Yaesu FT-450 tx problems

[Tinman590]

Ok I got a problem, I use a Yaesu FT-450at for 11 meters and last night I was talking local and the tx: When I key up the carrier would slowly rise It showed this on the meter and over the air to a guy I talk with alot. So we went to fm and it still does the same thing. I have eliminated the mic the power supply and antenna. So im guessing something internal but what? one the carrier does come up it talks at full power which am is about 40 watts. So any input would help. I tell you one thing im bout ready to just stick with my old cobra 29

[preacherman]

Does this happen after you've been talking for awhile?
At 40w carrier, it may be getting warm and the thermal
protection kicking in and rolling the power back. You
are right in that the power should not come up slowly,
but be there as soon as you key the radio. Is the
output reduced on ssb as well?
regards,
Preacherman

[TwentyTwo-Zero]

...it may be getting warm and the thermal
protection kicking in and rolling the power back...

That thought crossed my mind also. It could also be a component in the tx section is getting warm\hot and causing it's tolerance to change. If you are running that rig full bore (40 watt carrier) then that is probably what is happening. Try dialing it back to a 10 watt carrier and let it modulate to 40 watts from there. Also make sure you have free space around the rig so it can 'breathe'...

[WESTGATE]

a bad voltage regulator maybe, this happens to me but on unregulated power supplies with the rectifier diodes, weird

[Tinman590]

It starts as soon as you turn it on, I ruled that therory out this morning. I dont know who to send it to or what. I bought it from a guy on qth classifieds

['Doc]

I don't have a fix for your specific problem. I can say that in general, problems start showing up when things are being slightly 'over-done' in some way. The idea of reducing carrier power is a good place to start. And keeping the mic gain low enough to not be more than maybe half way into that ALC on the meter is also a very good idea. Still have a problem with slow 'rise' time? Best advice I can think of is to send it to someone who knows what they are doing and has the equipment to do it with. That's not the most inexpensive solution, just probably the best. No idea who that 'someone' would be in your part of the country, sorry.
Just on the off chance, is the power supply you are using for the '450 of adequate size to really handle it? No particular reason to think that it isn't, I was wondering cuz I didn't see it mentioned.
- 'Doc

[Tinman590]

Doc I should have covered that power supply question lol, I am running it on a pyramid 52 amp which is way more than enough, I also tried it on my astron 35 amp with the same results. Thanks for the replies fellas I will try to let yall know the outcome.

['Doc]

I would think that either power supply would be more than adequate. On second thought, that 50 amp is probably much too small. I think you should send it to me so you could get a bigger one...
- 'Doc

(holding my breath expectantly!)

[Tinman590]

I would think that either power supply would be more than adequate. On second thought, that 50 amp is probably much too small. I think you should send it to me so you could get a bigger one...
- 'Doc

(holding my breath expectantly!)

Uh let me think about it...........................................................................................................................................................no lol

[Tinman590]

Bad capacitor, fixed under warranty and its on its way back

['Doc]

Good!

[drdx]

That is good to know. I've had 2 450's and BOTH of them, on the first transmission after powering up, the carrier would start low and rise to full power, in about a second. After that it always keyed at full power. As it did it on both, I figured it was typical, but now I wonder if it was just a warning sign of things to come. Those are great rigs, lots of bang for the buck. The only thing I'd change on them is to make the am receive a little wider and warmer sounding, but am isn't the focus of that rig.

By the way, that radio is rated at only 25w carrier on am according to yaesu. [Please login or register to view this link]

-drdx