TS-940S won't power up. - elmers Forum at eHam.net

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eHam.net Forum : elmers : TS-940S won't power up.

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TS-940S won't power up.	Reply
by N1SQJ on September 21, 2009	Mail this to a friend!
My TS-940S always worked fine. While giving a whistle into the mic on SSB the rig shut off suddenly and will not power back on. I had it on a dummy load..flat swr...was trying to check peak wattage reading, so thats when it bit the dust. I checked 2 fuses they are ok. I checked for 28V on both taps, they are ok.. (32v and 34v). That voltage comes on when switched on, but nothing lights up and no power relay or anything else is heard. I'm hoping someone has an idea of the problem spot. Thanks! Rit W1RWV

RE: TS-940S won't power up.	Reply
by K5BOX on September 21, 2009	Mail this to a friend!
I had a similar problem and discovered the TIMER BUTTON was pushed in.Check your user manual

RE: TS-940S won't power up.	Reply
by N1SQJ on September 21, 2009	Mail this to a friend!
I thought of that, but that wasn't it. It's as if on the peak output, it overloaded something and some sort of protection kicked in.

RE: TS-940S won't power up.	Reply
by K4CFQ on September 21, 2009	Mail this to a friend!
Sounds just like the problem I had with my TS-940S. I ended up putting it in a shop for repairs. I forgot exactly what was the cause but a rather minor component failed and had to be replaced. Now the ole TS-940S works AOK. Note: Be sure and check your fans... over heating can cause a serious problem. The stock fans are known to give problems (slow or stop running) after a few years use. There is a mod to get the fans to turn on sooner, and many of us mod the TS-940S fan housing to incorporate computer case fans ... they work much better. I use a Silenx 80x80x15 12v fan.

RE: TS-940S won't power up.	Reply
by N1SQJ on September 21, 2009	Mail this to a friend!
I just did a resistance check on D1266 a silicon power transistor on the PS heatsink and it's open.. thinking I may replace all 5 transistors on that panel, since i hear that they just GO when they feel like it. I think I remember NOT hearing the fan on at time of failure, and it was getting warm, so hopefully I'm on the right trail. cant afford a shop right now, so going to try replacing these parts for now.

RE: TS-940S won't power up.	Reply
by N1SQJ on September 21, 2009	Mail this to a friend!
.... just switched the leads the other way and got a reading so its not open after all. hmm.. dunno.

RE: TS-940S won't power up.	Reply
by K4DPK on September 21, 2009	Mail this to a friend!
What about the 13.8 volt supply? Phil C. Sr. k4dpk

RE: TS-940S won't power up.	Reply
by K8GU on September 22, 2009	Mail this to a friend!
When you say you checked for "28 volts on both taps" are you talking about transformer taps or the power supply outputs? The power supply should be putting out a stable 28.5 volts, not 32+. One thing I would try is disconnecting the heavy power cable that goes to the PA. See if your rig comes on then.

RE: TS-940S won't power up.	Reply
by KL0S on September 22, 2009	Mail this to a friend!
Be really careful when you're probing around the AVR power supply board. I was hot on the trail of what was causing my 940 not to transmit and I was on the way to the PA board when I was checking the AVR board and inadvertently shorted the supply when measuring the voltage there....then the radio didn't work at all! Ended up sending it off to Clif at AVVid (check his feedback here on eHam). Clif is the man when it comes to fixing Kenwood rigs and especially keeping our old faithful 940 friends working. His rates are VERY reasonable with a quick turn around....highly recommended. Dino KL0S

RE: TS-940S won't power up.	Reply
by KA5IPF on September 22, 2009	Mail this to a friend!
Measure the voltage on the fuse on the AVR unit. It should be 28.5v DC. If not fix that first. The 2SD1266 is the regulator for the 21v supply which is located in the front left corner of the AVR unit. If it opens up (very common) then the 21v supply dies and the radio will not turn on. When you replace the transistor solder the leads to it. The plug gets overheated due to weakened spring tension and loses contact and is the cause of most of the failures. Clif

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