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FT-817 front BNC fault

Posted: Sat Sep 21, 2019 6:36 pm
by VK7HH
Here is an interesting fault I've found with my FT-817 and I wonder if anyone may know a fix or had a similar issue.

I've never used the front BNC connector until today only the rear which has worked fine. I switched to the front connector and noticed my test signal disappear.

I then plugged my test set in directly and the front BNC connector is 20dB down compared to the rear. It also shows a high SWR.

I checked for a dry joint at the BNC end, I didn't go checking under the board at the end of the coax tail. I guess the only other thing it could be is the relay?

Re: FT-817 front BNC fault

Posted: Sat Sep 21, 2019 10:45 pm
by VK3ALB
Hi Hayden,

Best you dig out your meter and poke around. There's not much in that part of the circuit. Refer to the pic and you can see I've marked the relay common pin. Check the continuity to the centre pin of nearby JP3003 which leads to the front connector. Compare to the rear connector. I reckon it more likely to be a connection than the relay itself, maybe even the cable feeding the BNC connector.
FT817 RELAY.png

Re: FT-817 front BNC fault

Posted: Sat Sep 21, 2019 10:49 pm
by VK7HH
Thanks Lou for the reply.

I’ll have a poke around tomorrow and see what I can find. You’re probably right, maybe a dry solder join or something

Re: FT-817 front BNC fault

Posted: Sun Sep 22, 2019 2:43 pm
by VK7HH
Hi Lou,
I did some testing again today. Checked connections, removed the board and reflowed them too. Still no good. I couldn't get consistent readings with my meter either.

I then use my signal generator and popped one of the probes on the input pad to the relay (where JP3003 goes into the board). The signal was weak. I then put the same probe onto the common point at L3082 and signal was strong. The only thing in the way is the relay.... now to source a replacement....

Re: FT-817 front BNC fault

Posted: Mon Sep 23, 2019 9:41 am
by VK5PJ
Hi Hayden, before you replace it, can you see coil voltage on it change when you select rear panel / front panel from the menu as they should CLICK when you change in the menus?

Peter

Re: FT-817 front BNC fault

Posted: Mon Sep 23, 2019 10:12 am
by VK7HH
Hi Peter,
Yes I can hear it click. I haven't checked coil voltages.

I can also confirm that the signal disappears from the rear connector when I switch it, so the relay is certainly switching.

It's an interesting design, Yaesu must have thought that the front BNC would get more use than the rear SO239 as the N/C is connected to the front BNC. If it's set to the rear the relay is powered up all the time.

Regards
Hayden

Re: FT-817 front BNC fault

Posted: Mon Sep 23, 2019 10:23 am
by VK4GHZ
Hi Hayden

Ask yourself, will you ever use the front BNC?

If it's sitting on top of a transverter box (or integrated into a transverter, like mine), then probably not.
After removing the relay, you could just jumper the relay contacts to the rear connector.
Saves the cost and hassle of replacing the relay?

Re: FT-817 front BNC fault

Posted: Mon Sep 23, 2019 10:37 am
by VK7HH
VK4GHZ wrote:
Mon Sep 23, 2019 10:23 am
Ask yourself, will you ever use the front BNC?
Most likely no, it's just a matter of annoyance of course! I only found out it didn't work the other day when I was going to use the front BNC on a small tape measure yagi for RDF. The connector was a BNC and I thought it was convenient to use the front but wondered why all the signals were way down.

Using it for my transverter as you say 99% of the time will be rear connector.
Sound advice about jumpering the contacts though.

Completely unrelated to that issue, I have an X-Ref in my 817 which I had locked to a 10 MHz reference. I had the 817 sitting on top of my transverter. I had to move it down to put something else on top of the transverter. In the process of moving it, the 817 screen started flashing and audio stopped (indicating it had lost it's reference). Re-powering the radio, changing coax to the GPS unit both didn't help.

The issue turned out to be a dodgy BNC to SMA connector which I had purchased from a local Jaycar. Once I swapped that out it locked no problems.

Re: FT-817 front BNC fault

Posted: Thu Sep 26, 2019 9:34 pm
by VK7HH
Whilst not directly related to the title of the thread, I found this slightly interesting.

Another amateur was having issues with their FT817 showing a High SWR message when plugged into a Minikits sequencer in a transverter from the rear connector on 70cm. This had not occurred before when using the same transverter. Plugging the 817 directly into a dummy load showed a low SWR (or none on the radio). After much fiddling with the sequencer board (thinking it was a bad relay, and checking several components) we decided to try a different lead from the radio to the sequencer board.

The SWR changed, still high but better. Taking it a step further we then plugged it into the front panel BNC and the SWR showed nothing on the meter. Same cable. My conclusion from this is that changing the length affected at what point the SWR reading was along the cable. Moving it from the rear connector to the front was adding that small length in from the front panel BNC.

Partially fixed, but still an odd issue.