Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Nov Mon 23, 2020 10:25 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 15 posts ] 
Author Message
 Post subject: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Thu 19, 2020 5:12 am 
Member

Joined: Mar Sun 09, 2008 8:05 am
Posts: 555
Location: Santa Cruz, California
On Ebay there are currently a total of three possible substitutes for this iconic set. They're not 7DP4's, but 7TP4's. A tube that I've read were used in studio monitors. I'm intrigued with possibly springing for one -- if not now, then at some point later as another becomes available -- as I have one of these sets and like the idea of having a spare in case the original goes south. One is in New Jersey and the other two are in....Brazil.

Questions then: how well do these travel? Seems very dicey with having these travel so far by common carrier(s) and bouncing along on terminal conveyor belts. And is it too big of a chance in assuming this tube will work in lieu of the original 7DP4's?

Here are the links:

https://www.ebay.com/itm/NOS-7TP4-CRT-T ... SwEVhfpEC1

https://www.ebay.com/itm/7TP4-CRT-Kines ... SwSyBfV50K

Chris


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Thu 19, 2020 7:13 am 
Member

Joined: May Sun 07, 2017 11:35 am
Posts: 1135
Location: Belrose, NSW, Australia
Depends entirely on how it's packed.

Forget bubble wrap and foam chips! You need a properly designed support such as a urethane foam nest.

_________________
Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Thu 19, 2020 11:05 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 657
Location: Columbus, OH
We have a couple of military tubes that works perfectly.

https://earlytelevision.org/7dp4_replacement.html


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 12:04 am 
Member

Joined: Mar Sun 09, 2008 8:05 am
Posts: 555
Location: Santa Cruz, California
That's good to know -- thanks Steve. I'm wondering if the GL-4592 is just a militarized version of the 7TP4? They seem possibly the same.

Chris


Last edited by KJ6OFC on Nov Fri 20, 2020 4:29 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 3:47 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 9643
Location: Redlands CA
If it has the original shipping box it might survive, I had a GL-4592 shipped and it was fine, it also had Mil Spec packing though.

The TP4 can run 12K of high voltage, the DP4 is rated at 8K max so realistically it might be running 7k in the set, which might be too low for optimal performance with the TP4?

I don't know what the spec is on the 4592 but it does work in the 621.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 3:42 pm 
Member
User avatar

Joined: Feb Thu 17, 2011 11:27 pm
Posts: 14169
Location: Long Island, N.Y.
Honestly, the 7DP4's are not known to have a high mortality rate from what I've seen in all my years collecting vintage TV's. At this point in time, if you use your sets now and then for short periods that have a good CRT, they will likely outlive you. Getting spare CRT's "just in case" is a pricey idea and very likely never to be used. I don't even understand why a collector with an mediocre CRT, say with a brighter on it that plays decent, replaces it? I have a 10BP4 with one on it and it's been playing perfectly fine for many years now. I guarantee I'll never need to replace it. Just my thoughts.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 7:00 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 813
Location: Rockaway , nj 07866
I've shipped picture tubes a couple times to California with no issues - I used FedEx to other areas too and on rare occasions u.s. post office ,I would never trust ups with a crt


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 7:05 pm 
Member
User avatar

Joined: Mar Sun 22, 2020 5:56 am
Posts: 962
Location: Arvada, CO
I think electrostatic tubes are rather long life in general. That excludes the 3KP4, as the filament was put under stress.

_________________
Electronics are filled with smoke. It’s my job to put the smoke back in when they fail.
Cheers,
Jay


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 8:24 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 1447
Location: Pewaukee, WI
Mr. Highlander wrote:
I think electrostatic tubes are rather long life in general. That excludes the 3KP4, as the filament was put under stress.
You're laboring under a misconception...
The RCA 621TS being discussed was the only 40's 7" set to use an ELECTROMAGNETIC deflection CRT...


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 9:11 pm 
Member
User avatar

Joined: Mar Sun 22, 2020 5:56 am
Posts: 962
Location: Arvada, CO
:oops: Uh Oh. Your right. I didn't look at the tube. I thought it was some variant of the 7JP4. I apologize.

