New Roundie sets scored

[DaveWM]

Yea no hurry, I have replaced those and had no visable change. the only one that I really matters is that HOT coupling cap, if its leaky at all it will cause the HOT current to be high. I like to use a VTVM to check the neg voltage at the grid, and a scope to check the PP.

[ctc17]

Just checked the cathode current on my 16xl today. 180ma, lower your line voltage a little. I wish there was an easy way to run these with the fly cage open because the thing just cooks in there. Im tempted to bend the lid 180 so its pointing up when closed. Some people cut holes and put fans. I dont like the idea of fans because thats forced dust injection, I do however try and run all my sets with the can open. Lowers the flyback temperature by about 80 degrees

[mstaton]

I have no easy way to lower line voltage. Line voltage is 120V. I suppose you can add a filter to the fan to keep dust down. It's almost hard to believe how good of a picture these can produce when working correctly. I'll check the current again tomorrow and readjust if necessary.

[ctc17]

If you cant get a center tapped filament transformer you can easily wire it to lower the voltage by 12 or 6 volts.
Yes they do produce an awesome picture but that fly is vary fragile. You want to do whatever you cant to keep it cool.
Its not the end of the world if it fails, you can sub just about any non Zenith round tube fly in there but its a major PITA. The last NOS fly for that chassis went for like $125.

[mstaton]

Yeah i saw your you-tube video on the fly replacement.
I have an extra 16XL with a good fly. The line cap blew up and it's a mess underneath, so parts it is. I already used the Hor. center pot on this one. I have another 16XL in the garage that may be fixable but I have not looked at it closely.

[miniman82]

I bought an RCA TV Isotap for real cheap on Ebay not long ago, you should be able to do the same I'd think. Makes a huge difference to HOT current, everything runs so much cooler and IQ doesn't suffer at all.

[andy]

...

[ctc17]

Good point, my 16 has the tap but like miniman I have an isotap.

[marty59]

I've got an RCA schematic as well as the Sams for my 16E. Naturally, if your line voltage "was" actually low then the original soldered connection was rated for 110-120Vac. RCA specs the high line tap at 128Vac so with todays line voltages being what they are that may be the better tap.

Would I be correct in saying that we should be concerned with the peak to peak value as opposed to RMS?

[ChrisW6ATV]

Originally Posted by mstaton

I have no easy way to lower line voltage. Line voltage is 120V.

Look up "line buck" and autotransformers. You can rig something like a 6-volt, 4-amp power transformer to cut the line voltage down by 6 volts for up to a 480-watt TV. Essentially, you connect the transformer's primary and secondary to cancel itself out and put the TV in series with the result. There was a discussion of this either here on VK or on the antique radio forum recently.

[Chad Hauris]

When I repaired my 1967 CTC-28 I hooked up the power line to the high line voltage tap. I think a few years later they began to use the normal/high switch.

On a 1968 Sylvania D12 set, it actually has a normal/low switch to boost the power transformer voltage in low line voltage areas.

I used a 1970's RCA XL-100 power transformer to buck the line voltage going to a Harman-Kardon A300 amp. The amp was causing 6V6 tubes to short out due to high B+ voltage caused by high line voltage. Some of the old equipment was rated with a 115 or 117 volt AC supply and todays higher line voltages can cause excessive power supply voltages.
I used one of the secondary windings (I think CRT filament) as the "buck" winding in series with the primary winding. You just have to make sure the phase is correct and measure the output voltage before connecting..one way of connecting the leads will add to the primary voltage and the other will subtract.

[damen]

Here it is all recapped and working. I was very lucky A friend in Georgia sent me a good used flyback and all systems are go 213 is as low as I can get the cathode current Sams shows 190 I will use a fan on the fly to keep it cool and hope this one will last.

[zenithfan1]

Wow! Great job! That picture is very sharp and the color looks awesome! I like that cabinet style too!

[DaveWM]

check your line voltage, if you have a variac see how low it can go before the width is a problem, check the cathode curret at 117vac

[sampson159]

is this a real zenith crt?that looks as good as it did when brand new!beautiful picture that puts modern sets to shame