[AMRadio] 6U8 Subststute?


jeremy-ca km1h at jeremy.mv.com
Sat Nov 10 15:20:17 EST 2007


The 6U8 was not reliable and was replaced by the 6U8A.
The 6EA8/6GH8 came along as having better performance in VHF TV tuners and 
FM radios. They can be substituted for the 6U8/6U8A in most circuits but not 
always. I believe Collins S Line receivers are problematic in one socket; 
not sure where.

If the 20A is running them too hot then I'd check out the circuit for 
something causing excessive current drain. I used a 20A decades ago and 
never had that problem.

Carl
KM1H




----- Original Message ----- 
From: "Jim Candela" <jcandela at prodigy.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Saturday, November 10, 2007 2:20 PM
Subject: [AMRadio] 6U8 Subststute?


>
>
> ----- Original Message ----
> From: Ellen Rugowski <ellenjoanne2003 at sbcglobal.net>
>
>
> Nope, not yet Steve.  Fred, KC1XF, is sending me a 6EA8 in the mail
> (that's
> just gathering dust for him), and it hasn't arrived yet.  It's a direct
> substitute for the 6U8, and others who voiced the same opinion as you -
> that
> the 6U8 is kind of wimpy, and the 6EA8 will be a better driver.
>  Hopefully
> it'll arrive in today's mail (Fred sent it out on Tuesday of
> Wednesday).
>
> 73,
> Ellen - AF9J
>
> Reply By Jim, WD5JKO:
>
>  Ellen,
>
>   The Central Electronics 20A uses a 6U8 also and these run pretty hot. 
> The tube lifetime is not very long. I have searched far and wide for a 
> more beefy substitute that shares the same base diagram. The 6EA8 or 6GH8 
> do not have any advantages over the 6U8 that I can see. I finally bumped 
> into the 6MU8. These have similar ratings except the pentode Pd is 3.8 
> watts whereas the 6U8 pentode Pd is 2.75 watts. The main difference 
> besides that is the 6MU8 has a taller glass envelope. The last I looked, 
> www.tubesandmore.com had the 6MU8 NOS for $2.75 each.
>
> Regards,
> Jim
> JKO
>
>
> http://tubedata.tigahost.com/tubedata/sheets/049/6/6MU8.pdf
>
> http://tubedata.tigahost.com/tubedata/sheets/020/6/6U8.pdf
>
>
>
>
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