Seeking Specs on 8908 tubes

[n7kn]

I pulled this square peg (octal based, more accurately) out of a Hy Gain 644
"Footwarmer". It was marked "HyGain 760002". I was told that it's an 8908.
Both tubes have suffered a "smoke leak" (vacuum leak) and need replacing.
None of my manuals give the specs for this tube. I would like to find a
less expensive substitute.
Does anyone have it in any of their books?

[Dennis W. Ostrowski]

There is NO direct replacement that I know of.

Maco, (a CB linear manufacturer in the 70's), worked with GE to put that tube
into a compactron based package called the M-2057. (later called the Y-2057).

The M in the tube designation stood for MACO. (MAjestic COmmunications Co,
Memphis, Tn.)

The closest match to an existing tube with an octal base is the 6LW6, but the
filament voltage is different, the transconductance figures are less, the
capacitance numbers are different, and I believe the base pin outs are
different.

If I remember correctly, that Hygain Footwarmer was a grid driven amplifier and
I had to change it's input and output tuning to match the pair of 6LW6 tubes.

The original tubes had their filaments connected in parallel, and you have to
connect them in series in order to use the pair of 6LW6's

The 6LW6 CAN be made to work as a sub. in that amp. because I have done it; but
that was long ago, and I don't trust the accuracy of my memory enough to provide
any greater detail.

I hope the limited amount of information that I was able to provide will be of
some use to you.

Regards,

Dennis O.

[n7kn]

Thanks for this infomation. It isn't much, but it's a start.
Unfortunately, my books don't cover the 6LW6 either.
If you replaced them with the 6LW6 and rewired the filaments in series, that
should tell me the 8908 is a 12 volt tube.
8908s are available through RF Parts for $100 each. I really don't think
this old CB amp is worth dumping $200 into.

I think I might be better off to salvage the parts for a future project
using 811As or some other currently produced tube.

Dennis W. Ostrowski <dwost...@lucent.com> wrote in message
news:3B575587...@lucent.com...

[Skipp]

Hi there,

I actually have the GE data sheet for that tube, but you won't find them
cheap or easy. Best to retrofit the amplifier with some 811a types and get
on with your life. I've only seen two or three mfgrs use that tube and
it's physical large so I just installed a pair of 811a's and they work
fine when set for the proper zsac.

cheers
skipp

http://sonic.ucdavis.edu

: n7kn <n7...@hotmail.com> wrote:
: I pulled this square peg (octal based, more accurately) out of a Hy Gain 644

[n7kn]

I would be interested in seeing that data.
And, that is the plan I'm leaning more toward. 811As look very appealing at
17.50 each rather than $100.
I would be very interested in a homebrew project involving four 811As that
has been written more recently than 1970.
I think the earliest design I have was published in QST in 1960.
73

Skipp <sk...@pilot.ucdavis.edu> wrote in message
news:9jag8i$gc5$2...@woodrow.ucdavis.edu...