Yaesu FT 920 with FL 2100B

Discussion in 'Amateur Radio Amplifiers' started by W8BXR, Nov 11, 2014.

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  1. W8BXR

    W8BXR Ham Member QRZ Page

    I recently bought a Yaesu FL 2100B and I can't get it to key from my 920? I read something about a sensitive switching transistor in the radio but have no Idea where to look and what part number, if they can be found. I bought an ameritron arb 704 but not sure how to hook it up or if I actually need it. Any ideas or sugesstions would be most appreciated. I also hear about something called a soft start. Thanks all Gerry kd8rfo 73
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If you didn't flip the TR-RY switch on the rear panel of the FT-920 to "RY" before you tried this, you blew the keying transistor inside the rig.

    The FT-920 manual specifically states the rig cannot be used to key an amplifier providing negative polarity keying, and the FL-2100B is negative polarity. However, if you switch to "RY," then the 920 uses a keying relay and not a transistor, and it can handle either positive or negative keying.

    Did you flip the switch??:eek:
  3. W8BXR

    W8BXR Ham Member QRZ Page

    Yep, I flipped the switch, so I guess I blew the keying transistor. So I'll have to find a shop to get it fixed cause I got no idea what to look for inside the cabinet and how it is put together. Thanks I guess I should have got a heathkit.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If you flipped the switch to RY before you ever turned on the FL-2100B, that should not have blown the keying transistor.

    It would blow if you did not flip the switch to RY before ever connecting to or turning on the FL-2100B.

    You can check this.

    First, disconnect the Yaesu and just short the two leads together at "RY" and "E" on the back of the amplifier (with the amp turned on, of course!).

    That's not hazardous voltage, it's about 16Vdc or so and won't shock you. Try that and make sure the amplifier relay keys okay. If it does, then the problem isn't the amplifier, it's the rig.

    Next, use an Ohmmeter to measure across the two leads coming from the Yaesu (with the amplifier disconnected, so you're connected only to the Yaesu).

    With the "RY" switch in the "RY" position, key the PTT on the Yaesu and see what happens on the Ohmmeter. It should go from an open circuit to a short circuit. If it does, there's nothing wrong with the Yaesu, either. If it doesn't, then the Yaesu keying circuit doesn't work.
  5. W8BXR

    W8BXR Ham Member QRZ Page

    The amp relay seems to be working. It makes a clicking sound and I assume that's the relay. I think I didn't make the switch on the 920 before I hooked everything up. I hooked up the ARB 704 and that's probably where I went wrong. So I need to get that component for the radio and try to replace it. I've got everything un hooked now and the 920 seems to be ok other than trying to use the amp. Thanks
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Can you get some local help from a nearby ham who knows amplifiers pretty well?

    Did you "test" the FT-920 as suggested above to see if its keying relay is working? Takes about five seconds, and you only need an Ohmmeter....
  7. W8BXR

    W8BXR Ham Member QRZ Page

    I've called some of the local hams and just waiting on one of them to come by when they can and get it checked out. Thanks all.
  8. W8BXR

    W8BXR Ham Member QRZ Page

    I blew the relay, so now it's waiting time until January to send it somewhere to get fixed. Then I'll send out the amplifier and have it checked out.
  9. W8BXR

    W8BXR Ham Member QRZ Page

    Yep you are right the keying circuit doesn't work. I don't know if I can bypass it somehow to get my amp to work or if it will set on the shelf until I can send it out to be fixed. thanks
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I seriously doubt you blew the relay. What you likely blew was the keying transistor which in turn keys the relay, because you didn't switch to "RY" first, before attaching the amplifier. That's pointed out in the FT-920 owners manual.

    No way to bypass this, the transistor likely needs replacement.

    You could use the amplifier without keying it from the FT-920, if you get a 2-pole footswitch and wire it up to key the amplifier and then the rig. This works completely independently of the rig's amplifier keying circuit. This is an example of a footswitch that will do this job perfectly: http://www.hamradio.com/detail.cfm?pid=H0-006038

    You connect it to the PTT line (NOT the amp keying line!) of the FT-920 and also to the RY and E terminals on the back of the amp, following the instructions it comes with.

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