are incredible.... Everything came into place !
Off Board PSU
Hi Brent,
I just built a PSU from one of your boards supplied by Lee.
Its got HexFred HFA04TB60 for recs, SPower 5V with Panasonic FC's. 4700uf in front (until the mundorf arrives) and 4700uf behind the reg and 100nf x7r's on both.
Its supplied from J805 and TX ground.
The PSU is giving me just under 5v on the output.
The Hex's are red hot and so is the TX!
Is this just too much for the TX or have made a mistake??
Cheers
Ian
PS the boards are excellent! Who designed them? The fact that they are reversable is Genius!
Hi Brent,
I just built a PSU from one of your boards supplied by Lee.
Its got HexFred HFA04TB60 for recs, SPower 5V with Panasonic FC's. 4700uf in front (until the mundorf arrives) and 4700uf behind the reg and 100nf x7r's on both.
Its supplied from J805 and TX ground.
The PSU is giving me just under 5v on the output.
The Hex's are red hot and so is the TX!
Is this just too much for the TX or have made a mistake??
Cheers
Ian
PS the boards are excellent! Who designed them? The fact that they are reversable is Genius!
Hi Lee,
Parts as follow
D1-4 hex freds
C1 4700uf/25v Pan FC
C2&3 100nf x7r
C4 4700uf/6.3v Pan FC
Here's what I did
Checked for about 9v ac on supply
Ran it into diodes only on the board to ensure polarity which checked out OK.
Added the caps and reg and checked for 5v on the output (measured 4.6 but that'll my cheap meter!)
J805 is TX side of FH11 (fuse closest the back) AC ground taken from the track in between the 2 fuses.
I can't see what I could have done. Its a straight forward PSU!!!! lol
Parts as follow
D1-4 hex freds
C1 4700uf/25v Pan FC
C2&3 100nf x7r
C4 4700uf/6.3v Pan FC
Here's what I did
Checked for about 9v ac on supply
Ran it into diodes only on the board to ensure polarity which checked out OK.
Added the caps and reg and checked for 5v on the output (measured 4.6 but that'll my cheap meter!)
J805 is TX side of FH11 (fuse closest the back) AC ground taken from the track in between the 2 fuses.
I can't see what I could have done. Its a straight forward PSU!!!! lol
I designed the pcbs and with some work with the pcb guy I deal with we got it sorted. Lots of checking and double checking.
Now then 4.6v is low, the SPower will happily run lots of amps and not sag. Did you test the psu before connecting it to what ever you are connecting it too?
Usually a short or very heavy load would get those high current parts hot but no voltage sag unless the tx was struggling to supply it.
P.S You dont need the bypass caps with the SPower as they are low noise and have their own filtering caps.
Brent
Now then 4.6v is low, the SPower will happily run lots of amps and not sag. Did you test the psu before connecting it to what ever you are connecting it too?
Usually a short or very heavy load would get those high current parts hot but no voltage sag unless the tx was struggling to supply it.
P.S You dont need the bypass caps with the SPower as they are low noise and have their own filtering caps.
Brent
Hi Brent,
I think I've got the supply connected incorrectly. I connected to the existing TX using the 9.3v winding and centre tap. I think I need to use both 9.3v windings? Looking at the manual thats how the existing 5v reg is connected.
It also only uses 2 diodes. Is this becaus we are only interested in a + rail?
Trying to thinkback to my collage days (20 years ago!)
I think I've got the supply connected incorrectly. I connected to the existing TX using the 9.3v winding and centre tap. I think I need to use both 9.3v windings? Looking at the manual thats how the existing 5v reg is connected.
It also only uses 2 diodes. Is this becaus we are only interested in a + rail?
Trying to thinkback to my collage days (20 years ago!)
Glenn2 said:
Hi Glenn.
I've had the same problem twice with cd63's. One had a trichord clock , the other a tent clock, both had their own dedicated PSU's for the clock module.
The cause was a faulty ground lead from the clock to the main PCB on both players. Make sure you check this out before changing the DAC chip!
Mags.
Brent,
Just removed D2 and D4 and it works a treat.
Shame I blew 5 630ma fuses on the way, could have been much worse!!!!
It was because I only want the +rail. The other diodes were connecting the (-) part of the wave stright onto ground!!! I should have considered the supply more carefully.
I'll get the next one right first time!!!
DOH!
Thanks for you help
Just removed D2 and D4 and it works a treat.
Shame I blew 5 630ma fuses on the way, could have been much worse!!!!
It was because I only want the +rail. The other diodes were connecting the (-) part of the wave stright onto ground!!! I should have considered the supply more carefully.
I'll get the next one right first time!!!
DOH!
Thanks for you help
Try disconnecting the ground lead between the clock and main PCB.
I had both of the players mentioned running without any ground connection between the clock and main PCB, both clocks had dedicated PSU's and both players exhibited the same symptoms. I've also had my CD80 running the same way before by mistake.
Mags.
I had both of the players mentioned running without any ground connection between the clock and main PCB, both clocks had dedicated PSU's and both players exhibited the same symptoms. I've also had my CD80 running the same way before by mistake.
Mags.