Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Sat 16, 2017 3:54 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 56 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jun Thu 29, 2017 2:29 am 
New Member

Joined: Jun Thu 29, 2017 2:00 am
Posts: 19
Location: Seattle
Hello,

If this seems lack-luster it's because I failed while posting it so I have to write it again :x Anyway, I have a 1974 Zenith Chromacolor II (chassis 25EC58) and I got it for free off the front porch of an abandoned pub. When I plugged it in, it arced extremely loud and split my eardrums. Luckily the TV breaker opened and it didn't harm itself too badly, I hope. So I tried it like two weeks later and it DID NOT arc, and instead just had no picture. However, the flyback was making a high-pitched noise, but it was not as high-pitched as most other flybacks, even from this TV's era. It also opened it's own breaker again after about 10 seconds. I think the problem is the flyback, but I could be wrong. If not, where can I find a replacement flyback for this TV? Is it possible to fix the flyback without replacing it? Please let me KNOW!

Thanks,
Jack


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jun Thu 29, 2017 3:08 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25799
Location: Detroit, MI USA
Chances are that the HV tripler is cracked, and arcing. Look at the molded plastic case closely. Those sets were not known for having many flybacks fail, but they ate HV triplers and CRT sockets like candy. No, you cannot fix either of those parts if they have been arcing, nor can you repair an arcing flyback on a solid state set. You must replace with the correct new part.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jun Thu 29, 2017 4:15 pm 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 282
Location: pensacola fl
Also check the safety capacitor(s) on the horizontal output transistor collector. If these fail your crt can end up with it's neck cut off! Zenith had a hand full of these spread out on the flyback and under the chassis. If yours has them on the flyback look under the chassis for more. Many times these caps fail by bursting and spilling their guts. Other newer zeniths had them on the back of the horizontal output transistor heatsink. Still newer versions had 4 legged capacitors on the heatsink. The white ones held to the heatsink with a tie wrap were always suspect and were replaced with an orange job that would fail in a way that it did not kill the crt. If your set has the orange cap okay otherwise get the right replacements for your own peace of mind. I am not sure if your is an upright chassis or a standard large bottom of cabinet type with the flyback on the right. If it is the later those capacitors have the number 22-5001 I think on them and are standard looking 2 lead capacitors. Again if your has them change them all at once please.Some are quite a distance from the flyback but are in the circuit as they are all in parallel even though they are scattered out!


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jun Thu 29, 2017 4:38 pm 
Member

Joined: Apr Sat 06, 2013 2:18 pm
Posts: 308
Location: New Hampshire
FBT's themself are not known to go on these. FIRST thing to do on these
is check the safety caps. IIRC there are 2 on the FBT & 3 more under the chassis.
They are marked 22-5001, change ANY & ALL that are white. Orange Sprague
ones are OK. THIS IS A MUST DO ! Use OEM if you can find them or get
advice for the modern eq. The wrong sub WILL fail.
After that unhook the tripler input from the FBT & draw an arc from FBT.
Should be a nice 1/4+ inch ark. If so bad tripler.
Also check the focus divider for cracks, swelling etc and the CRT socket
at the focus pin for smell, heat & green crud.

What happens is each cap that opens raises the HV by about 1.5-2KV.
This is hard on the tripler & focus. If they all open it can shoot arcs
like lightning bolts, its quite a sight !

Sounds like a lot to do BUT remember that is the best TV chassis ever built.
We were pulling them still running fine ten yrs ago when flats took over.

73 Zeno 8)
LFOD !


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Sat 01, 2017 2:30 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7472
Location: Beaver Falls, PA. USA
Yep, a shorted tripler; we were changing them out 35+ years ago, when those sets were relatively new. The advice on the 22-5001 capacitors is right on target. If you need a few, post an ad in the Classifieds; one of us may still have them.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 06, 2017 7:40 am 
New Member

Joined: Jun Thu 29, 2017 2:00 am
Posts: 19
Location: Seattle
Thanks all for the advice, but I have a question: what do you mean by "draw an arc from the FBT"? (sorry, I'm kind of new to a lot of this; the oldest CRT I've worked on was a G07 from a Ms. Pac man).


