Hello..my first TV
 

Hello to all.
Being a somewhat new member, this is my first post. I have been repairing/restoring radios and jukeboxes for many years but this is my first attempt at a television, so I have a few questions to get me on the right track.
First the hardware.... I picked this set up at a local auction. It is a Canadian General Electric model C2511. From the photos he posted, I believe that this is the same set that Tonyf had questions about in this post... http://www.videokarma.org/showthread.php?t=270485
The set appears to be in pretty good condition. Cabinet needs some work, but the chassis(s) look good with no rust or signs of rodent damage. The CRT (10fp4) tests good on my Sencore 465 with no shorts and an acceptable cut off voltage.
I figure that this set is a suitable candidate for restoration given the fact that I only have 30.00 invested and thanks to Mr. Covid, I'm going to be locked in the house with it for a while. I was able to obtain all print materials for this set from Radiomuseum as well as from Ronl.
I plan on replacing the electrolytics and all paper/wax capacitors to begin with which leads to my first question... must I use exact values for replacement or can I use the more modern equivalents? Such as .47 to replace a .5. I know that in most radio circuits this practice is acceptable, but never having worked on video circuitry, I just want to double check.
Once I get the capacitors done and have a chance to check resistors and make sure that everything else appears well, I will probably have some more questions prior to firing this beast up.
In the meantime, if anyone has something to add along the lines of things a beginner should know, please chime in..

Don

Really, the same general rules apply as for a radio, so yes, modern equivalents are fine unless you find something in the service literature that specifies a tighter tolerance.

Edit: Oh, and Welcome!

Finally got started on this beast. Being a Canadian model, it is set up for 25 cycle operation and has a separate chassis for the low voltage power supply. It is just a little thing :tongue:.

First thing I noticed was that the two rectifier tubes were 5R4-GY rather than 5V4G as shown on the chart. I don't expect this is a problem. One of the two tubes tested dead. Digging a bit deeper, I found that one of the two 30 mfd filter capacitors associated with the dead tube displayed a pretty much dead short. The date code on the caps indicates that they are the originals. All windings on the power transformer and choke associated with the bad capacitor ohmed out fine, so it doesn't appear that the problem extended beyond the dead tube. Hopefully, this failure was the reason the set was retired many years ago.
Anyhow, will restuff the electrolytics and replace the few paper/wax caps and a few resistors in this chassis and that should take care of the low voltage chassis.Then on to the main one.
Since I have one dead rectifier tube, should I replace with the 5R4-GY as was there, or should replace with 2 5V4Gs as called for in the tube chart??

Both tubes have the same pinout and the same heater voltage and current so the transformer doesn't benefit from either one.
The 5R4 is rated for higher max plate voltage and plate current so I'd stick with it.

The task continues...
Main chassis is on the bench. Check the tubes, clean things up and get to work on the guts.
First thing I notice is the HV rectifier doesn't look right. All documentation calls for a 1B3. Pretty big tube. What's there is not. It is a 1X2B. Since I don't think this tube was even thought of when the set was made, it can not be original. The retrofit appears to be very well done and I suspect the set was probably functioning fine after the modification was made, so you think I should treat it as original and just continue on with the recap and other work?

Looks ham and egged (mmmmm...ham and eggs...).

It will work, but the 1B3 has more headroom in the peak voltage spec and a tiny bit more current than the 1X2.

In a B&W TV, the lower HV rating of the 1X2B may not be a problem. But I'm sure it did work fine.

Strange though that it was modified. The 1B3 is still plentiful even in the year 2020.

John

Other than pin locations on a different socket, I'll check and see if any other mods were required to accommodate the 1X2 sub. If nothing else has been drastically changed, maybe I'll re-change things back to original with the 1B3. Good idea? or a lot of unnecessary work for no gain? Will the octal socket mount as the present one is?

Here's an article about new tubes introduced in 1949, including 1X2. That'd be congruent with your set's vintage.

https://www.americanradiohistory.com...-Page-0027.pdf

It's obviously original to the set.

I'm thinking it's original too. For example Admiral started using 1X2 in 1949 in their 20 series chassis.

The subject of this memorable thread was a Majestic set of about '49 vintage, and it used a 1X2. This feller started as a total noobie too, and cut his teeth on this set. Finally got it goin' like a boss.:yes:

http://www.videokarma.org/showthread...onarch&page=11

This is interesting.
Could this be an undocumented change? I have the complete service package , including revisions, from the General Electric Radio and Television Service Manual 1945-1949 courtesy of Radiomuseum, as well as copies of the RCC schematics of both the 1st and 2nd runs of production courtesy of RonL. Neither of these sources make any reference to the use of the 1X2B. This set has a serial number just into the range of run #2. R224581 started run 2 - mine is R224680. Would this qualify it for any possible undocumented late run changes?

