If you replace those two electrolytics in the voltage doubler circuit you may well get the power supply operating. Either one or both could be dried out to the point that they are no longer capable of doing their job.

You will get the practice in capacitor replacement, as you have many more to go after those 2. But at least getting those done should get you back to a higher voltage level. If a fuseable resistor or sandbrick resistor opens it's almost always all or nothing--to wit you wouldn't likely be seeing the paltry 30 volts you are seeing.

If you have to burn any gasoline running to the radio shop for capacitors you might as well shotgun the entire power supply and replace all the electrolytics; the odds are that they are all not long for this world if not already expired.

"Be careful as some chassis were conected directly to one side of the a/c line so depending on which way the plug is in the wall the chassis may be live or not."

HAHa I learnt this the hard way already. Testing to see if caps are hot Zaap. I was so happy, I thought I got the HV working again. But after some thought I realized it was 60hz because thats just how it felt. Bugger I said( I also didn't think it could get me with just one hand in there...maybe 2 fingers touched)

And just some test results from the caps. I got the charge to go up to 40v. They seem to be fixing themselves a little every time I power it on(30 to 40) But I don't think they will fully recover. Also I measured 60 volts ac With my tester at the same points. And it jumped around a little (40-90 vac).

With this in mind could it be the caps. I wanna say yes. But if anyone thinks its a little far fetched for the caps to bring the voltage from 30 to the proper 250 or w/e it should be. please say so.

Rudy

There goes one of your 9 lives as a repair technician:D

Alright so just wondering if these will be hard to find. Cause I've been looking online and I'm not seeing the exact values. 33 and 220 mfd and stuff
and maybe a guesstimated cost by someone?
30 mfd 300 vdc and it says 375 something ac
20 mfd 300 vdc 375 something
100 mfd 150 vdc 250 ac something

200 mfd 150 vdc

160 uf 300v

and 160uf 150 v

And I turned it on again. Got 45 volts. I should just turn it on 50 more times :P

The second voltages given on those are surge voltages. Not ac voltages.
With today's higher line voltage, I reccommend highly using 450 volt filters.
Bill Cahill

The values of caps is not that critical.Usually the manufacturer made the capacitance as small as possible because back then they costed more than today. The next higher value in cap and the same or higher voltage should be ok. eg. 34ufd 280v ,a 39ufd 350v would be fine. just go higher in cap and working voltage. These days caps come in standard values(same values)as resistors.(39,47,56,68 ect)Just use higher value of cap and voltage and you should be fine and be careful!:yes:

Alright so where does everyone get there caps from?
I went to some places in Winnipeg and it was like 8$ for each 350 volt cap. And at the other store it was nearly 17$. SO maybe the internet is the way to go or something, any one have any suggestions?

Oh and can I use axial caps. The kind with leads on both sides. Or must they be surface mount can type. With both leads on the bottom?
I didn't think it mattered but maybe it does.


OOOO I just found a bag of my capacitors and I had waaay more than I thought
I found a 33 uf 450 dc
a 40 uf 450 dc
20 uf 450 dc
100 uf 250 dc
30 uf 450 dc
i have enough 33 to parralel them up with 100 and make a 160
But these are all axial type with leads on both sides so are they useless? DO they they have to be "radial" (both leads on the bottom)

For just getting the TV to work, you can experiment with any properly rated
capacitors that will fit. Some restorers dismantle the innards of the big old
tubular capacitors and install modern replacements inside. I just saw a thread
for an old Zenith color TV with fine pictures illustrating the latter procedure.
See post 19 in this thread:

http://www.audiokarma.org/forums/sho...=170055&page=2


Be careful with capacitor that have been lying around for some time. Even
though they were never installed, they may have dried out. But then again,
they might work fine. Just be sure not to install them backwards.

Sounds like its worth a try to me. And wow these are tons smaller than the old ones.
I'm gonna switch the ones that I can, as for the one I can't replace should I fear it exploding or anything. Or should I just give it a shot, then replace it later if all goes well.

Electronically, except for the IF strip and the tuner, it doesn't matter. And you shouldn't need to change anything in the IF or tuner anyway, those caps there are usually ceramic discs and rarely go bad.

