Recently Acquired 1969 Motorola Color Tube Tv
 

Last winter I acquired a 1969 Motorola Color Vacuum tube tv. HT-617CW is the service model number. D20TS-921-D02 is the chassis model number. It appears to be a VERY high hour set from what I know about it. The color driver pots are turned ALL the way up. The tv has changed hands many times in its life. Was once used in a barber shop for awhile until 1990 when it needed repair work done on it. The person I got it from fixed it back in 1990 and ended up keeping it after customer would not pay up for repairs. It was in use throughout the 90s through the early 2000s then sat in a basement in humid Massachusetts until Late 2021 when I was given the tv by the now very busy and retired repairman.

The tv did work when I tried powering it up with a variac. No issues at first but when I turned the tv off I heard a loud "pop" sound and upon examining the inside of the tv their were two burnt carbon comp resistors with char rings around them, along with a ceramic cap that was burnt up (locating right at where the mains voltage comes into the tv) It looks like a filter cap may have bit the dust and open shorted. The #2 wire fuse on the top of the chassis is also burnt out and gone, no trace of it left. The circuit breaker fuse also tripped. I already replaced the two burnt resistors but obviously that is not all that will be needed to repair this thing. It looks like it was NEVER recapped at all in its life as far as I can tell.

I have been on a waitlist since January 2022 to get this thing fixed at a repair shop an hour away in Mass. I have virtually zero experience working on vacuum tube electronics of any kind. I am more used to working on vintage computers which is my main specialty. I am really eager to get this thing fixed but am puzzled as to why it worked fine when it was turned on with the variac gradually but it shorted somehow when it was turned off after a few seconds.

Any information at all about this tv or what may have happened is appreciated.

It's a handsome set, I hope you can get it repaired.

That ceramic across the line looks fine. It should be replaced regardless.

Most likely what happened was one of those filters was leaky and overheated while it was powered on. It was coincidental that it finally vented right when you turned it off. You really need to replace the electrolytics in the power supply, the fuses, and that across the line cap, then power up again slowly. I'd probably check the diodes in the power supply first too. None of that is particularly difficult to do, so you might want to try that yourself and see how far it gets you.

That is a great set but very dirty too. Make sure all those tubes are tested, then you can tighten up the socket pins.

Clean all pots with DeOxit and rotate 25 times each. The lousy parts are few but generally, some of the electrolytics may be all you need.

Otherwise the 1967-68 Motorola sets are about as rugged as a Zenith.

Very very nice find. I would love to find one like that...way overbuilt in a good way.
Should be fun to work on.

I've got a virtually identical set. Mine came out of the basement of a reapir shop in Indiana and needed rust treatment and a cataract removal (mine was MUCH worse than yours). It needed a few caps (I think several of the lytics we're bad) some adjustments and a focus divider arcing fix.
These use the SODPIL single tube color demodulator so it's almost as simple as a monochrome set.

Thank you!
 

Thanks to everyone for your comments and advice. I have to admit, when I first opened this tv up I was super intimidated by how complex it was and the rat's nest of wires and components under the chassis.

I am 27 years old so I never really grew up with vacuum tube tv sets, just the solid state CRT ones which look way less complex. It is mind boggling how much tvs have changed both in size and design over the last 50+ years.

The main reason why I had been hesitating to work more on this set was a combination of my lack of experience with anything vacuum tube related and just the fear of accidently messing something up or making the situation worse with the tv.

I get the feeling that these color table top tube tvs are hard to find, as I tried and tried to look for other similar sets and they seem to be nearly extinct. So I want to make sure that the repairs are done properly.

I have every intention and desire of getting this set fully restored to it's peak functionality. eg. getting rid of it's minor but annoying cataract, rejuvinating the high hour crt if possible or finding a replacement, cleaning the rust and dust off, recapping, ect. Basically give this thing the full TLC.

