Zenith 25EC58 - won't turn on
 

This is my one in the chrome cabinet, with the SC600.

I decided it was time to pull this one out and use it again, I hadn't turned it on since 2018, it worked fine then...

So I turn it on and get this weird intermittent buzzing in the sound, and I just swapped out the entire sound board, which did fix it. Then, a loose wire from the antenna terminals to the vhf tuner. Then, I adjusted the vert height and size, focus, G2 controls, color convergence, and after some time got a great picture. Now I'm all ready to sit down and watch it, but I noticed the remote (while it worked for channel and volume) wouldn't turn it on/off.

Thinking it was just an alignment issue, I got out a voltmeter and was just going to do the method where you keep clicking button on the remote and try to peak the voltage.

But after I unscrewed the remote receiver board and pulled it out enough to access it, the TV wouldn't turn on at all, not in auto or manual mode. (And I'm pretty sure it's not just a loose wire)

If you look at the pics, you can see where someone messed around with this before - those two components - that optical connector? and switch made of two diodes? seem to have been swapped out for a single component and a resistor.

The triac & isolator are replaced with kits
800-617 isolator
800-618 triac
Almost looks like they were removed & the triac jumped to make
it always on. If you do the triac be sure it has a mica & plastic hardware.
Other probs were leaky manual on/off & remote/manual switches.

Zeno:smoke:

Triac was usually jumped when cable came. The cable boxes had a switched outlet and made the on/off on the TV redundant.
Check the circuit breaker and ferroresonant capacitor. The cap opens and trips/kills the circuit breaker.
Also, check/replace any white safety capacitors. They would pop and slowly raise the high voltage until it could pop the neck on the CRT.
Check the capacitor/resistor connected to the horiz out transistor. 1.5 or 15 ohm (sorry, can't remember the actual values) and a small electrolytic paralled together. The resistor goes up in value killing the horizontal output and tripping the breaker.
Other than these, a very reliable set with a great picture.

I'll be watching this with interest. My chrome 25EC58 is in a similar state. I bought it last summer and spiffed it up a year ago ran it a few times and a couple of months ago when I plugged it in to try it it was stone dead.
I've also got a last gasp 1980 metal CCII that was my basement agile modulator monitor that got regular use do the same thing recently.... Switched on the power outlet that feeds it then tried to turn it on and nothing. I kinda want to add that triac bypass (or something to tickle the triac on when AC comes up for the first time)to the 1980 (with a defeat switch) as I have it plugged in to a remote switched outlet along with the agile modulator and a video source rack and miss the older NON-remote CCII it replaced coming on with the modulator and acting as a reminder the video rack is on (that video rack has ran overnight accidentally a few times because I didn't have TV glow to remind me to turn it off).

Just thinkin.........
There are empty holes on the PCB. IIRC there were 2 different
parts, one a photo-isolator the other a relay. They had different pin outs so some unused holes.
The replacements were the grey 1 inch long, flatish isolator.
I THINK the resistor was OEM, not added.
On the PCB if the transistors are plugged in you may have knocked one
part out & killed the ON /OFF so check that.

So back to the olden days....... All of these chassii were in 25" sets.
I was the jig man so being on the road was rare to me. When there was trouble in this area the road man would order a rebuilt selector assy instead of messing
with multi trips on an often int problem.

Zeno:beer:

I replaced the triac and isolator, and it would turn on again with the switch - I did both at the same time, so I don't know which was bad.

That resistor was in-between the triac and the photoresistor side of the isolator - I indicate where it is in the schematic (which I put as the first image) - it looked like someone actually cut across the trace connecting those, then soldered the extra resistor in. But I tried connecting across it with a clip lead, and it didn't seem to make a difference either way, so I just left the resistor as it was.

But it still would not turn on/off with the remote. I tried peaking that coil, and then I got it so it would sometimes turn on only if I held the remote right up to the microphone and clicked it several times in a row. I was still getting a slightly higher voltage there (I indicate where I was checking it on the schematic) with the switch vs. the remote even after I adjusted the coil - but the problem turned out to be the leaky electrolytic capacitor I circled.

Adam
I am impressed by the repair ! I also like that Pontiac, a REAL car:banana:
455 cid ? I ran Olds 455's & they were strong, quiet & 100% reliable.

