CTC 47 work goes on

[RCAkid]

Well, I found the tecnical manual that came with the documentation of the G-2000 and found the parts list and how to test the quadrupler and better schematics than the sams.

I have sent an email to Moyers to find out about the availability of the SCR's, flyback, quadrupler and commutator. I figured it would be a good idea to snag these components if they are still available.

I will be testing the quadrupler tonight. The whole problem could still be just a bad SCR. I will try to get multiples of those as a precaution since I am told they are prone to failure.

After close examination of the chassis, there was only one paper electrolytic, a 250uf 175v axial cap and I replaced it with a frankencap consisting of 2 100uf 250v and 1 47uf 250v caps. I checked the capacitance and it registered 249.5uf so I figured this should do well as a replacement as the original cap was +-20% and it was registering about 50uf higher than it was rated. It was a paper cap and needed to go, so it is gone.

The chassis is back in the set with no changes. Still no raster so now it is time to check voltages. I hope it is just something silly and not that quadrupler or flyback. The fly is a wierd little thing. I have not tested it for continuity though. I am not really sure how to properly test a flyback.

Anyway, that's where I am.

[RCAkid]

OK, an update on the G2000.

Thanks to Roundscreen for some tips to look for!


I ran the test procedure for HV to check the Quadrupler. With the kine connector removed from the crt as described, I checked the HV anode and only was showing 2kv at the hv anode. I removed the bleeder resistor from the anode bundle and still, only 2kv. I then checked for voltage on the F (focus) connection on the quadrupler and there were 0 volt where there should have been 2.5-4.5 kv. Now, all that being said assumes good SCR's. With the little bit of a makeshift tester I had for the SCR's, they appear to be the culprit or at least part of the problem. But it is also possible that the quadrupler just failed. But I have heard that when these typically go, they go fairly catastrophically and visibly (ie: arcing, cracking, melting a bit, etc). But in my experience with other "module" style sealed components this is not always the case.

The only cap I have replaced in this set thus far is that axial 250uf 175v electrolitic which sits right underneath the flyback (C108). I had to make up a cap of that value from 3 smaller caps (2, 100uf and 1 47uf +-20%), they test out at 249.5 so I figure that is pretty darn close. While the original electrolytic was just at the upper range of the 20% rating, I just make it a policy to replace old electrolytics like this and paper/wax caps because I know they will fail and this chassis is no fun to remove from the cabinet so I figured I would change it out while I was there. I have not yet, however, replaced the three can electrolytics. They are running cool and check out ok so I am leaving those be for now. But I know they will have to be changed out eventually.

Roundscreen led me to some possibilities on the vertical issue I have. Question, can transistors be tested for shorts while in circuit? I know caps and resistors can't be accurately checked in circuit.

Anyway, I will be ordering the SCR's and we will see what happens.

Roy

[batterymaker]

Hopefully it'll be something fixed with off-the-shelf parts.

Pls post some pix with the final results. I've not seen a 2000 in full operation before.

Bill

[RCAkid]

As soon as she is up and running I will post pics.

I talked with Bill at Moyers today and got the quadrupler, scrs and bleeder resistor on order. He is checking on a fly for my CTC-21 but I fear that is not to be had and will have to keep searching for a spare. The one I have in chassis is still quite good but it is great to have a spare on that.

Roundscreen shared with me that the vertical output transistor could short and overload the B+ effectively killing the hv. I was working with the vertical when I lost raster. Perhaps this is it. We will see.

It will still be good to have the spare parts though.

I see why Moyer's is so highly recommended. They are really cool and passionate about what they do. Bill had not really ever dealt with parts for the ctc-47 and was pretty excited about it himself.

But with the lack of a spare flyback out there, this one will NOT be a daily watcher, just used on special occasions. Bill at Moyers said there was not a cross with any other of the flyback manufacturers. I will have to keep an eye out for a parts ctc-47 and snag the fly from it.

[andy]

...

[RCAkid]

Would a large, plastic handled screwdriver do for this test? Do you recommend any other material to put around the handle so I don't cook myself?

Could I also just use my HV probe to check this and actually get a voltage measurement?

This would definitely verify the health of the fly.

[radiotvnut]

You'll be safe using a regular insulated screwdriver. Just don't get too close to the metal shaft and don't let the HV arc to the chassis or other components. I've used this method countless times on Zenith Chromacolor II's to check the condition of the flyback. Often, the tripler would fail and take the flyback with it. A good flyback should give you at least a 1/2" arc. A bad flyback may give a little spark as you touch the screwdriver to the output lead or it may do nothing at all. In the Zenith's that I tested, the bad flybacks always got warm and tripped the CB, even with the defective tripler disconnected. I've yet to encounter a bad flyback in an RCA. I was always lucky enough just to have a bad tripler in the sets I worked on.

[RCAkid]

Well, here is the deal....the fly is bad.

Just a tiny little blue spark when almost touching the wire.

Now I know why I don't have HV. I have located a quadrupler but now I have to try to figure out what to do with the flyback. Moyers doesn't have it and they have no crosses to other manufacturers.

Any suggestions on what can be done with this fly would be appreciated. I am not aware of any way of repairing a flyback.



I reckon she is done for now and the parts search goes on. Sad, such low hours on it too.

Roy

[radiotvnut]

When you find a flyback, change the quadrupler as well. If the fly is bad, there's a strong chance the quad caused it. Does the flyback get the least bit warm to the touch? If so, that could be more evidence that it's bad.

[RCAkid]

I have already ordered the quadrupler. I haven't put my hand on the fly but that is probably what was smelling at one time. An apparent short in the fly. Oh well. Just gotta button her up until a fly can be found.

This will be fun.

[andy]

...

[RCAkid]

Oh I know what you mean. The fly looks pristine. Doesn't appear to have gotten hot at all.

The bad news is that the schematic that I have doesn't show seem to show voltage check points.

Anyway, the tech manual also showed a test to see if the fly is being loaded. With the anode disconnected from the Quadrupler, the anode of the SCR, SCR 101 to be exact, should have a voltage of 400V. It shows only 69V. The fly does NOT get hot at all and, while I am not an experienced tech, and given a suggestion of low B+, perhaps an ecap in the power supply failed. I may be wrong here but a shorted fly usually gets pretty hot and smelly or arcs or something. The other thing is that the line for the 400V appears to be off of a different winding off the fly. While I may be wrong here, wouldn't it take something pretty catastrophic to kill the upper AND lower windings on the fly?

I think I may have located a pair of shorted transistors in the vertical circuit...I am verifying this but if a cap did fail, is it probably that it could have shorted the transistors and now that is overloading the B+ and causing a low B+ to the fly?

Please feel free to correct me on this if my logic is all wet. Solid state circuits are not warm and comfortable place for me.

Thank you all for your help!

[roundscreen]

Originally Posted by batterymaker

I've not seen a 2000 in full operation before. Bill

Here are some screen shots of a rca 2000.
Ed

[sampson159]

funny the amount of screen shots with family guy.we must be a bunch of kindred spirits.super looking picture.the color and contrast are amazing!

[roundscreen]

Originally Posted by sampson159

funny the amount of screen shots with family guy.we must be a bunch of kindred spirits.super looking picture.the color and contrast are amazing!

Thank you.
Ed