Відео

This is such a nice little scope. Got one cheap, and it is always my go to scopy for simple quick waveform inspection I really prefer the analogue displays - clean and crisp

I have a HP 8640B with no RF output. The Power meter light does not turn on. The unit turns on but no RF output and no counter output movement when the internal frequency dial is turned. The power supply LEDs are and no -5.2VDC. I removed the RF Divider Filter Assemble and the -5.2 VDC is correct. Can you please provide suggestions on what is drawing the voltage down to 0VDC? The rectifier boards and filter caps are good. Al

Sometimes it's okay to give up 😀 I don't know, maybe one pin of the pic needs a missing reference voltage or, as other people commented, the diodes are leaky. Good set of videos by the way.

Hi. This is Monty W5DN. 40 years in service business. This happens to all techs. Good try.

I feel your pain Stefan...working on my R&S FS300 spectrum analyzer without shematics is becoming an exercise In futility!

Great video. 👍🏻

I’m sorry for the sad end…To add an idea, it looks to me like it’s an analog problem. You are not reading the right amount of power, this might be that the incoming signal it’s not going through as it should. This also could be the reason of failing frequency reading, being not enough to satisfy the threshold of frequency meter section. I’m not familiar with that unit, but usually there is a rectification by fast diodes that can go bad giving enough signal to woke up PIC but low for the measures. Also bad coupling caps in the signal path might fail, the input circuit is called to face high power after all. Interesting difficult repair attempt, thanks for sharing it. 👍

please re-check the wake-up signal. according to the schematic, it's a square signal, with the frequency identical to the input signal, not a DC signal. Also 100 mV for 100 watts input is low, check the SWR bridge. You are transmitting into the dummy load, SWR can't be 3 !!

Thanks for keeping it real.

Sehr ärgerlich Stefan, wenn man soviel Zeit umsonst verbraten hat. Hab mir mal das Schaltbild runtergeladen. Die 150 mV Vorwärtsspannung für die SWR Messung scheint mir sehr wenig zu sein. Kann es sein, dass irgendwas mit dem T1 f. SWR Brücke oder mit den Schottky Dioden D43 D44 ist ?. Vielleicht ist ja auch was mit der Kompensations- Schaltung um VC1 nicht OK. Was die Frequenz betrifft: Hast Du schonmal an U2 (74HC14) am Pin 2 oder Pin 6 gemessen ? Dort müsste doch eigentlich ein gutes sauberes Rechteck HF Signal zu messen sein. 73 de DL1LAJ Andreas

Hello Stefan - that must be heart-breaking not to find the fault or collection of faults. However MFJ did not make good equipment.

Great job. 73!

Hi Stefan, can you help, I am not a technician but I have a IC290H which I am attempting to repair, a coil inductor has been removed from the radio,, it is located in the PLL section, circuit diagram lists it as L2 and part number LS178, I have not been able to find any information about the value of L2, any assistance would be greatly appreciated.. Peter.

Did you check the wakeup signal going into the PIC? Since that is derived from the freq input, it may be somehow alerting the PIC to the fact that there is a frequency to measure. Probably it should be high with nothing fed in, and then pulse low, or maybe just sit low with a signal fed in. The pullup is inside the PIC, and is around 10K ohms on port B, if enabled in the firmware.

Hello Stefan - That was an annoying result for you. I hope you will discover the problem soon. There is nothing worse than working on a scrappily designed and unrepairable item. Hoping you will have success in part 3 of your video.

I was shocked when the new PIC controller did not fix the problem! (Bet you were too 😮) As the display and its controller seem to be working I would look for a buffer chip between the PIC and display (plus associated circuitry of course) and any addressing lines. Regards, David

It seems that both design and manufacturing aren’t at the top. Different story the German dealer’s support…super. This kind of things fight us, but sooner or later we’ll win. Keep going, it’s an interesting fault. 👍

I think MFJ is really an electronics study course in disguise. Nearly 50% of their devices have problems due to quality control issues. The ham has to deconstruct, diagnose and repair and in the end gets a formal education on repair skills. A real bonus. LOL 73 Stefan, looking forward to part 3.

