10BP4 - bubbles in glass

[bandersen]

Originally Posted by leadlike

The two 10" tubes I have right now (both GE brand) both have bubbles on the faceplate, but they are towards the outer edge of the screen.

Looking at the label on yours makes me wonder-did the tv shop pull this from a 721ts when making a crt change? It lists it's "defect" as being the original tube in the set, which tells me it was worn out, which it kind of tested as being. Maybe they hung onto this one to sell back to some other poor slob as a gently used crt.

LOL - that could well be. I suppose it's a rebuild candidate too. After working with an electrostatic set lately, I'd forgotten how much of a pain it is to adjust a 10BP4s trap magnet, focus control and centering screws

[leadlike]

I just had to spend an hour setting up the GE 802 in the owner's home. Gotta love those magnetic focus sets.

As far as repairmen hanging onto junker tubes, I have plenty of proof that it happened-I have an entire tube caddy of nothing but used tubes. There are copious notes written on each box about how each tube wouldn't work in the Anderson family's set, but maybe in certain other sets, etc. It has scads of 1B3s that have an ashen burn ring around their bases from being run to death. Quite an impressive collection of worthless tubes that were waiting to go into an unsuspecting customer's set for the full replacement price.

[Findm-Keepm]

Originally Posted by leadlike

As far as repairmen hanging onto junker tubes, I have plenty of proof that it happened-I have an entire tube caddy of nothing but used tubes. There are copious notes written on each box about how each tube wouldn't work in the Anderson family's set, but maybe in certain other sets, etc. It has scads of 1B3s that have an ashen burn ring around their bases from being run to death. Quite an impressive collection of worthless tubes that were waiting to go into an unsuspecting customer's set for the full replacement price.

It was kind of an unwritten rule in Dad's shop to never throw away a 6GH8 or 5GH8 - they might work as a color oscillator, but not in horizontal circuits, or vice-versa. I fixed a metal cabinet set for a friend across the river in Portsmouth by merely swapping 5GH8's from one socket to another. His wife swore I did something else, but my buddy was right there to see me move them - and swapping them back recreated the problem (an AGC like buzz from leakage from the vertical oscillator). So what doesn't work in one set may work fine in another - the inter-electrode capacitance of tubes varies widely and can cause such problems. Similar effects carried over to IC's - the early Resistor-Transistor-Logic chips might work in one circuit but not another. I was left scratching my head when a calibration tech fixed a Doppler Radar Test bench by merely swapping two RTL chips.

Cheers,