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[Amps] SB-220 Project.

To: amps <>
Subject: [Amps] SB-220 Project.
From: Joe <>
Date: Mon, 3 Jun 2019 10:05:29 -0500
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I want to Thank EVERYONE who helped me bring this old SB-220 back from the Grave.

It so far is working beyond my expectations. So much so that I am actually somewhat scared of what other part may not handle the new capabilities. Someone made the analogy of installing a 454 V8 into a Ford pinto. And yeah... Good comparison.

Watching Grid current on key down, the highest it gets is about 180 ma. so way safe below the 240/250 limit true?

Yet I really do not know what it truly is putting out. My WATT meter was not too long ago calibrated against a Bird so I know it is close. Yet, with my TS-430S at 100 watts drive, it is pinning the needle on the watt meter full scale is 2KW. so it's making more than 2 KW.

Changes from "Stock" that were made are:

Harbach soft start,  Nice,,

Home brew HV cap and resistor section.

AnTeck Toroidal HV Transformer.  EXTREMELY Happy with so far. 1/3RD TO 1/4 THE PRICE of other replacements.

Changed the LOW/HIGH voltage switch into a Standby/Operate switch

Harbach RM meter HV Board,  Also Nice,
But not using the Bias section. With the New much higher HV Voltage the idle current with a stock Harbach Board was way HIGH like 250 ma. The tubes were turning orange doing nothing but idleing making no output power. I tried as Harbach said to add more diodes to the string to knock it down more and I did,  I added 10 more, and that knocked it down to about 180 ma. Better but still gets hot with not very long transmissions.

I loved the old home brew active bias that this amp had but got toasted, so hunted down a new one and someone suggested from Ameritron, their,......

EBS-1H Electronic Bias Board.
Works AWESOME!!!!!! In idle with no drive idle current is ZERO, slightest drive at all and you have bias and it's fully adjustable. I set it to where many said I should at about 150 ma.

The amp now in SSB the plates even at that 2KW+ out never change color at all, In CW at same output it takes a LONG CQ of say 30 seconds or so to start to get them to a dull RED.

ONLY with dead key down solid carrier can I get them to orange point and that is still like at 30 seconds or so. but they cool off very quickly.

so, so far very happy,

And again a GIANT Thanks to everyone here on list and many that helped me off list also.



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