Rca 621TS
 

I picked up this TV this evening. Drove to Houston, sealed the deal and drove back. Got in about 11pm.

Overall the set looks nice. It is an older s/n like C 0003445. Pretty clean inside and no rust except on the surface of the transformer. Here are a few pics of it:

http://i1060.photobucket.com/albums/...psdppgksds.jpg

http://i1060.photobucket.com/albums/...psdppgksds.jpg

http://i1060.photobucket.com/albums/...pslqa1bprd.jpg

http://i1060.photobucket.com/albums/...psoa8lfd0a.jpg

I tested the 7DP4 picture tube with my BK 467 CRT tester. Here is the result:
http://i1060.photobucket.com/albums/...ps4lshiq8q.jpg

And the LIFE TEST:
http://i1060.photobucket.com/albums/...psum3dnh5j.jpg

The HV lead was disconnected and in faint letters the word BAD was written on the top of the CRT:
http://i1060.photobucket.com/albums/...ps0l6y2nt0.jpg

What gives? The tube looks to be in excellent condition.

Very pleased with the purchase.

But wait, there's more!
I also got this from the same seller:
http://i1060.photobucket.com/albums/...ps4lodvbw7.jpg

http://i1060.photobucket.com/albums/...psxg1qiszj.jpg

http://i1060.photobucket.com/albums/...ps24qexnsn.jpg

Crist,
Glad you were able to buy the 721 with a good CRT, and that Philco. They will keep you busy for awhile.:yes:
Ed

Thanks Ed. They will.

I rechecked the CRT this morning. Yup, it checked that good and no shorts or anything like that. No rattles either. This CRT looks brand new and is a genuine RCA 7DP4 CRT. No evidence of being rebuilt either. I'm not sure those could be rebuilt anyway.

Also the TV does not have a back. So, if anyone has one let me know. I'm going to see if I can find a good picture of a back and see it one can be made without too much difficulty too.

Next up, I'll pull the chassis. Stay tuned.

Yes, they could be rebuilt. Scotty at Hawkeye was doing them before he shutdown a few years ago. Pretty much the same gun as any other early B&W CRT. Only difference being the electrostatic focus.

Bob,
OK, I didn't think they were re-buildable. Good to know. Why I think this tube is not rebuilt is that the neck is straight with no evidence of an extension being fused on.

OK, pulled the chassis. There very minor rust spots on the chassis but no big deal. The bottom line is it looks like somebody did a partial resto on it. I should have noticed the fuse holder as my first clue. This one will be a good one that's for sure. Seeing it has been partially restored, should I take the chance and power it up using a variac?

http://i1060.photobucket.com/albums/...psb56dewa0.jpg

http://i1060.photobucket.com/albums/...pspomjesfd.jpg

http://i1060.photobucket.com/albums/...pstz0viznw.jpg

http://i1060.photobucket.com/albums/...ps1v8zqigw.jpg

http://i1060.photobucket.com/albums/...pslclyyu4b.jpg

Well that sure is a nice clean chassis. Apparently the previous restorer didn't have the perseverance and/or resources to complete the project. Some folks very quickly jump to the conclusion that the big bulb must be at fault. At any rate this should be a very educational project.

[edit] Forgot to ask - is there any indication that the electrolytic cans have been restored?

Thanks Kevin.

Looks like the E-Caps have been re-stuffed. I looked closely and I might just power this thing up.

That circle on the base of the CRT with a date code seems to indicate it's a replacement tube, either new or rebuilt, I know they used that style at least as late as 1960.
What are the numbers?

3
---
48

I powered the set up.
First with the low voltage rectifier removed. All the tubes lit up. Then with the low voltage rectifier in but the H output tube plate cap removed. I measured 263 volts! Riders says 265 volts. I received good audio from a local OTA broadcast! Then on goes the H output tube cap connection. No raster. Bummer. Then I remembered the ION trap. Moved it around a little. Nice bright raster!

