8875 tube & Russian G17B

[KC8ZAO]

This is a question from a new ham.  I have been studying the different HF amps and the tubes they use.
One question, are the 8875 and the Russian G17b similar?  This is probably a stupid question for some of you but if I don't ask I probably won't get an answer :-).

[W7DJM]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=1502&item=5700948713&rd=1&ssPageName=WD1V

Is that what you are talking about?   Now, why?  Are you trying to convert an amplifier that uses an 8875(s)?

If it were me, I'd find a different amplifier that one with 8873,4,or 5's.

[KC8ZAO]

Thanks for the info.  Looks like I will try to find an AL-80b that I can pick up near Michigan and tackle a "project amp" when I have a lot more time on my hands and more experience in RF.  

[W7DJM]

In my opinion, an AL-80B is a nice amplifier for what it is, and the typical price on the market.

It is heavy enough that you can use if or some RTTY, no multi-multi contest use, though,

and it puts out PLENTY of power on SSB.

I had an earlier AL-80 (house fire) that I was going to (and still am) rebuild, but I got a good buy on a "B."


I'm guessing you got a buy on a "dead" amp for conversion?

[KC8ZAO]

No, I didn't buy an amp yet.  I was sort of looking before leaping into that big black hole called a money pit. :-)  I did that with a boat once.  The boat anchors went with the boat when I sold it.  Thanks again for your help.  I really do appreciate it.

Wayne

[W9GB]

If the amplifer has an 8875 .. it is probably a Dentron MLA-2500.  8875 is no longer made and rare to find as NOS -- it used conduction cooling.  Some users have converted these to other tubes - BUT require addition of forced air cooling (e.g. blower/fan).

If you want to buy and amplifier, spend an hour and read the eHam revioews and perform a GOOGLE search on the 2 or 3 candiates that you are interested in.
http://www.nd2x.net/index.html

Avoid the "sweep tubes" amplifiers -- they were built in the 1960s and 70s when sweep tubes were used in TVs - plentiful and cheap.  This is no longer the case -- the resale value on these amplifers is dropping fast -- some are being modified to use available Eastern Europe sweep tubes (El509/EL519) -- or surplus Russian miltary tubes (e.g. GI7b)
http://www.geocities.com/ko4nrbs/

Lawson Summerrow, W4EMF has performed a number of conversion and has web pages on the documentation.
Dentron GLA-1000
http://www.nd2x.net/w4emf-GLA.html

Dentron MLA-2500
http://www.nd2x.net/w4emf-MLA.html

Dentron Clipperton QRO
http://www.nd2x.net/W4EMF.html

w9gb

[WB2WIK]

The MLA-2500 didn't use conduction cooling, that I'm aware of.  It used 8875's which are transverse cooled (horizontal air flow across the tube, rather than vertical air flow through the socket and fins).  The conduction cooled version is an 8873, I think.

The Heath SB-230 and a Tempo 1kW desktop amp are the only "popular" amateur amps I can think of that used that turkey.

WB2WIK/6

[KC8ZAO]

Thanks one and all for the excellent feedback.  

Wayne
KC8ZAO
near Grand Rapids, MI

[W9GB]

"It used 8875's which are transverse cooled (horizontal air flow across the tube, rather than vertical air flow through the socket and fins)."

Steve - Correct the 8873 was the conduction (heat sink) verison.  Both the 8875 and 8873 are far too expensive if you can even find a NOS tube !

Greg
w9gb