Even the manufacturers will use axial caps in a pinch where a radial cap was designed for, on a circuit board. They would use caps with leads long enough so they can bend one end over to reach the circuit board with the cap standing upright. They want to ship product, and can't wait around for the radials to show up in a few days.

"Woot I know what I'm doing today then. Maybe I'll have a picture of a working Tv for you Guys today. Or a Tv with alot of blown up capacitors but I don't even care at this pointcause I just remembered I was gonna strip this thing originally.Ha"
I said earlier


Well I went, and was gonna try, till I took a better look. I can hardly get in back there to switch them. They are soldered in pretty well. And since they have 3 caps in one can I can't figure out which mfd goes to which lead. And without a schem I have nothing to go on. And to take the CRT out of this thing Is a big job in itself. The whole actual Tv and all its compenents are attached to a board. which came out of the tv box as a whole. So I at least wanna do all the caps when I do this Job. Not just the ones I can at this moment.
Bugger

It can be tricky to figure out those multicaps but you can do it. Most use this system: on the side of the can it will list the different caps, something like this-
(triangle) 160 mfd
(square) 80 mfd
(half circle) 20 mfd
(no mark) 20 mfd

If I knew what I was doing I would show the actual symbols instead of (triangle) etc, but look at the lable and you will see what I mean. Now, the tricky part. Look at the bottom, next to the leads on that can. Just next to the leads the base will be punched out in the shape of, you guessed it, a triangle, a square, a half-circle-and one won't have any pattern. That's how you can figure it out without the schematic. Still, having the Sams is really nice.

There are several good places online to get caps at a reasonable price. Am I right that you are in Canada? justradios.com would be perfect. Radiodaze is another one I use.

Thank you very much Bgadow
I did notice those triangles and squares. But I could not find them on the bottom of the cap, so I gave up. But like I said before it's almost impossible for me to see behind there just yet. But I will get it all apart and do it. And figure that multi cap out :)
And yes I am in Canada and most likely will use your websites you suggested.
Thanks again

If you look carefully at the bottom of the twistlok can where the live terminals are you will see that they protrude from the innards of the can through what is usually a brown bakelite or phenolic insulating material. On one side of each terminal (except for the "no mark" one) there will be an enlargement of the passage hole in the shape of a semicircle, square or triangle. Or the pattern will be embossed nearby.

Got your schematic!
 

Hello,

I found the proper RCC supplement for your TV, which appears to
go by the name Chassis T-109. Please give me a few hours to get
this stuff properly scanned. Bye for now.

Schematic and a few other pages
 

Hello again,

Here is the schematic (pages 71 and 72), a chassis diagram (p. 41)
and a sample of the service data (p. 38). I am also enclosing the
index from the cover, though the image is quite dirty. I can get you
all the remaining pages if you want. Good luck.

P.S.: I will only send the schematic with this message, remainder
to follow.

a few more pages as described
 

As described in the previous message. Regards.

Canadian set - the schematic references 25hz AC power operation!

You're right, and this brings a question. A transformer type set designed
for 25-Hz will work fine on 60-Hz, with only improved filtering. What about
a voltage-doubler set like this one?

By the way, the actual set discussed in this thread is the 60-Hz model,
as evidenced by the fact that it has a single filter choke.

Damn wish I had looked here an hour ago hahaha.
I just ordered all the caps by tediously looking inside and turning them and what not. But it's all good. :thmbsp: And thanks for the schematic. Hopefully most of the voltages are near spec. I can't wait for those caps to get here. I'll tell you guys what happens as soon as I do.
And I"m pretty sure this set has two Chokes. And it also says on the back it's meant for 60hz.
I can't wait:D
Rudy

It would also have improved filtering, as the filter caps are approx twice the size needed.

Filter Choke
 

Hello again,

Hope the schematic is readable. I can read the posted images on my screen,
but printing yields marginal text for me. Il you look at the chassis layout
(second image in post 57 above), you will see the chokes on the left
side, L-500 and L-501, the latter for 25-Hz only. On the picture you posted
earlier, I can only see L-500. By the way, you could trace the wiring to
this choke and check with your ohmmeter to make sure it is not open.
The nominal resistance (36 ohms) is given on the schematic.

T-301 near the top looks similar, but is the audio output transformer.
Good luck.

I know I have checked one choke. It came in at 39 ohms. The other one is closer to the middle(guess you can't see it in the pic), then yes there is a small trans for the audio output.

Tomorow it's all getting checked and the caps I ordered should be in. So the final word on this TV should be up tomorow. Exciting stuff

What may look like a choke is the vertical output transformer (T-400). It is
shown at the right of V-15 on the schematic. Next to it on the schematic is
L-400, the vertical sweep coil assembly part of the deflection yoke on the
CRT neck. The deflection yoke also contain the horizontal sweep coil assembly
(L-401) shown at the bottom right of the schematic.

OMG I got 300+ volts. But it scared me to let the tubes fully warm up because this 300 volts was higher than the original capacitor rating. Which was just 300v. Any suggestions on resistors to put in series with the diodes to lower this. I know I have some 25 ohmers kickin around.
I wanna see this thing glow!

If it's slightly higher (say, 320 - 340), and starts going down as the set heats up, it's ok - those caps have a 'surge' rating.

Or, you could get a Variac :)

Well I let it warm up fully(after I put in a 25 ohm resistor). And there was SOUND :music:
Yet still no picture. BUT I could definatley hear it sweeping.( The hissing ringing sound you get with all TV's)
But this is no surprise to me as I've only replaced 2 of the 4 large electrolytics. I was just eager, and I know its bad, but I couldn't resist.

So yea that's about it for now. Just keeping all you guys up to date.

And as for the screen not lighting up. Does everyone still think it is because of the caps or is it possibly dead?

Hello again,

Great progress indeed!

Here are a few things to consider, regarding the picture.

You must have high-voltage on the CRT second anode (the terminal on the
side of the CRT with a funny cable ending in a round piece of rubber-like material).
Testing for high-voltage without a HV probe can be tricky, but there are a number
of simple things you can check. You said you tested most of the tubes. Did
that include the HV rectifier inside the metal cage? With power off, and chassis
DISCONNECTED from the line, you can remove the cover of the cage, undo the
top cap of the 1X2A tube and pull it. Be careful when setting your tube tester,
this heater takes a very low voltage.

Also, in the third picture of your post number 19, you showed the rear side of
the horizontal output (=flyback) transformer. I notice that a big yellow capacitor
has traces of heating on it, it would be a good idea to replace it. There is also
another capacitor, a red tubular one with capacitance unreadable, connected
to the damper tube (12AX4GTA). See the resistor alongside this capacitor?
Il looks like it took a beating, the color bands are unreadable. It would be a good
idea to check this against the schematic and replace if necessary.

You may also want to take voltage readings at the CRT electrodes. If you trace
the wires from the CRT socket to the chassis, you should be able to find in particular
those that go to the cathode (pin 11) and grid 1 (pin 2). On the cathode,
according to the schematic, you should get +113 V, and on the grid you should
have somewhere between roughly 0 and +120 V, depending on the brightness
setting.

Also, be sure to measure the cathode voltage on the 12C5 audio output tube
(point V). This tube operates as a voltage divider to provide plate voltage
to many stages in the receiver. The nominal value shown on the schematic
is 132 V. This will confirm that most of the stages are drawing the correct
amount of current.

Good luck, keep the news coming!

REmember the crt acts like a capacitor at the h.v. spot.Take a srewdriver and short to gnd that spot to discharge the charge held by the crt.

Good advice, just be sure to slip the tool gently under the high-voltage
insulator on the CRT, in order not to scratch the glass.

It would be best to first attach a jumper to the screwdriver, connect
the other end of the jumper to the chassis, and then touch the HV
terminal with the screwdriver.

Wellll I did all the tests electroking told me to do.
The 12c5 at cathode has +122v after warm up.
Pin 11 of the picture tube has 120-140 volts depending on channel.( Tuned or not tuned)
pin 2 goes up to 70 volts then down to zero as you adjust brightness.(not exactly 120v)
The resistor you mentioned I also suspected of being shot. But with very close inspection you can still see a brown then green then brown stripe. JUST BARELY. And the resistor reads 127 ohms on my meter(Which is not the greatest, but it works) so it's kinda close. But maybe not close enough?
The capacitor you saw I will replace momentarilly I did order some of those charred brown looking ones. Also the one paper cap in the tuner circuit.

Oh and I almost forgot. I do think I tested the HV rect tube when i tested all the others. I'm pretty sure it was within spec. And I know that I am always very careful pulling things like that out and putting then back in. SO I'm pretty sure that tube is fine but if you insist I check again I will be glad to.

And the HV is in the thousands I am guessing. So it would probably blow my meter which only goes to 1000vdc.

Could those little paper caps really be stopping any picture from being produced?

I also have one more electrolytic I should change. But I dont have the exact replacement. It is 200 mfd. and I Have 100 and some 30's. I think I may just strap them all together till I get close. It's better than nothing right?

Rudy

P.S. What actually makes the picture tube glow. With these voltages should I at least have a dot on the screen already?

Hello again,

To answer your question, if you have correct voltages on the electron-gun
electrodes, you should get a spot on the screen, but only if HV is present.
Your measurements show positive results, but there are many more things
to check, and because of the distance I cannot think of all of them at once!

In my opinion, the next step would be to measure the cathode voltage
on the 12BQ6 (or 12CU6) horizontal output tube (pin 8). The schematic gives 3.6 V
across the 33-ohm resistor, which corresponds to about 110 mA cathode
current.

It gets hard to go much further without an oscilloscope, but let's see what
you get. Bye for now.

P.S.: for anyone just joining this thread, schematic is in post 56 above. Regards.

P.P.S.: also check voltage on G2 (pin 10) of CRT, this will tell whether the boost
B+ generated by the horizontal ouptut circuit is present. Be careful to use the
highest range on your multimeter.

Ineteresting.....Because there is no 33 ohm resistor hooked up to that tube. And the voltage I got across pin 8's resistor was only .5 volts. This is the one that you said looked burnt or possibly dead. and it supposed to be 150 ohms according to it's bands.
I will go look some more and also test the voltage at from chassis to pin 8 and see if i get the 3.6 volts it should have.
And I looked at the screen and I'm not seeing any bright spot. And I can clearly hear the buzz/whinning sound most crt tv's make. Is this a good sign the ht is working?

Cause if so..It brings me back to my original thoughts which is that the pic tube is dead......But I really hope not.

I did the test from pin 8 to chassis . Only .5 volts .....

Little more info: I made the other 200uf and put it in. Then replaced that yellow cap which was burnt. And still no picture.
And this scared me. But every now and then I hear arcing.....!This is during tube warm up and I always shut it off asap! It may be from my shabby work I did putting in the caps but boy was it scary. Usually it doesn't though

wiring around horizontal output tube (V-18)
 

All right, let's not get confused here. Looking at the schematic around V-18,
I see:

cathode (pin 8) connected to ground through a parallel network of
R-453 (33 0hms) and C-439 (.1 mfd 200 V);

grid 1 (pin 5) connected to PC board through R-450 (150 ohms);

grid 2 (pin 4) connected to width control through R-454 (680
ohms).

If you found a 150 ohm from cathode to ground, that is strange, and
probably the sign of a previous botched repair. But maybe the 150 ohm
resistor you saw was R-450 above. Just as a reminder, the pins are
counted clockwise as seen from the bottom, starting from the indexing
tab.

The buzz means that the horizontal oscillator is running and probably
being amplified by the output tube, but until the circuit is fully functional,
no normal operation will happen. If you get the chance, please do check
the G2 voltage of the CRT. As I told you, this is fed from the boost
voltage generated by the damper tube (V-20), and is an indication of correct
operation of the sweep circuit. I bet this is not OK at present.
Good luck.

Sounds good. Gimmi half an hour maybe less

Ok and I have checked checked and rechecked pin 8. It does have a .1 mfd cap but its definatley a cap that has brown green brown bands on it. And it measures in at 126 ohms or so. It doesn't really look like it was put in by someone else, but who knows.

And another side not... There is a wire in the crt pins that connects two of them together. It looks like it is supposed to be there. And in the schem I thought I saw something that resembles this on the schematic so it may be right BUt just thought I'd put it out there. Its from pin 10 to pin 6 of the crt.

And you are onto something here. My meter gave me zero volts at pin 10 of the crt. 0v And the damper tubes seems to go through a variable resistor before reaching the crt, if I am right. This is for adjustment for vertical height located at the back of the TV.

"This brings me back to arcing. It seems the damper tube is connected to the same hv coil as the 1x2b.(I'm guessing that's how it boosts it) When I had the cage off I saw this transformer coil w/e it is. It sorta looked chipped The rubbery coating sorta flaked off. Maybe the arcing happened there somewhere causing some sorta problem with the damper tube causing my 0 voltage at G2. This is just a huge guess but I noticed there connected through this so it could be true. " This is a BIG GUESS

Hello again,

Maybe the cathode resistor is correct after all, but if you only measure 0.5 V across
it, it means current is only 4 mA, definitely low.

(What I meant here is that sometimes component values are changed in production).

The jumper you see at the CRT pins connects the focus pin (6) to either pin 2 or
10, as selected for best results when installing the CRT. This is no problem.

I think I will call it quits for today, don't give up hope, the diagnosis will come up,
and the cure will follow! Let me know what you find out, but as I just said I won't
be replying until tomorrow. If anyone else wants to join in, I trust you're welcome.

Yea if any one has ideas or things for me to check just say it. Nothing sounds stupid to me and it's all worth checking.
And ElectroKing your help is greatly appreciated. And yes we will tackle this problem another day still :thmbsp:

Oh and if anyone is having trouble reading the schematic open it in paint and invert the colours. It helps.

New Info: The damper tube produces 350 some odd volts. Then it goes down through a 270k resistor(that reads 350k on my meter) and goes directly to G2(pin 10) of the CRT. At the Crt the voltage on G2 is 250 volts.
Tell me what you guys think. I must have fudged my first test.

Two more ideas, and I promise I close Audiokarma for the night!

1 - Capacitor C-440 (0.068 mfd, 600 V) just below the damper tube on the
schematic is a filter for the boost voltage rectified by the damper. If
it leaks, it may lead to the loss in voltage observed. This capacitor
has a low capacitance here because the frequency is high (15 kHz, not
60 or 120 Hz as in the power supply).

2 - With power off, the main winding of the flyback could be tested for continuity.

From top to bottom, the terminal numbers and resistance values are:

7 (cap of HV rectifier)
460 ohms
6 (cap of H ouptut tube)
24 omhs
5 (cathode of damper)
4 ohms
9 (end of winding in deflection yoke)
31 ohms
3 (end of C-440 not connected to plate of damper)

Note that the first section has higher resistance because it has many turns;
it is the part of the transformer that generates the high voltage pulses
to be rectified by the 1X2.

If the readings are approximately OK, the transformer is probably still good, even
though there may have been some arcing in the past.

Good night.

Do you hear a raspy low frequency sound? Like a little motorboat motor in there? If so, the vertical is working and you no doubt have at least functional horizontal.

Don't overlook the obvious - the brightness might be down on the TV :)

You can't, unless you can easily (safely!) see up into the HV rect, see it glow normally. BTW, if you get an HV *pop* when you discharge the CRT, you no doubt have HV, which is going to be on the order of 12,000 - 16,000 or so. If you've got a hissing - like a gas leak - coming from the HV box, you have HV, and a good amount. Shut the set, discharge it well, and CLEAN THE HV BOX. Dirt might cause leakage, arcs, flashovers, and scary things that can be bad for the set.

Don't ever measure the horizontal output tube's plate - there's a big pulse riding on it.

BTW, sounds like you're gonna need an oscilloscope - get one that can go over 10mhz. They're cheap and a great investment.

Ahhhh I was checking those resistances earlier. They seemed alright but I did not check from 7-6 or the nine one. So I will do this.

And this has been driving me nuts. On the schematic you sent me v-2 is on the left and v1 is on the right.
But on the back of the TV in its tube diagram V1 is on the left and v2 on the right. SO I checked the tubes and surley enough they were as the schematic you sent me v2 left v1 right. BUt on the back of the tv (Which had to of been right for this model) It is reversed. SO if the tv's original cover does not lie. These tubes are reversed. And need switching.
I will put a picture of the tv's diagram momentarily.
Also one of these tubes was a weak one. And if they really are in reverse maybe it is because the heater voltages were different causing earlier melt down.


Hmmmm... no motorboat noises. But I will listen harder.
Haha I also thought the brightness might be the cause. So I fiddled with all the controls and it just wouldn't work.(Bummer)
But cleaning it sounds like a good idea. It was very dusty. I'll blow it out tomorrow when I am checking the coil resistances

Pictures in 2 minutes