SB-401 output

[W6CUX]

Jim,
If you are tuning the driver coils with the RF probe in 
place, it is probably detuning the coils on 15 & 10. You 
should tune those coils as well as the het osc coils for max 
grid current as read on the meter. The het coil adjustment 
will be different when the het signal comes from the SB-301 
than when it is the oscillator. I have found that it is a 
compromise adjustment when you want to both transceive and 
transmit. Also make sure you have 6146s or 6146As and not 
Bs. I never could those to work on the higher bands.

The fact is you don't need grid current to operate the 
finals class AB1. The ALC just turns the gain down anyway.

gud luck es 73, Stu W6CUX

----- Original Message ----- 
From: "James Sutherin" <JSutherin at FBAINC.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Tuesday, March 08, 2005 1:18 PM
Subject:  SB-401 output


I'm currently working on getting a SB401 going again.
I have peaked the Het osc and the driver grid coils. I 
noticed for 21,
28 & 29 The grid drive was about 2.4 +/-volts as measured on 
pin 2 of
the 6CL6 driver. The other bands 80,40 & 20 were about 
4.5+/-. This also
affected the driver output as measure on pins 5 of the 
6146's The
voltages were measured with a RF probe and a VTVM. I also 
notice there
was almost no grid drive on 15 - 29.5 MHz, while on 80,40 & 
20 there
sufficant grid drive.

Was there any mods that were used to increase the upper band 
drive, or
is there something else I should be looking for?


Thanks
Jim K8DHC

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html