#1
|
||||
|
||||
RCA CTC-4: dead front end :/
Ok, I've gotten my 4's basic stuff working, except the front end. Inject into the IF isn't doing much, the tuner isn't doing squat. It's intermittent (sometimes), though, but more 'not working' than 'working' Which is annoying.
I'm not sure where to look - voltages seem fine, the service manual naturally doesn't say what the AGC range is, the Sams resistance check seem fine... I an re-check the tuner and if strips, but I dont' seem to be getting anywhere. Oddly, when it powers up,you hear what almost sounds like the sound going through the FM band quickly. There some secret about these sets that I'm missing? |
#2
|
||||
|
||||
If injection IF signal into the IF circuits isn't giving you signal then your IF is defective and you should worry about your IF before you even look at the tuner.
One of my CTC4 sets the alignment was abominable...sound, luminance and color could all be obtained with fine tuning adjustment, but I could only get one at a time depending on adjustment....the IF adjustments were fine and it was a resistor problem...I unsoldered one end of EVERY IF resistor and changed every one that was off tolerance or borderline and the IF started working like new.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#3
|
||||
|
||||
Tom has a good start. A good running set without any signal should
give you strong snow & a nice water fall of audio noise. AGC can be substituted with a little bias box. AGC problems were quite rare. almost always IF problem gives bad or no snow & washed out pix. I would NOT consider IF alignment at this point & if you get there replace ALL IF tubes with brand name NOS tubes first. The 4.5 & 41.25 ( IIRC) can be touched up after the set is strong. Just flag your diddle stick so you can go back. 73 Zeno LFOD ! BTW if you have an IF generator you can walk through the IF stages. Another great little tool is a tuner subber. Strip a click tuner out of a junk solid state set. Give it B+ & a voltage divider for AGC. Short the AFT line to ground. All works on batteries OR get one off Ebay ! |
|
|