Yes, I can agree! Saturday and a nice cold beer is perfect..

@@TRXLab and for me - even more perfect when I can watch you do a repair beside enjoying mein bier. . Have a nice week Peter

​Good day sir peter, where are you located. i mean your exact location, i wanna send down my hf radio to you for repair.

Das freut mich! Danke

es ist nicht immer die Sicherung lol

Thanks Pasquale, yes it is a very nice build radio.

Thank you! I have to agree simply because when I started in electronics i destroyed more that I was able to fix. That is a matter of fact. Nobody should be frustrated if a repair drives you crazy!

THank you

LOL, ja da hast Du recht...

You are basically right, but there are thousands of this radio type in the field and only very very very few have this issue. That means it is not a design error...

That is what warranty is for, finding parts which don't fulfill the requirements, since you can't test all parts in mass production.

You are right, it is new and in warranty

If you are referring to the two 220uF large electrolytic cans, that is glue to secure the components to the board so that vibration does not break the solder joints. --n1bs

Glad that you liked it! Mainz is nice :-)

Thank you! Well, it is all about time....

LOL

You can not always find or know the cause, but if a new radio has issues like this, it is most of the time a part which is not holding it specs. Provided that there is no design error, which we can exclude in this case.

For DC a coil or choke is very low resistance, but for radio frequencies it is high resistance. Considering that, means the radio frequencies can't get into the DC supply path.

@@TRXLab That very understandable and the schematic makes a lot more sense. I don't do much with RF except of some tube radio's, so your video's are quite interesting. Dankeschon Peter, gruesse aus die Niederlande.

Good luck with the project! Yes, always using digital PDF on the computer

Yes radio is under warranty and that is what warranty is for sorting out parts which are out of spec.

Thanks for watching!

No, not really since the capability is by far not reached...remember the drive for this part comes directly from the FPGA.

Just a faulty component

it is warranty

No, the 8V is needed for several circuits of the radio

If you do many Yaesu radios, you might get the feeling that those radios are more often defect than others or that older radios are more reliable, but let me assure you it is not the case.

@@TRXLab more of a rhetorical statement really, my old Drakes just never quit hihi Stay well 73

@@jeffminnick5209 it is really not meant as rhetorical statement. When tube radios and tube TV's were new, these technologies were frequently in repair shops, which we do not see this day's anymore.

@@TRXLab indeed, all things being equal I still prefer kenwood and icom though... have a great day Peter, nice to chat!!!

Three asterisks is Yaesu speak for "not installed". If you look on the parts list, you will see there is no entry for these components. There is no entry for R4017 for example. R4017 is in parallel with a 0 ohm "resistor" so it would have no effect anyway. --n1bs

I think one time designer thought it placing some small value resistor to power that MMG3H21N IC amplifier, so they were thinking adding two resistors in parallel to accommodate power dissipation. but, decided to just put short 0 ohm in stead. AG6JU

@@Porco_Utah Yes was my 1st thought, but if you see at same snapshot at your left , you can see a resistive Π network which consists of R4001, R4002 and R4003. Two resistors of three have the ***. SV7GBR

I thought the same thing. I believe that Yaesu has created a design that can overdrive Q4002. If you pull the datasheet, the maximum DC collector current spec is 300mA but there is zero collector current limiting for that class A amplifier. There is an internal biasing network in the Freescale designed component, and maximum RF input is noted at 12 dBm which is 16 mW. If the input from the previous circuitry exceeds that (130 watt RF output for a 100 watt spec would suggest this), then Q4002 might be in an overdriven state. As we know, class A amplifiers have great linearity but suffer from inefficiency. If you trace back the DC path to the 5VDC source, with a zero ohm R value ICC can be greater than maximum allowed. An 18 ohm collector resistor would limit peak DC collector current to under 300mA, but that would lower class A efficiency. I think that Yaesu is relying on drive not exceeding 16 milliwatts and also relying on the internal biasing, but they may have run into end to end RF gain limitations. That MMG3H21N is a SOT-89 which is only a good choice if it isn't overdriven because theta JC isn't the greatest in SOT-89's. In this case, it is spec'd at 38.6 degrees C per watt. Without DC collector current limitation my guess is that this amplifier gets hot when continuously driven (like in FM or FT8 modes). The RF gain of the MMG3H21N is ~20 dB so that part's output with max input would be (12dBm + 20dB = 32dBm) if my calc is correct. If the drive is 6dB over 12dBm specified, then dissipation could easily get to >4 watts. At 50% efficiency that would create 2 watts dissipation which is only 80 degrees C above ambient, not enough to exceed max Tj....unless the DC biasing losses are brought into the equation. The only reasons for two parallel resistor pads would be to be able to adjust DC bias in the case Yaesu engineers wanted to fine tune performance. However, factories never want to have to select resistors so if end to end RF gain was suspect, then perhaps the business decision was made to put zero ohms in the DC path and live with warrantee claims. This is of course conjecture, and without knowing RF drive input it is hard to say how the MMG3H21N failed...but I doubt as if this is a component failure knowing Freescale's (now NXP) quality record has been. I wouldn't just button this one up and say it is repaired without measuring input RF and ICC. Easy to measure with a 1 ohm resistor in the collector circuit and a watt meter on the RF cable just to the left of the Q4002 in question.

Not clear to me what you mean??

Something for experienced folks only!

@@TRXLab Yes! It is my work to keep such equipments up and running again, like you do 🙂

Not necessarily normal, but the radios are adjusted that way from factory. I would always recommend reducing the output power to approximately 80-90W

You are right and if the part is fulfilling its specs it is the normal behavior.

That happens from time to time, but therefore we have warranty!

Anthony, pls have a look at my comments. I think that there should have been at least 18 ohms in the collector circuit of the MMG3H21N in order to limit DC bias current to the part.

i know some times from servicing new warranty electronics some times the engineering is at fault. strange problems come up that the design has not been thought of. it happens in new designs . take time prove a circuit some times design issues. @@dondonaldson1684

Contact yaesu Japan

@@TRXLab Roger that Thanks

All good here. The upside of the story is this country is completely different to what it was...

God Bless you Peter and family. We bare no grudges, just wish you all continued good health and stay strong. The past is the past, if Germany is strong again, that is good. If we are all friends again, then no drop of German & British bloody was spilled in vain. 73's Mein Alt Kameraden (?) Thanks Love from Wayne, Barbara & Nina. Full support as always. 👍👍👍👍👍👍👍❤️❤️❤️❤️❤️❤️❌️❌️❌️❌️❌️❌️🫂🫂🫂🫂🫂🫂🫂