|
Title: SB200 Amp Post by: KS4QF on September 05, 2022, 01:05:27 PM I recently rebuilt a Heath kit SB200 Amp. As long as the amp is in standby mode the receive is normal. When I take it out of standby and apply the HV, the receive goes down. I've been building amp since I was 14, I'm now 67 and never faced this problem. Any ideas of what might be the solution to fix this problem?
Max/ KS4QF Title: Re: SB200 Amp Post by: w4bfs on September 05, 2022, 02:29:40 PM try removing the amp key line from the sb200 and carefully measuring the dcv on the center pin to ground. on an unmodified sb200 this is 100Vdc or maybe a bit more. if there are modifications to the amp - fess up
Title: Re: SB200 Amp Post by: KS4QF on September 05, 2022, 05:07:44 PM Bought this amp from a silent key. It has a soft start circuit and I installed a soft key board to be able to use my FT991A. I'll keep digging,. Thanks for the reply.
Title: Re: SB200 Amp Post by: KD6VXI on September 05, 2022, 10:03:02 PM Unplug the key line from the back of the amp, see if the problem goes away.
Guy just had a similar problem on eham. Turned out the key line from TX to thr amp had a short in it. New rca cable fixed him up. Maybe you'll get lucky! If not, I'd double check the wiring on the soft key. I built a soft key using a resistor, diode and an Irf640. --Shane WP2ASS / ex KD6VXI Title: Re: SB200 Amp resolved. Post by: KS4QF on September 06, 2022, 07:01:09 PM Thank you, thank you, thank you. I got my receive back. The Harbock Soft key circuit was causing my problem. I also am using a Ameritron 704 softkey circuit. I took the Harbock unit out of the amp and she is working like a real champ. I didn't need both keying circuits. I am now keying the SB-200 amp with the 704 keying circuit only. Thanks for bringing it to my attention. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
I appreciate everyone that responded to my question. Max/KS4QF |