Ctc-16 - Page 6 - Videokarma.org TV - Video

DaveWM · #76 10-30-2009, 10:20 PM

that was the only one I did (since the vert output tranny was smoked I did repalce that one, it was leaky, IIRC the resistance measurement was correct as well), that was the cathode bypass cap I think, it was on the board. I have not touched any of the big can caps yet.

Bill R · #77 10-31-2009, 12:46 AM

I would adjust for correct linearity and look for the problem in the vertical sweep circuit. Probably a bad cap. Check B+ in the vert circuit as well. You just do not have enough vertical sweep. This will also effect convergence.
With their age the Selenium rectifiers on the convergance board should probably be replaced. I don't recall changing many in the day, but they are much older now. I think those are more reliable than ones used in the power supply. I would change them. If for no other reason to make the set more reliable.

Bill R

Bill R · #78 10-31-2009, 12:58 AM

By the way if you haven't done it yet check the Horizontal output cathode current. It should be under 210ma I think. Also check things like regulator current, HV, and Boost voltage. I am not looking at the schematics, but some sets use a boost voltage from the HV in some sweep circuits, as well as B+. I don't remember on the 16. I think it would be about 800 volts.

freakaftr8 · #79 10-31-2009, 01:36 AM

Also a 150k resistore between the vert lin and hold controls like to open up in resistance causing issues too! Had this happen on my CTC-16 and one of my CTC-17's. Dave you have done an awesome job at this set!! Beautiful !

andy · #80 10-31-2009, 10:29 AM

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DaveWM · #81 10-31-2009, 04:14 PM

well for grins I picked up some new sweep circuit tubes, I will try them, and then proceed from there. IIRC all the resistance checks in the sweep circuits were GTG based on the sams. freaking HOT was an expensive bugger.

Charlie · #82 10-31-2009, 07:14 PM

Yeah, 6JE6's and and similar run pretty high. You really wanna treat that baby with kindness!

DaveWM · #83 11-01-2009, 01:52 PM

ok replaced same issue. so I guess its time I broke down and

1) double check the caps in the sweep circuit, starting with the cat bypass on the horz osc (30uf part of the can cap)

2) check the resistors again (I think I did this based on the sams pin resistance readings already)

3) go thru the full setup routine of the Horz and HV per the service manual
(check HOT current, check HV)

4) get the scope out and look at the waveform on the osc, maybe trace from the plate of the horz to the grid of the HOT to see if any oddness takes place.

I realize I need to get the linearity done 1st before any more messing about with the purity/convergence.

prob should check voltages while I am at it in the sweep circuits.

DaveWM · #84 11-01-2009, 04:00 PM

would a low HV like 21k vs 25k cause horz lineairiy issues?

DaveWM · #85 11-01-2009, 04:03 PM

I was getting ready to set up my horz eff and HV but before pulling the chassis to disconnect the cathode shunts and attach the ma meter I took a reading with the HV prob on the anode, 21k not 25k...

I will also check the horz osc cathod bypass cap, jic its weak and the horz osc is being effected by that.

freakaftr8 · #86 11-01-2009, 04:44 PM

I think 21k is alright as long as your efficency is low.

DaveWM · #87 11-01-2009, 06:40 PM

well I installed a top side fuse holder right by the HOT, I have a 250ma fuse ready for it. I went ahead and added a 1uf non polar cap across the fuse holder so I can just pop the fuse and attach my meter.

I put the test leads on the 1k resistro on the HV regulater, left them hanging out the back. I actually had just about finished an intall of a term strip right next to the fuse, it was test points for that same resistor, then had a moment of clarity and realized that would put a 390+ term exposed at the back of the chassis

so I undid that and will live with having to pull the chassis to take the voltage drop reading. After pulling that bone head idea I decided to take a break and go do some DXing on my new Zenith TO.

I will do the current and voltage checks tomorrow when my head is clear.

DaveWM · #88 11-01-2009, 08:05 PM

adj a few degrees the HV adj up to about 23.5 now. HOT current 189, HV reg V drop on 1k resistor 1.2v (shoulda checked the res value 1st).

need to check all the B+ values next.

got the fast acting .2 amp fuse ready to go, more horz sweep checking tomorrow to try and figure the horz linearity issues. Overall looking very very good. Will begin full house recap of all cans soon, will of course recheck the HOT after that.

DaveWM · #89 11-01-2009, 08:37 PM

pic of the hot fuse location. quick easy to check the HOT current just pull the fuse and take a reading, sorry for the blur.

No holes drilled easy to undo if for some reason a future restorer does not like it.

Bill R · #90 11-01-2009, 10:31 PM

Is the picture not filling the screen horizontally. It looks like it is in the pictures. If not try adjusting the horiz centering control. The low HV will not cause a horiz lin problem, but a lack of horizontal scan will cause a low HV. 23.5KV may be ok. It should be measured with a dark screen.

Bill