I wonder if you remember how you turned off the power.
Did you turn it off with the TV switch or did you turn it off with a switch at the variac?
The variac is a large coil, turning the power off to it can cause an inductive kick-back and produce a voltage spike. The voltage spike could cause something on the TV power input to short.

Trying to rejuvenate a color CRT is very iffy, there is a good possibility that it could make the CRT worse.

Color set can get out of adjustment and require a pattern generator to correct the convergence, etc.

When this set was produced a color TV was the most complicated electronic device in a home by a wide margin.

SS sets 1980 and newer are typically several times more complex than anything from the tube era....The difference is SS sets hide their complexity in integrated circuit chips and by encapsulating much of the wiring in the PCB. Tube sets every component is serviceable.

If your set is like mine it's a 25XP22 CRT (I forget if mine is a AP, GP or XP, but they're all interchangable) which is a major blessing. The 23" and larger console CRTs are MUCH easier to find than the 22" and under table model /mini-console CRTs. Basically all console sized delta-gun CRTs (and a good portion of table model CRTs) the same envelope size are compatible. They made delta gun rectangular CRTs from 1965-around 1980 when inline gun tubes replaced them in new TVs. There is one thing to be aware of in 1968 the US government passed a law changing CRT size measurement from the industry standard of glass bulb diagonal to being the diagonal measure of phosphor screen viewable area. So the same tube made in 1967 as a 25XP22 would be labeled as a 23VXP22 if made in 1969.

There's tons of worthless SS 70s consoles in ugly Mediterranean cabinets with compatible CRTs out there like Zenith CCIIs and RCA XL-100s (granted the XL-100 name lasted far past the end of the delta gun era). Zenith came out with black matrix CRT technology (calling it Chromacolor) in the 1970 model year and RCA and others soon licensed it, and it is a MASSIVE improvement in picture quality. The Zenith Chromacolor CRTs tend to be VERY long lived. I've upgraded some of my 60s sets to 70s Zenith black matrix tubes and it always makes a nice improvement in picture.

I checked the tv and the picture tube has a label on it that says "21GWP22" I am unsure though if this is the original picture tube that came with the set when it was new though.

I do remember turning the tv off directly on its own power/volume knob, the variac remained on and at the same voltage when the popping noise occurred in the seconds after tv was shut off.

Yeah that makes sense to me I figured it was a capacitor issue. I traced down the likely origin of the problem as being somewhere in the power supply circuit.

Diodes going bad? I did not ever think to suspect diodes could fail, were early diodes more prone to failure back then?

Also what are your thoughts on there being performance issues caused by all those old carbon comp. resistors? I know they are notorious for drifting upwards in value as they age. They are also noisy usually. The issue though is that carbon film resistors will introduced inductance into the circuit which I heard apparently may cause issues in a vacuum tube circuit. Is it worth messing with replacing all the carbon comps and if so what should I replace them with?

According to the pictures furnished, it looks like the original CRT. It's made by Motorola if the label shows an EIA number 185. That CRT wasn't that great!

Shorting of electrolytics in the power supply could kill the diodes.

My approach to resistors would be to first see what circuits have problems and then test the resistors, rather than a blanket replacement. The small inductance of a spiral resistor is not likely to cause trouble unless it is actually carrying high frequency signals (IF or RF). In the typical case, resistors in these circuits are bypassed by small capacitors anyway. In tube circuits, stray capacitance can be an issue, so component placement and lead length can have an effect, again, mostly in the IF and tuner. So, I wouldn't worry about the resistor type in video and sweep circuits, but have a bit of caution when working in the IF and especially the tuner.

The most likely parts in electronics of that era is the electrolytic capacitors.
That is why the best thing to do is assume they are bad before applying power.
Semiconductors are easily damaged by excessive current or voltage. A tube can withstand an overload for a few seconds but semiconductors will die in an instant, often without making a sound or without any smoke.
Of course any part can go bad. Many times TVs or radios are retired because something went bad and the owner doesn't want to bother getting it fixed.