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 06, 2017 3:06 pm 
Member

Joined: Apr Sat 06, 2013 2:18 pm
Posts: 308
Location: New Hampshire
With an insulated screwdriver get it near the unhooked triple input
wire at the FBT. If the horz is working you will get a health arc. (10KV)
If you get it but no HV 99.9 % the tripler is shorted.
73 Zeno 8)
LFOD !


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 06, 2017 8:13 pm 
Member

Joined: Mar Tue 03, 2009 11:12 pm
Posts: 1362
Location: Hutchinson KS
I remember these sets quite well! We had quite a few with broken off crt necks, arcing yokes and damaged vertical sweep modules. All because of those "safety caps"!


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Sat 08, 2017 1:44 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7472
Location: Beaver Falls, PA. USA
Disconnect the wire from the flyback at the tripler; the terminal on the tripler will be covered with a blob of silicone rubber. Lift the wire from the flyback out of the way, so it cannot arc to anything, and carefully turn the power on. If the breaker holds, the tripler is shorted. You'll probably hear some sizzling from the high voltage. Don't try this without checking the 22-5001 capacitors first.

_________________
Tim KA3JRT


Last edited by Tim Tress on Jul Sat 08, 2017 1:57 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Sat 08, 2017 1:56 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12389
Location: Omak,wa,usa
hello guys,
yep safety caps i still have my zenith service bulletins talking about changing those caps being factory service for zenith I had to change a lot .

that a good chassis


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Sun 09, 2017 7:45 pm 
Member

Joined: Apr Sat 13, 2013 12:16 am
Posts: 33
If I remember right those 22-5001 white caps are located on top by the flyback and trippler as well as 2 or 3 underneath the chassis.
Wasn't there like 5 of them? Anytime the trippler goes bad definitely change the safety caps.


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Sun 09, 2017 11:04 pm 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25799
Location: Detroit, MI USA
There shouldn't be any sets remaining with the original white caps still in place, but stranger things have happened.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Mon 10, 2017 4:12 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 652
Location: Pewaukee, WI
Mr. Detrola wrote:
There shouldn't be any sets remaining with the original white caps still in place, but stranger things have happened.


I've seen some in the last few years. I had one with ~half white half orange drops. It was working with the white caps for a while then they failed and HV got so high the HV connector started arcing to the yoke....Cabinet was lousy on that set, I had an Avanti with almost the same chassis (all drops on the Avanti), was low on space and prefer tube chassis so I sold (more like gave away IIRC) the arcing set at the ETF.
Still got my flatchassis Avanti though. :D


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 13, 2017 5:23 am 
New Member

Joined: Jun Thu 29, 2017 2:00 am
Posts: 19
Location: Seattle
I'm having a hard time identifying the 22-5001 caps. I saw two long white caps to the right of the FBT that are kinda gross looking and say "MP-CER" on them. I have not looked in the bottom section yet because I haven't had the time to and I'm kind of lazy :lol: . I just want to know if I'm on the right track with these long white caps. If it is any help, I have the version with the FBT and tripler on the right of the back of the machine, enclosed in that crazy white curvy cabinet with the plastic pedestal base.


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 13, 2017 3:55 pm 
Member

Joined: Mar Tue 03, 2009 11:12 pm
Posts: 1362
Location: Hutchinson KS
A thought just occurred to me about this set, are we positive this is an all solid state set and not a hybrid? I thought the Chromacolor II meant the hybrid model that was cheaper than the all transistor Chromacolor model. I don't have the service lit for this chassis to make sure.


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 13, 2017 4:28 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 652
Location: Pewaukee, WI
Every Zenith I've seen (and I've seen many) has the flyback on the right (most makes did that), and if there is a tripler it will be close to the fly. The chassis number tells us what you have. I've got schematics for most Zenith color chassis of that era so I could probably get you a copy of the schematic if you need it.
There were 4 main chassis generations that populated that cabinet: Tube/SS hybrids, the horizontal flatchassis SS (broad side faced up), vertical chassis (broad side faced the back and yoke/CRT neck stuck thru center), and the system 3 board only sets.

