[TinCanAlley]

Originally Posted by vol.2

Yes, it's a better safe than sorry thing. The issue could arise if you accidentally touched something that is on the line side of the transformer. If that happens, it will short out your probe ground to line voltage.

However, if you were to accidentally touch the line side of the transformer with you hand, you could then be connected to the breaker yourself, and that could hurt or kill you. This is generally why some people recommend an isolation transformer no matter what. I do enough electronic repairs that I bought one and just use it.



I feel like I would start getting suspicious if it was more than 100mV, as that might indicate weak filter caps. If it's much over 150-200mV that would make me concerned, and any much higher than that I would turn it off and start hunting for the bad component. Certainly if it was over 1V or more.

In terms of AC Vs DC probing: The DC probing doesn't show the ripple because you have to crank up the volts/div so high that you lose the visual resolution to see the ripple. Looking at AC only means the DC component is gone, and you are then just looking at the waveform centered in the middle of the scope (vertically). So that's why you see the ripple in AC coupled.

I don't know what that particular set looks like, but my 1975 Sony 9" is about the older thing I have and it's B+ is rock solid at 130V with less than 20mV of ripple, so I know it's possible.

I don't know what the ripple is, it was more a question about the ripple noted for the capacitor. I'm assuming that's the maximum ripple current the capacitor can/will pass. While my jailbars have reduced in intensity, they are still there. All the Zenith jailbar fixes I can find aren't for this chassis, but they all point to filtering capacitors near the power transformer. So I'm hoping it will be one of the caps in that area.

I'm going to start testing voltages tomorrow. Right now I'm installing an IC socket and new IC on the sound board in hopes of restoring tone control. I've check the wiring and pot and it all appears good. That leave the IC as the tone control goes directly into pin 1 of the IC. Seeing as how the IC on the Chroma board caused tint and color saturation issues, I'm willing to take an 8$ gamble and install an NOS IC.

I don't need a fancy isolation transformer, do I? There's a unit on Amazon for 136 and it seems decent for the price. It handles 500W. Is that good enough, or it is wiser to get the 2000W version? I'm not sure if this set exceeds the 500W unit's 4A.