View Full Version : philco with low focus voltage


DaveWM
02-28-2011, 09:44 PM
max I can get is 4.8kv just short of focus. does the 66 meg every cause issues? it looks like it forms a voltage divider, goes from the focus rectifier to ground. Not sure how to check since I dont think any of my gear can go that low. there is also a 4.7 meg in series with the focus pin on the crt.

ctc17
02-28-2011, 09:58 PM
Check the disk cap, that resistor is 66kv at 6kv. Its a VDR thats there as arc and focus overvoltage protection. Remove it from the circuit and see if anything changes.

Sub the diode and check the disk cap.

Tomcomm
03-01-2011, 02:59 PM
There's a 66meg resistor in the ctc2B that pulled my focus down. Checked its resistance with two DMM with 30 and 40 meg max. Both measured around 24meg. It was in there since '54 and gathered lotsa crud on its surface. I removed it and wiped it down with languor thinner. It now exceeded the range of my meters so I stuck it back in. Got expected focus voltage range so I assumed the cleaning worked. Lotsa luck..........Tom

DaveWM
03-01-2011, 08:50 PM
thanks for the input guys, I will be checking it out later.