Hooked up my converter box and now the audio isn't so good on channel 4. But I got a picture! Horizontal sync needs lots of help. I'll bet its a mica cap. All-in-all, this set looks like it'll do good.

http://i1060.photobucket.com/albums/...pskgpdn2ox.jpg

It looks like someone eliminated the PM ion trap and used the resistor in its place. :scratch2:

I think he eliminated the electro-magnet, installed a resistor in its place, and installed a permanent magnet ION trap.

BTW, I'm making a list of all the resistors and capacitors used in this set.

I'll do my usual practice of going up in wattage on the resistors.

I'll use the yellow tubular film caps from Sal or Just radios all rated at 630V.

All micas will be at least 5% 500V rated.

The E-Caps will be 450V or 500V except for the few odd values and much lower voltages. Those will still get at least 250V simply because the leads are thicker and less prone to breakage.

I know there is a door knob cap rated at 500pf but no voltage is given. I'm guessing at least 10K?

Are there any other caps that are rated at a higher voltage? I see C141 a 56pf cap in the yoke. Would this be like a 1KV or higher?

Be sure to check the string of 6.8 meg resistors in the HV supply. Those were a problem for changing value.

The more I see the more I kick my self for not making an offer when I had the chance...I did not want to try to make a new offer-up account at work.

Guys,
I've scanned the Riders info on this TV. It's from Riders TV 1 pages 44 thru 75. I then enlarged the Schematic and Wiring Diagrams and made separate files for those whose size is 36x24 for us old geezers.

I've uploaded them on Dropbox.

The Manual is about 12megs and the Schematic and Wiring Diagram are about 1meg each.

https://www.dropbox.com/s/awm0knizur...anual.pdf?dl=0

https://www.dropbox.com/s/52cxfm9kln...36x24.pdf?dl=0

https://www.dropbox.com/s/ajfa53b9r9...36x24.pdf?dl=0

Looks like there's been some repairs there already. But I agree. A problem area with 621TS's.:smoke:

I meant it the other way around! Subsituting a PM ion trap for the EM ion trap and using a resistor in its place. :scratch2:

Yes, the 7DP4's were rebuildable. I have a Dunbar rebuild in mine, couldn't have seen many hours either since it tests like brand new. That's in my blonde model, I still need to pick up the mahogany one I won out of Connecticut recently.

Just a quick update. I ordered what I need from Just Radios, Digikey, and eBay. Tomorrow I'll enlarge the schematic and Wiring Diagram/Parts Placement drawing.

I got the schematic and Wiring/Parts Placement Diagram enlarged to 24 x 36. Just right!

I then started to work on the chassis. It is bit grimy and it has a layer of white corrosion all over. I think the plating did its job! To clean the chassis right, I decided to pull what I could off the chassis.

I pulled the yoke, the big resistor in the HV cage, HV cage, flyback, and HV rectifier tube and mount, and the resistor cage.

http://i1060.photobucket.com/albums/...pse3512l58.jpg

The big resistor had opened some tome ago and was replaced by 2 10K 20W resistors.
http://i1060.photobucket.com/albums/...ps7z6hruzq.jpg

Here is a picture of the bottom of the socket from the 1b3GT HV rectifier tube.
http://i1060.photobucket.com/albums/...psfizvksz4.jpg

While removing the resistor heatsink cage I found a wire that had barely been soldered on to one the resistor's terminals!
http://i1060.photobucket.com/albums/...psbfr5lf4z.jpg

I'll have more pics later. Lots came off the chassis.

Hey Crist, if you look closely it almost looks like they were soldered correctly at some point in time but the resistor had gotten so hot the solder has run down and has formed a drip on the bottom end of the terminal.

Gregb

Yeah, I can see where you'd think that. But the terminals are shaped like that! I have no reason why.

