View Full Version : Sony 5-303W

11-25-2012, 12:47 PM
My Sony 5-303W which has been in my collection for many years finally got its long overdue servicing. One day while watching it the raster faded away and I was left with no picture. Installing a recapped sweep board fixed that plus I installed a NOS Sony picture tube to replace the original which was quite dim. After scavenging parts from several sets I now have a nice example of the model complete with carry case, instruction manual, external antenna adaptor, original earphone and good power cord. Everything works good but I have a couple of issues. First, after it has been on for a couple of hours, I notice the vertical height seems to increase slowly as though something is drifting with temperature. Is this normal for this model? I remember reading when this model was being developed, thermal drift was a problem Sony was trying to correct with respect to settings of the vertical and horizontal hold controls. Second, the new picture tube is a Sony substitution which came with a new CRT socket and rewiring instructions. That went well but the HV anode connection on the original tube had a little dimple in it that the HV cup snapped onto. The replacement tube looks like most CRTs without this bump. The result is the anode connector does not fit tight despite my having spread the prongs to tighten it against the sides of the connector hole on the CRT. It makes a noticeable effect on the picture as it is not a completely secure connection. There was nothing in the CRT box that mentions this. Any thoughts?

I had no idea these sets could look so good until I saw mine with that new tube installed.

11-25-2012, 02:13 PM
I should look for a tube for my 303 and 305. They both have been going dim for the last couple years....especially the 303. I've had that 303 for like ten years now. Picture is okay as far as geometry, but has been going dim, and I have noticed an odd effect that makes faces look silver. Seems to be a contrast problem, but I'm not sure where that is coming from. I don't have a CRT checker, so have no idea what the state of the CRTs in both these sets are.

I would imagine that if the anode wasn't quite right, you would HEAR an arc or maybe a hiss?

Sandy G
11-25-2012, 02:53 PM
I heard/read somewhere when the face of the CRT turns "Pinkish" they're about done for.

11-25-2012, 03:01 PM
I have noticed an odd effect that makes faces look silver. Seems to be a contrast problem, but I'm not sure where that is coming from.

You are describing the classic symptoms of "double peaking" of a CRT cathode. With much age, the cathode current vs drive voltage can become very non-lnear. At some mid level of drive the cathode current may actually *decrease* with increased drive and then with more drive increase again, The dip in (what should be a linear curve) produces a strange effect on the highlights, as some bright areas are rendered much darker than they should be.


11-25-2012, 03:26 PM
A weak CRT will cause a silvery effect in the picture. As for the turning pink, that is the plastic cover over the CRT. I think it is caused by ultraviolet light affecting the plastic. Mine has a slight pink tint to it that is not present at the sides of the screen cover which are not visible from outside the cabinet.