harbach mod for heathkit sb221
I bought a sb 221 heathkit amp. I would like to mod it for 10 meter as well, but i know nothing about electronics. I have been reading ads and I keep seeing these ads that say they have had there amp mod with a harbach mod kit. What is it and am I on the right trail to find out what I need to know. I hope this question make sense to you. Thank you
The Harbach kit does not normally include the 10 meter mod.
It normally includes the "soft key" and "soft start" modifications, which (1) allow keying with modern, solid state transceivers; and (2) provides inrush current protection. Nothing to do with 10 meters.
If there's nothing wrong with the amplifier and you have a way to safely key it with your exciter, I wouldn't modify it at all. The original design was brilliant.
Harbach Electronics products are among the best, but like WIK said, most of the mods they offer are for updating an older design and for improving performance..
Lou Parascondola, W1QJ of King Conversions converts HF amplifiers to operate on the 6 meter band. In doing so, he removes the band switch, tank circuit, and other components not needed.. Some of these components are what you need to enable your amp to function on 10 meters. He often lists the SB-220/221 components for sale on some of the classified sites.
Here is the link to King Conversions' website.. Contact Lou and tell him I sent you.. He most probably has everything you need..
No need for soft start-Heath SB-220
There is no need to install a soft start kit in the Heath Kit Sb-220, for filament current. The filament transformer is just barely able to produce the required amps for the two 3-500 tubes. This is part of the design. When you turn it on, the current sags enough to protect the filaments, then goes to full current. If you are not familiar with HVDC=NO NOT REMOVE THE COVERS=.
Originally Posted by KD8LCL
THERE ARE MANY PLACES IN THIS AMP WHERE LETHAL VOLTAGES ARE PRESENT. IF YOU KNOW NOTHING ABOUT WORKING AROUND HIGH VOLTAGE DC AND HIGH VOLTAGE RF= just use the amp as is and don't try to improve on a proven design=OR TAKE THE GOOD PROBABILITY OF DYING.
Due to the CB craze in 1970s and rampant selling of illegal CB amplifiers, the FCC required legitimate mfg. to make changes to their designs or kits to make it difficult for usage of these amplifiers in the CB allocations (NO, easy "snip a wire" mod).
I bought a SB-221 Heathkit amp. I would like to mod it for 10 meter as well, but i know nothing about electronics.
For Heathkit, these can be identified by the usage of the number '1'.
Heathkit SB-220 (before) became SB-221 (after).
Since you have no electronics knowledge, you have 2 choices.
1.) Enjoy the amplifier on ALL the other bands you have access to.
The amplifier is most useful for 80 and 40 meter contacts.
2.) Contact King Conversions or other qualified amplifier repair centers regarding the parts, cost, and time for converting this SB-221 to a SB-220.
Nullius in verba
Proceed with caution and knowledge
Although I usually recommend digging in with meters and soldering iron as a learning tool--HV supplied amps are not the best of places to start gaining knowledge.
Do you have a manual and schematic of your amp yet? Now would be a good time to begin studying both--this way you can visualize the relatively simply construction of an HF amplifier--and get close to how it was made and what is necessary for it to operate correctly once put into your transceiver output chain.
A really good purchase is a 1960s or early 1970s ARRL handbook. These can be found in quantity on eBay for around $5 and sometimes less each. In it you will find great information about the components in this type of gear, how to use test equipment, and gain an understanding of what the various component stages in the amp accomplish.
For the 10m modification, you essentially need some components that have been left out of the unit as it now is. Understanding the ones that are currently there will inform you of what and why you are adding new ones for. As noted, many of the parts you need are available from folks who do conversions of the amps to 6M, or part out basket cases.
As recommended by others, try to use this amp as it now stands. 80 and 40m are its best uses--10m is really spotty now in the solar cycle, and when it improves, you will be astonished what a barefoot 100w will accomplish.
SKCC #4473, [URL="http://klara.us"]KLARA[/URL] ARRL VE Liason
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I believe at one time Heath did offer a mod kit for the 221 with proof of license - anyway, I have a 221 that has the fifth input coil and tap for the output and a five position bandswitch, but no marking for the 10 m position. I obtained a 220 manual and it is all installed and wired per the 220 manual - the original 221 manual that came with the unit has a note by the builder (no callsign unfortunately) that he installed the 10m "kit" but no schematic...that is where I draw my conclusion that Heath may have had a kit.