Always interested to see your thought processes involved in troubleshooting problems. I really enjoy your channel.

I have Yaesu 101 ZD mk1

Is it necessary to have a separate antenna tuner with this radio? I haven't used this radio for the last 15 or more years. I used it as a CB radio, I didnt know what I had. Now I have my Ham license and want to use it for more.

The PIC has separate protection bits for different areas of the Flash. I would have your friend try to read anything he can from the old chip. If he can get the bootloader, then you can download the hex file for the rest of the firmware. Most likely it's all protected, but there is a small chance they didn't protect everything. If you read the Flash and it's protected, you will get all 0's or all 1's (can't remember). Most USB EPROM programmers can also handle PIC chips. I might try changing that HC14 Schmitt trigger IC, as the soldering looks horrible. The input to the PIC should be a steady square wave, not what you seemed to have, with the longer low time sometimes. Perhaps the PIC doesn't like what it is being fed. Maybe the firmware checks to see if the freq of the input is steady, and rejects it if it's not. Good luck. Another idea would be to remove the HC14 and feed a nice 0-4V square wave into pin 6 IIRC of the PIC, through a 1K resistor just to be extra safe, and see what happens. Keep the frequency low, like 1 MHz, so that the 1K resistor doesn't mess it up too much.

In fact, there is a lot of programmers for PIC microcontrollers, you can also easily build your own (as long as you have a PC with a RS-232 port), but. The main question is if the PIC is locked or not. If it is not locked, then it is easy, just read the firmware from the broken chip and burn it into a new one, but if it is locked, then this is no more an option. I looked at that fimware update tool. I am not familiar with M$ Window$ (in fact, I'd never used that thing), but it looks like it contains strings with something, that looks like a content of an intelhex file, which, in my opinion, is that firmware. I am almost sure that if you find someone who is familiar with Ghidra (or similar tools) and all that Window$ stuff, then it is possible to extract that firmware from the update utility, furthermore, I think this could be relatively easy job.

Great challenge you’re facing 😊 Dealing with PICs is t something I particularly enjoy, so I stick to tubes 😊 I was hoping the CMOS IC was the issue because at least you can then deal with it simply, but no … that would have been too easy 😊 Good luck 🤞

Hello Stefan, if your friend with more PIC knowledge have the CCS Pic-C compiler, there are a couple of bootloders available that can be used to program the PIC at first time. I have programmed PIC´s in many years, but never used bootloader acctually as a developer you always have hex file. Then there is a question about the EXE program you got if it is able to communicate with the bootloader from CCS or if it is another bootloader, ther are a copule of PIC develop softwares that maybe have different bootloaders but CCS is a certified Microchip dealer so it´s good chans there boatloaders will work with your EXE. If you got stuck , maybe i can try to help you to program a bootloader on the PIC18 you have. // added info I checked my CCS compiler and i have bootloaders for PIC18 , it uses A5 for activae loader on boot but i think it can be removed so it goes directly to load at first startup, then then there is a choise if program should load in bottom or Top of chip and baudrate to use, standard was 9600 , the easiest way for me to test is to get a copy of your EXE file then i can try different setup until it loads from the EXE file, if you need the help. 73 Peter

Good to see you Stefan. I'm looking forward to part 2 of this repair. 73 OM

Stefan- The very large toroids sometimes crack the solder joint during shipping. MFJ did not hotmelt glue them down. So sometimes you'll find these have been resoldered. This won't fix the issue of the vid, but just an FYI. I also found while working on these, is a lot of wave solder flash/splatter all over the board & sometimes that flash will lay on the IC pins.

lots of PICs fail in the MFJ antenna tuner products. They have no shielding and they are close to the power RF parts. If that friend of yours can trick that PIC to be readable (very-very small chance of success but i've seen cases that it could be read in certain conditions - for example higher Vcc could "unlock" them - at least the older versions), then the HEX could be read and transferred to a new PIC. But before that, try to borrow a good PIC and test the tuner with it, to be sure it's working. Since MFJ is out of business, maybe another company is doing their warranty work.