_________________
Electronics are filled with smoke. It’s my job to put the smoke back in when they fail.
Cheers,
Jay


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Fri 20, 2020 11:45 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6193
Location: Montvale NJ, 07645
I have shipped CRT's and received them. Biggest one I shipped was a 21" color roundie to Florida. Never had a problem.

The most likely to get damaged by vibration are electrostatic deflection CRT's, but I still think that the odds are in favor of shipping them with plenty of bubble wrap. I just sent a 7JP4 clear across the Country and it arrived OK.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Sat 21, 2020 6:38 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 657
Location: Columbus, OH
We have shipped almost 100 CRTs from the museum. Only one didn't make it. We double box them with padding between the boxes.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Sat 21, 2020 7:30 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 9643
Location: Redlands CA
Steve McVoy wrote:
We have shipped almost 100 CRTs from the museum. Only one didn't make it. We double box them with padding between the boxes.



That one was probably the 16AP4 I bought. It broke because the neck was sticking through a hole in the cardboard packing, a sideways jolt knocked the neck off.

I've had mixed luck with shipping CRT's. Original boxes help.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Sun 22, 2020 2:29 am 
Member

Joined: Jan Thu 16, 2020 12:29 am
Posts: 813
Electronic Memory wrote:
Mr. Highlander wrote:
I think electrostatic tubes are rather long life in general. That excludes the 3KP4, as the filament was put under stress.
You're laboring under a misconception...
The RCA 621TS being discussed was the only 40's 7" set to use an ELECTROMAGNETIC deflection CRT...


Which I agree with, in the USA, except, if you include video monitors/viewfinders with a smaller size. Also used at this time was the 5" 5FP4, which is electromagnetic.

In the UK though there were two electromagnetic TV sets in 1939, the HMV904 and 905 that used the Emiscope 3-1 and Emiscope 3-2 CRT's, 5" and 7" respectively. A 5FP4 makes a good replacement for the 3-1 and a 7DP4 for the 3-2 with some modifications.

If you go from a non aluminized tube to an aluminized one, it is important that the EHT is a least 5 to 6kV. This is because more beam energy (electron energy) is required to penetrate the aluminization. After that threshold the light output is higher than a non aluminized CRT as its all reflected forward. Unfortunately in sets like the 904 & 905 you cannot use an aluminized CRT as the EHT is only around 2.5kV. At least in the 621TS the EHT is high enough to support an aluminized CRT.

If you increase the EHT, the size of the raster decreases and you need more deflection current. This is because, all other things equal, the amount of defection in an electromagnetic CRT is inversely proportional to the square root of the EHT. This is one of the main reasons why electromagnetically deflected CRT's won out against electrostatic CRT's in the TV industry. In electrostatic deflection, the deflection is inversely proportional to the EHT itself, so if you double the EHT you need to double the deflection voltage and for a set over 12" screen, you start to require deflection voltages of over 1kV peak to peak. But in mag deflection the square root relationship assists considerably. In addition there is the considerably simpler gun structure for the mag deflected CRT.


Top
 Profile  
 
 Post subject: Re: RCA 621TS Picture Tube Thoughts?
PostPosted: Nov Sun 22, 2020 7:36 am 
Member
User avatar

Joined: Mar Sun 22, 2020 5:56 am
Posts: 962
Location: Arvada, CO
Yes, small ones. I didn't do research, and I looked like a clown.

Hey Steve! That 19EKP4 I bought from the EFT was really great. Here's what I did with it: viewtopic.php?f=12&t=374530

_________________
Electronics are filled with smoke. It’s my job to put the smoke back in when they fail.
Cheers,
Jay


Top
 Profile  
 
Post New Topic Post Reply  [ 15 posts ]  Moderators: Mr. Detrola, 7jp4-guy

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests



Search for:
Jump to:  




































Privacy Policy :: Powered by phpBB