Zenith 2250R

[benman94]

I'm seeing them just fine on my Galaxy S9 with Chrome, but they won't open correctly on my Linux desktop using Firefox.

[Zsuttle]

Either way, anyone have any ideas? I figure one of two things, Is it possible that the listed 15k resistor is too high? If I did my math correctly, to drop the voltage to 180 volts from 300v, you'd need a resistor of 8k.

Or the Horizontal Drive potentiometer is testing at around 34k ohm instead of 25k. In that case could it be substituted by removing the 4.7k ohm resistor that it is in series with?

[Kevin Kuehn]

Sounds to me like your screen(pin 4) may be drawing too much current which would cause the screen voltage to be low. Have you checked the cathode voltage(pin 8) against what Sams calls out? The horizontal drive will adjust the cathode current and generally you want to adjust for lowest current by inserting a ma meter in series with the cathode. A Sams folder should give some specific directions for setting the drive control. Also I'd try another damper if you have one. Specifically what schematic are you using?

[Zsuttle]

I'm using Sams Set:114 Folder:13 Replacing the damper did improve the voltage slightly, to around 7.5kv. Doing so improved the Screen voltage to around 115v. The cathode voltage was sitting around 11v (Sams lists 10v) before and after replacing the damper.

[Kevin Kuehn]

Originally Posted by Zsuttle

I'm using Sams Set:114 Folder:13 Replacing the damper did improve the voltage slightly, to around 7.5kv. Doing so improved the Screen voltage to around 115v. The cathode voltage was sitting around 11v (Sams lists 10v) before and after replacing the damper.

So your HV increased from 2kv to 7.5kv? Thats quite an improvement in my book. Did you see the Horizontal Sweep Circuit Adjustments on page 10 of your Sams? Also check R103 (470k under the HV rectifier socket) to make sure it hasn't drifted high, as that can really drop your high voltage if you're measuring at the CRT HV anode.

[Kevin Kuehn]

If you have them, try a few other 6BQ6 horizontal output tubes. Riders calls out 10kv for high voltage. 12v on horizontal output pin 8, 141v on pin 4, and 12v on pin 5. Nothing magical about those numbers, they're just ball park and vary from tube to tube.

[Zsuttle]

Well, I've checked all of the voltages on both the horizontal output and the damper and everything matches up except the screen voltage on the horiz out. I tried a spare 6BQ6 that tested NOS and it didn't change. R103 on the anode lead tested about +8% but it's noted as a 20% resistor on the datasheet.