[ICOM] IC 735 Amplifier Keying circuit ?

[Gary Fiber]

Likely the relay if I remember correctly is an OMR-109. Its been 11 
years since I fielded daily tech support calls at Icom.
That relay, even though says it can handle some 2 amps of current, its 
the back emf from keying other relays within the amplifier that appears 
to get it and welds the contacts closed.
You are best to use a keying buffer from Ameritron, Sultantronics and 
others with any amplifier other than an Icom amp.
Also you can build a keying circuit using a 12 volt relay with 
appropriate contact rating. Just connect the coil of that relay across 
the ACC socket's 13.8 volts and PTT connections.
Every time you key the radio that external relay will close and your amp 
keys. You may want to put a snubber diode across the external remay 
coil, it helps with back emf and also speeds up the opening of the relay.

Hope this helps...

Gary K8IZ


On 3/27/2012 5:47 AM, Taylor Jim-CJT001 wrote:
> Good morning to the group.
>
> I just noticed that the relay that is used to key an external amplifier has become intermittent at least this is my suspicions. I can key the microphone several times and eventually the amplifier will key. At this point I'm not sure if the contacts are pitted, or some other issue is making the relay intermittent. With an ohm meter, sometimes the relay makes a high resistance contact, other times it appears not to close at all, and sometimes it seems to work correctly.
>
> The schematic calls it rly1, but on the board it is labeled as rly2. The relay is a small cylindrical probably reed type relay. The relay is my suspicion, but I guess it could be the transistor that drives the relay as well. Haven't checked that far yet.
>
> Has anyone noted this problem and or replaced the keying relay ? is the relay available from Icom ? is there a substitute out there ?
>
> Regards,
>
> Jim Taylor
> WB8HMD
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> To support QSL/QTH.net: http://www.qsl.net/donate.html
>


-- 
Gary Fiber K8IZ
GROL PG-19-6691 with Shipboard Radar Endorsement
Washington State Resident