By Dan Mundy, CET/CSM

I have posted this as a troubleshooting aid for the IK circuit. I don't have the manual in front of me so this may be a little generic.

The IK circuit sends out a 100% white pulse during the vertical blanking interval. There is a pulse for red then green and lastly blue. Each pulse is on a different scan line. The IK circuit then matrixes them together, amplifies the 3 pulses and send it back to the jungle IC.

Using a scope with delayed sweep or set at the vertical rate and expended 10X you should be able to see the 3 pulses at the IK output from the CRT board and note that the amplitude will grow or shrink depending on the screen setting.

If one color is missing then you have an amp circuit problem for that color. If none of the pulses are there and they go in from the jungle IC then look for a bad IK amp transistor. If the pulses are there but do not very with changing screen voltage the feedback to the jungle IC or the IC itself is bad. Some times the jungle IC has small Mylar caps off of it and if there they have been known to short. Sometimes the caps are built into the jungle IC and can still short.

Many times the IK circuit just goes out of tolerance meaning the current drawn by one crt is no longer with in acceptable range and the picture is blanked. If this is the case then increasing the screen voltage will solve, for a short while, the complaint.

Daniel Mundy, CETŪ/CSM
HiFi Buys a Tweeters Etc. Company
Atlanta, GA 30331