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THE AM BULLETIN BOARD => Technical Forum => Topic started by: KC4VWU on September 23, 2017, 03:18:09 PM

Title: Anyone else had kenwood TS-450S problems?
Post by: KC4VWU on September 23, 2017, 03:18:09 PM
I know it isn't BA gear, but have to ask.

My problem started after the rig had set for a couple years. Hooked it up to talk to some friends on 10m slopbucket one evening, all was fine. Next evening after I had turned it on about an hour or so before the roundtable began, rx audio slowly went quiet and no power out. Checking around the net, I found the dreaded C-104 problem that seems to be pretty common. Out came the IF board and replace it with a higher working voltage part (it had spilled it's guts, sure enough, and I cleaned it up with 91% isopropyl). Receive volume back to normal, but USB now generating a carrier of about 10w, LSB barely enough to make the frequency counter register a solid count, and AM carrier seems to be unstable. Haven't cleaned the pot yet, could be the problem there. I've just ordered the whole lot of 'lytics to do the entire rig. Seems that Kenwood had a problem with the 450/690/850/950 run with their cap choices, marginal working voltages, plus the fact the rig is around 25-30 years old now.

I was thinking of putting this up for sale, but it can't leave in the condition it's in. It's a really clean rig, not abused, loaded with filters, voice module, tone board, and auto tuner. I'll probably end up keeping it and parting with the FT-897D. Just looking for the easy way out before I have to bury my head in it.

Any one else had or heard of similar problems?

Tnx, Phil 

Title: Re: Anyone else had kenwood TS-450S problems?
Post by: KD6VXI on September 23, 2017, 03:48:26 PM
Replace the Caps. Busch a common problem now that cap kits are available on eBay.

I need to do my 440 as well..


Title: Re: Anyone else had kenwood TS-450S problems?
Post by: kb4qaa on September 23, 2017, 06:46:32 PM
First I've heard of significant cap problems on the TS-450.  However, in the last year there have been more than half a dozen posts on QRZed of undiagnosed major problems.   This seems like a trend.

Previous to this the most common problem has been PLL unlock problems indicated by error sound and dits across the display. This is usually an easy fix by adjusting the three (?) VCO's.  A few posts scattered across the years about the hold up/memory battery,  but it has not been a problem for me.

The TS-450 has been an almost trouble free design with only two or three minor factory bulletins, unlike the more popular but oft troublesome TS-440.

Title: Re: Anyone else had kenwood TS-450S problems?
Post by: KC4VWU on September 23, 2017, 08:44:54 PM
It really surprised me as well, but as was noted in several places on the internet, closely checking C-104 proved it was leaking. The cap I removed was a 470mf 10v Elna brand. Not the first time I've seen an Elna with some age on it give up the ghost. It did fix the lack of receive audio volume and I did regain power output which was practically non existent in any mode. It was probably affecting the ALC in some way (dragging down a power rail?).

All the electrolytics from Mouser was a whopping $15 plus shipping. I guess I'll start with re-capping the whole IF board first, check it out for a while, then proceed from there. I'm just glad they're not SMD's.

Title: Re: Anyone else had kenwood TS-450S problems?
Post by: KA2DZT on September 24, 2017, 08:00:15 AM
Generating a carrier on SSB.
Common problem with Kenwoods.  Had the same problem with my TS-120.  The problem is the grounds on the audio board  Tighten all the screws holding the boards to the frame.  Problem usually starts on 10M then progresses to 15M and 20M.  Last time I fixed my 120 I finally had to bond all the ground points on the audio board together with wire and then run a ground wire to the ground lug near the carrier control.  Not sure what a 450 looks like but most likely the same poor design construction.

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