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Hy gain model 488

rogodee

New Member
Jan 22, 2026
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I have a Hy Gain model 488 amplifier with an issue. When I turn it on from sb to tx, the receive cuts out. The amp outs out power, ect, but I lose the rx when I put it on tx.
 

Is this in a mobile setup or home? What do you have for an antenna setup? Coax cables in between in good working order?
 
I have a Hy Gain model 488 amplifier with an issue. When I turn it on from sb to tx, the receive cuts out. The amp outs out power, ect, but I lose the rx when I put it on tx.
When you put it in tx does the relay pull in?
Or does it pull in when you key the radio?
I don't remember, does that one have a preamp?
Is it new to you?
I bought a skyhook amp one time and discovered that the standby switch was actually a tx/rx switch.
Previous owner bypassed the key circuit and switched the relay manually no ssb delay needed......

73
Jeff
 
A more-common scenario is that someone drove it with excess power and blew out the transistor that senses the radio's RF and closes the relay. The schematic calls it the "RF Sniffer". Has two NPN transistors. Most any generic small NPN transistors would probably do the job okay. 2N3904, 2N2222, 2N4400 are typical examples among literally hundreds.

If you can see the relay operate when the standby switch is thrown to operate side, that would be my educated guess.

Unless someone has modified it, and then all bets are off.



73
 

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In my mobile setup, the foot warmer would stay transmitting after unkeying while on SSB. Turned out to be a bad coax from the radio to the amp. Changed it out and things were ok. I did double check the magmount antenna with the old MFJ antenna analyzer and things checked out.
 

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