Yes, stay away from the IF and Tuner since you don't have the test equipment for readjusting them. An exception might be carefully cleaning the contacts in the tuner.

What would my options be as far as replacing the picture tube go? I am not concerned about whether the replacement picture to would be original for the time period of the tv so as long as it physically fits and is electrically compatible.

The picture tube has a minor cataract and is very high hour so I may end up having it replaced eventually if not now.

NOS is fairly rare but the first places I would check are the early television museum earlytelevision.org, and one of our videokarma members (ohohhodafarted) websites. Besides that the only source is another delta gun color TV the same screen size (also somewhat rare).

CRTs we're meant to be rebuilt not replaced but it's a process that takes highly specialized equipment and skills that died with the CRT TV era.



If you were closer I'd be tempted to trade my working but musty smelling 23" moto for your 21".

I was worried that replacements would be rare. I did find an ebay listing for a picture tube that I thought was compatible. It is a 21GFP22. I am a bit skeptical though that it actually works and has no issues as the tube has a sticker on it saying "intermittent short". The seller insisted it works but I am not going to buy it when I have no way of testing it for quite some time.

https://www.ebay.com/itm/35355898043...YAAOSwTyhg4B50

Where is the anode connector on your tube? The 21GFP22 has it on the side, like the 23EGP22. I suppose if you had to, you could replace the HV anode lead with a longer length to use.the more common CRT types with the anode button at the top. The "22" CRT types, AFAIK, will also fit; that means you could use 22JP22 or 22QP22. I have a TS-918 with the GFP tube, fortunately mine is still very strong and makes a nice picture.

Well the current crt picture tube in the tv which appears to be the original is actually a 21GWP22. However I read somewhere online that a 21GFP22 was compatible as a replacement which was why I was looking at the one I mentioned on ebay. The 21GWP22 picture tube has the anode at the top. I may want to replace the rubber anode cap as well since it is white from oxidation and may be breaking down chemically. I would be willing to pay a reasonable price for a guaranteed working preferably low hour CRT picture tube that would work in my TV. It does not have to be original or time period accurate. As long as it will work!

If your chassis has the HV cage at the left side (viewed facing the rear of the set) then you could use the GFP tube without any modification since the side anode button will be near the HV cage.

I can confirm the HV cage is indeed on the left side of the tv when viewed from the back.

I have identified the primary point of failure in the tv as an impregnated wax paper cap in the power supply circuit. The capacitor failed open and is located right under the line filter and next to where the line power comes in. I noticed the tv has another with an identical value of .15mf and 400V on the top of the chassis. I will also replace that one as well, as the reliability of wax paper caps is notorious for not being good. Will check over the fuses and the circuit breaker once more as well.

Honestly should have realized this sooner, I did see it but did not realize it was a wax paper cap due to the plastic shell on it.

On the plus side ALL the electrolytics in the tv including the can caps all tested GOOD according to the capacitor wizard, which was a big surprise to me.

Don't trust that; electrolytics in the power supply and sweep circuits need to be replaced. Same with the paper caps in power supply, sweep, and audio. But for next power up, electrolytics.

Alan is correct.
I had to look up "Capacitor Wizard". That is an ESR (Effective Series Resistance) tester. ESR is important consideration sometimes in solid state circuits, but not very important in tube circuits.
Tube circuits are effected more by electrical leakage and effective capacitance.
A capacitance leakage tester set to the proper voltage and with one capacitor lead disconnected from the circuit is the proper method.
Once one lead is disconnected you may as well replace the capacitor.
Even modern capacitance meters have there problems, excessive leakage can throw off the reading.

I did not realize ESR was not as big of a deal in vacuum tube stuff. I kind of figured it was too good to be true that ALL the electrolytics in this tv were somehow not having some issues. The storage conditions of this tv over the most recent 20 years prior to me getting it were not ideal at all, humid hot and sometimes flooded basement. Honestly surprised it managed to turn on at all the first try before that safety wax paper cap split open.

It sounds like it is more practical and easier time wise to just replace all the electrolytic ideally since disconnecting one lead is already half the work.

