Brought back a NICE Zenith flat-chassis set !!

[rca2000]

Not likely that I will....I just wanted to "see'. I was ready in case I heard ANY sizzle or arcing.....but I did NOT hear any. it was only on long enough to get a picture of it--then I pulled the plug.

[Jon A.]

Sounds good. I heard an unusually loud crackle in the video once a safety cap lead was clipped and the set powered up.

[zeno]

If your 22-5001 caps are white change them, if orange they are OK.
The HOT in the Zeniths are rugged. In most sets a bad cap would
mean instant death to the HOT. The flat chassii NEVER had sets
destroyed by open caps. There are 5 of them IIRC 2 on the FBT
& 3 under the chassis. Early upright chassii also used 5 caps.
If the set is run long term with an open cap or two the focus divider
& CRT socket go bad. You also get a strong crackle on turn on.
If more go you will see an awesome lightning show around the anode
& divider.
Congats on the set. The CRT looks good as new from what I see & the
set is super clean, wish it were mine.............

BTW IIRC you can get at the dial lamps from the front. Uses either
#159 or #259 bulbs, can interchange.

73 Zeno

[rca2000]

I only now notieced the channel bulbs were out. I figured they were #44 or 47, not #159. No matter....I have some 159 or 259's in my nightstand drawer for stereo dials IIRC.



Here is a question--likely for the "oldsters" here.

I KNOW and understand how a bad retrace cap(sometimes called tuning cap or safety cap) can and WILL cause a serious increase in HV on a SS set. I think I first read of the situation from radio-electronics, in an article from the late '70's or so by Jack Darr. He explained the whole deal with the tuned ckt, and how if a cap in the collector of the H-out opens--it upsets the tuning--and the HV will the increase--sometimes a LOT !! He spoke of some engineers from Admiral or maybe Zenith, who purposely tested this theory--and said the HV would spike to OVER 40kV, and said that was as high as the meter went !! Of course--this was as a warning to make SURE the tuning caps in certain sets--such as Zenith flattys and the 4-lead caps in the vertical sets too--were good. I learned all of this in the late 1980's or so.....and MUCH , MUCH more from his articles....


HOWEVER....I am curious. Did this happen in TUBE sets? I know that if the shunt reg opened up, the HV could go over 30KV. or so. BUT ..was their any sort of tuning caps off of the plate ckt of the H-out tube, as in the SS sets--that could cause this??

[radiotvnut]

Open capacitors or ones that have changed in value will cause the HV to increase. How much of an increase will depend on how many capacitors have opened or shifted in value. If any capacitors short, it will trip the circuit breaker.

[old_coot88]

Originally Posted by rca2000

Here is a question--likely for the "oldsters" here.

Yo dude.

......I am curious. Did this happen in TUBE sets? I know that if the shunt reg opened up, the HV could go over 30KV. or so. BUT ..was their any sort of tuning caps off of the plate ckt of the H-out tube, as in the SS sets--that could cause this??

NO. In tube sets, regulator failure would simply let the no-load voltage float up to 30KV or so.
But the SS "safety cap" failures that literally cut the necks off CRTs were utterly unheard of until they started happening.
Seems like that unlike a tube, the output transistor is a 'hard switch', capable of driving the "fly-back" spike ((from which the HV is derived) to far higher levels than a tube could possibly manage.

[TVTim]

Originally Posted by rca2000

First pictures::

These are NOT real good--it is still in the van, but I wanted to get something to show everyone.

I could not get a good angle. WIll get a good pix once it is in my new garage.

That is just beautiful!!

[Jon A.]

Originally Posted by old_coot88

Yo dude.

NO. In tube sets, regulator failure would simply let the no-load voltage float up to 30KV or so.
But the SS "safety cap" failures that literally cut the necks off CRTs were utterly unheard of until they started happening.
Seems like that unlike a tube, the output transistor is a 'hard switch', capable of driving the "fly-back" spike ((from which the HV is derived) to far higher levels than a tube could possibly manage.

So the "HOT redplating" I've heard of could be caused by a regulator failure? Better to blow *a* tube than *the* tube.

[old_coot88]

Originally Posted by Jon A.

So the "HOT redplating" I've heard of could be caused by a regulator failure?

No. Red plating of the H output tube is from excessive plate current, usually caused by loss of grid drive or a shorted flyback.