Repair of Canadian RCA B&W TV chassis CT1905A 01. (tv model 19TC318B)
 

Hiya folks, I'm new to the forums so don't bash me too much ahaha. I recently purchased this older Canadian RCA television. i replaced all the wax/paper capacitors but haven't gotten around to the Electrolytics.

I had ordered separate capacitors in hopes to replace the ones in the metal cans but can't seem to figure out which lead would go where.. I have 2 small 10uf ones and a 22uf one.

Sorry for the super embarrassing question, It's my first vacuum tube based anything.

The metal can is the - terminal. The ones insulated with rubber are the positive ones, with color-coded terminals (for the older cap).
For the new cap, the - terminal is indicated by a --- strip if is radial, or if is a axial cap, the minus terminal is at the side with metal, and the + is where the rubber is located.
In the Internet various sites can explain about it better.

Hi Alex, I think i understand what you mean, The minus leads of the newer capacitors should be grounded to the chassis, as per the original metal 'can' was. And the positive leads would respectively go the wires that were unsoldered.

Simple enough i reckon if i'm not mistaken, What i can't seem to figure out is which capacitor leads into which wire. The original innards of the electrolytic was pure liquid minus the rubber/latex insulation...

Correct about it being colour coded. i do see a red lead. a golden-ish coloured lead. and a silver lead. however there is no indication as to which capacitor 'positive' would go into which lead. And i can't seem to find a schematic for it either. thus my situation this moment.

This cap is very confuse, really...
At first "seems" to be a 10+10+20µF cap, but then the instructions are not so clear... indeed, if it have 3 terminals (in the rubber seal), one can be 10µF, other 10µF, and the remaining be 20µF (the one with less voltage rating***). Now, if have 4 terminals, the four is common to what ones?

Normally these caps all share the can as a negative terminal, but I dunno if is a special part with some internal isolated cap, or a series combination.

If anyone know about this type of cap, will have less guesswork...

***this can help to try to find about the circuit connection; for the 20µF, will go to a circuit with less voltage

I agree the labeling is confusing. It's a British cap design (Don't think I've owned any British made electronics)so it's different than an American can.

The 50V caps positive most likely goes to the cathode of the audio output or vertical output tube and would be in parallel with a resistor going to ground. You can probably identify it that way...If that doesn't help you might want to get a 22uF cap with the same voltage rating as the 10uF caps have (that way it you mix them up they won't explode...most sets won't be bothered by that much capacitance difference, and you can always use a replacement with a higher voltage rating than the original.

One other way you can possibly identify which is which is if the set will still run on the old cap measure the voltages on the terminals with the set running....one should be under 50v the rest should be significantly higher.

Hi Electronic M.

I see what you mean about the Resistor soldered/grounded to the chassis. On one of the lugs of the electrolytic before i had taken it out there was a resistor connected to it, with an additional yellow wire trailing off onto one of the vacuum tubes. It could probably be assumed that is what you meant for the 22uf capacitor. I'll see if i can show ya some photos just before i get into any soldering just to be sure!

I had posted on RonL's post in hopes to find a schematic(obviously in his own time).
The old capacitor is literal mush and liquid so it wouldn't work out to test it...

Anyways here's a bunch of pictures.

https://media.discordapp.net/attachm...507&height=676

https://media.discordapp.net/attachm...507&height=676

https://media.discordapp.net/attachm...507&height=676

That resistor goes between the chassis ground and the silver lug which is also connected to a yellow wire, there is a purple wire connected to the red lug going towards the left side of the chassis into what looks like a resistor and a round radical ceramic capacitor.

And the gold lug goes between that sand encased 2200ohm resistor that is 5 watts and connects to a vacuum tube, and another white/red wire that connects to a different vacuum tube...

I'll take more photos and draw out what i mean that'll hopefully explain it better then i seem to be able to ahaha

Hi everyone. I'm sorry for the lack of posting it's been kind of busy here.

