Tech-Master NIB TV Kit #5516

[bandersen]

Glad you got the CRT focus sorted out and nice work! One thought - you might want to add a thermistor to give the tubes a soft start. Something like a CL-90 has a 120 ohms cold and around 3 ohms hot.

[Crist Rigott]

Originally Posted by bandersen

Glad you got the CRT focus sorted out and nice work! One thought - you might want to add a thermistor to give the tubes a soft start. Something like a CL-90 has a 120 ohms cold and around 3 ohms hot.

Thanks Bob!

Do you think I'll still need the thermistor even though the tubes have that 11 second delay built in?

[Crist Rigott]

With the TV plugged into the wall (124vac) I'm getting 135v B+ and 13.2 to 14.6Kv depending on the brightness setting.

This is with a 10 ohm resistor in the filament string and a 15 ohm resistor in the power line going to the rectifier.

[bandersen]

Originally Posted by Crist Rigott

Thanks Bob!

Do you think I'll still need the thermistor even though the tubes have that 11 second delay built in?

Not sure what you mean by that ? Is there some device providing a slow 11 second filament power up ?

[dieseljeep]

Originally Posted by bandersen

Not sure what you mean by that ? Is there some device providing a slow 11 second filament power up ?

According to the tube manuals, all the newer issue 600ma tubes have controlled heater warmup of 11 seconds.

[Crist Rigott]

Originally Posted by bandersen

Not sure what you mean by that ? Is there some device providing a slow 11 second filament power up ?

On the 25DN6 tube data sheet they talk about controlled warm up period.

"Thermal characteristics of the heater have been controlled such that heater voltage surges during the warm-up cycle are minimized provided it is used with other types which are similarly controlled."

Then further down on the data sheet it states:

"Heather warm-up time. (Approx.)" 11 seconds

Most all of the tubes used have these statements in their data sheets.