CDTV Front Panel and Buttons not working

07 September 2018, 18:25

Hello All!

I am lucky to have gotten my hands on a Rev 2.2a CDTV which boots however the front VFD Display and buttons are not working. The CDTV Mode LED works and lights up orange but nothing else seems to be lighting up/responding.

Any ideas as to what could cause the front display to not even light up? Or what pins to check for voltage?

Thank you!

Docy · 09 September 2018, 13:15

All front panel handling is done (primarily) by the LC6554H (U62) chip.

Since your display is not coming up (the A500 inside work, I assume) you may check several things:

1)
Is U62 in the socket?

2)
locate CN16:9 and insert a CD (will change level if CD is inserted)

3) locate CN16:8 and send some IR command - level there will reflect the IR signal

2) and 3) measured with respect to GND (CN16:10) and have a 5 Volts level

4)
CN16:1,2,3 are the reply lines of the keys - CN16:1 is not connected
CN16:4,5,6,7 are the scan lines for the keys
check them for some 5 V like level and press some buttons, they change to 0 Volts then

5) check CN15:8 and CN14:1 (VF1, VF2) with a multimeter(!) vs. GND - should be ~22 V

6) check CN15:8 vs. CN14:1 (VF1 vs. VF2) with a multimeter - should be ~3,5 V heating voltage of the VFD filament

7) check Vpp against GND (no separate connector available, you may go to U62:51)
should be also ~(-)26V

07 September 2018, 18:25	#1
Kovlor Posts: n/a	CDTV Front Panel and Buttons not working Hello All! I am lucky to have gotten my hands on a Rev 2.2a CDTV which boots however the front VFD Display and buttons are not working. The CDTV Mode LED works and lights up orange but nothing else seems to be lighting up/responding. Any ideas as to what could cause the front display to not even light up? Or what pins to check for voltage? Thank you!

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09 September 2018, 13:15	#2
Docy Registered User Join Date: Aug 2018 Location: here Posts: 2	All front panel handling is done (primarily) by the LC6554H (U62) chip. Since your display is not coming up (the A500 inside work, I assume) you may check several things: 1) Is U62 in the socket? 2) locate CN16:9 and insert a CD (will change level if CD is inserted) 3) locate CN16:8 and send some IR command - level there will reflect the IR signal 2) and 3) measured with respect to GND (CN16:10) and have a 5 Volts level 4) CN16:1,2,3 are the reply lines of the keys - CN16:1 is not connected CN16:4,5,6,7 are the scan lines for the keys check them for some 5 V like level and press some buttons, they change to 0 Volts then 5) check CN15:8 and CN14:1 (VF1, VF2) with a multimeter(!) vs. GND - should be ~22 V 6) check CN15:8 vs. CN14:1 (VF1 vs. VF2) with a multimeter - should be ~3,5 V heating voltage of the VFD filament 7) check Vpp against GND (no separate connector available, you may go to U62:51) should be also ~(-)26V

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