Hi,
The super careful me plugged in a Marantz CD17 - 120 V unit into our 230 V mains. I heard a loud hum saw the filaments of the display ( no blue display) and in about 10 seconds realised the mistake and turned of the power at the mains.
Then plugged in the unit to 120 volts through a step down transformer and there was no display. I assumed the transformer was burnt , though in 10 seconds I didn't think that would happen. I opened up the top to find the laser moving when power was turned on.
I put in a disc and it spun and then found that the machine was working OK with normal sound. Even the IR remote works.
But no display. All dc (regulator) voltages seemed to be OK.
Looks like there is no display filament voltage. Where do I measure this and how much should it be ? I see a three terminal connector near the edge of the main board. Is this the supply to the filaments ? Can I check the filament resistance to see if it is blown. If so where ?
Can someone please help me.
Thanks,
Ashok.
The super careful me plugged in a Marantz CD17 - 120 V unit into our 230 V mains. I heard a loud hum saw the filaments of the display ( no blue display) and in about 10 seconds realised the mistake and turned of the power at the mains.
Then plugged in the unit to 120 volts through a step down transformer and there was no display. I assumed the transformer was burnt , though in 10 seconds I didn't think that would happen. I opened up the top to find the laser moving when power was turned on.
I put in a disc and it spun and then found that the machine was working OK with normal sound. Even the IR remote works.
But no display. All dc (regulator) voltages seemed to be OK.
Looks like there is no display filament voltage. Where do I measure this and how much should it be ? I see a three terminal connector near the edge of the main board. Is this the supply to the filaments ? Can I check the filament resistance to see if it is blown. If so where ?
Can someone please help me.
Thanks,
Ashok.
Filaments OK.
OK I found the filament terminals. They have a 3.8 volt ac signal on them and they glow dimly. I can see it when I turn of all the room lights ( its night time here).
So that means possibly no signal on the electrodes . How do I check this out. Any suggestions from our digitals experts ? What else could go wrong in the display circuit ?
Note that I didn't see any disply at all when first plugged in at 230V . The filaments were visible dull red with room lights on.
Now its visible only with lights off which I think is normal.
Thanks.
Ashok.
OK I found the filament terminals. They have a 3.8 volt ac signal on them and they glow dimly. I can see it when I turn of all the room lights ( its night time here).
So that means possibly no signal on the electrodes . How do I check this out. Any suggestions from our digitals experts ? What else could go wrong in the display circuit ?
Note that I didn't see any disply at all when first plugged in at 230V . The filaments were visible dull red with room lights on.
Now its visible only with lights off which I think is normal.
Thanks.
Ashok.
hi,
generaly, the display is powered with 5v ac for filaments and something like -26v for electrodes.
check if you have something like this. if yes, the display can be dead
if not, that's a psu problem
generaly, the display is powered with 5v ac for filaments and something like -26v for electrodes.
check if you have something like this. if yes, the display can be dead
if not, that's a psu problem
And so?
You have subconsiously got rid of the display...what on earth would you need it for?...use the dimmer function and reduce it even more 😀
cheers
t
You have subconsiously got rid of the display...what on earth would you need it for?...use the dimmer function and reduce it even more 😀
cheers
t
Checked it on a scope.
Hi apolon34 ,
I found 10 volts peak to peak on the filaments. That is about 5 volts peak ac.
The other terminals have pulses of about 5 volts on them. No sign of any higher voltages on any terminal.
Could this display work with lower voltages ? Is there a 24 volt coming down the connector cable from the main board ? I don't see it.
Thanks for the information you gave me.
Ashok.
Hi apolon34 ,
I found 10 volts peak to peak on the filaments. That is about 5 volts peak ac.
The other terminals have pulses of about 5 volts on them. No sign of any higher voltages on any terminal.
Could this display work with lower voltages ? Is there a 24 volt coming down the connector cable from the main board ? I don't see it.
Thanks for the information you gave me.
Ashok.
Any suggestions ?
Can anyone tell me where to check to determine at what point the 24 volts is failing ?
Thanks,
Ashok.
Can anyone tell me where to check to determine at what point the 24 volts is failing ?
Thanks,
Ashok.
I checked some more and determined that it looks like the connector to the display from the main board does not carry any voltage higher than 5 volts. There is a VF0 terminal which I guess is at 0 volts (?).
I removed the front panel and from the display pcb it looks like there is a chip under the display - that is awful ! Couldn't possibly sit down to remove the multiple pin display . Since the main board to the front panel is very small , it obviously carries only signal and supply lines. Display voltages must be generated on the front panel pcb.
Any idea what chip that is?
Would anyone have a schematic of the display module ?
I couldn't even find any sources for a service manual on the web. Would anyone have a url ?
Thanks.
Ashok.
I removed the front panel and from the display pcb it looks like there is a chip under the display - that is awful ! Couldn't possibly sit down to remove the multiple pin display . Since the main board to the front panel is very small , it obviously carries only signal and supply lines. Display voltages must be generated on the front panel pcb.
Any idea what chip that is?