I think that back in those days, they just did whatever they had to do to make the sets work and keep the assembly line running.

They made changes all the time, some for cost, some for performance improvements, some for parts availability.

It's possible that there could have been a service bulletin issued but no subsequent reprint of the service data.

It would seem though that the tube complement chart inside the TV would at least reflect the change. On one of my TVs, the tube chart had the changes rubber stamped, but if yours had a sticker over the rectifier - maybe it dried up and fell off? Any sign of glue remnants around the rectifier position on the chart?

In any case, the tubes are close enough not to matter IMO.

John

Thanks for all the feedback. Looks like I'll just carry on and treat the alterations as original. Took a close look at the tube layout chart in the cabinet and there doesn't appear to be any changes or signs of changes ever made to it. As I said at the beginning of the post, this is my first attempt at a television, and I'm finding it an interesting effort so far.
About half way through the recap.. lots of drippy wax jobs to change, but there are numerous modern version under there as well. I expect this set was reasonably well serviced in its life before me. I have attached a photo. Should I need to replace these guys as well? They are over speced for the job being 1000 volt in place of 4 and 600 volt units

Is that ceramic across the line? If so, you should replace that with an "X" type capacitor.

But I remember back in the 60s when RCA had a recall because they had brown plastic caps right across the AC line that would fail and spew carbon and metal bits like a blowtorch. The cap RCA supplied looked like that ceramic, and I never saw one fail, but X and Y caps are now used for this purpose.

John

No, the photo shows part of the vert sweep circuitry, only a few of 5 ceramic bodied caps under the hood. I already put safety caps across the line.
Do you think I should be safe leaving the ceramic bodied caps there? They are not original, as the parts list specifies paper/wax where they are.

Unless someone else has info that I don't know about, I'd leave the ceramic body caps in there assuming they're the same value (or really close) and equal to or higher than the original voltage ratings.

John

Flat ceramic disc caps are usually best to leave unless tested defective, BUT tubular ceramic bodied caps (as the last picture on the last page shows) should always be changed.
Disc ceramics use ceramic dielectric and rarely fail. Tubular ceramic caps usually are paper dielectric and are VERY high failure. Paper dielectric capacitors are not just paper/cardboard tubes they were sold in plastic shells (I see some in your pictures too), ceramic shells and metal shells....No matter the shell material paper dielectric capacitors are BAD and should be changed.

The plastic shell caps and ceramic shell paper caps are known to explode when they overheat.

I can't express how much I appreciate the guidance you folks have been sending my way. Makes this task a learning experience..
So the recap continues along with checking resistor values. Have only found 1 resistor that hasn't measured almost right on as have all the others. Most have been within 3% of marked values. The one bad one was marked 10k and measured 251k:thumbsdn:.

Next question regards a selenium rectifier within the filament string. I have yet to test it and am just wondering if I should just replace it since I'm in there.
Would a couple of 1N4007s do the trick? Part sheet just describes "selenium rectifier" nothing further. What purpose does this serve?

V2, whatever tube that is, gets filtered positive DC on its heater, supplied by that circiut. The little selenuim is a full-wave rectifier. If replacing with Si diodes, you may need to bump the value of that 1 ohm resistor up a bit to avoid overvolting V2's heater.

Scratching my head here... why is V2 heater also connected to the upper leg of the AC heater supply? :scratch2:

What is V2 and what is its function?

jr

Coot,
V2 is the oscillator tube on the tuner... pretty sensitive area to be messing with if not necessary I expect. Maybe I best leave it be for now.

jr,
Tube is a 12at7. Split filament maybe?

Yes, so indeed, the heater for 1/2 of the tube runs on AC and the heater for the other 1/2 runs on DC.... I don’t believe I have seen that before. Curious! :scratch2:

jr

Yes, the whole 12AT7, 'AU7, 'AX7 family have split heaters with pin 9 as common. So they can be run in series on 12V, or in parallel on 6V. But V2 in your set evidently has 6V DC on one and 6V AC on the other.

(Edit) jr_tech nailed it first. I never seen that arrangement before either. Just a SWAG, but since V2a is the tuner's oscillator, the DC heater scheme is to minimize 25 cycle "FM-ing" of the oscillator.

Just a quick pic of the schematic showing the tube's full use.

Thanks! oc’s theory is likely correct.
Interesting!

jr

This made me wonder as I had never seen a ceramic tubular fail, but then, my experience has been limited from 70s TVs until present.

