6BK4 versus 6BK4A
 

I thought I read somewhere here that there is a difference.
I guess there must be a difference.
Can someone tell what it is?
Thanks

Just a wild-guess... perhaps they improved the lead-glass shielding to reduce X-ray emissions from the tube? Color TV x-rays were a big deal sometime in the late-1960's as I recall.

I think it was the 6bk4c that had the heavy leaded glass. AFAIK they are all interchangeable, but later tubes are probably more reliable.

John

6EL4's are a great sub for a 6BK4. To be safe I always use one of either 6BK4C/6EL4 who needs extra xrays these days.

In fact during the xray scare days there were stickers we put on the sets that said we changed the tube to the type with the better shielding

Thanks guys. I just wonder what actual effects come
 

to the person recieving that radiation.
I was going to put the original 6BK4 but I guess it would be stupid to do so. I definately do not need any more radiation.
I am guessing it promotes spots of skin cancer maybe even effects on some internal organs like the eyes.
It creeps me out to think my favorite hobby is dangerous. I hope to have kids someday!

If someone has one of those stickers I would love to reproduce it for all of us to use!

TV X-ray danger... I am a nay-sayer. According to all that I have heard, the X-radiation produced by the high voltage supply in a color TV is harmless, unless you sleep inside the HV box for 1,350 years or something. Same as "drinking diet coke causes cancer". It does, if you drink 80 gallons per hour for 200 years, or something like that. I just love those government scare studies. "all things in moderation"

I would be more worried about RF radiation from cellphones. They say that brain tumors are on the rise, and on the same side of the head usually as where the victim holds a telephone among those who are glued to their phones in all phases of life. RF radiation, or just damaged tissue from hearing hours of "MaryboughtanewvacuumcleanerJoehadanaffairwiththem ailman'swifeinKansas,andOh,Ijustmissedmyfreewayexi tandIranaschoolbusofftheroadWOOPS!gotta-gonow-OhButIforgottosaythatIneedmorevinegarformyfootfung us-canyoupicksomeup?bleep-bleepDroppedcall...." That would give ME a brain tumor, and a pain in the buttocks as well. Glad I am not one of those people!

Enough of that I guess...

How about a 6BD4? Those are kind of rare, and are electrically the same as a 6BK4. Those seem to be in only 1955-57 color sets. They're neat looking, with a larger base than the 6BK/6EL4s. I wonder if those were even less shielded, or if they just weren't as good-working as the later tubes?

Charles

I've often wondered just how much exposure can have an affect on a person. I'm usually using the 6BK4C/6EL4 and 3A3C... and I've spent plenty of time behind the set with the cage cover off. I feel the same way as Charles... you probably have to spend lots of time cuddled up next to the tube. It would, however, be interesting to have a meter and gauge the amount of x-rays near the back of a set.

I have an interesting tube... looks to be a HV rectifier... a 3DR3. It has a thick lead shield covering the entire tube and it's heavy! I've never seen a set using this tube... I'm assuming it was likely used in the later years... maybe late 60s / early 70s.

They're used in the GE C-2 chassis from the early 70's.The only sets I remember seeing those in.

Yes; GE only as far as I know.

Charles

xrays - makes me think of that funny scene on Everybody Loves Raymond when all three male family members are waiting for the microwave to heat something up, so they all place their hands over there you-know-whats : ) Maybe that would help when sitting real close to these tvs too...

There is an article on the web somewhere (I cant seem to find at the moment) where experimenters are using 6bk4s as x-ray tubes in homemade x-ray machines. They dont work that well. the guy who wrote the article had a 6bd4, and it worked the best. Apparently the lead shielded 6bk4c is useless in this duty. They run these under completely different conditions than in a television set. I believe the formula was a whole bunch of voltage and a cold cathode.

I think the 6bd4 wont take quite as much current as a 6bk4 or 6bk4c. Since I tend to set the 6bk4 slightly hot, I would prefer a newer tube.

I think that a 6bk4 will only make little (if any) x-radiation unless the set is *broken*. 21.5KV isnt enough HV.

**edit** Found the link. I guess the best x-ray emitter ws a 6en4, not a 6bd4.

http://www.belljar.net/xray.htm

John

I seem to recall hearing that GE had to recall some sets in the late 60s due to defective tubes that emitted too much radiation. After that they seemed to really be on their toes.

I don't ever recall hearing of an epidemic of cancer among tv repairman, which I will take as a good sign!

I have the service manual for an Admiral color tv with a 21AXP22. It says not to operate the set without the safety glass as there will be xrays emitted from the center of the screen. The safety glass was enough to stop them.

A possible epidemic of cancer for TV repairmen from the 1960s/1970s would be lung cancer. Every one of them that I knew smoked.

I never thought about it much, but you're right! Only one shop owner I know has never smoked; all others do/did.

But off hand, I can only think of a handfull of TV collectors who smoke :scratch2: Most are nonsmokers (and unmarried)

Charles

I'm married & I don't drink or smoke.

There were a very few color sets in Australia that used tubes when color TV started in the mid 70's except those that were imported in test trials & those that were brought in by Europein migrents.

The most common was the Dutch made Philips K7 chassis that used a PD500 as a shunt regulator tube & was used inconjunction with the GY501 EHT rectifer, Philips in Australia had at one stage plans on the drawing board to manufacture these sets for the Australian market but in the end opted for the fully solid state K9 chassis instead.

The only tube color TV avaible in this country were sets based on the UK made Decca 30 chassis & these sets used a trippler & only 6 tubes.

Isnt't there a electronic tubes catalagoue that explains every tube?

There is a book that RCA had back in the early 1970's that explained most receiving tubes in the USA. I have a copy that I bought in 1976 at the beginning of my repair shop venture. It has been invaluable to me over the years. It also lists diagrams for color, and B/W kine's. too.

Check eBay.

The 6BK4s had a higher plate voltage and powere idssipation than the 6BD4. The X-rays produced by the HV regulator were proportional to the magnitude of the high voltage. In the 20-25KV range, the X-rays are pretty soft, and are absorbed by the metal HV cage, the cabinet, and the safety glass in front of the cRT (which also produces X-rays). As Charles stated earlier, the only danger might come from very prolonged exposure to an unshielded regulator or CRT ave very close range. Just don't sleep wit under your pillow while it is operating!