Pix looks great. If it were 30 yrs ago I would try to hire you.
BTW if the cabinet is stainless steal ( not wood grain ) its super rare.
Never seen or sold one. They look like it came from a lab or OR.

73 Zeno:smoke:
LFOD !

'74 Grandville 4-door hardtop - 455
I like these big early 70's GM boats - I used to have a 72 Buick Centurion with a 455, also had a '72 Impala with the 400 small block.

Yeah, this one has the stainless steel cabinet, I have another Zenith with this chassis in the Avanti cabinet - Which worked great until I took out the remote board to compare it to the one in this set - still have to put it back.

Has anyone tried to modify one of these so you don't get the bendy picture at the top when playing tapes? I read (I think here somewhere) that the horizontal afc circuit needs to be modified.

Hey nice!

Would be interested in some more pictures if you're so inclined. Especially of the rare steel chassis.

Had 61 Fiesta wagon & a 63' 98 4 dr both with 394 cid another great Olds mill. Then had 2 1970 ( green & blue ) 88 4dr HT's & a 72 Toronado all 455's. Got the wife a 65 F85 Cutlas 330 cid w/ 4 bbl. fast car & she loved it.

Anyhows The ONLY mod I know of is replace the 9-57 module with one
marked 9-57-VCR from Zenith. The -VCR is a blank 9-57 PCB with a later
9-90-01 attatched to it as they have different connectors.
The 9-90-01 has an IC & a horz hold control. The original horz hold COIL
is not used. When this subject comes up I say "show me yours" but
all you hear is how easy it is to mod !

C U Later
Zeno:beer:

I'd love to find a 63 394 supposedly all the 49-63 rockets would bolt right up to the hydramatic in my 47 Oldsmobile (I want to keep the stock transmission because changing the steering column or adding a shifter is blasphemy to me) and it would be cool to have an engine that can keep up with interstate traffic without being completely floored...The flathead 6 isn't terrible but it leaves some things to be desired.

I've got that same model chrome Chromacolor...I remember offering Adam a grand for his before he moved south...A few years later I only had to pay around 1/3 of that for mine.

I'd imagine that it might be possible to figure out that VCR mod by looking at service data for sets that used both modules, but I don't have the newer module to play with, and if it wasn't used before 1978 I probably don't have service literature either. I'm with Zeno on wanting to see it documented.

Guess I should track down a couple of optocouplers and diacs for my sets.... hope compatible optocouplers are still easy to source.

I found the triac on eBay, the optocoupler at a place called Talon electronics.

I've got a 21" Zenith color, 14A9C50 mostly tube hybrid chassis, in a woodgrain metal cabinet, with the remote, and a bad flyback - I got to start looking for that.

I have the Zenith color tv manuals up through 1980, I'll see if I can find any information on that 9-57-VCR module. There's also a good discussion on how this on/off mechanism actually works in the TAB manuals Zenith color tv vol. 3 - I really didn't get how this works until I read that.

I wish I had moved more of my stuff out here than I did, old stuff just isn't available in AZ like it is in MI and WI, in the 6 years I've lived in AZ the only TV I've found locally is a Zenith Flashmatic console - it's a rare one - but with a damaged cabinet and a bad CRT (if it wasn't a flashmatic I would have parted it out)

If the flashmatic has a good hand unit it worth getting. Last two I seen on
E-bay went in the $400 range for mint ones. The 9-57-VCR may have been
covered in "Tech Topics" but we only found out about it from the Boston
distributors head tech ( Roger Eaton USMC ). He was famous for shooting at a Jap
(MGA) Zero with a 50 cal on Midway, its in the movie. A real nice guy.

Zeno:smoke:
LFOD !

I have tried to find a 9-57-VCR no joy. To reverse the mod you gotta
have schematics for sets that used each one. One thing is has the 9-90-01
been modded also ! IIRC the early CC2 chassii ( plain 9-90-00) also had "top hook" or "flagging" but only the top inch so no big deal.

For motor look for a 371. IIRC used 57-59. It had an option "J-2" a
tri-power. A real beast but on ANY 371 you gotta watch the cam, many went soft.

Zeno in snowy N.H.

I looked through the Zenith manuals up to CM-131 Nov. 1979, and found no reference to the 9-57-VCR.

Here's a pic of it where you can see the reflective cabinet.