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Author Topic: FT-950 not powering up , MANY have this failure  (Read 19393 times)
KQ6EA
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« Reply #15 on: October 24, 2011, 10:53:18 AM »

Any idea what might cause these parts to fail?
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N4ATS
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Posts: 809




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« Reply #16 on: October 24, 2011, 02:43:37 PM »

Yep , powering the radio down via the power supply instead of using the power switch on the radio to turn it off THEN turn off the power supply. Looks like as the voltage drops , the current rises to the point that the SMC Diodes blow open.
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KB1BBY
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Posts: 5




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« Reply #17 on: November 23, 2011, 02:30:57 PM »

What an EASY fix. Are Q5401 & Q5402 SURFACE MOUNT or THROUGH-HOLE type transistors? Also, what about the diodes? I've not seen the inside of an FT-950....YET (LOL). Hearing these parts are on the PA unit makes me think they are probably THROUGH-HOLE components, but please let us all know for the sake of overall repair simplicity.
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K2CMH
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« Reply #18 on: November 23, 2011, 04:03:05 PM »

I had that problem happen to mine, all of the diodes/transistors on mine were SMT.  Note that these were not the finals that went out.
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KB1BBY
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« Reply #19 on: November 23, 2011, 08:24:35 PM »

Logically, why would they? The finals are much larger RF output transistors which have absolutely nothing to do with CPU power or the various low power & signal circuits at all. Q5401 & Q5402 are obviously low power signal or switching transistors, thus very small 3 lead/contact components. As a general rule, the smaller 2 or 3 lead/contact components such as discreets & transistors are not very hard to deal with, even in the SMD/SMT realm. It's the multi-pin (especially flat pack) IC's which can be very surgical to mess with. A CLEAN & well grounded micro-tip solder iron and a good pair of tweezers should do the trick here and very little else should be needed. A little bit of light gauge flux-type solder wick would be handy to have on hand as well. I generally won't do any board level work without having some on hand (just in case). The same ebay seller has yet ANOTHER one of these dead FT-950's selling on eBay right now. TOO BAD my extra cash is tied up in Christmas shopping until next Friday LOL. Getting that easily fixed rig for a third of retail would be just SWEET...even if you don't like or want an FT-950.....fix it & resell it for double the eBay DOA price....EASY MONEY.
« Last Edit: November 23, 2011, 08:53:02 PM by KB1BBY » Logged
K2CMH
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Posts: 275




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« Reply #20 on: November 23, 2011, 08:50:05 PM »

>Logically, why would they? The finals are much larger RF output transistors which have absolutely nothing to do with CPU power or the various low power & signal circuits at all. Q5401 & Q5402 are obviously low power signal or switching transistors,

They wouldn't, I just mentioned it because I think someone up a few messages mentioned something about the finals.  I just wanted to make sure that it was clear that was not what happened to me.
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KB1BBY
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« Reply #21 on: November 23, 2011, 09:21:54 PM »

Understood. I'll go so far as to say that you'd probably have to do something REALLY WRONG to blow the PA drivers or finals in the FT-950 (especially barefoot, running no amp). Modern PA ciruits in these rigs are designed to handle twice the RF output which the ALC circuits are electronically limited to allow.....plus the switching foldback protection cicuits. I remember when Yaesu came out with the FT-890AT in the early 90's (great little HF rig). One of the Lentini Communications techs in Newington, CT gave one of those rigs a down & dirty "poof test" by sticking an allen wrench/hex key in the antenna port center hole. Then he walked away with the rig transmitting @ 100 Watts. Came back 10 or 15 minutes later, shut it down to cool. 5 minutes later it was powered up, plugged into a resonant antenna then placed into normal operation with no problems at all. After i've completed my Christmas shopping, I just might buy meeself an FT-950. The FT-450 just seems so tiny and the various eham reviewers mentioned a flimsy little control dial or encoder, which gives me great pause. I loved the old IC-736, but it's high time for a newfangled HF+6M DSP type rig.
« Last Edit: November 24, 2011, 07:21:40 PM by KB1BBY » Logged
K2CMH
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« Reply #22 on: November 24, 2011, 09:35:24 AM »

I have really enjoyed my FT-950.  For the money, I think it is a great value.
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KB1BBY
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« Reply #23 on: November 25, 2011, 03:55:28 AM »

Judging from the vast majority of reviews i have read, i think this rig is one of the best designs in it's price range. Yet like most rigs, there are mods that can be made to improve performance and certain overlooked vulnerabilities. Hopefully the engineering department will start to implement the use of beefier diodes, which will prevent this power-up problem from occuring. AFTER REPLACING the 2 diodes & 2 small transistors on the PA board, I want to make an unusual suggestion which may or may not work to reset the processor chips in this rig (depends on the type of proccessor). Having worked in a multitude of engineering labs in my past contracting travels, I have found that this method does sometimes work on some processors and certain types of memory chips, REGARDLESS of what many engineers will say. Remove the processor board and place it on a static protected surface, preferably a grounded desktop static mat. If there is any type of memory battery on the board, DISCONNECT IT. Discharge any and all electrolytic caps on the board. Fast & dirty way is to just use a jumper wire to connect both cap leads together (don't do this with large electrolytics though). Now use any means of conductive material required to SHORT ALL PROCESSOR PINS TOGETHER. use small pieces of aluminum, solder wick or even some clean tin/aluminum foil. Basically, just make sure that ALL PINS around the entire chip are making conductive contact with each other. Best bet is to make sure the conductor is grounded. Try to keep all the pins shorted together and grounded for at least 20 seconds. Put the processor board back, connect all plugs, connectors and harnesses and fire up the rig. If this does NOT work on the FT-950 chips, please post it here and i'll delete this suggestion. This method may have no effect on the particular chipset in this rig, but i figured i'd throw it out there for someone to try. As long as you excercise all ESD precautions (proper grounding while working on any electronics), you have nothing to lose by trying this. It might just save you from needing to replace the processor board.
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WB7X
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« Reply #24 on: November 29, 2011, 09:58:59 AM »

You guys are scaring me.

I just ordered a new 950.

What do you think happens if there is a "mains" power failure from the power company?
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SM6XUN
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Posts: 31




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« Reply #25 on: November 29, 2011, 10:37:40 AM »

You guys are scaring me.

I just ordered a new 950.

What do you think happens if there is a "mains" power failure from the power company?

Great choice!


It would be nice with a preventive fix to this problem, just soldering some R/C network or zener somewhere..  Cool
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K2CMH
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Posts: 275




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« Reply #26 on: November 29, 2011, 03:24:27 PM »

I purchased a PwrGuard by West Mountain Radio that detects low DC voltage and immediately cuts power if it drops below a threshold.  I don't know if it will help or not, but it couldn't hurt.
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KJ4I
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Posts: 111




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« Reply #27 on: December 01, 2011, 09:05:54 PM »

I have my power supply with FT-950 plugged into a medium size UPS unit. Not so much as to keep the radio usable during an outage but for the same reason you would plug your computer into one. At least it gives me the chance to shut it down safely should I have sudden power failures hopefully avoiding any damage.

BTW; I love the FT-950. Great bang for the buck.
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VK6NDT
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Posts: 38




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« Reply #28 on: December 12, 2011, 10:22:57 PM »

Understood. I'll go so far as to say that you'd probably have to do something REALLY WRONG to blow the PA drivers or finals in the FT-950 (especially barefoot, running no amp). Modern PA ciruits in these rigs are designed to handle twice the RF output which the ALC circuits are electronically limited to allow.....plus the switching foldback protection cicuits.

Mine failed when the power supply voltage went up to 16V instead of the 13.8V that should be run at. no over volt protection or anything. Yaesu were happy enough to repair under warranty though. bless there cotton socks!
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K4VW
Member

Posts: 3




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« Reply #29 on: December 13, 2011, 04:43:56 AM »

Hey Guys, Tried to turn on my 950 this AM and it is as dead as a hammer.  Noticed over the months of operation the radio was very funny about having 13.8 VDC and would flash on and off if got down to 12.5 Volts.  But now it's dead.  Has anyone found a fix?  Will try removing the memory battery today and also start shopping for a good back-up radio.  Jim, k4vw
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