DuMont 108A - Mansfield FOUND!!!!!

[bigaudioal]

I have been looking for my Mom's first TV for some time now, DuMont RA-108A - Mansfield. At an estate sale on Sat. in Buffalo, NY Tim (Kamakiri) happens upon this beauty! I cannot thank him enough for finding it, grabbing it and then being SO willing to trade/sell me the set. I love the old TVs themselves, but REALLY love the first sets that my parents remember watching as kids. It is a connection to their past that I get to enjoy owning and watching these sets.

Some people that you come across in life are special. Tim is such a person, and so glad I have met him through this hobby. He not only is a wiz at getting these sets going again, but is a true friend and wonderful person. Thank you so much, Tim.

[Kamakiri]

The best part about this hobby is being able to help bring such an important memory back to life.

That's what it's all about, Charlie Brown

[wiseguy]

I have a Ra-109, and it is a Great performing set, Even listening to the FM Radio is nice, it's really hard to Take Decent Pictures with these sets running .

[bandersen]

I just noticed on the RA113 on my workbench that when it's in FM radio mode the CRT screen is blank but the filament is still lit. So the CRT is slowly wearing out while just listening to the radio I've seen in other combo sets they cut the filament juice to the TV circuits when not in use.

[wiseguy]

same here but Sweep/HV is killed in the Radio mode, When you Select AM radio is Different, it Turns on the AM Chassis and Filament to Tubes in that Chassis, I have not looked at the Diagram in a while to see what goes on.
High performance set in it's day, I Really like this set. it's just so heavy!

Bigaudioal you will Love it

[Raddion]

That is one gorgeous looking television set, congrats!!!

[Kevin Kuehn]

Maybe as long as there's no beam current, the cathodes not taking a beating, and leaving the filament lit may actually save it from premature burn out?

What a nice guy, Tim.

[bars&tone]

Congratulations on acquiring the set you have been looking for!

[kramden66]

Glad to see you finally got the exact one you've been looking for , is mom still with us to appreciate this ?
I checked my ra-109 , mine is the one without the phono and am radio and yes in fm mode the crt is still lit , glad I don't use mine for radio and even if I did it would require a switch so I can go from the modulator to antenna to get fm , I think the only combo I had that shut the filament of the crt off when in radio or phono was the ge 802 or 801 , I get my model numbers confused.

mike

[N2IXK]

Originally Posted by Kevin Kuehn

Maybe as long as there's no beam current, the cathodes not taking a beating, and leaving the filament lit may actually save it from premature burn out?

Not sure about that. Operating tubes for long periods of time under cutoff conditions contributes to a particular form of degradation called "cathode interface formation" (aka "Sleeping Sickness"), in which the active emitting oxides interact with the cathode base metal to form a resistive layer which in turn begins to "insulate" the remaining active oxides from the base metal. This caused all kinds of problems in vacuum tube computers, which might have flip-flops and gates that stay cutoff for hours at a time. Eventually, special cathode chemistry (ultra high purity nickel alloys) developed for computer service to combat the problem, but ordinary TV types (including CRTs) aren't likely to use them.

Probably the reason that sets with "instant-on" almost always have dead CRTs....

[Kevin Kuehn]

Strange that the DuMont engineers would have stood for that, or possibly they didn't really understand the long term consequences at that time. I suppose with a TV CRT, that the useful life span of the CRT possibly catches up with any cathode interface formation - based on a hunch that most folks, used primarily the TV function.

[bigaudioal]

Originally Posted by kramden66

Glad to see you finally got the exact one you've been looking for , is mom still with us to appreciate this ?
I checked my ra-109 , mine is the one without the phono and am radio and yes in fm mode the crt is still lit , glad I don't use mine for radio and even if I did it would require a switch so I can go from the modulator to antenna to get fm , I think the only combo I had that shut the filament of the crt off when in radio or phono was the ge 802 or 801 , I get my model numbers confused.

mike

Yep, Mom and Dad still around. Both in their late 60's. I also scored two of my Dad's first set (630 clone. 1948 Crosley 307TA). One was working for a time, then lost both pic and audio. Have a nice bright raster. Set was completely recapped, except for the tuner. So doing that now, which is a PAIN IN THE BUT. 2nd Crosley being picked up next week. So will have a parts set at minimum for it. Hope to get that working soon. Will be great to have both my Dad's and Mom's first TVs in working condition.

[Phil Nelson]

I would not recap the tuner (or replace any other tuner components unless really necessary).

Phil Nelson

[wa2ise]

Originally Posted by Kevin Kuehn

Strange that the DuMont engineers would have stood for that,

Maybe the boss didn't want to pay for the heavy duty switch the heater circuit would call for, or a separate heater transformer and regular switch for the TV only tubes. But as few people listened to FM radio back then, maybe you're right that most everyone watched TV. And that the feature of FM radio was thrown in as a selling point, and it wasn't expected that anyone would actually use it.

There was an Emerson portable TV with AM radio, using series string tubes, so you couldn't kill the TV tubes heaters.

[Eric H]

Many of the combos I've seen left the heaters all lit while in Radio or Phono mode, kind of surprised that DuMont would have done that too but I guess it's hard to engineer a switch that will selectively cut off certain tubes, it would also be another failure point.

Are you going to call this set Jane (Mansfield)?