Minty Motorola 9T1 restoration

[bandersen]

A local collector I'd done work for previously dropped a Moto 9T1 a few days ago for restoration. He hinted it was in very good condition.

That turned out to be quite the understatement! I do not believe the back has ever been off this set. The screws holding the masonite back on were pristine

Only cosmetic issues are the knob brights fell out (have two) and a little scratch in the embossed "Motorola"

Every tube and capacitor is Motorola branded.

[AlanInSitges]

Holy crap look at that thing! What a perfect specimen.

[Notimetolooz]

Very nice!

I guess very once in a while a example shows up that has been sent here through time from the past!
In this case I would be tempted to re-stuff all the caps instead of making it obvious the caps are new. A lot more work doing that though.
Pretty tight chassis also.

[bandersen]

Yep, all Moto tubes. The getter is used up on the 6SL7 and half gone on the 12SN7s, but they all light up.


I spent several hours tying to slowly reform the caps while using an Amperite ballast tube. They are still warm to the touch but I was able to get some life out of the screen and speaker.



I am able to pick up 87.7 MeTV FM (AKA NTSC channel 6) radio, but their video subcarrier is so weak now I have trouble getting it on any set.


With a strong signal source on the antenna terminals. Not a bad start.

[Electronic M]

Originally Posted by bandersen

Yep, all Moto tubes. The getter is used up on the 6SL7 and half gone on the 12SN7s, but they all light up.


I spent several hours tying to slowly reform the caps while using an Amperite ballast tube. They are still warm to the touch but I was able to get some life out of the screen and speaker.



I am able to pick up 87.7 MeTV FM (AKA NTSC channel 6) radio, but their video subcarrier is so weak now I have trouble getting it on any set.


With a strong signal source on the antenna terminals. Not a bad start.

Bob, back at the end of JULY the FCC mandated all NTSC analog cease even ch6 METV FM Chicago. METV FM was able to strike a compromise with the FCC that their NTSC analog video carrier is now replaced with an ATSC carrier, but they are still transmitting analog audio at 87.7.

[bandersen]

Well that explains it and marks the final end of an era in my area

On to more positive thoughts... I carefully snipped out the 5 HV caps and tacked in ASC replacements.
I took a lot of reference photos and am carefully storing all the old caps. I'll be giving the owner two repairs estimates. One with all new caps and one for a full restuffing. Either way the caps will be saved. They have nice Motorola logos under all that wax.





That got me this. OK reception but unable to get a sharp focus. After a few rounds of troubleshooting, it suddenly started working much better. For a while... then back to a muddy image. Let it cool down and sharp picture gain.



Still have a few paper caps to replace so I'm not too concerned yet.

I did learn something useful while digging through the HV bleeder resistors. They all have around 700-1,000 volts across them but they appear to only be 1W carbon comps. Those have a max voltage rating of only 500. I've seen other electrostatic sets use 2W which are good to 750. Either way, that's really pushing them.

Now I do have a supply of Vishay VR37 resistors good for 3,500 volts I can pop in, but they are light blue and will run the originality.
Still on the fence - originality vs reliability Will consult with the owner.
https://www.vishay.com/resistors-fix...product-28907/

[bandersen]

I'm using a 7VP1 scope CRT by the way. The 8BP4 tests like new on my Sencore CR70 but I have yet to try it out for real.

[Kevin Kuehn]

Wow, someone definitely took very good care of that all these years. Maybe it was a closet TV.

[bandersen]

Lol. I got around to testing the tubes and half are bad. The 6AG5 RF amp is full of shorts. The 6SL7 and two 12SN7 and very weak. A few 6AU6 are marginal. Suprising it works as well as it does.

I'm thinking they used it a moderate amount and never had it serviced. It's a shame, but they have to go.





That ratio detector cap has blown t's guts. Amazing the set works as well as it does on all these bad parts.


I've never seen one of these sets with every single screw on the HV cover in place.


Chassis is stamped Dec 14, 1949


No nonsense recap is done. I saved all the original caps and took loads of reference photos. If the owner wants the restuffed, I will.

[bandersen]

Nuts. Intermittent fading problem persists. Trying to determine if it's a connection or thermal issue.

[AlanInSitges]

There are some cursive-logo tubes available on eBay, I might be tempted to replace the bad ones with matching tubes. Such a nice set.

[vortalexfan]

It looks like Motorola used Copper-Oxide Coated chassi in their TVs like Zenith did in their sets, I wonder if that was a Chicago thing...

[edison64]

I noticed that there are several yellow branded Motorola tubes in that set, it would have originally came with all white logo and apparently it must have been serviced at some time because the yellow logos if I remember right, service or warranty work was denoted by yellow logo tubes. Are the date codes very similar on both tubes?

[bandersen]

I suspect you are correct about it having been serviced. There are three 12SN7 tubes and they do not match each other.

I replaced the 12AT7 mixer oscillator and placed a shield on the 6AG5. It seems to be stable now. Will periodically run it a few hours over the next few days to make sure.

Coincidentally, I picked up a cosmetically minty 9T1 of my own in July, 2019. I have not pulled the chassis yet but only one tube appears to be Motorola branded.

[dieseljeep]

Originally Posted by edison64

I noticed that there are several yellow branded Motorola tubes in that set, it would have originally came with all white logo and apparently it must have been serviced at some time because the yellow logos if I remember right, service or warranty work was denoted by yellow logo tubes. Are the date codes very similar on both tubes?

The yellow branded Motorola tubes are Sylvania sourced. They're probably original. That must be the first model run where Motorola had the tube supplier print their logo on the OEM tubes. The earlier models were equipped with tube branded with the supplier's name.