What is the easiest way to remove old can caps? And what about the simple axial stand alone ones? Luckily this tv does not have a ton of electrolytic just a handful or so. The frustrating thing I noticed is how hard it is to find the higher value ones that are both high voltage and high mf. Even on digikey it appears that some of the ones I need are just not in production anymore.

Will definitely make sure to replace them now that I know that ESR is not necessarily telling the whole story about the health of these caps.

From what I have read online though the ceramic ones should be fine still as they are VERY reliable. Which seems to make sense as I have yet to ever run across a bad ceramic cap yet in all my time of working on electronics (albeit almost all of my experience had been vintage 80s and 90s computers)

It is just funny how it always seems with any electronics 30 years and older, solid state or not, computer, tvs radios ect almost always start having issues with capacitors. I would say nearly every issue I had was a capacitor related problem.

I mean were electrolytics not as reliable decades ago or is it just age catching up with them?

You don't need to remove can caps unless you are planning to restuff them using the unroll the bottom crimp method. You can just disconnect all the positive leads from the cans and wire new caps in elsewhere. If you do want to rebuild the (pull off cardboard sleeve if present) cut can ~1" up from base, drill holes in base so wires from inside can reach terminals, install new cap bundle and cover with cardboard sleeve (or metal foil tape top back on) method is faster and poses less risk of accidentally stabbing your own hands multiple times (I've tried both methods ask me how I know).

Old capacitance standard values went 1, 2, 3, 4, 5, 6, 7, 8, 9 (and powers of 10 multiples there of)
new capacitance standard values go 1, 2.2, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2, 9.1 (" ")

So if you can't find an out of production 200uF lytic go look for a 220uF...In fact look for it anyways because if you find the old 200uF it'll be MUCH more expensive. Lytics usually had more than 20% tolerance on capacitance.

Never order a cap with a lower voltage rating than the original.

Mouser and digikey have capacitance and voltage filters to make searching easier.

Ok that is a relief, and makes things way easier knowing that. Another question though. It it OK to replace an electrolytic cap in the tv with a ceramic cap as long as it has the correct mF as mentioned and same voltage or higher. Or will the ceramic cap bother the tv? For example replacing 10uf 15V electrolytic with a new small ceramic one which is 10uf and has a voltage rating of 50v?

I am asking because I have a ton of ceramic caps laying around and it so happens SOME of them seem to fit the values needed for the lower volt/low uf caps.

Here is a page from a very useful website "Phil's Old Radios".
He has many articles about restoring various radios and TVs. (Radios and TVs are mostly made of the same kind of parts.
https://www.antiqueradio.org/recap.htm

I hope you are not confusing your capacitor types.
Here are some general guidelines.

"Paper caps" are capacitors that use paper (sometimes soaked in oil) as the dielectric (separator). The outer case can be many things, like a cardboard
tube sealed with wax, a ceramic tube sealed with wax or plastic or a molded plastic case. Most paper caps were phased out before about 1970.
All paper caps should be replaced with ones using a plastic film instead of paper.

"Ceramic caps" are often small ceramic tubes with wire bonded to the ends or (more recently) discs of ceramic with wire leads coated with ceramic.
Unless physically damaged ceramic caps are nearly always fine.

"Mica caps" early on are rectangular stacks of mica sheets with wire leads that have a molded plastic case. Modern ones are dipped in a epoxy like brown plastic. Mica caps are MOSTLY fine. Try not to twist old rectangular cases micas around the leads, that could cause the seal to fail. Some in circuits with a large voltage difference across them or large pulses have been found to fail.

Many times ceramic and mica caps are used in tuned circuits, if you replace them the new caps will not be exactly the same and you will need to re-tune the circuit. That can take special equipment.

The most unreliable caps are electrolytic. Because they contain liquid or at least moist paper they eventually fail. Generally I replace electrolytic caps if they are older than 40 years.

