Re: 549 transformer question


Chuck Harris <cfharris@...>
 

Michael,

Flybacks failed, but it was a pretty rare happening
when you consider the massive number of TV's that
were made. I have had dozens of TV sets from the '60s
onward, that never suffered a flyback failure.

What percentage of the sets you serviced got a new flyback?

I would guess less than 1%.

Ask the same question of folks that have scopes that left
the factory with the brown epoxy impregnated HVT's, and I
think you will find 50 to 75% either already have a replaced
HVT, or are nursing one along until someone (hopefully me)
starts winding again.

-Chuck Harris



Michael A. Terrell wrote:

Chuck Harris wrote:
And yet, as smart as Tektronix was, they had a host of HVT failures
when the TV set manufacturers didn't.  And it took them 10 years
of seemingly fumbling around to come up with a solution.
Chuck, TVs had a lot of bad fybacks, often burnt to a crisp. The early, wax sealed
were the worst. The heat they generated would cause the coating to deform, and if the
home wasn't air conditioned you would find drops of wax on the floor, under he set on
some models. They were a lot more reliable after the switched to the silicone rubber
molded designs, but it wasn't unusual to have to modify a chassis because the OEM had
to redesign a flyback. A couple GE color flybacks came in a new steel subchassis,
because there were so many differences. Spring and fall in S.W. Ohio had the highest
failure rate, in homes with people who smoked. Nicotine would cover the outside of
the CRT, increasing the load on the Second Anode supply. We saw about 90% of the
failures during these times as the humidity spiked, making the nicotine more conductive.

BTW, the first color TVs used the venerable 807 tube for the Horizontal output tube.
I laugh when hams deride using 'sweep tubes' for RF, when they started out as
improved versions of the 807. The first change was to re-base it from a five pin base
to an octal base.





Join TekScopes@groups.io to automatically receive all group messages.