Would anyone have a schematic of the display module ?
I couldn't even find any sources for a service manual on the web. Would anyone have a url ?
Thanks.
Ashok.
Attachments
I think I have...
the remains of a CD-14...somewhere....
I guess it uses same display board as CD-17...?
Arne K
the remains of a CD-14...somewhere....
I guess it uses same display board as CD-17...?
Arne K
ashok said:
Had a broken display on a CD60 (characters lit up that shouldn't randomly) and it turned out to be the chip underneith the display.
Was a TFK chip from telefunken. But i think the cd17 is newer and made in japan (?), so probably you have some jap version of such a chip. I couldn't buy a replacement (unless >1000 at a time 😉 ), so i took one out of a CD40.
But in your case, could be the display, this chip or the powersupply (or a combination). Getting the servicemanual seems like the best thing to do.
Good luck
Zener?
Hello ashok, If your display is a vacuum tube display there is a zener diode in the supply of the display. Very probably the zener is KAPUT hence the low voltage as zeners fail by short circuit. Find the zener and replace it. Could perhaps be the BY85 24V zener, but that is a very vague schematic I possess😎
Hello ashok, If your display is a vacuum tube display there is a zener diode in the supply of the display. Very probably the zener is KAPUT hence the low voltage as zeners fail by short circuit. Find the zener and replace it. Could perhaps be the BY85 24V zener, but that is a very vague schematic I possess😎
Re: Zener?
Exactly, must be the same unclear scan of the schematic that I have.
Check that zener, most probably that's the problem.
Elso Kwak said:
Exactly, must be the same unclear scan of the schematic that I have.
Check that zener, most probably that's the problem.
A ray of light ( hope)...........in the distance !
Hi Elso and Carlosfm,
I would be really grateful if any one of you can email me a scan of the diagram you have? A fuzzy one is better than no diagram.
I haven't been able to find an alternative source for it yet.
ashokm(at)sify.com
Is the zener on the main board or the display board ?
I used the machine several times with the dark display and it didn't feel good at all. The brain keeps nagging me in the background all the time. I'll have to fix this.
Thanks .
Ashok.
Hi Elso and Carlosfm,
I would be really grateful if any one of you can email me a scan of the diagram you have? A fuzzy one is better than no diagram.
I haven't been able to find an alternative source for it yet.
ashokm(at)sify.com
Is the zener on the main board or the display board ?
I used the machine several times with the dark display and it didn't feel good at all. The brain keeps nagging me in the background all the time. I'll have to fix this.
Thanks .
Ashok.
Re: A ray of light ( hope)...........in the distance !
Dunno, it's on the schematic.😀
It doesn't specify the location, and I don't know the insides of the CD17.
Anyway, you have mail.😉
Check the bottom right corner of the schematic.
ashok said:
Dunno, it's on the schematic.😀
It doesn't specify the location, and I don't know the insides of the CD17.
Anyway, you have mail.😉
Check the bottom right corner of the schematic.
Thanks to all for your posts, especially .....
Thanks especially to Elso Kwak , Carlosfm and Apolon34.
I did find that the -24 volts to the display started on the main board and reached the display via the connector. This voltage was missing.
The rectified 24 volt ac appears as a -ve 28 volts across a 100uF/50V capacitor ( CY81 ) . It then goes to the regulator transistor QY81 .
There was no voltage across the regulator transistor or the 100uF cap. I found that the rectified voltage went to the supply capacitor through a 10 ohm SMD (RY80) resistor. This was blown.
I soldered a 1/4 watt 10 ohm resistor ( axial leads) across this SMD part. The resistor was mounted vertically.
The display now works fine. However it might have been a fusible resistor and I will have to look for one fusible 10 ohm SMD resistor ...............whew, that might be a problem.
Thank God for that resistor , it saved the rest of the circuit from cooking.
Apart from other parts an exploding capacitor can really ruin the insides ! I get a nightmare just thinking about it.
Well all's well now . Thanks again to all and especially to Elso , Carlosfm and Apolon34.
Cheers,
Ashok.
Thanks especially to Elso Kwak , Carlosfm and Apolon34.
I did find that the -24 volts to the display started on the main board and reached the display via the connector. This voltage was missing.
The rectified 24 volt ac appears as a -ve 28 volts across a 100uF/50V capacitor ( CY81 ) . It then goes to the regulator transistor QY81 .
There was no voltage across the regulator transistor or the 100uF cap. I found that the rectified voltage went to the supply capacitor through a 10 ohm SMD (RY80) resistor. This was blown.
I soldered a 1/4 watt 10 ohm resistor ( axial leads) across this SMD part. The resistor was mounted vertically.
The display now works fine. However it might have been a fusible resistor and I will have to look for one fusible 10 ohm SMD resistor ...............whew, that might be a problem.
Thank God for that resistor , it saved the rest of the circuit from cooking.
Apart from other parts an exploding capacitor can really ruin the insides ! I get a nightmare just thinking about it.
Well all's well now . Thanks again to all and especially to Elso , Carlosfm and Apolon34.
Cheers,
Ashok.
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