It may be possible to dump the PIC program with a programmer like TL866a. It should be also possible to program a blank PIC with the same device. You need that the devices list include your PIC of course and a TL866a as well. As your PIC is failing, as it seems, only on the counter function, you may be lucky enough to revive it. I wish you will be able to post a successful part 2😁

Guten Tag Stefan. One problem is pic processor have a bit which can be set to prevent the code from being copied. I understand the idea but it makes servicing next to impossible. Living in the US, it was widely announced MFJ was going out of business months ago. I had hoped another interest would buy out the company assets and carry on support but I have no info on any such arrangements yet. It seems your pic may be working since you were able to invoke several options successfully. I'd be very surprised if the pic is the issue, especially since you updated the firmware. Did you happen to notice the original firmware level and the level after the update on the display. As a general rule processors either work 100% or totally dead the VAST MAJORITY of times. Maybe I'm confused but you did show the input signal to the pic was intermittent and other issues like a missing R and a very sloppy installation of the IC next to the PIC. Based on what you shared, I'd replace the R then check function and if no joy, then remove the sloppily installed IC, check the pcb traces in that area and maybe replace that IC. All of these steps should be executed before worrying about the PIC. I will look to see if there is any new news regarding a new owner for MFJ and report any possible news to you. Personally, when I have had people send me projects which were already messed with and messes created by someone else, I send them back. Life is too short to waste precious time on others failures. IMHO. 73, WA4AOS, Glenn

Hopefully your friend will have an answer. I have zero experience with PIC microcontrollers, but as yours seems to be mostly working perhaps it is possible to copy an image of the software from it to the new chip. Regards, David

Best of luck Stefan with finding any help from MFJ *(Manufacturers of Fine Junk)* MFJ are gone out of business some time ago. I prefer my manual tuner/matcher, nothing much ever to go wrong. 73 Stefan

Can you also reset the test counters?

Nice Work! Keep going. Thanks for sharing it.

Hello Mr Stefan. I have a second hand 605 and when i switch it on everything is ok. After 10 minutes (i guess when capacitors are loaded) the beam becomes thick. Like the oscillation in your video. Do you suggest anything i could do ?

Stefan...I've had very good success getting parts from companies who don't sell to the public by asking for a handful of product samples...It's worked every time so far for everything from microwave capacitors and noise source diodes to panel lamps for scientific equipment repairs....Great work...keep it up...!

Sprich Deutsch, Mann! Das ist ja zum fremdschämen.

Verstehe ich nicht.

Stefan, kann Dir nachfühlen. Der Ehrgeiz, das Gerät bis auf die letzte Schraube in neuwertigen Zustand zu bringen, lässt einen nicht los. Aber ich denke, hier hast Du einen sehr guten Zeit/Aufwand Kompromiss gefunden, hier nen Haken an den "never ending story" Transceiver zu machen. Was geschieht nun mit dem aufgeflitzten FT221 ? Bin auf Deine nächsten Videos gespannt ! 73, bleib gesund, DL1lAJ Andreas

Danke, sind immer wider sehr lehrreich Ihre Videos

War wieder ein sehr interessantes Projekt, habe es wie immer aufmerksam verfolgt. Danke für deine Videos Stefan. 73 de Herbert DF8RU

Hello Stefan - I admire your skill and patients.

Phew! What a long one...bet you'll be glad to get back to "less challenging" repairs! 73 - Dino KLØS

Thank you Stefan. It was very educational following your work.

ein schöner Abschluß. Stefan 73 de OE8XKX

When inserting back into compartment, do not insert battery all the way in. Just enough to close the top, this way you don't pull on the board next time just pull battery a little at a time on each side and it will come out. Make sure you test it, plug can fall off when inserting back in. Use vaseline on gasket for a tight seal.

I was thinking about terminator 1000. "That's it you're dead!"

So many capacitors, I am definitely not looking forward to it. Thank you for sharing! 73, KD2TDE

That's an interesting problem. I recently got one of these (mine does not have an A at the end) and the positive half of the sine wave seems to be clipped a bit. I am going to look into it so I appreciate you recording this video!

"Sounds of Mungo Jerry in the background, very relaxing." You are droll! Amazing restoration, great creativity.