Surge-supressor resistor in power supply

[frenchy]

The CTC-10W I'm working on has this big flat, black 'surge suppressor' resistor in series with the line voltage. But a big 1/3 hunk of has blown off of it. Schems say it should be 79 ohms cold, I'm reading 131 ohms (thanks to the missing chunk). Set works (no color but I'm working on it) but wondering how much could this 131 vs 79 ohms be affecting the set operation, and how... or is it negligible? Can I just install a jumper instead of this thing, or just leave it there as is? What is it supposed to be protecting, the entire set against a lightning strike or line voltage surge damage or what?
thanks!...Frenchy

[holmesuser01]

My 10C ran for years with this resistor jumpered. I used one from a degauss circuit. Seems to work OK. Just makes the set a bit slower to power up. This resistor is the main reason that my set was dead when I got it in 1974, After that, the kine got broken, and somebody wiped out all of the tubes. Then I got it.

I have a feeling that this resistor eases the start-up surge through the diode power supply.

[Don Lindsly]

The 131 ohms will affect the warmup time more than the operation. The resistor should be a couple of ohms hot. The best way to verify that is to check B+ and/or 6.3 volt filament voltages. If they're OK, the resistor hot-value is OK. Of course with a piece missing it will have lower power capacity and ultimately shorter life. If you only use it occassionally, you may never notice.

The CTC9s and 10s were good products and were the fisrt generation of reliable and serviceable color TVs. I believe the main difference is the addition of the service switch and improved vertical circuit on the CTC10. I could be off a digit.

[frenchy]

Ok I'll check the heater voltage on the crt next time I power it up for a test, then jump it and see if any difference. Hmm maybe I'll try heating the resistor up on the bench and make sure it goes to a few ohms first. This set was a bit odd to me to begin with as they had installed a filament booster, but the crt tests just as good on my tester as my other 21' pic tubes. Possible the filaments were all too low with this busted resistor. But in the end I'll probably find the booster was needed somewhat anyway for legit reason(s)...Frenchy

[frenchy]

Follow-up:
Filament voltage with existing damaged suppressor after fully heated up = 6.44 volts
Voltage with resistor bypassed = 6.7 volts

So not spectacular but nothing to sneeze at either, 1/4 of a volt, that's about a 5% increase in the filaments. I'll see if I can notice any slight improvement in the brightness out of the pic tube with the booster off of it and the resistor bypassed.