That CTC-11...

[freakaftr8]

Hey guys, Gary called me tonight and I went to check out the 11 he got.. Guess he powered it on a variac even though it has been ran before. I brought my tube tester. Half the tubes in this set are Zenith, realistic or GE... Well, sounds like the flyback makes these loud sqealing noises and the crt goes berzerk.. We unplugged the set. I told him to order caps and get out his ESR meter... BTW, that set has an 21FBP22 in it, he tested the emission at 85%red 90%blue 91%green on a bk 466. What causes this sqealing, it only did it once upon startup... It was nice and loud too!

[jpdylon]

by bezerk, did the picture tear off into little strips? Could be the horiz. oscillator freq. is off

the core of the flyback could be loose and causing that squeal

the HO tube could also be making that noise. I have a zenith that has the high pitch squeal. HO tube is the culprit.

get it fixed before you run it again.

[freakaftr8]

No the pic just went to big white bars. this noise was abrupt and lasted half a second. All tubes check out great. The sound was more like a shreeking screech...

[nasadowsk]

Check the HV box and make sure all the HV areas are clean. Might be flashing over - that'll kill the picture and make lots of scary noises.

[oldtvman]

make sure all the factory shielding is in place around the IF sections, I had a ctc 9 that showed the same syptom, when I put the bottow shield back on the bottom of the IF section it worked fine.

[freakaftr8]

Cool, Ill check it out tonight, we found some bad caps in the filter section.. Going to replace all caps. Also some wax caps in the Demod section have no ESR, going to replace those too... Ill keep you updated. I want this set! Im trying to buy it from my friend.

[freakaftr8]

Well I found a puddle of wax under the flyback. Im assuming this is normal.. the flyback looks dry, but could use a recovering, I was thinking about doing this to my ctc-16, whats some good stuff to use?

[jpdylon]

A puddle of wax indicates overheating. I use low-acid type RTV silicone to recoat the flyback.

Make sure you check to see if the HO tube and Damper are good and adjust the HO cathode current. No more than 205ma or it will run hot. If not attented to it will kill the flyback. YOu also may want to check the HV regulator current and adjust the HV using an appropriate HV probe and high input impedance meter . Should be around 24-25kv with brightness at minimum.

[freakaftr8]

Ok well not to sound dumb but how do you check the cathode current, can I use a dvm? and which pins to I check the current at? And in which condition should I check the current, set running with the tubes pulled or not and Where can I find a HV probe, and in that since how do you check HV?. These are the only things I dont know yet... I have to do this to my ctc-16 as well.. 300 bucks and the 11 is mine... ouch... I only have room for one more set and I want a rectangular set...

[jpdylon]

The sams should be able to point out the exact procedure for the cathode current, and some sets (I think the 16 chassis has it) have a jumper you remove to connect the ammeter between the jumper and ground. If you don't have the sams, disconnect the cathode lead from the HO tube at the socket and connect your meter between the cathode pin and the lead you just disconnected. THe tube has to be IN CIRCUIT and the set running to do this. If your DVM has a provision for measuring current in milliamperes it will do fine.
This procedure can be a pain if if the cabinet doesn't have a removable bottom, and its even better if you have a test jig so you can operate the chassis out of the cabinet.

Hv probes come up from time to time on ebay. I got my fluke for about 20 bucks shipped and it works well. YOu just need to make sure your meter has a high input impedance or it will cook, at least 1 meg ohm. YOu connect the meter to the probe, and the ground on the probe to the chassis. Carefully slip the probe under the cap and touch the HV lead. Adjust the HV control for hte proper voltage at minimum brightness.

[andy]

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[freakaftr8]

Well I just bought a HV probe, EICO Model HVP-5 with meter built into the probe.. Hope it works.. Thanks for the help guys.. Youre awesome.. BTW, how do you adjust HO cathode current? I know how to adjust HV..

[Bill R]

Cathode current is adjusted with the horizontal efficency coil. It should be labeled on the chassis. Use a plastic tool, and do not force it or the core could seize up in the coil.

Bill R

[freakaftr8]

Awesome!!! Thanks guys! There is a 250v 160mfd cap in the can cap to the right of the black beauty shorted, no reading on my esr, goes way high, unreadable on the 200mf setting.. This could have been a cause to the shreeking (very loud noise) that came from the area of the flyback... But not too sure, looking for a sams for the ctc-11 still...

[Phil Nelson]

Originally Posted by freakaftr8

we found some bad caps in the filter section.. Going to replace all caps. Also some wax caps in the Demod section have no ESR, going to replace those too

You can just about guarantee that all electrolytic and paper caps in a forty or fifty year old set will be bad. If they haven't failed yet, they will soon.

It's hard to resist the temptation to power up a set immediately, but it's more prudent to replace the filter electrolytics first. Powering up on a variac offers no real protection against burning up an expensive power transformer. Yes, I have done that, and it cured me of the temptation forever.

Some old electrolytics may "reform" after a fashion, but they are not reliable to use for the long haul, in my experience.

It's also a good idea to carefully clean the HV section, as nasadowsk suggested. HV can do funny things, especially in a set where HV components are coated with carbonized cooking grease & tobacco residue. I would do this even if you are not currently experiencing Bad Things from that section.

I have a CTC-11 on the workbench and a copy of the Sams. If you send me an email by going to http://antiqueradio.org/contact.htm , we can figure out how to get you a copy.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html