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RCI-2950DX transistors or mosfets?
- Thread starter dc2rf
- Start date
Hotrod is right. it swings to about 25 watts on a "whistle".
Update:
After digging into the posts in the CB modification section of this board, I seem to have found some info on this subject of the mosfets. The majority opionion is that the 'fets are no better, and possibly worse than the original transistors. it's not an upgrade, just a solution to the problem of transistor unavailability.
Thanks for the all the replies to this post.
73
Update:
After digging into the posts in the CB modification section of this board, I seem to have found some info on this subject of the mosfets. The majority opionion is that the 'fets are no better, and possibly worse than the original transistors. it's not an upgrade, just a solution to the problem of transistor unavailability.
Thanks for the all the replies to this post.
73
Last edited:
Firstly irf 520n were never designed as rf transistors, 2sc1969 were. Secondly no-one will notice an extra 10w from 25,most would struggle to notice a difference at 50w, its a lot of work for no gain,wait to your 2sc1969's blow then consider mosfets, mosfets are also known to explode if you set bias too high, about 6-8w AM swinging 24-32 pep on AM or 24w pep on SSB is ideal on the 1969's, bare in mind components around them are designed to work at those power levels, you start screwing every ounce of power, you'll sound dreadful, inevitably blow your finals and possibly damage surrounding components too
If you want the radio to do the best it can do, leave it alone.
If you want the radio to do the best it can do, leave it alone.
I am taking out the finals of non transmitting 2950 dx that has those irf520s. I am hoping that if I put the 2sc1969 in its places, it will last. was wondering, where on the service manual does it say what you need for the finals and drivers? Its such a complicated schematic. thank you
Whooaa Nellie!
Can't just swap between the one type and the other type part.
Circuitry and components wrapped around the driver and final transistors are very different, from the original 1969 circuit, and the post-2007 radio with the IRF MOSFET parts.
It's a major changeover, even if you're familiar with all the nitty-gritty details.
And if you aren't, you'll find that simply swapping between the one part and the other just won't work. In either direction.
73
Can't just swap between the one type and the other type part.
Circuitry and components wrapped around the driver and final transistors are very different, from the original 1969 circuit, and the post-2007 radio with the IRF MOSFET parts.
It's a major changeover, even if you're familiar with all the nitty-gritty details.
And if you aren't, you'll find that simply swapping between the one part and the other just won't work. In either direction.
73
Agreed. When RCI had to make the switch to mosfets a good portion of that section of the radio had to be re-engineered. You will have quite a bit of work to change the radio over to the old school finals. They are not a direct swap. Best bet is stick with the 520, 2030's, or the 13n10 mosfet depending on what you can find for your repair.
I have noticed the irf520 is very cheap on ebay. american seller, 10 for $7.95 why is that? where should buy them to get reliable ones? thanks
The IRF520 has three things going for it.
First, it's an old design that any manufacturer in that business can make with the factory they already have. No need to buy fancy new (expensive) equipment to make these. Pretty sure they no longer have to pay royalties to International Rectifier, who invented the part in the first place.
Second, anything made by multiple competitors will always be cheaper than a part made by only one.
Third, it's made in monster quantities to use in anything from a LED yard light, compact fluorescent bulb, or engine control unit.
The bigger the manufacturing quantity the lower the unit cost.
This all adds up to a component that's stupidly cheap, even when you buy it from a reputable source. Naturally the fly-by-night sources are cheaper yet.
Just one little problem. Well maybe a couple.
It can't stand SWR, and tends to fail if it's gets much over two to one. No SWR in a LED yard light. Just wasn't built with that in mind.
It's not efficient. The IRF520 and siblings waste as much as twice the power supply's power as a RF amplifier transistor. If you sell a part for RF, efficiency is an important feature to provide. This is why they tend to run hot, along with the modulator transistor that feeds power to them.
And there's the problem. If you design a MOSFET to be a RF amplifier, it's built differently on the inside. Makes it cost a LOT more to make and sell.
When a factory can choose between a IRF that costs a quarter, and a Mitsubishi "RD-HHF" part that costs four bucks, which way do you think they'll go?
The manufacturer's attitude will be "It blows up too soon? Well, come back and buy another one".
And if you think a radio that doesn't commit suicide so soon would compete with the cheaper radios, you're free to start your own factory and brand. You'll find out.
73
First, it's an old design that any manufacturer in that business can make with the factory they already have. No need to buy fancy new (expensive) equipment to make these. Pretty sure they no longer have to pay royalties to International Rectifier, who invented the part in the first place.
Second, anything made by multiple competitors will always be cheaper than a part made by only one.
Third, it's made in monster quantities to use in anything from a LED yard light, compact fluorescent bulb, or engine control unit.
The bigger the manufacturing quantity the lower the unit cost.
This all adds up to a component that's stupidly cheap, even when you buy it from a reputable source. Naturally the fly-by-night sources are cheaper yet.
Just one little problem. Well maybe a couple.
It can't stand SWR, and tends to fail if it's gets much over two to one. No SWR in a LED yard light. Just wasn't built with that in mind.
It's not efficient. The IRF520 and siblings waste as much as twice the power supply's power as a RF amplifier transistor. If you sell a part for RF, efficiency is an important feature to provide. This is why they tend to run hot, along with the modulator transistor that feeds power to them.
And there's the problem. If you design a MOSFET to be a RF amplifier, it's built differently on the inside. Makes it cost a LOT more to make and sell.
When a factory can choose between a IRF that costs a quarter, and a Mitsubishi "RD-HHF" part that costs four bucks, which way do you think they'll go?
The manufacturer's attitude will be "It blows up too soon? Well, come back and buy another one".
And if you think a radio that doesn't commit suicide so soon would compete with the cheaper radios, you're free to start your own factory and brand. You'll find out.
73
Try Chris Holland.
superiorcb.com
He is a factory RCI repair center.
73
Jeff
Superior CB Inc. | CB Radios Sales & Repair in Ontario, California
Superior CB Inc. is operated by Chris and Veronica Holland. As a boy, Chris started talking on the CB radio at age 11.
superiorcb.com
73
Jeff
thanks, will give a tryTry Chris Holland.
He is a factory RCI repair center.Superior CB Inc. | CB Radios Sales & Repair in Ontario, California
Superior CB Inc. is operated by Chris and Veronica Holland. As a boy, Chris started talking on the CB radio at age 11.
73
Jeff
I had heard he was no longer factory RCI repair.Try Chris Holland.
He is a factory RCI repair center.Superior CB Inc. | CB Radios Sales & Repair in Ontario, California
Superior CB Inc. is operated by Chris and Veronica Holland. As a boy, Chris started talking on the CB radio at age 11.
73
Jeff
Interesting.. I hope you're wrong. I've heard nothing but very good things.
I did take a look at his website after seeing this, and it hasen't changed.
I did take a look at his website after seeing this, and it hasen't changed.