Yaesu FT857D strange behaviour

[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.

[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

[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

[Transwarp]

I'd be interested to see what amps the radio pulls at switch on using a car battery and meter to check.

[2E0BSL]

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.

[Transwarp]

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.

20 years back l had a brand new 857 and Palstar linear PSU and never experienced this problem for the time l had the radio which was about 12 months before l sold it on.

[2E0BSL]

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.

20 years back l had a brand new 857 and Palstar linear PSU and never experienced this problem for the time l had the 857 which was about 12 months before l sold it on.

interesting. I put a Mydel mp8230 switch mode in place of the Palstar and the 857 doesn't glitch now. Maybe I ought to do a recap. I posted the article with the mod from another ham who had the same problem.

https://www.qsl.net/pa3fqh/ep920/ep920.html

[Transwarp]

@2E0BSL
There's a list of age related failings with the 857's, not all will suffer with as dependent on what life they've had and how looked after. Think Yaesu stopped making them around 2016 so anything from over 20 years old to at least 10 years they are now.

Personally l wouldn't modify a PSU to suit a radio as shouldn't need to, but that's up to you of course.

It's interesting to see how these more modern SMT and CPU based sets are standing up to time compared to older school ones.

[2E0BSL]

@2E0BSL
There's a list of age related failings with the 857's, not all will suffer with as dependent on what life they've had and how looked after. Think Yaesu stopped making them around 2016 so anything from over 20 years old to at least 10 years they are now.

Personally l wouldn't modify a PSU to suit a radio as shouldn't need to, but that's up to you of course.

It's interesting to see how these more modern SMT and CPU based sets are standing up to time compared to older school ones.

Turns out it's not the 857. Tested with another PSU, it's fine. 857 draws 2A on receive, the caps insidenthe 857 caused my Palstar PS30m to trip over current momentarily and oscillate on power on. It had a fault in the protection circuit which I disabled by lifting D12. Adjusting current trip VR2 made no difference anyway. There was a mod to fix it but it didn't work in this case. Pondering my next move.