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Yaesu FT857D strange behaviour
Posted: 29 Apr 2026, 20:52
by 2E0BSL
My FT857D has been intermittently resetting on power up. Some years ago on a field trip, it had it's polarity briefly reversed. I suspected a partially damaged reverse polarity diode but cannot find one on the circuit diagram. Any ideas? Thanks in advance.
Re: Yaesu FT857D strange behaviour
Posted: 30 Apr 2026, 00:28
by MrWeetabix
does it work normally other than it resets on power up? Kinda sounds like a memory battery if so. I am basing that on no hard facts by the way. haha
Re: Yaesu FT857D strange behaviour
Posted: 01 May 2026, 11:45
by 2E0BSL
Thanks for the reply. After swapping out my PSU (Palstar PS30m) I found a known problem with the PSU. It doesn't like FT857D when powering up and goes into oscillation, causing problems with other radios also. For anyone interested
https://www.qsl.net/pa3fqh/ep920/ep920.html
Re: Yaesu FT857D strange behaviour
Posted: 01 May 2026, 13:01
by Transwarp
I'd be interested to see what amps the radio pulls at switch on using a car battery and meter to check.
Re: Yaesu FT857D strange behaviour
Posted: 01 May 2026, 13:27
by 2E0BSL
Transwarp wrote: 01 May 2026, 13:01
I'd be interested to see what amps the radio pulls at switch on using a car battery and meter to check.
I did some digging. The FT857 has got high internal capacitance which temporarily shorts Palstar causing linear PS30m PSU to oscillate. My FT950 also does this. It's a known problem with Palstar/ Manson series PSUs. Will have to mod PSU to stop it.