[Heathkit] SB-201/200 no output on any band

[Carl]

I think Id start by pulling the AC cord.

Then check for continuity from the input connector to C-16 while 
manually closing the relay contacts. If that checks out verify that the 
band coil and the knob pointer agree.

Since you get the correct grid voltage and idling current that part is 
confirmed.

Im assuming that the input assembly was also changed during the upgrade 
and that the coax from the relay and the heavy wire to C-16 were 
installed.

Carl
KM1H


----- Original Message ----- 
From: "Tom Chesek" <tchesek at epix.net>
To: <Heathkit at mailman.qth.net>; <HEATH at LISTS.TEMPE.GOV>
Sent: Saturday, October 18, 2008 5:40 PM
Subject: [Heathkit] SB-201/200 no output on any band


I have an SB-201 which was converted to an SB-200 equivalent with a 
complete bandswitch swapout. I cannot tell you if it ever worked after 
the swap. This amp has the Harbach power supply mod and antenna relay 
including the resistor change that comes with the relay kit. The tubes 
are a pair of Cetrons which are soft but verified as working in my other 
SB-200 amp. Using the Taylor tubes from my SB-200 make no difference at 
all. There is no output on any band. I've cleaned the bandswitch with 
Deoxit, verified that the wafers are aligned with each other corectly, 
and verified that each contact has good wiping action. I have verified 
the -2vdc bias by measuring with a DVM and get a reading of -1.78vdc. 
The filament voltage measured at the tube side of the bifilar choke 
measures 6.72vac. The HV reads just under 2400vdc on the built in meter. 
The idling plate current reads about 98ma. PC1 & PC2 both have NOS 
carbon resistors. R21 and R22 are new also.

I've tried drive on each band from 30 watts to 100 watts with no output 
measured on the amps' meter or on the watt meter inline to the 50 ohm 
antenna load. If I drive it with higher power, such as 100 watts, the 
tubes will start to "cherry up" in color if I keep the key down for 30 
seconds or so. It almost appears to the that no rf is passing beyond C24 
but I have swapped that cap with the one in my working SB-200. All 
screws have been tightened to be sure the ground paths are intact.

Nothing is going up in smoke so where is my output? This is driving me 
nuts!

73 and Tnx,

Tom K3TVC

ps: for what it is worth I know that at one point this amp was modified 
for 11 meter use and then changed to the current SB-200 configuration.

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