eHam Forums => Amplifiers => Topic started by: KA3JOI on November 22, 2003, 04:51:57 PM

Title: Connecting a SB200 to a TS850S
Post by: KA3JOI on November 22, 2003, 04:51:57 PM
I need help in connecting a SB200 amp to my Ts850S. I understand the rig has a 12VDC relay and the amp has a 120VAC relay in it. This definitely is no good !!! Do i need to build a interface ? Thank you.

Title: Connecting a SB200 to a TS850S
Post by: DK3QN on November 24, 2003, 02:09:19 PM
Hi there,

The relay switching voltage of the SB-200 is in the range of minus (!) 120 volts DC. I don't quite remember the DC current.

In case your TS-850's relay is capable of switching this kind of voltage and the approriate current you may directly drive the SB-200 from the 850 internal relay.

Otherwise (most likely) you need to switch the SB-200

a) by an inter-connected relay which can switch the -120 volts at some 100mA or so. The bad story about this option is that there are now 3 relays in a row which need to be switched over until your amp goes into transmit: the 850s' relay switches the interconnected relay (say on the 12 V DC level), and then the interconnected relay switches the SB-200 relay. This all takes time, probably 30 to 50 milli-seconds or so which makes SSB VOX or CW semi-break-in a no-no!

b) you may substitute the inter-connected relay by a semiconductor circuit (transistor) switch where the transistor must be strong enough to switch the SB-200 relay voltage (remember 120 volts negative at a significant current) to ground. This may shorten the switch-over time by some 5 milli-seconds. Not really a break-through with respect to the delay problem.

c) you may rework the SB-200 relay circuit. See info elsewhere on the web (there is a kit available). This would be the 'smartest' way as it eliminates the slow change-over relay of the SB-200 (my guess: 20 to 30 milli-seconds delay for the 'original' relay).

d) a very 'pragmatic' solution: use a well insulated foot switch and connect it to the SB-200 relay post via a shielded cable where the center of the cable goes to the hot relay contact and the shield to the ground (cabinet part). You need to step onto your foot switch a little earlier and in addition to pressing PTT or start talking into the mike (VOX) whenever you want to go TX. Very basic but works.

Hope this helps.

73, Klaus, DK3QN

Title: Connecting a SB200 to a TS850S
Post by: KV2F on November 24, 2003, 10:37:11 PM
Go to and purchase a soft key module for the SB-200.  Price two years ago was $22 including shipping.  Easy to install yourself, directions are clear, and you'll never have to worry about harming the keying relay on your TS-850.  Harbach is now run by Jeff W8CQ, nice fellow to do business with.  He also has a number of other mods for the SB-200, some of which I have installed in mine.  By the way, I just checked Jeff's web site.  He has posted a message saying he's moving to Ohio and the product descriptions and ordering instructions will not be available on the web site until December 1.  
Arnie KV2F  

Title: Connecting a SB200 to a TS850S
Post by: W9GB on March 13, 2004, 12:59:33 PM

Here are the standard references for SB-200 amplifier owners: