Kenwood TS-180S finals replacement

[W9CNW]

I recently acquired an old Kenwood TS-180S and the finals need to be replaced. It still has the old yellow dot SRF1714's in it. I have read that the Motorola (not MA/COM) MRF454's and the 2SC2290's are the replacements for the 1714's. I see RF Parts sells matched pairs of 454's for about $93 while the 2290's sell for around $75 per matched pair. Disregarding the price, which would be the better set to get? Which set will drop-in easier? I imagine either way some modifications will be required, am I right? Any info is appreciated.

73,
W9CNW

 

[ExitThirteen]

After doing a little research, I'd recommend going with the MRF454's. I don't think you have to do an awful lot to them once you drop them in, but it wouldn't hurt to retune the input, to ensure the impedance match between the driver and the finals are good.


~Cheers~

 

[TonyV225]

I would say either or would be just fine I like the 2SC2290 Transistors and have good luck with them although the 454 is a sturdy transistor and would be a great choice if you can find a "matched" set.

There isnt alot you should have to do otherthan just a quick check of the tune as Exit had said.

 

[MudDuck442]

Not to start confusion here but due to circuit design in the rig, I would go with the 2290 pair. The reason is matching the input and output impedance as well as in circuit gain as well as idle current. The 454 would work with some circuit changes but would not just do a drop in replacement in either case although with the 2290 you would require less changes.

 

[TonyV225]

Thats also what I was figuring because the 454 is a bigger wattage power transistor.

 

[W9CNW]

Thanks for the replies. Most of the info I saw during earlier research was almost 20 years old and said to use the MRF454's. The info I saw about the 2290's was newer and I wasn't sure if people chose them over the 454's for the simple fact that they are easier to come by as well as being cheaper.

 

[MudDuck442]

Back then they were cheap, plentiful, and also a trusted Motorola part. I was never a fan of the mrf455 too much gain but the 454 I had used in many projects and homebrew designs. The 2290 is a stout transistor though and has some great charachteristics. When ran properly the IMD performance is good linearity can be achieved.

 

[Markinmo]

W9CNW, how did your repair turn out, I just lost the finals in my TS180S and am thinking of replacing them.

 

[kc4eoe]

I know this is an old thread, but many of these Kenwood TS-180s rigs are still being bought and sold, both at hamfests and online. Most will come with burned up finals and with today's prices for parts, "Forget about it"! .... I snatched my cooked PA board out and moved the plug in wires from it to the Preamp board next to it. Now it works fine as a QRP rig. I could find no info on how to do this online, so I took a chance and it was successful. Radio now has IP voltage and 10 plus watts (depending on which band) out with super nice modulation using just a hand mic. I was totally elated to get it working again since it is very clean with a beautiful face and all the lamps working. It receives like a champ. Wattage will vary with the front control from near Zero to full QRP wattage. You can always put an amp inline if you ever need more wattage and you just saved a huge headache.

 

[nomadradio]

Now there's a cool solution I hadn't heard of.

Adapt and survive!

73

 

[jvincig411]

From Jvincig411@aol.com, I have a TS 180S with no trans output. Are the finals bad?

 

[nomadradio]

I have a TS 180S with no trans output. Are the finals bad?

Maybe.

My car won't start. Is the crankshaft bad?

Maybe. Or maybe it's a clogged fuel filter. Or something else.

Zeroing in on which one of a list of possible faults is causing a problem is called troubleshooting.

But you already knew that. Best place to start with this fault is to put a receiver on the same frequency the TS180 is meant to be transmitting. A coax jumper is attached to the receiver, and the outer shell of the plug on the far end is backed down to expose the center pin. That center pin is now your (short range) receiving antenna. If you can't hear anything in the monitor receiver, take the covers off the TS180 and transmit. You can "sniff" the inside of the radio with the tip of the jumper's plug while it's keyed up, and see if you can hear a weak signal that way.

If you can't, the finals probably are not the problem, since nothing is being driven into the finals. A radio that has only failed final transistors will still have the transmit signal feeding into the bad finals, and you will hear that on a monitor radio just fine.

But that's usually the starting point to troubleshoot "it won't transmit", is to find out if anything is feeding into the finals to start with.

73

 

[jvincig411]

From Jvincig411@aol.com, I have a TS 180S with no trans output. Are the finals bad?

Forgive me for asking dumb questions. When I push the mike to transmit I can see an output on the meter and modulation response on the meter. I have changed the 2-SRF1714 and a 2SD235 on the 100 watt final board. Still nothing. Could I have burned the 2SC2075 and the 2-2SC2509's and the 2SC733 on the 10 watt drive board. Also when the unit shut down because it overheated I thought it blew a fuse. On the side of the unit there is a small panel which has something that looks like a fuse behind it. The component is white and marked with a + and - sign. I lost track on which way it goes back. Can someone tell me does the + face the front of the receiver or the Back?