Keep in mind that these guidelines are based on probability. Some people come back from Las Vegas with more money than they started with, but not many. Also no one ever made radios or TVs to last forever.

Pay attention to the way that capacitance is expressed.
1000 pf (mmf) (uuf) = 1 nf = 0.001 uf (mf).
1000 nf = 1 uf (mf).
Most ceramic caps are less than 1 uf (mf). Even film caps seldom are more than 10 uf (mf) and they are very large in that value.
Mica are commonly in values 1 pf (mmf) (uuf) to 1000 pf (mmf) (uuf).
The reason for the most part for using electrolytic caps is that they are smaller and less expensive that other types for the same capacitance.

Based on the values it sounds like the 'ceramic' caps you have ar ceramic encased Tantalum dielectric caps.
I believe modern tantalums will sub fine for lytics, but haven't tried those in tube gear to be sure.
Ceramic dielectric caps are usually disc caps and typically aren't seen in values above 0.1uF. The old school ones that look like 30s era dog bone resistors are typically pF (aka mmf in old speak).

Paper caps shouldn't be replaced by ceramic dielectric caps as ceramics are not temperature stable and exhibit piezo electric dimensional changes in dielectric thickness and thus capacitance as voltage is applied so in some applications where they get high voltage AC waveforms they will pass them in a non-linear fashion.

Tantalum caps can be useful for their small size, BUT they degrade permanently and fail if they are EVER reverse biased. So, typically used only for bypassing power to ground, not as interstage coupling or waveform generating components, where the voltages on either end can rise at different rates during turn on.

Safest thing in restoring old gear is to replace electrolytics with electrolytics.

I just pulled this capacitor out of the tv and I am not sure what type it is. It is definitely not an electrolytic. I can not identify it but it resembles the "black beauty" or "black cat" capacitors. Can anyone identify it?

https://imgur.com/a/KWQtDRu

That is a Motorola brand cap and I don't know whether it is paper of plastic film. It is a molded plastic case.
There were some caps by Sprague that looked similar. The ones with white printing were paper, the ones with red printing were plastic film.
That was a situation that was not very common where it was hard to tell from the general look.
Those could actually be made by Sprague but branded by Motorola, that kind of thing happened many times.
If you have a capacitance leakage tester that tested using hundreds of volts it would tell if the capacitor is good.
I'm pretty sure someone else may know how they are constructed.
I have cut similar caps apart but it can be hard to tell, the paper can be extremely thin and look transparent like plastic. They also can be very tightly wound.
Also from the time the TV is from they could be either one. Sometimes the SAMS parts list states if it is paper or plastic. SAMS also lists electrolytic caps separately.
With out knowing for sure, I would not replace those unless they were suspected to cause a problem.

If I couldn't prove it's not paper I'd change it...$0.50 and a minute of soldering is easier than having more things to doubt after a recap when it doesn't work.

Ditto.

Where was this in the circuit?

The capacitor was physically on the top part of the chassis near the high voltage box. As far as the schematic goes it looks to be in the general area where the vertical output tube is and the other stuff related to the vertical.

Electronic M has a point. I could go either way with this.
However if you are a newbie to this kind of stuff (and you sound like you are) you may create more problems than solve them.
Not only do you have to get the type, value and voltage rating right but you must not make a mistake connecting to the right points. With electrolytic caps you also get the polarity right. It takes a level of concentration that someone that has done a lot of can take for granted. I have come to this conclusion after helping many newbies.
I would definitely replace the electrolytic caps, those almost always have a metal case even if that is covered with a plastic film or cardboard.
You really should get the service info on the set, that may clear up some facts like the type of capacitors and where they are in the circuit.

Yeah I am going to be very careful and take my time with this recap and repair for sure. I will also check everything over before I attempt to power back on. I am taking photos of everything in the chassis as well after and before each step. I do have the sams photo fact for this tv luckily but it only seems to state if a capacitor is electrolytic or not. The part list makes no disctinction between ceramic, mylar, wax paper ect though.