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VCR Panasonic nv-333

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acj1980
(@acj1980)
Posts: 221
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God evening.

Yesterday i got a old "lady" the Panasonic nv-333 from around 1983, it have an issue and i ca´t figure it out,

The fault description is: the record botton lights on no matter if the power botton is on or off, the clock is running, and i can ajust it when the power buttom is set at "on", the lightsensor on the tapedeck does not light up at all, no bottons ca be activated, nothing happens when i push them.

 

The green programme numbers is always on, even if the powerbutton is "off"

My thoughs is maybe the microcomputer is dead or maybe missing a reset signal to gen into function again, but i´m not sure, does anyone have experience with this model?

 

Best regards from Denmark

Pic2
Pic1

 

 
Posted : 15/11/2023 6:06 pm
irob2345
(@irob2345)
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We saw a similar model in Australia, the NV300.

It's a very long time ago but I seem to recall something about a combination of lit LEDs indicating what fatal fault was present. A bit like the BIOS beeps in a PC when the machine has a fault that prevents the display from working.

You'll need the service manual. Good luck!

 
Posted : 16/11/2023 7:23 am
acj1980 reacted
freya
(@freya)
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I would start by checking the power supply voltages are correct, the manual is available. 

PANASONIC NV-333 Service Manual download, schematics, eeprom, repair info for electronics experts (elektrotanya.com)

 
Posted : 16/11/2023 7:59 am
acj1980 reacted
acj1980
(@acj1980)
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@freya Thanks, i have it here, and take a look on the power supply and then the microcomputer

 
Posted : 16/11/2023 1:02 pm
irob2345
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With that combinations of LEDs lit, the uC is trying to tell you something.

Start with that assumption. You'll save a lot of time!

 
Posted : 18/11/2023 1:35 am
Marconi_MPT4
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Posted by: @acj1980

the lightsensor on the tapedeck does not light up at all

This light sensor uses infra red LED's so the light output is not visible, you will need an IR detector probe to see if they are working. 

A common problem on these machines is the infamous(!) mode switch. Poor contact often results in confusing codes sent back to the CPU which either throws it into panic mode, or the firmware waits forever until the correct code appears in order to complete power off sequence. A squirt of switch cleaner might help, but be careful if you remove the switch as it will have to be correctly timed when refitted...!!

Rich

 

 
Posted : 22/11/2023 7:31 pm
irob2345
(@irob2345)
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I seem to remember the NV300 had an incandescent lamp. IR LEDs came later.

You can generally see IR LED output with a phone camera.

 
Posted : 23/11/2023 7:22 am
freya reacted
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