UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Tenma 72-6802

Diabolical Artificer · 18th Nov 2018, 7:15 am

Brightness/intensity and other CRT voltages are usually derived from a simple potential divider, IE a load of resistors and pots in series with a positive voltage at one end, and ground or a negative voltage at tother end.

So the brightness pot should adjust the cathode - grid voltage, grid should be at - something volts in relation to the cathode, adjusting the pot you should get - 20/30v or whatever to - 5v say, something like that.

To fault find see if you can find a pinout for your CRT, find the cathode pin, black probe of DMM on that, red probe on the grid.

Here's some bumf to give you an idea - https://www.robkalmeijer.nl/techniek...e45/index.html

Andy.

18th Nov 2018, 7:15 am	#5
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,658	Re: Tenma 72-6802 Brightness/intensity and other CRT voltages are usually derived from a simple potential divider, IE a load of resistors and pots in series with a positive voltage at one end, and ground or a negative voltage at tother end. So the brightness pot should adjust the cathode - grid voltage, grid should be at - something volts in relation to the cathode, adjusting the pot you should get - 20/30v or whatever to - 5v say, something like that. To fault find see if you can find a pinout for your CRT, find the cathode pin, black probe of DMM on that, red probe on the grid. Here's some bumf to give you an idea - https://www.robkalmeijer.nl/techniek...e45/index.html Andy. __________________ Curiosity hasn't killed this cat...so far.