I took this cap from my old TV stock:

https://i.imgur.com/ylTauxc.jpg

...and cracked it open. What I found was that this capacitor is a foil and plastic film, not paper. This cap would have been factory installed from the 60s to the 80s in a transistor TV, so perhaps paper ceramic caps were gone by then.

https://i.imgur.com/XWf07HG.jpg

But what the heck, caps are cheap enough and cheap insurance. Change all tubulars seems to be good advice on tube TVs. I suspect any ceramics in later transistor TVs are fine.

John

They made those ceramics as far back as the 1950s. Most caps before 1960 were paper. I believe 58-64 were the transition years from paper to film. I have seen those ceramic tubulars bad in mid to late 60s TVs recently. I have also found some defective orange drops in 60s sets. And some 30s-50s sets are having substantial mica cap failure. Anything over 60 years old that isn't in a vacuum is potentially subject to degradation so suspecting everything is valid. I tend to consider ceramic tubulars as being much much worse than the other caps mentioned.

It is possible those tubular ceramics are good in 70s sets but they were the among the safety caps recalled in early 70s SS Zenith sets, and (8 years ago when I was buying parts local) I had a NOS 3KV tubular ceramic I was told was film that had a higher voltage rating than the 2K the circuit specified dead short after a few months... Because of all that I just change them all so I don't have to worry.

Those Zenith caps weren't ceramics. They were wrapped plastic made by American Radionics IIRC. I think I may have one. I'll look for one tomorrow.

I changed a hundred or more of those for that recall campaign (along with some yokes, vert output modules, and CRTs) and the replacements were made (I believe) by Sprague. They looked like huge four lead Orange Drops.

But I did see some of those ceramics fail in GE SS TVs now that I think about it. Those were retrace capacitors on the horiz output, and if one opened, they would cause excessive HV and over voltage of the collector of the output, like the Zeniths did, but never blew a yoke or CRT. We learned early on that if a GE had a blown horiz output, just change the caps under the heatsink.


John

Took a small rest to digest all my Easter eggs, now onto the electrolytics :D.. My original plan was to do the terminal strip trick, however, this huge uncluttered chassis is so stuffed with components in the one area I need access to that I will be restuffing..
The two top units in the photo are quads with so many wires attached that its going to take me most of the afternoon just to mark things up so I can get them out. I just finished restuffing the single unit on the bottom. It is the 2000 mfd unit tied into the selenium rectifier which I have already mentioned earlier in the thread. The one ohm resistor attached to that one actually still measures correctly.
I am still wondering if I should replace that selenium while the chassis is on the stand. The fact that it is such a low voltage and current unit has me wondering if its still good for the long haul, but I would hate for it to fail a short way down the road. Thoughts?

I'd say better to do it now than have to haul the chassis out again later, since it's already a known failure point.

Seleniums don't age well. I'd replace it with Si diodes. Then if the supply is outputting more than 6.3 VDC under load, bump up the value of the 1 ohm resistor as needed.

Tomorrow's task... Just as the schematic shows for the selenium I expect... ac in at both anodes and dc out at the junction of the two cathodes?
(my inexperience is showing:scratch2:..

Yupp. And with Si diodes, the banded end is cathode.

In the future you'll probably encounter seleniums having a + sign on the cathode, which seems dumb as heck.:screwy: The only rationale would be "The B plus comes outa here"

they taught us how to remember diodes LONG ago in electronics class, " A = arrow for anode "

also the mnemonic for resistor color codes that was VERY un-PC :o

Thanks guys..

Another question. With all the interconnect wires coming out of the chassis, I failed to notice, until now, a somewhat random looking wire emerging through a non-factory looking hole on the rear of the chassis. No connector, in fact no exposed conductor. Tracing the wire to its source, I find it attached to the plate of the 6AL5 "clamper" tube. Now, the socket of this tube is enclosed in a screwed down metal shield so access for any reason would necessitate first removing the shield. I am wondering if this was added sometime in the set's life to enable plate voltages to be measured for service purposes..
Stupid question...Should I just leave it hanging out? Could leaving it there possibly introduce any instability due to the fact that it originates in a shielded part of the circuit?
Also, the 1/2 watt resistor that is also attached to pin 2 is reading high , about 2.3 meg should be 1.5 meg according to schematic was getting ready to change and just looked at the parts list to confirm the power rating. Parts list call for 3.9 meg. I suppose I should go with what's already there. I'm colour blind but wifey confirms its brown, green, green.

The 6AL5 is associated circuit-wise with a 6SN7 (V11). What circuit is this in? Sync?

The 6SN7 is the phase inverter/clipper sync separator circuit