I took the advice of Electronic M and soldered the capacitors. negatives to the ground. and each lead to their appropriate wires. The 22uf 50volt one to the yellow wire and resistor parallel to ground. and the other 2 10uf 450volt ones to their respective wires. I powered the television and it booted up properly. I didn't leave it on for a long time. Only for about 20 ish seconds, As that was the time it took for the Amazon stick that i have connected through a Some adapters to boot up to the menu.

I'm assuming if i did it wrong there would've been some sort of failure within that 20 seconds of time booting up. There was still a little bit of a hum still but it wasn't as bad. I'm assuming that it might be caused by the RF adapter i'm using being cheap.

Unfortunately with the way it was situated i couldn't reuse the original canister for the electrolytic, I decided to keep it off the chassis. The capacitors are all 'floating' so to speak, They're all soldered appropriately, With very strongly adhesive electrical tape. and heat shrink to ensure the none of the connections or joints are able to touch eachother. or anything else.....

I still have to replace another electrolytic canister which i have to replace. It's certainly much more easier to identify what goes where as there are markings with shapes on them. which describe what is what. which i'll probably change out after the holidays..

Hi folks

Finished the last of the electrolytic replacements. All went well until it turned on. Screen came on for about 4 seconds and then went from a normal picture to pitch black and then the chassis started to spark on the underside where i couldn't see. I immediately turned it off and discharged so i can pull it out and review my work.

No burn marks. no melted wires, None of the capacitors i changed were bloated, poofed. shrunken.. So i thought okay maybe it was a freak accident. something might've been touching. so i immediately isolate EVERYTHING in the area. like completely overkill. And then turn it back on. It turns on! no sparks! hurray!... But now there is vertical failure.

https://media.discordapp.net/attachm...321&height=350

I feel actually sick to my stomach. So I'm going to leave it be.. No idea what to do now. but I guess no Christmas movies.

Hi to all,
Hi Ruru,

OK, loss of V scan, although depressing, should be fixable.
Please turn down brightness to just visible, an overbright single line can burn-in the CRT's phosphor.

some ideas :
contact RonL here, he may not have received your request :
https://antiqueradios.com/forums/vie...2378&start=180

Please post exact & full TV model on chassis sticker or metal plate or rear of TV. Sometimes, it's just a series of letters & numbers inked somewhere on the metal chassis.
RCA B&W TVs of the 50s use probably quite identical schematics in USA & Canada, maybe we can find the US equivalent on the ETF Museum (Early Television Museum) schematics database (see below).

All RCA post-WWII B&W ETF schematics are here, includes some Canadian models (scroll down).
Search is by chassis #, be sure you have it for your TV :
https://www.earlytelevision.org/tv_s...grams_rca.html

As you have already "recapped waxies, etc.) think of simple things : corroded tube pins or socket, socket contact not gripping well tube pin, noisy/cut track inside V Height pot or Linearity pot.

Do you have an oscilloscope ?
if so, you could trace V oscillator operation, then follow the signal to V output tube.

The V section of a B&W set is quite simple: Sync separator, V oscillator, V output tube. If the tube location sticker is still present, it's easy to find the 2 or 3 responsible.

A word of caution ! if the TV is "Hot" (transformerless), you will need an isolation transformer powering the TV to safely connect a Scope.

keep us informed of progress or difficulties...

Best Regards
jhalphen
Paris/France

PS : i suggest you change the name of the thread to "Repair of Canadian RCA B&W TV chassis xxx (or model xxx).
it will greatly help future searchers & collectors.

Hi Jhalphen, Thank you for the reply!~ I'll try to answer to the best of my ability.

I believe the loss of Vscan has to do with the Type FP Electrolytic capacitor that was replaced last night. It was suggested that a 40UF 350v cap was replaced with a 47uf 400v cap. As it was described to me as being the 'Modern day Equivalent'.. I believe this to be most likely the cause of the failure. however i am not certain.

Using the diagram on the back of the television which lists the tubes aswell as the output. I can say it's my opinion that the Vertical output block i'm fairly certain is what sparked up like a rocket. However on inspection i didn't see anything that would elude to damage last night. I'll be reviewing it again now that i have some free time.

I've contacted RonL and he mentioned taking a look for me! Incredibly nice of him to do so. I've been waiting to hear back but as it's the holidays I'm certain that everyone is just busy.