Here is a picture of the chassis as of right now. I'm going to install the yoke support so when I work underneath, it'll sit on the support and protect the IF Cans. I also cleaned and masked off the sockets to protect them while cleaning.

http://i1060.photobucket.com/albums/...pskzwgpoju.jpg

Here is a close up of the area where the support was screwed to the chassis. It is a good indicator of how dirty the chassis is.

http://i1060.photobucket.com/albums/...psdaim5bdj.jpg

I started on cleaning the chassis. I'm using a green colored cleaner that the wife uses as a general purpose cleaner, and a fine grit Scotch-Brite pad. Then I followed it up using the cleaner and 000 steel wool. Then a wiping down using WD-40. Cleaned up nice.

Anybody know the name of the stuff that you wipe on and it protects the bare metal?

I've got my work cut out for me for the rest of the day.

http://i1060.photobucket.com/albums/...psytbly3yq.jpg

I use Boeshield on bare metal

Steel wool can work havoc if the fine wires get into things. Inspect closely and be sure they're not in there.

10-4

I'm pretty much done cleaning up the chassis top. I still have to do underneath. I didn't use the steel wool. It started to shed and I didn't want those little shavings getting everywhere.

I did remove the big solder blobs that were at each adjustable coil. these will be re-soldered, but neatly this time.

http://i1060.photobucket.com/albums/...psnynhdag4.jpg

I cleaned up the adjustable coils on the top of the chassis in preparation to solder the caps to the chassis. I used my 150 soldering iron to apply a small amount of solder to form a nice fillet.

http://i1060.photobucket.com/albums/...psp2drm7yr.jpg

I then noticed that the hold down screws on T107 were over torqued. It looks awful.

http://i1060.photobucket.com/albums/...ps9ctcfkxl.jpg

So I pulled the transformer and disassembled it. I straightened the screws. While I had it apart I dusted it off and cleaned it gently with some alcohol. These pics are before I cleaned the coil.

http://i1060.photobucket.com/albums/...pseie9brcq.jpg

http://i1060.photobucket.com/albums/...pso1pg7rl7.jpg

I reassembled the transformer and cleaned up the case and terminals. Ready to install.

http://i1060.photobucket.com/albums/...psjgqefk4m.jpg

Re-installed and ready to wire. I'll do that later while I'm recapping etc. I also cleaned up the case on T108.

http://i1060.photobucket.com/albums/...psj7ghizq7.jpg

Next up will be to paint the top transformer cover. The transformer underneath looks very good.

My order from Digikey came in already and while the transformer paint is drying, I'll re-stuff the caps.

Time to re-stuff the E-Caps!

There are 5 of them. The ones that came off the set are on the left and what I'm going to use is on the right. 4 of them use the cardboard covers. One cardboard cover on a shorter caps was already removed when somebody did the partial restoration.

What I plan on doing is to use 5 new bases because I don't want the twisty mounting ears to break off when installing them in the chassis. The cans that use the cardboard covers will be cut off about 1/2 above the base. Then I'll epoxy a PVC sleeve to the base. Install the new caps and slide on the cutoff can. Then slide on the cardboard cover.

The 1 E-Cap that does not have a cover, the can will be cut off right at the base. The base and can will be trued up and again a PVC sleeve will be epoxied to the base. I'll install the new caps, and slide on the polished up can.

I'm using all Nichicon 105 degree caps and most are at least 10,000 hour caps.

http://i1060.photobucket.com/albums/...psbiifbeee.jpg

That chassis looks great all cleaned up. Was just thinking, if makers of slug-tuned radio IF transformers had made them that way, with the little ceramic caps instead of the silver mica jobs, we wouldn't have SMD today. But I'm sure it would have cost more.

Right! As I'm working on this TV, I have noticed the "step up" on the quality of the design. That coil was beefy and well made.

