blonde '62 Magnavox 27" info & help

[airgrabber-6]

Hopefully picking this set up on Thursday, with any luck. It's a blonde '62 Magnavox with a 27" CRT. Love the rounded screen, cool styling, and seemingly "advanced" features. It has a light-sensing photocell that automatically adjusts picture brightness and "power tuning." Is the 27" screen the biggest you could buy in 1962? Anyone have any information or comments (good or bad) on this set? Schematic availability? Tips, advice or common pitfalls? Someone warned me that the 27" CRTs are often weak or dead. Are replacements available or can they be rebuilt? Thank you for your help.

It's identical to the set on this link except the finish: http://www.tvhistory.tv/1962-Magnavox-Brochure-2.JPG

[jr_tech]

Originally Posted by airgrabber-6

Hopefully picking this set up on Thursday, with any luck. It's a blonde '62 Magnavox with a 27" CRT. Love the rounded screen, cool styling, and seemingly "advanced" features. It has a light-sensing photocell that automatically adjusts picture brightness and "power tuning." Is the 27" screen the biggest you could buy in 1962?

Yes, I think the 27" monochrome sets were the largest available in the early 60s....DuMont did make a 30" monochrome set in the mid 50s, but it was a round tube.
jr

[airgrabber-6]

Originally Posted by jr_tech

Yes, I think the 27" monochrome sets were the largest available in the early 60s....DuMont did make a 30" monochrome set in the mid 50s, but it was a round tube.
jr

Thanks! I thought that 27" was pretty large for the time period. Hope the CRT tests good. The seller told me the last time he tried it (10 years ago) that it worked...I asked him not to power it up again. I assume that big-screen DuMont is a pretty rare bird?

[electroking]

Regarding the 30-inch DuMont, just have a look at this thread:

http://www.videokarma.org/showthread.php?t=14750

Good luck with this project!

[DaveWM]

I have the 27" crt, and it was big buck back in the day from the price list I have seen, like double a 21-23".

That is an easy chassis to work on, I think 3 of the caps are the white tube
1kv type that may or may not be bad, the rest are prob ok.

uses a power transformer so not a hot chassis, and a voltage doubler which prob has a bad cap (all 3of mine did)

Don't rejuve the crt, even weak they can make a decent pic, and you will have a hard time finding a replacement so no need to risk it.

Flybacks run hot on that so dont be suprised if you see leaking tar, it may look bad but will prob be ok, just leave it be.

Lastly if you get a very slow hula movement in the vert (1 cycle aprox 15 seconds) make sure you have a good clean PCB to Chassis connection on the deflection pcb. It just uses sheet metal screws and a clamping pressure to make contact between the PCB ground and the chassis ground.

[airgrabber-6]

Originally Posted by electroking

Regarding the 30-inch DuMont, just have a look at this thread:

http://www.videokarma.org/showthread.php?t=14750

Good luck with this project!

Thanks and thanks for the link! Cool stuff!

[airgrabber-6]

Originally Posted by DaveWM

I have the 27" crt, and it was big buck back in the day from the price list I have seen, like double a 21-23".

That is an easy chassis to work on, I think 3 of the caps are the white tube
1kv type that may or may not be bad, the rest are prob ok.

uses a power transformer so not a hot chassis, and a voltage doubler which prob has a bad cap (all 3of mine did)

Don't rejuve the crt, even weak they can make a decent pic, and you will have a hard time finding a replacement so no need to risk it.

Flybacks run hot on that so dont be suprised if you see leaking tar, it may look bad but will prob be ok, just leave it be.

Lastly if you get a very slow hula movement in the vert (1 cycle aprox 15 seconds) make sure you have a good clean PCB to Chassis connection on the deflection pcb. It just uses sheet metal screws and a clamping pressure to make contact between the PCB ground and the chassis ground.

