[Heath] Operating instructions for Heathkit Apache transmitter (TX-1) & Single Sideband adapter (SB-10)

[Glen Zook]

The truth be known, the maximum rated SSB input for the 6146 and 6146A/8298 is 85-watts per tube and not the 90-watts input for CW.  As such, 170-watts input is the maximum ICAS rating for the tubes.  However, for long tube life, running the input power at no more than 150-watts and even like 140-watts or 130-watts will result in several times the tube life and, again, the station on the other end will not know the difference.


You really need to reduce power on 15-meters and 10-meters if you are going to use the TX-1 Apache on those bands.  On 15-meters about 90% of the power that the transmitter normally runs on 80-meters and for 10-meters about 80% of the power that the transmitter normally runs on 80-meters.


Heath was infamous for specifications that were at the maximum, sometimes even a little bit over maximum.  


One thing about the grid current for the 6146 tubes is that RCA originally specified a maximum of 3.75 mA per tube.  Then, that maximum was dropped to 3.5 mA, followed by 3.25 mA, and finally at 3.0 mA.  This was because it was discovered that the tube life suffers the higher the grid current.  I like 2.0 mA to 2.5 mA per tube for best tube life.

 Glen, K9STH 
Website: http://k9sth.net

      From: Kenneth G. Gordon <kgordon2006 at frontier.com>
 To: A Lawrence Fibich <lfibich at sbcglobal.net>; Heath at puck.nether.net 
 Sent: Saturday, September 10, 2016 6:35 PM
 Subject: Re: [Heath] Operating instructions for Heathkit Apache transmitter (TX-1) & Single Sideband adapter (SB-10)
   
What Glenn said. !!!!!!

NEVER exceed 6 mA grid current for a pair of 6146s. Your tubes will "go-away" in very short 
order. 2.5 mA grid current for one, and 5 mA for two is, IMHO, the absolute maximum.

130 watts OUTPUT from a pair of 6146s indicates something more than 200 watts input. If 
you try to get this much output steadily, the tubes will go-away even faster. If you can see 
the tubes, look at the plates when you hold the key down. I'll bet they are red hot. NOT 
GOOD!

A pair of 6146s will output about 100 watts on 80 meters when tuned up in CW. On AM you 
had better drop the "dead carrier" to no more than 80 watts output.

Dial it back.

Otherwise, you will lose not only tubes, but also power transformers and other components.

If you have the 110 page manual, then the procedure beginning on page 93, just under the 
paragraph beginning with the word CAUTION to the end of that page, and the first 5 steps 
on page 94 are all you will need to use to tune the transmitter up into a decent antenna. You 
do not have to set the bias as mentioned on Step 2 on page 94 more than the first time you 
check it.

Follow the steps exactly. Do them one at a time until you get good at it.

Although it may look complicated to you at first, with practice it becomes easy. 

Notice the admonition to NOT exceed 6 mA final amp grid drive !!!

Notice that the transmiiter is loaded to full output on CW when the plate current is 250 mA. 
!!!

This means that INPUT power is around 180 watts. Since the rig is operating in Class AB-1 
(if you have the final amp bias set correctly as mentioned on step 2 page 94), the output 
power would be no more than 100 watts since the average efficiency of an AB-1 amplifier is 
no more than 60%. 60% of 180 watts INPUT is 108 watts OUTPUT. Given other 
inefficiencies in the output circuit, 100 watts. OUTPUT.

Good luck.

   
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