should I cut the tension band or mounting hardware on a 25GP22?

[Electronic M]

Yesterday I got a NOS Channel Master brand 25GP22 from Bob G.
I'm trying to install it in an Admiral that used a 25AP22....According to my sams CRT sub book they both cross to a 23VALP22 (yet neither is listed as a direct sub for the other) so I think electrically and bulb size wise it should work.
The new 25GP is a "speed fit" (all mounting hardware, degaussing coils, and shields come mounted to it) tube for Zenith sets, and the mounting ears that bolt it to the set are WRONG for the admiral (can't bolt it in).

I'm going to have to reuse all the mounting hardware from the previous CRT to make it mount, and that means I'm either going to have to cut the tension band (there is NO safety glass on this CRT) and remove the mounts it came with (which is 1 cut and guarantees a clean fit) or cut each ear off the mounts (8-12 cuts, and some hacking of the admiral's hardware).

What should I do?

[zeno]

Must be a built in safety screen. Dont remember ANY
rectangle color CRT without it. I wouldnt mess with the tension band
unless someone has done it. IIRC Admirals had big rubber
corners you had to cut for some swaps like the 23EG's BUT its
been over 40 yrs !!!! Zeniths had the ears as mounting &
the big fold-up DGS shield but I dont remember any big
rubber corners. Truth is its been to damn long & my memory
sucks..... May be you are hoping for a sub where there is none ?

73 Zeno

[dieseljeep]

Originally Posted by Electronic M

Yesterday I got a NOS Channel Master brand 25GP22 from Bob G.
I'm trying to install it in an Admiral that used a 25AP22....According to my sams CRT sub book they both cross to a 23VALP22 (yet neither is listed as a direct sub for the other) so I think electrically and bulb size wise it should work.
The new 25GP is a "speed fit" (all mounting hardware, degaussing coils, and shields come mounted to it) tube for Zenith sets, and the mounting ears that bolt it to the set are WRONG for the admiral (can't bolt it in).

I'm going to have to reuse all the mounting hardware from the previous CRT to make it mount, and that means I'm either going to have to cut the tension band (there is NO safety glass on this CRT) and remove the mounts it came with (which is 1 cut and guarantees a clean fit) or cut each ear off the mounts (8-12 cuts, and some hacking of the admiral's hardware).

What should I do?

You don't ever want to mess with a tension band CRT.
More often than not, it'll implode in your puss. The tension band is cemented on with some form of epoxy resin.
Even cutting off the ear mounts, with the tension band, makes it rather hard to install in the original front bezel.
When altering anything on a tension band CRT, make sure to wear eye protection, or even better yet, a full face shield.

[radiotvnut]

A TV repairman friend cut the tension band on a 25V CRT and it wasn't long before it went BOOM! It's a miracle that he wasn't cut to pieces.

[jr_tech]

"should I cut the tension band or mounting hardware on a 25GP22?"

Do not cut the tension band !
The tension band provides implosion protection for the tube by placing the front panel of the tube in compression. Tension is likely on the order of 1000 to 1500 lbs. Without the tension band, you have a very unsafe condition, a tube that could implode easily. It is unlikely that you have the tools to re-band the tube after changing/removing the corner ears, so the tube will continue to be a hazard even when installed in the TV set.
Cutting off the ears is a less hazardous operation, but not risk free. Wear a "flack jacket" and full face mask, and be sure your neck is protected.

jr

[Electronic M]

Originally Posted by dieseljeep

You don't ever want to mess with a tension band CRT.
More often than not, it'll implode in your puss. The tension band is cemented on with some form of epoxy resin.
Even cutting off the ear mounts, with the tension band, makes it rather hard to install in the original front bezel.
When altering anything on a tension band CRT, make sure to wear eye protection, or even better yet, a full face shield.

On this jug the Band is wrapped over the shield and mounts and there is no cement on it...Perhaps it is not a proper tension band?....At the least it is meant to hold the mounts on the CRT.

I'm probably going to hack saw/file the ears off the mounts, unless someone tells me that band is not bad to remove or comes up with a better idea.

[jr_tech]

There were many slightly different methods, some used epoxy under the rimband, others did not. Epoxy or not, the tension band is likely vital to the implosion protection system.
How about a picture of what you have?

jr

[Electronic M]

Here you go.

[jr_tech]

Ok! Then there appears to be no bonded safety glass... The tension band over the clam-shell is indeed the only means of safety protection. I would not remove the t-band! Even if you did, I suspect that you might find that the ears are spot-welded to the clam-shell and you would have to cut them off anyway, which would be very hazardous with the tension removed.

Jr

[Electronic M]

I'm leaving the band and sawing off the three mounting ears (per corner). The corner set's original corner brackets look to fit correctly that way from the test corner I did.

There are 8 push on rubber bumpers (as part of the admiral's factory mounts) that break the unsupported parts of the sides into thirds...They will be tighter with the band on, but I can make them just fit.

[DaveWM]

I ran into the same thing with a quik fit crt for a zenith. I think you did the right thing to no mess with the band. I ended up not using it but will save for a zenith that fit as is.

[dieseljeep]

Originally Posted by DaveWM

I ran into the same thing with a quik fit crt for a zenith. I think you did the right thing to no mess with the band. I ended up not using it but will save for a zenith that fit as is.

I honestly, never saw a CRT with all the mounting hardware installed. I knew they existed, but never considered it, because of the cost.
Most of my customers, that owned Zenith sets, requested a Zenith CRT, to be installed. I always considered, the regular type Zenith CRT's, to be the easiest CRT's to replace, the Motorola's, the worst. You had to fiddle with the mounting ears and the CRT went in from the front.
I guess C-M tried to win over more customers, with these schemes. I never liked the picture quality of even a brand new C-M. Most of the better line rebuilts, had a better picture.

[DaveWM]

I guess in a real high volume shop they make sense, but to me its really not that big of a deal to reuse the hardware.

The funny thing is even though its a zenith quick fit with all the hardware, it did not fit the zenith I wanted to use it in.

I have a Y zenith and the CRT was for an X, no joy. I ended up using a VDC standard replacement, still banded but no ears, The band made it somewhat of a difficult fit into the old magnetic shield (the crimp coupling would not fit inside the shield, I had to notch the shield for it). All that work and then I find the shadow mask had a defect resulting in a slight purity issue that I can't work out. I should have just left the old CRT, it was tired but at least no purity issues.

[andy]

...

[ohohyodafarted]

The correct answer is DO NOT REMOVE THE TENSION BAND WHILE UNDER VACUUM

I watched Scotty at Hawkeye do some rectangular tubes for bowling alley monitors. The band was removed only after the crt was at atmospheric pressure. After the tube was rebuilt and under vacuum, the final step was to replace the tension band using steel strapping like is used in strapping wooden crates. A special tool is used to apply the tension on the steel strapping and then another tool is used to place a clinch fastener to hold the bands tight. All done while tube is under vacuum. When I saw Scotty fasten the new band and tension it, I was afraid it would implode, but actually the tube is more likely to implode with the band removed.

I would use a high speed carborundum cut off wheel to saw the ears and remove them.

Bob