3ca3 tube = 3a3c for color TV?

3ca3 tube = 3a3c for color TV?

Post by french » Thu, 07 Apr 2005 14:20:07



is a ctc-16 color tv specifying a 3ca3 rectifier ok to replace with a
3a3c or 3a3?  (I have a bad 3ca3, a bunch of NOS 3a3c's and no 3ca3's,
that's why!)  thanks!
 
 
 

3ca3 tube = 3a3c for color TV?

Post by Bill Sheppa » Thu, 07 Apr 2005 14:39:00


Frenchy,
              The 3A3 and 3CA3 are electrically interchangable, having
the same pinout.
              Physically, I don't remember if they are the same height
or not (been a lotta years). Provided they're the same height, they
should interchange OK, since on the CTC-16 chassis, the anode cap 'plugs
in' to the flyback when the HV cage is slid shut.
                    Bill(oc)

 
 
 

3ca3 tube = 3a3c for color TV?

Post by french » Thu, 07 Apr 2005 14:51:51


Quote:

> Frenchy,
>               The 3A3 and 3CA3 are electrically interchangable,
having
> the same pinout.
>               Physically, I don't remember if they are the same
height
> or not (been a lotta years). Provided they're the same height, they
> should interchange OK, since on the CTC-16 chassis, the anode cap
'plugs
> in' to the flyback when the HV cage is slid shut.
>                     Bill(oc)

yes the lid closes down on this tube.   Height looks exactly the same
on my 3a3c's as the weak 3a3 that was in the set, I will change it out.
 thanks!...Frenchy
 
 
 

3ca3 tube = 3a3c for color TV?

Post by robert case » Thu, 07 Apr 2005 15:05:11


Quote:

> is a ctc-16 color tv specifying a 3ca3 rectifier ok to replace with a
> 3a3c or 3a3?  (I have a bad 3ca3, a bunch of NOS 3a3c's and no 3ca3's,
> that's why!)  thanks!

Should work.  The specs and pin-out look to be the same, but
maybe the top cap size is slightly different.  Just be sure
to quickly kill the power when first firing the set up if
something bad starts happening.
 
 
 

3ca3 tube = 3a3c for color TV?

Post by french » Thu, 07 Apr 2005 23:02:03


Then again I may just pick up solid state replacements for this tube
and the 2av2 focus tube, since there's no filament draw off of the
flyback windings it should be easier on the flyback.  Anybody have any
nays on this idea?  thanks......Frenchy
 
 
 

3ca3 tube = 3a3c for color TV?

Post by Bill Sheppa » Fri, 08 Apr 2005 00:10:41


Frenchy,
              Before putting in SS replacements, be sure the overall
operation of the set is worth the investment. 30 years ago they were
pretty pricey, and i have no idea what they bring today.
                 The power drawn by the filaments is not a big issue
compared to the stress in the main windings, particularly the HV
winding. I.e., when the flyback fails, it's gonna break down whether
you're running SS rectifiers or tubes.
                 On that set, it's not a question of whether the fly
will fail, but when. You can extend its life by being sure the 6JE6's
cathode current is dipped, using the 'horiz efficiency' adjustment. It
should be no more than 210 ma., prefertably 200ma. Insert the
milliameter in the cathode leg, which is pin 3.
                 Bill(oc)
 
 
 

3ca3 tube = 3a3c for color TV?

Post by french » Fri, 08 Apr 2005 01:07:30


Price of the SS rectifiers is no problem, looks like they are in the
$10 range each.  Figured removing two filament draws off of the fly
could always help a little in extending the fly's lifespan.

This is a VERY clean set, not used much by an old lady, fly looks
perfect externally and set works great after previous guy just did an
alignment on it.

Are there other adjustments that help the fly out, like making sure the
width is absolutely the least needed to fill the screen?  How about the
HV adjustment in back, what is the desired setting?  Also the cage does
not seem to have any venting holes or slots like my CTC-5.  Would
adding a tiny pc fan to suck air thru it help?  thanks

 
 
 

3ca3 tube = 3a3c for color TV?

Post by Bill Sheppa » Fri, 08 Apr 2005 03:19:12


Frenchy wrote,

Quote:
>Are there other adjustments that help the >fly out, like making sure
the width is
>absolutely the least needed to fill the
>screen?

