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  1. O

    Repair RF amplifier board

    I would like to re post old thread, now amp is build as it should, Issue is that signal don't boost at all, I have one power supply, for drain and gate. On gate side I have voltage down converter, and can confirm that voltage converter can supply actually around 12-14V 1.5A under working...
  2. O

    Repair RF amplifier board

    I read article, actually he made 3 version based on the MR300AN/BN, he also get some reward from NXP for building that amp, in article that I also share previous link, he mention that this kind of mosfets are usually soldered directly on chassis, but not this one, which need thermal paste, but...
  3. O

    Repair RF amplifier board

    Do I need to close this tread, and after I get missing parts open new one if I stumble again :-) or not, need to order thermal paste, build proper radiator, etc
  4. O

    Repair RF amplifier board

    Means, maybe everything is in bad grounding, I will need to look this page again what author made
  5. O

    Repair RF amplifier board

    I can confirm that removing thermal pads achieve something, now I have continuity between left side ground (53V) and drain, and right side (12V) and drain, before removing pads I only have continuity between both sides and gate, presume that is resistance but it's the same in the value on the...
  6. O

    Repair RF amplifier board

    Please can you clarify something for me, because I don't have that strong power supply to offer right now, can offer 53V and up to 5A. can I configure bias voltage/current settings for gate or not, not to run amplifier like in production stage, so that I forget that story for now, until I buy...
  7. O

    Repair RF amplifier board

    Not sure, for gate side there is on board voltage regulator (WS78M05A2218), who downgrade voltage from step voltage regulator 10.5V to around 5V. Although I couldn't find datasheet for that regulator, presume that belongs to LM7805 family, and datasheet for 78M05 says that max current output is...
  8. O

    Repair RF amplifier board

    Agree Mosfets are original from Mouser, board was purchased on Ali, yes just because mosfets are 46€ each I limited current on power supply up to 0.8A (0.3x2 for bias current +0.2A excess), that I have some protection when I configure bias gate, because of that I wonder if this could be issue...
  9. O

    Repair RF amplifier board

    No, that was mine old radiator from some PC, you only get purple board, but they put something there
  10. O

    Repair RF amplifier board

    Can you just comment me this please, I put under mosfet thermal pad (it's not electro....), mosfets have big area under for cooling, but also for grounding, can this cause that!!!??? I will for that before, and thanks; Robin
  11. O

    Repair RF amplifier board

    I didn't run into that article before, but I read mosfet datasheet, and for gate side max is 10V, but sure I didn't set voltage regulator more than, think 10.5-11V, because board has voltage controller which can't bare more than 13V, although truth is that mine voltage regulator is not high...
  12. O

    Repair RF amplifier board

    They told you that you don't need to adjust anything, that is already done at manufacturer, but issue starts immediately when I put NXP new mosfets (suddenly voltage drops), what could I do wrong, burn them with high temperature, and they are predicted for such role, don't know. I found this on...
  13. O

    Repair RF amplifier board

    Nop, that would be issue, I tried already couple of times, but excuses are that he need to ask manufacturer, so that would be noise in communication!!!??? Yes, this trimmer are not rounded and imprecise, but predicted for fine tuning, and can't be that suddenly voltage drops from 53 to 12-14V...
  14. O

    Repair RF amplifier board

    Voltage regulator is this one , but the same is also when I put power supply 12V, everything is new, and main power supply running drain side (53V) I blocked current up to 0.8A, that I'm sure that mosfet will not be burned when configuring them, although I suspect that something already burned ;-)
  15. O

    Repair RF amplifier board

    Sorry, I bought cheap RF amp on ebay, but it's just board, you need to buy mosfets for board, MRF300AN and MRFBN, what I get from supplier as description are here: 600W 1.8-30MHz HF Power Amplifier HF RF Amplifier Board SSB HF Amp Board for Shortwave Radio DIY Features: -...
  16. O

    Repair RF amplifier board

    I need to repair this RF amplifier, although it never work, it's cheap one, and you don't have any schematic at all, and take care for heat dissipation, you need to buy MRF300An and MRF300BN mosfets, which I did but when everything connected, and board need two power supply one for drain and one...
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