RF-Kit B26 RF 2k Kit #6 Replacing the BLF189 LDMOS Chips and recalibrating

[@kb4gap565]

I will add that I do appreciate your making this video. I'm very interested in buying this amp and am trying to learn all I can before pulling the trigger. With tubes for my present amp being almost as much as the purchase price of the RF-KIT amp I think it makes good sense. Thanks for your time and trouble !

[@JayUJay]

It is a fun project, and looking forward to changes and modifications from RF-Kit and the users. It is fun and completely fiunctional. I have a pile of tube amps here... (3cx800.....)

[@W4EEY]

Thank you! Great job. Appreciate you sharing this information as I will be doing this soon on a friend's amplifier. Best wishes and 73 de W4EEY

[@JayUJay]

See you in Dayton!

[@paulziminskin2ghr282]

I believe the LDMOS failure is due to the fact it needs to be soldered to the heat riser, I have never seen an LDMOS not soldered to the copper heat spreader. there needs to be a robust electrical connection and the heat transfer is much better if the device is soldered. Looks to me the failures are due to Over Heating. LDMOS are very robust , but when over heated they fail quicklty..

[@JayUJay]

Hello PaulZ, Naw they are fine and the failures were accountable for various reasons. This was 5 years ago and the 2 amps that I have are working great with heavy use, although I try and keep them around 1KW or less, normally. Newer versions of this amp are not soldered but they changed the method they are dissipating heat to the pallat.

[@paulziminskin2ghr282]

@@JayUJay Sorry I do disagree I have worked with many and all the failures were due to not being soldered LDMOS do not fail when shorted or opened load when operating they are very robust, You will read the perferred method is soldering, I speaking from experience.. No hard feelings and good luck and best of 73

[@dwarslopers]

Cool! With cat assistance at 14:12 :-) Can you explain, why the transistors where broken?

[@JayUJay]

I had a You-Tube mob on me about lack of ESD precautions... don't show them furry 'Jings' inspecting things!

[@kb4gap565]

Maybe you might next time try removing the solder so as to not need to heat up the board as much?? I have used solder wic and a solder sucker. I'd be afraid of ruining the board with the extreme heat. but that's just me !

[@JayUJay]

Try chip-quik. Lowers the melting point of solder/mixing with what is there. Saved my but on many projects... clean it up with a bit of wick and set your new parts. uj-

[@larryboekeloo5514]

The LDMOS failures seem to be quite common for this amp. I was thinking about purchasing one but I'm hesitant seeing all of these failures. Had the problem been resolved as to why the LDMOS continue to fail? Thanks.

[@JayUJay]

I had 2 chips pop back when the videos were made. Both explainable and problems resolved. There is more that can be done to mitigate failures... but I am good now. They happen with other amps I am certain, but this DIY amp is what you hear about. Good luck- UJay

[@norman-justerieyazon4819]

When recalibrating the quiescent current how much current did you use on the blf189?

[@JayUJay]

I would need to lok it up. Much has changed for this amp. I will check the old notes. 2.5a sems to be familiar.... but not 100% sure. will check at some point and reply here!

[@Ashavechog]

Is that the recommended heat sink compound??

[@JayUJay]

It is one of them. This had good ratings everywhere.

[@izzzzzz6]

Does the cat never burn himself on the soLdering iron?

[@JayUJay]

@izzzzzz6 - the soDDer guy! The cat, Jings, is very careful around 'the soddah'... lolz.

[@izzzzzz6]

Use a piece of thick solid copper wire to spread the heat across both legs at the same time, with 2 people or an elaborate wire bend you might be able to do both sides at once. Also, it was painful to see you breathing in all those solder fumes.

[@JayUJay]

Especially since I am in cancer treatment now...

[@claudiofiorentini6362]

Nice job! Could you send me the schematic, please?

[@JayUJay]

There are some available on the groups.io page for this amp also the website. Search for RF-Kit. Good luck!

[@mehmetrasidogunc260]

Good Video, you Use 60/40 solder wire or other (63/37) and your solder wire has Flux ? 73' TA4AU

[@igorlapko]

I cut the terminals with carpet knife when removing old ones- it saves a lot of time. Besides looks like still too much paste. Also I prefer touch the component’s surfaces and terminals as little as possible by bare hands, I do not know, whether it makes sense probably this my personal obsession after several failures ....

[@JayUJay]

Yes I used 60/40, or something close for attaching them and used an amazing product called 'ChipQuik' for removal.

[@JayUJay]

@@igorlapko ChipQuik.

[@RD4D]

Hi! Price?

[@JayUJay]

If you are in the USA, Check DX Engineering website- Outside of US check rf-kit.de - Good Luck!

[@stanleybadams]

Should have tinned your iron first, go slower, too much of a rush.

[@JayUJay]

Yes- I would have had to tin big bertha iron. I use a brass looking 'suede brush' to clean it and then tin it... Maybe off camera? I did, honest! Bigger issue was lack of ESD precautions.

[@nopenadanowaynohow]

others solder them to the spreader, not heat sink compound. which you used far far too much of.

[@JayUJay]

Hi Don, Appreciate your observation, usually it is the lack of ESD precautions that gets my balls busted. Thanks for the new one. In addition to the goop, and soldering- the actual preferred method for mounting to the spreader is indium. 73.