You can try dropping the 6JE6 screen voltage a bit.

It's not an 'adjustment' per se, but there's a tweak you can do. If you
can get hold of three disc ceramic 6KV caps rated at 47pf, 100pf, and
150pf, try this: add the 47 across the damper, from cathode to plate.
This will drop the 'JE6 plate current slightly, maybe 5 ma or so, while
increasing width slightly. Then try the same with the 100 and the 150.
But there's a trade-off as in the old saying "there is no free lunch".
This tweak, combined with dropping the 'JE6 screen voltage, also drops
the HV. So you can only go so far with it. But I have used it to reduce
current in the 'JE6 by as much as 20 ma, while maintaining width and HV
regulation. This was in cases where the current was running excessively
high, i.e., 220 ma and above.        

Quote:
>How about the HV adjustment in back,
>what is the desired setting?

HV should be 25 KV. If you don't have a HV probe, adjust it to where the
pic doesn't 'breathe' or bloom thru the full brightness range.  

Quote:
>Also the cage does not seem to have any >venting holes or slots like my
CTC-5.
>Would adding a tiny pc fan to suck air
>thru it help?

It sure couldn't hurt.

Also, a heads-up: the two ground lugs on the right-hand end of the
chroma board tend to go open, which kills the heater voltage on the two
6GU7s. This starts a failure cascade that can actually kill the 3A3 and
flyback if not caught in time. The 6GU7s' plates go 'waaay positive,
driving the CRT G1s positive, which sends the beam current out the roof,
which can fry the 3A3 and flyback in short order. So be sure and
re-solder those two lugs (!)

Also the AC power switch was prone to arcing internally and catching
fire. So NEVER let the set run unattended.

Good luck with it. Sounds like a rare cream puff indeed.
                              Bill(oc)  

Header address is a spam trap. E-mail: oldcoot88atwebtv.net  Change 'at'

 
 
 

3ca3 tube = 3a3c for color TV?

Post by french » Fri, 08 Apr 2005 04:02:31


Quote:
> Also the AC power switch was prone to arcing internally and catching
> fire. So NEVER let the set run unattended. >>

Guess I could just solder the switch closed and use a cord switch, or
find a replacement control.  Thanks for the other tips and will keep
them in mind as I work on it....Frenchy
 
 
 

3ca3 tube = 3a3c for color TV?

Post by Bill Sheppa » Fri, 08 Apr 2005 06:33:01


From Frenchy:

Quote:
>Guess I could just solder the switch
>closed and use a cord switch, or find a
>replacement control.

The switch that was prone to arcing had a molded black bakelite shell
with the two lugs coming out the back. Your set may or may not use this
type. The type with the metal body did not have problems.
                  Bill(oc)  
 
 
 

3ca3 tube = 3a3c for color TV?

Post by french » Fri, 08 Apr 2005 07:18:02


Quote:

> From Frenchy:

> >Guess I could just solder the switch
> >closed and use a cord switch, or find a
> >replacement control.

> The switch that was prone to arcing had a molded black bakelite shell
> with the two lugs coming out the back. Your set may or may not use
this
> type. The type with the metal body did not have problems.
>                   Bill(oc)>>

It's black alright.  Maybe could just remove the bakelite, if that is
what is igniting?  What initially caught fire due to the arcing?
 
 
 

3ca3 tube = 3a3c for color TV?

Post by Bill Sheppa » Fri, 08 Apr 2005 08:35:35


From Frenchy:

Quote:
>It's black alright. Maybe could just
>remove the bakelite, if that is what is
>igniting? What initially caught fire due to
>the arcing?

What actually started the arc was diminishing spring tension on the
little 'flipper' that bridges the contacts in the 'on' position. Once a
steady arc got started, it would soon ignite the bakelite.
                You can usually tell by the 'feel' whether the switch is
working solidly or not. If it's getting wonky, AC hash lines may appear
in the picture when you wiggle the switch. If yours is working solidly,
it'll probably be safe for the remaining lifetime of the set.
                In any case, never leave a vintage TV, particuloarly a
color set, running unattended, as the primary fire danger is in the
flyback area.
                 Bill(oc)