As someone bloody insane enough to have a Cub shipped over to the USA that ended up needing a new tripler, I've been following this thread in the shadows...
FYI, Donberg have jacked up the prices even more- when I tried to order a HRT 241BP, they did the HRT 240BS substitution, but also charged me 51.70 EUR, more than double their listed price on the website. Not good. I paid it and it fixed my Cub, but... it's been bothering me that there seems to be something special about the focus network on that tripler. While waiting for it to arrive, I had been wondering many of the same things about substituting other triplers. From what I can tell, the design of that "universal/Philips" style being mentioned appears to electrically match that of many triplers used in 1970s-era American-made TV sets, aside from physical dimensions, mounting, et cetera.
But why is the Cub's focus network different than the typical standard? Strangely, I believe this answer actually lies in the type of tube socket used by the Cub, in a sense. The Mitsubishi 370GUB22 seems to be a rather obscure tube: the only references I can really find online outside of Cubs are in B&K/Sencore CRT tester documentation, which reveals one uses a CR-23 adapter to test said tube. I spent a while trying to figure out what exactly CR-23 means, until I stumbled upon https://www.radios-tv.co.uk/bk-467-adapters/, which claims "Model CR-23 Adapter: Tests RCA 90 deg. Bi-potential in-line 19VHYP22, 19VJKP22. Many video arcade game monitors."
This eventually led me to this very interesting 1979 paper from RCA, in which the following can be found:
![Image]()
It would seem that the tube base/socket (circled in red) used in the Cub was originally devised by RCA for a new line of tubes in the late 1970s in which focus voltage was increased from 20% of anode voltage to 28%, necessitating a new socket design that could handle the increased focus voltage.
This probably explains why the tripler has an "unusual" focus network... the RCA TV sets that we had over here that used those tubes did not have triplers, in fact, the Cub's usage of one is rather anachronistic by the standards of American TV sets and monitors of the early 80s... we mostly stopped using them by the late 70s in favor of the "modern" style flybacks you'd find in, say, a CM8833.
As to how Mitsubishi ties into this, it's pretty simple: they had a license from RCA for RCA CRT technologies and their tubes were often very good clones of RCA tubes. From what I can tell, the 370GUB22's physical dimensions are an exact match to that of many early 1980s RCA "13V" size tubes, e.g. A33AAB20X...
FYI, Donberg have jacked up the prices even more- when I tried to order a HRT 241BP, they did the HRT 240BS substitution, but also charged me 51.70 EUR, more than double their listed price on the website. Not good. I paid it and it fixed my Cub, but... it's been bothering me that there seems to be something special about the focus network on that tripler. While waiting for it to arrive, I had been wondering many of the same things about substituting other triplers. From what I can tell, the design of that "universal/Philips" style being mentioned appears to electrically match that of many triplers used in 1970s-era American-made TV sets, aside from physical dimensions, mounting, et cetera.
But why is the Cub's focus network different than the typical standard? Strangely, I believe this answer actually lies in the type of tube socket used by the Cub, in a sense. The Mitsubishi 370GUB22 seems to be a rather obscure tube: the only references I can really find online outside of Cubs are in B&K/Sencore CRT tester documentation, which reveals one uses a CR-23 adapter to test said tube. I spent a while trying to figure out what exactly CR-23 means, until I stumbled upon https://www.radios-tv.co.uk/bk-467-adapters/, which claims "Model CR-23 Adapter: Tests RCA 90 deg. Bi-potential in-line 19VHYP22, 19VJKP22. Many video arcade game monitors."
This eventually led me to this very interesting 1979 paper from RCA, in which the following can be found:
It would seem that the tube base/socket (circled in red) used in the Cub was originally devised by RCA for a new line of tubes in the late 1970s in which focus voltage was increased from 20% of anode voltage to 28%, necessitating a new socket design that could handle the increased focus voltage.
This probably explains why the tripler has an "unusual" focus network... the RCA TV sets that we had over here that used those tubes did not have triplers, in fact, the Cub's usage of one is rather anachronistic by the standards of American TV sets and monitors of the early 80s... we mostly stopped using them by the late 70s in favor of the "modern" style flybacks you'd find in, say, a CM8833.
As to how Mitsubishi ties into this, it's pretty simple: they had a license from RCA for RCA CRT technologies and their tubes were often very good clones of RCA tubes. From what I can tell, the 370GUB22's physical dimensions are an exact match to that of many early 1980s RCA "13V" size tubes, e.g. A33AAB20X...
Statistics: Posted by techfury — Fri Mar 22, 2024 3:24 pm