The White cabinet with the curvy pedestal base then it is the Avanti cabinet. Which was made through most of the 70's and had everything from tube/SS hybrid hand wired chassis to 2 circuit board system 3 electronics inside depending on year. Zenith Avanti sets are probably the most desirable 70's Zenith cabinet, both among TV collectors and those into space age furnishings.
I've got an Avanti with the same chassis (it is all SS). http://s1095.photobucket.com/user/Elect ... t=3&page=3
Once you get yours working if it has uneven color intensity horizontally across the screen like mine look for/change a 100uF 50V lytic below the chroma board on the chassis underside.

If the caps near the flyback have white tubular ceramic cases (they usually have dirt and gunk sticking to them) they are bad, if they are shiny orange (under the dirt) they are good. IIRC the 25EC58 does not use white tubular caps in any other stages so if they are there they need changing.

Orange: Image

White: Image


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 13, 2017 4:39 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 652
Location: Pewaukee, WI
SteveT wrote:
A thought just occurred to me about this set, are we positive this is an all solid state set and not a hybrid? I thought the Chromacolor II meant the hybrid model that was cheaper than the all transistor Chromacolor model. I don't have the service lit for this chassis to make sure.

Ennt! Wrong.

Chromacolor was Zenith's trade name for the Black Matrix* CRT that they invented...All the TVs that had it were labeled Chromacolor (Hybrid and early SS) or Chromacolor II (SS only). Zenith labeled only the Chromacolor equipped sets that had an ALL SS chassis Chromacolor II...Some early SS sets only say Chromacolor (took marketing a bit to tack on the II). I've got a 25EC58 Zenith too and can verify it is all SS.

*Black Matrix was a process by which the phosphor dots edges were masked off by a black material. This improved contrast, purity, convergence, and focus achievable and on average in these CRTs. Instead of needing to make the electron spot smaller than the phosphor dot to avoid hitting adjacent dots (as the old tubes did) the spot could be slightly bigger than the phosphor dot (and the extra would hit the black material which served as a guard band).


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Jul Thu 13, 2017 9:17 pm 
Member

Joined: Apr Sat 06, 2013 2:18 pm
Posts: 308
Location: New Hampshire
My earlier post got lost so it seems. Sry for duplications if it shows up.

Chromacolor ( CC ). Original name for the new black matrix CRT @1969.
Super CC. D-line all CC TV's 1973 ( 1972 release )
CC 2 E-line all upright chassis & flat chassis 17"-25". Models with
the flat chassis were switched to the upright sometime mid line. Two models
of the flat chassis still in F-line, very slow sellers so probably got relabled & were
part of the last runs.

This set is a flat chassis, probably an Avanti. It has a breaker. Only the SS
sets had one, hybrids all used bel fuses. If an upright would be a 25EC45.

73 Zeno 8)
LFOD !


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Sep Sat 09, 2017 9:12 pm 
New Member

Joined: Jun Thu 29, 2017 2:00 am
Posts: 19
Location: Seattle
Its been some time, I've finally got around to looking in the bottom for safety caps. I'm finding one orange one labeled 22-5001 on the horizontal module, and a ceramic white cap under that labeled MPCE which could have some relevance. The AGC module to the left of those caps has a another orange cap that is shorter than the first orange one and has no 22-5001 on it (instead it says 225PX) and way in the corner under where the FBT should be there is another orange one labeled "SPRAGUE 7334". Which of these should I pay attention to? Should I just deal with the white tube one on the Horz?


Top
 Profile  
 
 Post subject: Re: Zenith Chromacolor II (chassis 25EC58) going wacko
PostPosted: Sep Sun 10, 2017 1:58 pm 
Member

Joined: Apr Sat 06, 2013 2:18 pm
Posts: 308
Location: New Hampshire
IIRC there are 2 on the flyback itself & 3 more UNDER the HV area
hand wired in. There are NONE on modules.
Sounds like at least a few were changed.

73 Zeno 8)
LFOD !


Top
 Profile  
 
Post New Topic Post Reply  [ 56 posts ]  Moderators: 7jp4-guy, Mr. Detrola Go to page 1, 2, 3  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB