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HYS TC-300 Amplifier Bias Mod?

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Firebreather
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HYS TC-300 Amplifier Bias Mod?

Post by Firebreather » Thursday, 07 September 2017, 9:44 AM

Hey gang,

I picked up a Chinese made HYS TC-300 amplifier (looks similar to the RM KL300) from a guy liquidating a bunch of his gear for $25. The amp was like new and still in the original box so I figured I couldn't go wrong for $25. I hooked it up last night to mess around with it and with my Lincoln II+ turned down to 1.5W dead key, this cheap little splatter box sounds pretty good on AM. With swing I had it peaking around 125W with good, clean audio. SSB however is a completely different animal. Even with my Lincoln peaking between 8-10 watts PEP, the SSB audio is atrocious. No combination of wattage reduction/mic gain reduction could clean it up to where I would be happy with it. I'm not saying I'm surprised by this, but I've also heard of guys doing an A/B bias mod to these amps to clean them up on SSB. Has anyone heard of this mod? And if so, does anyone have any specific info on how to perform it? If I can clean up the SSB performance of this amp, it would make a great backup for my current 2 pill mobile amp. If not, perhaps I'll just keep it as a backup AM amp. Any and all thoughts welcome. Thanks!




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Re: HYS TC-300 Amplifier Bias Mod?

Post by MDYoungblood » Saturday, 09 September 2017, 5:33 AM

A lot of those Chinese amps are thrown together with whatever transistors they have on hand until the stock is depleted, that has MRF 247's in it, it took a little engineering to get them to work on the HF bands, they are more suited for 2m and with a couple of changes they make a great 2m amp. Your Lincoln II is still too hot for it but for that price use it until it blows I say, would last longer if you had a Uniden Bearcat 980.

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