STEP BY STEP MRF477 TO 2SC1945 LINCOLN REPAIR

Replacing the MRF477 with a 2SC1945 in a President LINCOLN.
As long as the output circuit of the transceiver has no other faults results are good and since making my other video this has been tried in many radios with varied results, as much as 22 watts PEP has been achieved from a JACKSON although it is wise to keep power down to 16 watts for a good service life.
Bias current adjustment procedure = http://www.cbtricks.com/radios/uniden/hr_2510/hr2510_tx_adj.htm -

Thanks to all those who have reported there results as it all helps others!
2SC1945 ELEFLOW now available direct from "weazle66" at EBAY.

Category:

Science & Technology

Tags:

• MRF477
• 2SC1945
• LINOLN
• REPAIR

[zx636racer]

Like always good videos mate I am on need of 2sc1945 to replace the final of my htx100 I found the replacement on eBay from the roc

And of course they are fake 1 the position of the bce are backwards 2 the rf power limited 2.5 /3 watts max if you have them let me know how to buy them much thanks sir

[weazle66]

@zx636racer So you got a cheap 2SC1945 and it was fake - what a surprise!, I sell real 2SC1945 transistors on Ebay - look for seller "weazle66", soon i may also have a MRF477 replacement to.

I have seen fake MRF477/MRF497 transistors on Ebay very cheap and lots of people are buying them but it won't be long before they know what they really have!!

[G0HZU]

I'm amazed you fitted the new part without renewing the thermal grease. The metal heatsink face behind the transistor has a cast finish (uneven) so you absolutely have to fit thermal compound to fill in the microscopic air gaps. I would have polished (smoothed) the chassis metal behind the transistor and still used a thin coating of grease. I saw poorly fitted transistors like this all the time.

[weazle66]

@G0HZU Who say's i never put any thermal grease on the transistor? You Maybe?... unlike those that cover the transistor in it and make a a mess i just put a small dab on the back of the fin so when the transistor fixing screw is tightened up the grease spreads under pressure so just enough to do the job but without looking a mess!.... oh and i get people who never think or ask before they speak all the time!!

[emercito]

Could you make a Fet mode on this transceiver? I have got this equipiment 5 years ago and the final stage has burned and i did something like CBTRICKS´ website sucssessfully with irf 640, but incorrect biasing lead the fet itself destroyed.

[weazle66]

@emercito The problem with this transceiver is it was not designed for a MOSFET device and it is more difficult to convert than you may think, many people have tried and failed which is why i just use a 2SC1945 bi-polar transistor as it is easy and simple with very little modification and the result is good.

The other problem is the the IRF520/IRF640 type MOSFET's were not designed as RF linear devices and are a poor substitute for the originals.

[zx636racer]

Got the 1945 transistors and I'm geting 20 watts on my htx100 thanks

[zx636racer]

Thank you sir I all ready purchase the 2sc1945 from your eBay store. and if you get the new replacement for the mrf477 will buy it thank you so much for your videos and all the info that's on your videos .soon I will post a video of my moded to portable back pack htx100

[wagonmaster390]

Great info...thanks, cheers & beers.......390

[weazle66]

@djaaron2006 I would not like to say without doing some tests on the radio, if it is just the driver and/or final then it will still TX enough power to be heard on another radio close by - if this is the case then you can check if the driver and/or final are blown by checking the bias current on each using the service manual.

The bias current should be around 50-60ma (SSB -TX no audio) - if you can't set the bias correctly then this usually points to a bad transistor.