[Ron Ramirez]

Well,

I have a left channel again. Sort of. And I have managed to localize the trouble - and it had nothing to do with the low-high filter mod.

Using the signal tracer, I had volume in the left channel all the way to the input terminal of the volume control, but lost it at the left channel wiper.

After looking things over...and over again...something told me to look at the left channel 7199 tube, V20.

I discovered that the wire where R134, 820K, connects to pin 3 (pentode section screen grid) was broken! So the pentode section of V20 was getting no screen grid voltage. R134 is highlighted in the partial schematic below.

[Image: http://www.philcoradio.com/images/phorum...00_033.jpg]

I went ahead and re-replaced R134 as the alternative was to lengthen its lead, I had several on hand, and they were cheap, so I just replaced it.

Then I fired up the TA-600 again.

At first I only had hissing in the left channel - which was an improvement over before, when I had nothing.

Some snapping, crackling, and popping followed - at which point the left channel came back to life!

But it is coming and going. I then discovered by poking and tapping components around V20 that I could make the left channel come and go.

So some very close inspections of solder joints are in order, and I may have to replace a few more components.

At least it is easier to work around the 7199 than it was in the front section of the chassis.

I'm getting there...slowly but surely...