| tubee |
Hi everyone.
I have modded a Philips 304mkII:
*Byv's in PS with a 1ohm R to transformer.
*New lytic caps, almost all are replaced.
*Removed 74LS74, want to put a DS8922 for dig out.
*Kwak clock 7 to Xin of SAA7220
*Divided clock /2 to TDA1541
And some other mods.
Now when i power up the CDP, nothing happens, the display stays black, only the CDM arm goes to most outward position and stays there.
I checked all voltages, everything is allright.
What could be wrong here? I am thinking of a malfunction of u Processor. |
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| awpagan |
| quote: | Originally posted by tubee
Hi everyone.
I have modded a Philips 304mkII:
*Byv's in PS with a 1ohm R to transformer.
*New lytic caps, almost all are replaced.
*Removed 74LS74, want to put a DS8922 for dig out.
*Kwak clock 7 to Xin of SAA7220
*Divided clock /2 to TDA1541
And some other mods.
Now when i power up the CDP, nothing happens, the display stays black, only the CDM arm goes to most outward position and stays there.
I checked all voltages, everything is allright.
What could be wrong here? I am thinking of a malfunction of u Processor. |
You halved the clock of the dac?
Dac is the main place for clock then decoder.
saa7220 is the digital filterwhich you may want to bypass.
nothing on the display either?
does the prcessor have it's own clock?
allan |
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| tubee |
Hi Allan thanks for reply
The clock is 11mhz into SAA7220, divided it by two to dac(74HCT163), and divided it by 4(same 74HCT163) and 16 (2nd 74HCT163) for dem-reclock, goes to pin 16 of dac via 100pF cap. Original 470pF SMD cap is removed.
But i did this earlier with a CD640, with good results (exept the dem reclock)
Kwak works allright on this 640 player. Measure the 3 outputs: all +/- 2.5 V, so they have all a signal.
I want to keep 7220 in for dig-out, Nonos i tried allready with that 640.
Before mods the player was fine:xeye:
I still dont know why the display is not enlightened, if the clock to dac is wrong, the display should still work. Maybe the other micro-processor of display is faulty. The processor has its own clock indeed, will measure the frequency of it (should be 6MHz i think) with a loan scope from friend. |
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| awpagan |
| quote: | Originally posted by tubee
Hi Allan thanks for reply
The clock is 11mhz into SAA7220, divided it by two to dac(74HCT163), and divided it by 4(same 74HCT163) and 16 (2nd 74HCT163) for dem-reclock, goes to pin 16 of dac via 100pF cap. Original 470pF SMD cap is removed.
But i did this earlier with a CD640, with good results (exept the dem reclock)
Kwak works allright on this 640 player. Measure the 3 outputs: all +/- 2.5 V, so they have all a signal.
I want to keep 7220 in for dig-out, Nonos i tried allready with that 640.
Before mods the player was fine:xeye:
I still dont know why the display is not enlightened, if the clock to dac is wrong, the display should still work. Maybe the other micro-processor of display is faulty. The processor has its own clock indeed, will measure the frequency of it (should be 6MHz i think) with a loan scope from friend. |
hi Tubee
the saa7220 is just the digital filter
the dac should be 11.2*mhz or full clock speed.
maybe the decoder came be halve clock but depends on with chip
the processor can check for 2.5v same as before
allan
just reread
I have modded a Philips 304mkII:
*Byv's in PS with a 1ohm R to transformer.
*New lytic caps, almost all are replaced.
*Removed 74LS74, want to put a DS8922 for dig out.
*Kwak clock 7 to Xin of SAA7220
*Divided clock /2 to TDA1541
And some other mods.
The TDA1541 is the DAC
should be main point for clock
anything else is referenced to the dac clock
except processor ( has it's own clock ) |
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| tubee |
Hi Allan
I did such mods before, and on which frequencies it al works: (modded a plastic CD640) ;)
The SAA7210 decoder gets 11.2896Mhz (MCL) from SAA7220
The SAA7220 gets 11.2896 Mhz from cristal or external clock, eg Guido Tent's XO clocks, or in my case Kwak version 7 with 11.2896 freq.
The Dac TDA1541 gets from SAA7220 divided by 2= 5.***Mhz (CLBD)
In Nonos, so without SAA7220, the clock to TDA1541 has to be divided by 4, only then it will give music.
I tried on that CD640 first /2 clock in non-os to dac: you will get awfull digital noise then on output.
Private i am very busy, will lend a scope soon.| quote: |
The TDA1541 is the DAC
should be main point for clock
anything else is referenced to the dac clock
except processor ( has it's own clock ) |
I want to reclock the clock signals as much as possible, also dem-reclock to pin 16 of dac.(176khz) |
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| tubee |
I have discovered a fault solder joint in display pcb, now i can start the 304 up, but it only scans cd and then stops. The display does't show disc info (tracks)
The uprocessor has some faults i think, but in service position A & B it can play discs.
I reclocked Mcl on SAA7210 decoder, reclocked SAA7220 separate also, reclocked the 1541dac (/2) and dem-reclocked 1541. All with 163 dividers. And this reclocking works! So far i can hear on headphones there is less glare, slightly better soundstage/depth. Btw kept the 5532 in it, but putted in sockets to exchange ic's later. Better coupling caps of 10uF mkt bridged with polystyrenes 15nF.
Learned something. To check the clock i replaced the original cristal, but for the time being on solder side: result is a huge digital noise on output when playing. I didn't know 1 cristal can give that amount of rubbish. With a copper shield on SAA7220 the noise is allmost gone. With final kwak there is no noise at all.
Shall do a selftest of uP to check them. |
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