After having my suspicions on a couple of recent activations I have this evening come to the conclusion that my FT817 has developed a fault. Experimentation has lead me to the realisation that power output on 2m is considerably reduced - of the order of 1 Watt on the high power settings. The rig indicates a high SWR (4 bars) and the PO display is only around 3-4 bars. On the lower power settings I see readings of around 0.5 and 0.3 Watts.
Strangely enough the problem does not seem to be present on UHF or HF though I admit I haven’t been exhaustive in my tests on these bands.
I’ve used an external SWR meter to measure the output power which while not particularly accurate has in the past demonstrated an accuracy of around 10% down to the 0.5 Watts level.
The problem manifests itself via both front and rear antenna sockets.
I’ve tried a couple of antennas both of which seem fine with other rigs.
I’ve tried running the rig off both its AC adaptor and a SLAB.
I’ve tried the various reset options detailed in the manual.
I’ve had a look inside and there do not appear to be any obvious signs of component failure.
Does anyone out there have any experience of similar problems or have any ideas for things I could try before I bite the bullet and send it off to the Yaesu for repair?
In reply to M0RCP:
I don’t have much 817 experience other than owning one, have you tried using a dummy load? Maybe you could bodge some dummy loads from a junk box, I know the 817 folds back the rf power with higher swr, just not sure how much. The built in swr indicator on my 2002 serial number 817 is quite inaccurate (I don’t think it functions as a true swr bridge, could be wrong on that though). What I’m wondering is, maybe your swr bridge has drifted and is indicating a false high swr and electronically attenuating the power. I think it can be adjusted somehow. There are a couple of websites refering to 817 swr.
That may not be of help, but food for thought perhaps.
I had exactly the same problem with my first FT817 - not the ND, the early model. The 2 metre output dropped to a very low level with the other bands unaffected. Fortunately it was still within the warranty so I sent it back for repair. I was told that it was a transformer gone o/c but they replaced it after a wait for the spare part and the trouble did not occur again. I believe it isn’t an expensive fault, and I suppose it is small comfort that it is not unknown!
I don’t think it functions as a true swr bridge, could be wrong on that though
Exactly. It displays the reflected power or at least tries to. At voltages below 12.0 V my ND shows three bars even at a perfect dummy with SWR 1.0. At 8.6 V even four bars appear, but this is only 1 V away from complete shutdown.
I don’t think it functions as a true swr bridge, could be wrong on
that though
Exactly. It displays the reflected power or at least tries to. At
voltages below 12.0 V my ND shows three bars even at a perfect dummy
with SWR 1.0. At 8.6 V even four bars appear, but this is only 1 V
away from complete shutdown.
I just read this and wonder if that could be Rick’s problem. If a cell had gone down in the internal battery pack maybe that would explain both the meter reading and the low power. The voltage indicator would be a give away of course.
I just read this and wonder if that could be Rick’s problem. If a cell
had gone down in the internal battery pack maybe that would explain
both the meter reading and the low power. The voltage indicator would
be a give away of course.
Agreed Steve. If the rig is fairly old, the cells will almost certainly be NiCads, which will probably suffering from the dreaded memory effect and or dead a cell or two… Replace them with NiMH cells and this will more than double the battery capacity into the bargain.
Fascinating reading. I can’t help Rick but like some of those who also can’t help, I too wont let that stop me from posting!
However, rather than ignoring the facts so I can quote my favoured diagnosis I can suggest what you should do first.
Try the set into a proper dummy load/accurate meter on all bands and from a fixed supply voltage. Once you know which bands it seems to be OK on and which bands are iffy you are in a better position to diagnose the fault. Until then all bets are off. Although I think the correct diagnosis was given early on in the thread.
Andy
MM0FMF
EDIT: Oh look Brian has gone and spoilt the fun by using the facts!
No, he says in his opening post that he has run the rig off a SLAB,
and in any case, if it is a cell down, why does it only affect 2
metres?
Good point.
When I bought my 817, the battery pack was Nicads and it was totally shot. For someone who sells batteries for a living, there was really no excuse for not replacing them
Ended up selling the 817 as I found the FT-857 to be head and shoulders above it.
Sure, the 857 is heavy and it loves eating batteries. However for /P work, it buries the 817!
In reply to M0RCP:
Further to my previous waffle, in order to support my favoured diagnosis.
Are you aware the 817 has 3 separate circuits to determine reflected power, I wasn’t until I read about it on the KA7EOI webpage, very interesting stuff. It seems there’s one each for hf/6m, 2m and 70cm.
How’s the dummy load test coming along Rick? Hope you can get it squared away soon.
Thank you for all the suggestions. The FT817 has now been sent off to the
Yaesu service centre. Sam there offered the opinion that it might be a
driver transistor or possibly one of the output mosfets that is at fault.
I’ll report back here when I hear more.
I suspect the repair will not be cheap but then again it will be a lot
cheaper than a new one. I doubt any suggestion that we should get an FT857
as a back-up will be well received by the XYL.
You could always say that when you get the rig back you will sell it again for what you paid for it, then with any luck by the time it is back from being repaired she will have forgotten all about it.
Oops, letting me secrets out of the bag. Forgetting Helen reads this sometimes.
In reply to G8ADD:
I always wondered why I got the numbers of these rigs that adorn the shelves here in the dining room confused, now I know why. They are changed regularly to make think he has only got a few!
AAV you are well and truly rumbled, what do you mean is this a new dress?, I have had it for years, yes and the shoes are really old and well worn too. Honestly!