The Chassis Model is CT1905A 01. The model of the television is 19TC318B .
It seems that the schematic can be found in a book called RCC Television service manual. 1964 Supplement NO. 49

I do have an oscilloscope however i don't know how to use it unfortunately. I had borrowed it from someone else but hadn't actually had needed to use it. The television i believe does have a power transformer in it. or what I'd describe as one. but being unable to use the scope confidently I'm unsure if that'd be the greatest route to go.

I'll certainly try to change the thread name however i can't quite seem to figure out how to!

Hi to all,
Hi Ruru, Thanks! for the reply.

Precise model # and chassis # is precious data.

About the electrolytic cap you replaced, it's spot on. 7 microfarads higher has no importance. Electrolytics, historically, always had very wide % variations, often - (minus) 5/10% and + 20% tolerance.
I think you wired it in correctly as +/- polarity inversion usually results in a show display.
However, with the evolution of markings & brands, some have the + clearly identified, on others, a black line indicates minus (and no + marking). When replacing many or if tired, we all make mistakes sometimes, even the best of us.

V output tube "flash & bang" (once): could be a partially shorted/intermittent tube. Have a known good or new one to substitute?
Tubes are tough animals, but the TV is from the 60s and may have been watched thousands of hours.

Thread name change: you created the thread; go back to your first post and you should be able to edit the title.

Best Regards
jhalphen
Paris/France

Hi Jhalphen. Sorry for the later reply it was rather late for me when i had replied.

I'm happy to know the 7uf different wasn't enough to cause an issue. All negatives to each capacitor are marked with a - symbol. And also have shorter leads. They were all grounded to the chassis. And each positive went towards a certain coloured wire or wires marked with symbols, And those symbols were marked on the electrolytic with each value, Which is how i replaced the capacitors all together.

https://media.discordapp.net/attachm...507&height=676

That shows the underside of which wire is which for which symbol. Here is the canister.

https://media.discordapp.net/attachm...901&height=676

https://media.discordapp.net/attachm...507&height=676

I'll have to grab some more photos of how i wired it. And showing which capacitor goes where. Which will hopefully help out. I unfortunately don't any other vacuum tube technology. This is my very first one.

If the set used the transformer to power the heaters (they'll be parallel wired if that's the case) one thing you can do as a diagnostic check is use a clip lead to connect the grid of the vertical output tube to the heater. The 60Hz 6.3v sine wave of the heater will be amplified by the output tube if it is good and make some sloppy unsynchronized vertical deflection. That test confirms the output tube, output transformer and yoke are OK... If you don't get some deflection focus troubleshooting on the output tube, transformer, yoke and the B+ feed for them. If you do get deflection with the grid to heater jumper then remove the jumper and focus on the oscillator.
There were a variety of oscillator circuits some create the whole drive signal in the osc tube and feed it to an output that's just an audio amp, and others (multivibrators)use feedback from the output (usually plate) to make the oscillator oscillate.

Hi to all,

an attempt : entering RCA chassis # CT1905 into a Google search lands on this ETF document, a RCC Canadian TV chassis database & schematics.
The 10 page (3.9Mb) document shows schematics used in chassis CT1905 & CT2303.

@Ruru : does this bear any ressemblance to your TV ?
https://earlytelevision.org/pdf/rca_ct2303_canadian.pdf

Best Regards
jhalphen
Paris/France

Hi Jhalphen. Reviewing the document you sent. The layout of the tubes located here

https://media.discordapp.net/attachm...ality=lossless

Seem similar to my chassis. but i've taken notice that not all the tubes are the same. And there are some differences between what's written there and on the diagram at the back of my television.

https://media.discordapp.net/attachm...507&height=676

Here is a topdown of the actual chassis before i replaced anything when i first bought it. Before i had an actual area to work on it.

https://cdn.discordapp.com/attachmen...b3e619f3a88bf&

The chassis is listed on the PDF document you posted however the pages sadly aren't there. It looks incredibly similar to my perspective but just enough differences to where i'm not sure i'd fully rely on it