Jumping the resistors will certainly raise the heater current. This will
hasten the life in the CRT that is left. But, considering that it is almost
gone anyways, there is not much difference here.

As the CRT is going weak, the auto controlled bias circuits keep biasing the
CRT more and more to maintain its performance as best as possible.
Eventually they run out of range, and cannot maintain the proper current.
This also means less anode current, and thus the set is designed to go in to
protection when the anode current is below a certain amount.

Raising the heater current allows for a greater amount of emission. I have
seen tubes last anywhere from a few days to a few months like this. There is
no accurate way to predict anything with this type of affair.

The greater heater current may also cause the flyback to run a bit warmer,
and it may also put a bit more of a load on the horizontal output
transistor. This area is a bit robust, and should normally be able to take
the added load. After running the set for about an hour with some type of a
cover over it, if you can, take a temperature reading of the horizontal
output transistor. It should not exceed about 60 to 70 degrees Celsius. At
about 80 to 90 degrees Celsius, the transistor would be working at near its
maximum temperature range for long duration operation.

--

Jerry G.
======


wrote in message
oups.com...
This set has a weak CRT and blinks on and off. I jumped the two
parallel resistors on the CRT board which are in series with the heater
and the pix came on. The same thing happens if I tweek the screen up
slightly. I decided to do both and the picture seems to be holding. I
realize this is a "deadman walking" however I would like to give the
customer some rough idea as to life expectancy. Does anyone have any
information, after returning a set like this, (with an explanation of
course), perhaps feedback from customers on this? Also, it occurred to
me that jumping the series heater resistor will increase the heater
current through the flyback. Should I be overly concerned about this on
a set whos' days are numbered anyway? Thanks, Lenny Stein, Barlen
Electronics