Thank you Dave, that's exactly the sort of information for which I was looking. The voltage doubler cap will be the first one I check. Also...provided they test out of range, can the three white ceramic caps be re-stuffed or is it preferable to just replace them? I can bring the set up on my Variac very slowly to see if I get raster either before or after recapping.

[DaveWM]

just replace, they are hidden on the underside of the vert chassis, near the HV section. They "may" be ok, pretty sure the are paper inside, but the hard tube shell prob protects against moisture better than the old wax tube kinds. I think storage conditions matter a lot here on whether or not they are going to be ok. I find about 7/10 are ok of the ones I have checked.

My prefered method of startup on old sets is to pull the HOT tube out (not just disconnet the plate), being very careful not to pull the plate cap off the tube, Check the B+ for shorts with a meter, looking for around 10k after the caps charge up a bit. if that goes well then a metered variac (both current and voltage) is used to bring up slow, maybe 10v watching the current, should be very low, if that goes well then I move up to about 20vac and let it set for a few min again watching the current. I keep doing this and monitoring the can for heat. If I can get up to about 70vac with no issues then I stop, replace the HOT and do again but this time ramping up to 115vac over about 10 seconds, looking/smelling for signs of distress.


I am sure everyone has there own approach, but I like this for that era sets that have been idle or unknown for a long time.

Not a big fan of shot gunning with out even check out, I like to base line the set before messing with it. Now if its older with wax paper caps, thats a diff story, on that I would just go ahead and replace them, then do the above.

[airgrabber-6]

Originally Posted by DaveWM

just replace, they are hidden on the underside of the vert chassis, near the HV section. They "may" be ok, pretty sure the are paper inside, but the hard tube shell prob protects against moisture better than the old wax tube kinds. I think storage conditions matter a lot here on whether or not they are going to be ok. I find about 7/10 are ok of the ones I have checked.

My prefered method of startup on old sets is to pull the HOT tube out (not just disconnet the plate), being very careful not to pull the plate cap off the tube, Check the B+ for shorts with a meter, looking for around 10k after the caps charge up a bit. if that goes well then a metered variac (both current and voltage) is used to bring up slow, maybe 10v watching the current, should be very low, if that goes well then I move up to about 20vac and let it set for a few min again watching the current. I keep doing this and monitoring the can for heat. If I can get up to about 70vac with no issues then I stop, replace the HOT and do again but this time ramping up to 115vac over about 10 seconds, looking/smelling for signs of distress.


I am sure everyone has there own approach, but I like this for that era sets that have been idle or unknown for a long time.

Not a big fan of shot gunning with out even check out, I like to base line the set before messing with it. Now if its older with wax paper caps, thats a diff story, on that I would just go ahead and replace them, then do the above.

Dave, I like your progressive and gentle method of bringing the set up...I think I'm going to copy your procedure rather closely. Thank you for the info!

[airgrabber-6]

Well, the old 'vox is now home...bought it for the princely sum of $25. It had been in the same family since new. I will post some new, better pictures soon if there's any interest.

[Phil Nelson]

Sure, I would be curious to see a photo of it working. Pose a small child next to it to exaggerate the scale, as they did in those old Philco photos of the "world's largest radio."

Phil Nelson

[airgrabber-6]

Originally Posted by Phil Nelson

Sure, I would be curious to see a photo of it working. Pose a small child next to it to exaggerate the scale, as they did in those old Philco photos of the "world's largest radio."

Phil Nelson

Phil...it's not quite in working condition yet. But I can probably provide the child to pose next to it!

[airgrabber-6]

Some pictures from last night, it's finally in my basement...

[DaveWM]

get it up and runing and watch leave it to beaver, peter gunn, mike hammer, hitch... the list goes on, some really fun old programming out there that was done in B&W, and no need to fuss with convergence

[old_coot88]

Here's hoping that your find is an exception to the rule, and that the CRT still has some emission left. Without exception, every 27-incher I've ever seen was flat on emission.
Bill(oc)