SR-655HPC will not transmit or will not modulate on AM – Stryker Amateur Radios

Use this list when an SR-655HPC (V1, V2, or HPC+) will not transmit, will not key, or “won’t modulate” on AM. Work top to bottom. If the meter shows SWR HI (or HI SWR) when you key, start at step 4. The 655 does not show E4; E4 is the 447HPC2.

Confirm the generation first: Which 655 do I have?

1. Mode and band

Set the radio to AM if you are trying to talk AM. The 655 is AM / FM / PA only — it has no SSB.
Start on band D if you have not programmed the radio. SR-655HPC Setup Guide · How do I get to bands F–L?

2. Microphone

Hold the mic with the grill toward your mouth and press PTT for the whole sentence.
Try a known-good Stryker-compatible mic. What microphones are compatible with your radios? The 655 mic is a 4-pin. How many pins does the SR-655HPC microphone have?
Do not open the radio to turn internal modulation pots unless a technician asked you to.

3. Power and talkback

Turn RF power / variable power up from minimum.
Turn talkback up and key. If you hear yourself, the radio is keying. How do I hear myself with talkback on the SR-655HPC or SR-955HPC?
Watch the display on key-up. A big voltage drop is a power-wire issue. When I transmit the display shows my voltage drops

4. Antenna, coax, and SWR HI

SWR HI on the meter (and usually a beep) means high SWR. The radio stopped TX on purpose. Check the antenna, mount, and coax. Radio shows SWR HI When you key the microphone to transmit.
Try a known-good coax. To tune a new antenna you may need to turn TSR off in the function menu, then turn it back on: High SWR shutdown - How to Temporarily Turn it Off.
If another radio works on the same antenna and the 655 does not, skip to step 6.

5. Version 1 only — connectors

On a full-size case with no vents (V1), a loose front-board jumper/connector can kill audio or talkback. Follow Low Speaker Volume or Low Talkback Even With Control Set to Max (V1 only). Do not solder extra jumper wires unless support asked you to.

6. Still dead — send it in

If AM is selected, the mic keys, the meter is not showing SWR HI, voltage holds, and V1 connectors are seated, request an RMA: repairs.strykerradios.com.

Related: Programming the SR-655HPC if the problem only appears after a software write.