# Micro 1/2" viewfinder CRT troubleshooting

#### bv_09

Joined Sep 17, 2020
1
Greetings everyone!

I saw a video from 12voltvids about this tiny 1/2" viewfinder CRT which he managed to power up and get a picture on and decided to try this hack for myself. I play a lot of classic tetris on the NES and thought it would be super cool to get my NES running on this thing.

I have exactly the same CRT (from an old Sony Handycam viewfinder), soldered a couple of wires to the live and ground pins but the tube is showing no signs of life. In the video he says it takes around 4V at 0.1A, so I set the current limit on my supply to 0.8A and voltage to 4. It only takes around 2.4V before it reaches the current limit. Haven't tried to add a video signal yet.

Anyone have any idea what the problem could be? or where I can start looking?

This is my first practical project so any help would be greatly appreciated.

Thanks!
BV

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#### DickCappels

Joined Aug 21, 2008
6,640
What do you mean by "not showing signs of life". Is this the heater power supply that you are talking about? 100 uA is a lot of current in such a small CRT but it also sounds like a very light-duty heater (for filament).

#### MisterBill2

Joined Jan 23, 2018
7,221
A CRT needs quite a bit to show any life. Heater voltage, electrode voltages, and deflection waveform voltages. So with a power supply and no clue you can easily turn it into scrap in just a few seconds. If it uses magnetic deflection then you also need the deflection coils. Without all of that you get nothing.

#### DickCappels

Joined Aug 21, 2008
6,640
Upon review, 100 uA would not current for a heater.
It looks like the deflection yoke and centering magnets are there.

Warning based on an expensive experience be careful to make it impossible to have any beam current when there is no deflection. That happened accidentally with a custom avionics tube and it cost me $2500 #### MisterBill2 Joined Jan 23, 2018 7,221 Upon review, 100 uA would not current for a heater. It looks like the deflection yoke and centering magnets are there. Warning based on an expensive experience be careful to make it impossible to have any beam current when there is no deflection. That happened accidentally with a custom avionics tube and it cost me$2500
With applying a random heater voltage it may be that the TS has already achieved destruction of the device.