In the Galaxy DX2547, they replaced the 2SC1969 Final Transmitter Amp, and its Driver, 2SC2166C, with MOSFETS IRF520. Why? Why would that be an improvement, technically? Thanks for sharing your knowledge.
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Later version of Galaxy DX2547 used IRF520 MOSFETS in final, and its driver
- Thread starter Jack Sullivan
- Start date
My friend, I hate to say it.......but..... you're a little late to the party.....
It wasn't meant to be an upgrade, it was a substitute for parts that were discontinued. We went through your same heartache about 14 or 15 years ago when the switch was made.
In 2007, a rule in the european union took effect, called "ROHS" for reduction of harmful substances.
It banned a whole list of toxic substances from any product sold in the EU. One of these is lead.
Not only did manufacturers now have to use lead-free solder, but lead-free parts as well. Older parts either had a lead-solder surface finish on them or solder inside. New ones must be lead free. Parts that would be re-engineered as lead free were judged by sales potential. And if the sales volume of a part wasn't enough to justify the retooling cost, it got discontinued.
The IRF520 is a part made in high volumes for switchmode power supplies and similar circuits. And it survived the lead-free transition. The Mitsubishi 2SC1969 and 2SC2312 did not make the cut. Got dropped forever by Mitsubishi.
Since then the familiar SSB final transistors have been made only by third-party outfits, not by Mitsubishi, the folks who originated them. But those companies don't make them in the volume that Mitsubishi did, and that makes them harder to buy. Also drives up the price. You may not care if the price is a couple of bucks higher than in the old days, but a factory sees this differently. A 2SC1969 that costs the factory four bucks won't be chosen while a thirty-cent IRF520 available. Only has to outlast the warranty. Well, most of them anyway.
73
It banned a whole list of toxic substances from any product sold in the EU. One of these is lead.
Not only did manufacturers now have to use lead-free solder, but lead-free parts as well. Older parts either had a lead-solder surface finish on them or solder inside. New ones must be lead free. Parts that would be re-engineered as lead free were judged by sales potential. And if the sales volume of a part wasn't enough to justify the retooling cost, it got discontinued.
The IRF520 is a part made in high volumes for switchmode power supplies and similar circuits. And it survived the lead-free transition. The Mitsubishi 2SC1969 and 2SC2312 did not make the cut. Got dropped forever by Mitsubishi.
Since then the familiar SSB final transistors have been made only by third-party outfits, not by Mitsubishi, the folks who originated them. But those companies don't make them in the volume that Mitsubishi did, and that makes them harder to buy. Also drives up the price. You may not care if the price is a couple of bucks higher than in the old days, but a factory sees this differently. A 2SC1969 that costs the factory four bucks won't be chosen while a thirty-cent IRF520 available. Only has to outlast the warranty. Well, most of them anyway.
73
If you can even find the 2sc1969 final you will be surprised what real ones cost these days. Want an even bigger shock, try finding and pricing the Toshiba 2sc2879 finals.
"If it works - Don't Fix it" - Murphy
Sadly, many looked at the MOSFET as the Upgrade - replacement to the obsolete Bipolars.
There is nothing wrong with using Bipolar - in some ways, manufacturing them was already a highly efficient means of production - so the "cost per watt" was pretty low.
It is due to the "digital" switchover - is where the big push to make MOSFET more of the go-to platform as FET to MOSFET and their hi-power platforms got as efficient as Bipolar as well as their Large Scale Integration Technology that made FET/CMOS/MOSFET technology more cost effective for a larger scale of operation and integration from TTL to MOS platforms made the transition more appealing than keeping Bipolars - that being being Linear - has lost their edge to the now faster MOSFET designs.
So in a way, even though MOSFET was not perfect replacement - the sheer number of FET-based devices make the choices more cost effective for the company and the end user - you just had to do the legwork to make the interface for the device work as the replacement.
Only now there is a "blowback" to Bipolar and even their Tube counterparts they ran over back in the 50's - because as we learn from their improvements in MOSFET we found a lot of the Digital transformation era was getting lost in fidelity and preservation, even the performance of Analog in comparisons to Digital or digitization sampling developed it's own share of problems.
Aspects in comparison, the linear operation of Bipolar and the high-impedance yet power-packed ability to provide considerable ranges of functional dynamics thru the use of tubes - as well as the appealing power of sound and fidelity reproduction thru the use of older platforms - let alone the efforts to preserve the former platforms by the enthusiasts - keeps pressure in the market to allow Bipolars to appear as the market demands.
The market demands; asks and bears the burden of the costs of maintaining the older equipment and their simplicity in function - keeps the Bipolar and Tube realm on the market. It's generated a new economy because of niche marketing and the cost of all this being inevitably placed on the end user demanding fidelity, simplicity and ease of maintenance of the platform they - READ:Consumer- chose to keep.
So in a way, because of what we've learned to use, known for a long time, fallen in love with for it's simplicity and ability, and became passionate about - has kept the Bipolar and Tube cousins to the MOSFET - able to be sourced, at a price. They let the NOS dry up - to place pressure for the continuation of the platform - by driving the cost as an expense - against the ones that demand the product to bear the brunt of maintaining the platforms that is using the device
Just had to wait out the wave and place pressure on the market...
