At 10:33 11/22/97 -0500, you wrote:
>Besides not having 10 meters, is there any other diferences between
the
>SB221 and the SB220. Is the SB221 a newer amplifier, and if so, does
it
>include improvements that eliminated the parasitic problem.
===============================================>
Len.
I'm sure you will get replies from others on this question, but here is
what I think I know about the SB-220 vs. SB-221.
Except for 10 meters being an after-add to the bandswitch wiring, they
are the same amplifier, except....
Late versions of the SB-220 and, I suppose all of the SB-221 runs, had a
different capacitof for C1 which had just a little bit wider plate
spacing in the design. This was an attempt to stop arcing and spitting
when the parasitics might occur.
As for my SB-220 which I had for many years,
AA)
I put the old W4UX electronic bias circuit in it (QST; May, 1974).
BB)
Dropped the switch relay voltage (keying) down to just a few volts at
just a few milliamps (Hints & Kink; QST, January, 1988),
CC)
Added a standby switch by putting a very small SPST switch in one of the
small front panel holes that had one of those 4 small chrome headed
screws in the four corners.
(I've seen some pretty terrible standby switch installations in my
hamfest tours)
DD)
Put back-to-back 1N1004 diodes across the panel meters.
BTW, when you load it up, do so in CW at 99 WPM.
That way you limit the voltage driop from the power supply,
and tune the amp for where it will normally be running, as opposed to
loading it for a lesser voltage set of operating parameters.
I never did have to replace the tubes, and I never had spitting during
operation.
The elimination of tube idling current between dits and dahs or from
riding along with voice modulation was a very wonderful add to the
amplifier.
None of those other wonder adds were ever implemented into my
amplifier.
I have added the low voltage relay activation and W4UX circuitry to my
TL-922A also. They are nice mods.
Similar EBS circuitry and relay voltage mods have been made to my 4-1000A
amplifier (6,000 VDC)
I have, as of yet, not made any similar mods to my Ten Tec Titan.
The Titan is so wonderful, I don't think I can bring myself to alter it
in any way.
73,
N5RP
Bob Perring
12715 Westmere
Houston, Texas 77077
tele: (281) 493-5780
fax: (281) 493-5780
Std e-mail: perring@infocom.net
Int'l e-mail: N5RP@compuserve.com
<underline><color><param>0000,0000,ffff</param>http://www.infocom.net/~perring/bucky.html
</color></underline>
Bob Perring
12715 Westmere
Houston, Texas 77077
tele: (281) 493-5780
fax: (281) 493-5780
Std e-mail: perring@infocom.net
Int'l e-mail: N5RP@compuserve.com
<underline><color><param>0000,0000,ffff</param>http://www.infocom.net/~perring/bucky.html
</color></underline>
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|