I started by cutting of the base of the donor cap for the tall uncovered capacitor (C116). I use my band saw and shim the can up from the table of the saw using a piece of 1/16 plywood. This gives me a more even cut.

http://i1060.photobucket.com/albums/...psjntyewwv.jpg

http://i1060.photobucket.com/albums/...ps0ew8tfax.jpg

Then on the 4 other donor caps I marked up from the base 3/8. I know I said 1/2 but 3/8 will work just as good.

http://i1060.photobucket.com/albums/...pszfaeqdt7.jpg

Here is what it looks like inside of the donor caps after cutting off the bases.

http://i1060.photobucket.com/albums/...ps0y5cjnq8.jpg

And a shot after I removed the guts from them.

http://i1060.photobucket.com/albums/...ps2oftay99.jpg

Then I took the old uncovered C116 and cut its base off as low as I can go. You can see a little bit of the phenolic base still attached to the upper cans guts.

http://i1060.photobucket.com/albums/...psjysbgyhg.jpg

C116 the tall uncovered cap with its guts pulled.

http://i1060.photobucket.com/albums/...ps324eibjc.jpg

The other 2 tall covered E-caps (C127 and C128) with the bases cut off. These bases were cut off with a 3/8 lip to them so that when these cans are mated to the donor bases they will be the correct height.

http://i1060.photobucket.com/albums/...pshdvi1x0s.jpg

Here C127 and C128 with their guts pulled.

http://i1060.photobucket.com/albums/...psmygkr209.jpg

And finally here is the line up of the 5 E-Caps. L to R are the 2 short covered ones C131 and C132, then the 2 tall covered ones C127 and C128, and finally the tall uncovered cap C116.

http://i1060.photobucket.com/albums/...psuopgwzwn.jpg

I cleaned and deburred the cans and bases.

I then made the PVC sleeves from PVC pipe I got at the Home Depot. I true up 1 end on my disc sander using the 90 degree guide. Then I mark the trued end with an arrow. This is the end that will be glued to the base. I true that end up so the can will stick straight on the assembly.
I then mark off a 1 inch cut line and cut it off using my band saw. I then clean up both ends using my #11 hobby knife and sandpaper. This is repeated for all 5 sleeves.

http://i1060.photobucket.com/albums/...pscymhkfna.jpg

The sleeves are then epoxied to the bases using 15 minute epoxy. I only apply the epoxy to the edge that will rest on the bottom in the base. In the case of C116 were the base is cut off even, I visually align the sleeve to the base.

I then made up my capacitor assemblies. I used Nichicon 105 degree caps that I get from Digikey. The caps are hot glued together and wired using 6oo volt wire. The assembly is put into position in the base and the the insulation of the wires are marked. The assembly is removed from the base and the wires are stripped at the marks.

I use hot glue to glue the caps into the bases. I usually glob on a big dollop and then insert the caps into the bases. This is allowed to set up and the the wires are soldered to the proper terminal. The ground wire is left unconnected till the cap is inserted into the chassis, then it is soldered to a twisty tab.

Here is a picture of C127. BTW, I used 47uf caps instead of the 40uf called for, a 22uf instead of the 20uf, a 82uf instead of the 80uf, and a 270uf instead of the 250uf.

http://i1060.photobucket.com/albums/...psygpojphn.jpg

Here is a picture of C116 before the caps are inserted into the base. It has 4 caps.

http://i1060.photobucket.com/albums/...pstso4zg9y.jpg

Another view.

http://i1060.photobucket.com/albums/...ps5ftcyrsi.jpg

The base of C116 with the wires soldered to the terminal.

http://i1060.photobucket.com/albums/...psd3hp7dfy.jpg

Top side of C116.

http://i1060.photobucket.com/albums/...psv0xbjuf1.jpg

Crist, What kind of blade you have in your band saw that cuts those cans so smoothly? Or have you already cleaned and de-burred your donor cans before you took those first pictures. :)

I think it is an Olson 1/4 .014 14tpi. Haven't cleaned them up yet.

So that's a fairly thin, primarily for wood cutting blade? Anyhow it sure cuts smooth, but I'm sure that has a whole lot to do with the saw operator. :thmbsp: