Zenith porthole 24G26 no vertical

[kramden66]

maybe one of you can give me an idea where to go , only has a vertical line that you can't do anything with , you can see it react when you do the height , lin , even the expander switch but it stays a line but you see it reacting , it doesn't grown, the output tranny reads ok in ohms , its tough to figure out all the voltages since they aren't writen and this is all there is , no other sams coverage , no service manual , any idea what to do ? should i be looking at the osc ? i don't know the voltages ( all of them on the osc or output they aren't writen on schematic ) l70 seems ok too.

http://www.cerant.com/TV/TV%20Zenith...Ds/SD24G26.pdf

thats the schematic

thanks
mike

[sean]

If it is a vertical line then there is nothing wrong with the vertical. You have a problem in the horizontal but it would be after the flyback since you can see a line on the screen. Maybe an open horizontal coil on the yoke (L61 or L62)?

[kramden66]

what i meant is a line going across the screen , a horizontal line showing that there is no vertical sweep, i didn't think of trying the yoke but could check there.

mike

[Kevin Kuehn]

Voltages are listed on Riders schematic. Unfortunately I don't have a way to scan or copy the large format pages. Here's a picture of the vertical section. PM me an email if you can't read it here and I'll send a higher resolution picture. [edit] Well that's not going to help you much, I see it's the same schematic as Sams. But there are some tube pin voltages listed on both.

[kramden66]

all i can recall is that pin 3 of the 6v6 is the right voltage , i have to make notes on the voltages , also forgot to point out there was a 6w6 in the 6v6 socket - why i don't know , no idea if it would work with that in there either.
thanks for the pic .

mike

[kramden66]

Here are the voltages - 6V6 pin 1 is 0 volts , pin 2 is -8 volts , pin 3 is 400 volts , pin 4 is 400 volts , in 5 is 115 volts , pin 6 is 68 volts , pin 7 is 0 volts , pin 8 is 37 volts ..... 6sn7 pin 1 is -28 volts , pin 2 is 78 volts , pin 3 is 0 volts , pin 4 is 3 volts , pin 5 is 5 volts , pin 6 is .640 volts , pin 7 is -8.5 volts , pin 8 is 0 volts.

looking at the schematic it looks like the osc 6sn7 is not right with voltages , why ? i'm trying to figure this out.

mike

[Phil Nelson]

Originally Posted by kramden66

there was a 6w6 in the 6v6 socket

My tube references do not list those as interchangeable (although they appear to have the same internal diagram).

This page lists data sheets for both tubes:

http://tubedata.milbert.com/sheets69.html

Perhaps comparing data sheets will tell you whether 6W6 is a reasonable sub for 6V6 in this particular circuit.

Phil Nelson

[kramden66]

could the intergrator be the fault ?

[Kevin Kuehn]

Is it safe to assume you've replaced all the paper and electrolytic caps, as well as checked resistor values in the vertical circuit? That would be the first step. Not sure how you're getting 115V on pin 5(grid) of the 6V6, unless you're measuring AC volts? There should only be a 3.3 meg resistor going to ground and one end of a .1uf cap tied to that pin. Pins 2 and 7 are the heater supply and should have around 6.3Vac across them. Pin 6 has no internal connection to the 6V6 and must be a tie point for some other point in the circuit. Better double check the wiring around that stage.

[kramden66]

yes its been recapped and resistors checked , will double check them , i will check the wiring around that stage , seems like the 115v should be on the 6sn7 not the 6v6 , its like the voltages are reversed.

mike

[old_coot88]

Originally Posted by kramden66

maybe one of you can give me an idea where to go , only has a *horizontal* line that you can't do anything with , you can see it react when you do the height , lin , even the expander switch but it stays a line but you see it reacting....

mike

Could you describe how the line reacts, ie., does it jump up and down, change brightness, or what?

Are you using a digital meter to take voltage readings? If so, do you by any chance have an analog VTVM that you could use instead?

[sean]

Could you have disconnected the 4.7meg resistor R55 and accidentally re-connected it to the other side of the 0.1uF coupling cap C63? That might explain why you have 115V on the grid of the 6V6, 5V on the plate of the 6SN7, and lack of vertical sweep.

[kramden66]

c62 which is .01 was never changed , it was a micamold that was tucked under L70 and hidden , so i replaced it and i seen sweep , it was letterbox but i wasn't running at full voltage either , one cap could ruin your whole day , this is why i've had the arguement with a couple people that its impossible to make a set run with the original capacitors all it takes is one , so assuming that the vertical wasn't full because i was running at a lower power the problem is solved , i wouldn't have found this if you didn't ask about the 4.7meg resistor which might not be 4.7 in the set , that and r57 may not be the same values as in the schematic , but progress has been made

mike

[kramden66]

ok at full voltage letterbox and it wont get bigger so this shouldbe able to be resolved easier ( i hope ) then the previous issue , also an arching that happend below the 1b3 socket - thats why i wasn't running at full power , what a snap/pop it makes and then it could be seconds or a minute later before it does it again

mike

[Phil Nelson]

Originally Posted by kramden66

an arching that happend below the 1b3 socket

Clean the entire HV area, especially that socket, with isopropyl alcohol (rubbing alcohol). Also look under the 1B3 socket for resistors. I have found burned ones there.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html