Always nice having a Schematic- especially a "service schematic" that shows test points and voltages etc. It is troubleshooting and repairing electronics WITHOUT any supporting documents that I'd like to see. That is were the real expertise is shown. Instruction and helpful cct troubleshooting shortcuts/hints/tips would be most appreciated for those situations.
Thanks Mike, you are a great teacher. Time to try and fix my Cobra 89 XLR, low transmit power (around 1 Watt). I have the schematics. Ooh boy, here we go.
Bravo.......I'm lucky if I have wire schematic .......old school.....90 % of time its the cord.....switches.....fuse......great to see though process.....cheers
copykon When your paying a tech to do the work it can get to that point. If it's a family heirloom price may not be of concern. It does get to a point where some radios are in such rough condition that it is honestly cheaper to buy one in better condition then it is to restore a radio in horrible condition. The advantage if your fixing it for yourself is the only cost is parts. A lot of the shops out there today don't do repairs, they just tell you you need to buy a new one from them. Those are the shops to avoid.
I enjoyed this video very much. Thank you for mentioning voltage levels while you are testing. Nobody else seems to do that. Hopefully, one day I will understand the part about using an oscilloscope to test the transmit output without blowing the scope. I am hoping to use an old Tecktronics dual trace 100Mhz. I still would need a frequency generator and counter before I begin. Probably an attenuater or something for the pl-259 output too. I'm finding that it can be difficult to locate schematics for old radios for free or even data sheets for IC's. Buying a $15 to $30 manual is tough when the radio is valued at $20 (I'm just tinkering, not pro repair). I got what you said about downloading manuals for other radios with the same chassis. But, how do you identify similar chassis without having seen a bunch of radios's? Does the board have some sort of ID number on it? Also, how do you visually identify smt components and their values? Because of newer smt, I am glad you are using vintage radios in your vid's.
I have found the voltage regulator dying, I don't remember numbers etc, but it was just behind the crystal section on the right , in front of and to the left of the RF section, have found the zener diode let go More than once.
Hey Mike, I really like your trouble-shooting Skills and I am just wondering... when repairing a CB radio do you need to have the antenna plug in. I am a bit confuse about how this works. I would really like if you can explain this for me. Thanks for the great Video.
+AS28g To test transmit you should have a dummy load attached. It's best not to transmit on air when working on radios. And on receive you would have a signal generator or communications test set attached to supply the input signal.
Family has been in the electronics repair business since the 1940's. Have a building full of service manuals for everything from TV's to record players to CB radios. And yes, there is pretty much a manual for every different radio.
great vid. Can i send you a saturn galaxy base that has no trans or recev. it has worked in the past but just stoped., i dont think it has been monked with,. it does power up. id lv too see it back up and running again. 73
hey Mike. My Uniden Washington is original and mint, barely used. This radio (8719 pll) has stopped showing output whatsoever when hooked up to an swr meter. meter needle doesn't move. BUT on the RF meter on the radio it still swings and bounces up on am and ssb. However I notice it has more sensitive swing on USB than on LSB... Is the damn thing fried? It's almost as if it transmits but not at the power it should. And yeah, no needle movement on my inline swr/power meter...yet it seems to be putting out power?! Perfect coax connections too. I'm stumped. It does transmit as far as a couple streets over on my b100 antenna. I'm so frustrated. I can't figure it out. Are my finals fried? Is "half-fried" a thing? What gives?
For starters test into a dummy load not a antenna. You want to eliminate any possible outside faults. If you have low or no output power into a known good test system just trace the RF power amplifier circuit with a oscilloscope to see if and where your losing stage gain.
@@mikesradiorepair thank you for the advice. I opened up the pcb area underneath and turns out one of the coils' legs was unsoldered (broken joint) and I soldered it back on. Someone had spread the coils once upon a time and while I was pinching them back together the other day I must have accidentally pressed too hard and broke the joint underneath. Works perfect now. Love your videos by the way!
This is great stuff Mike. Doing a series on troubleshooting cb radios will bring your already great channel to the top of RU-vid. Even I enjoyed watching this type of video. Keep them coming brother.
Best way to start is buy some faulty radios so you own them, Then try fix them. Don't go straight into other peoples radios. Even if you understand the schematic because you need to also practise soldering and neatness. Nobody likes a bad repair. Or a ton of solder.
Mike, thank you so much for your time and expertise. The new video repair series will be a hit for sure. I can't be the only newbie out here, calmer ing for more. I for one want to say Thank you "Teacher". I will be on time to class. Joel
I commend you for your enthusiasm as well as for wanting to educate your application in a broad scope. I myself started out as an FCC license first class technician. But this is not about me it's about the subject matter in question. Please elaborate on certain loading and burdens that test equipment can provide or in this case abstract and subtract one's critical findings. You may want to let the observer know that he or she must be aware of the equipment that they're using, that it can absolutely cause a irregularity and what we would take for granted as a normal reading such as an old v o m Simpson is an example. "Ohms per volt". Keep up the good work and may the electron force be with you....!!!
I have a Washington that was modded before me. Sometimes it wont be able to put out or receive and if i tap on the middle left top of the radio it works again. Something must be loose. Buying the service book . Thanks for the video.
I have a 40 channel CB radio it’s the switch to the weather channel it works we can hear the weather channel talk but do you take the switch to CB you get nothing you don’t hear nothing the radios on Push the mic nothing want to do our CB guy passed away 2 to 3 years ago we have nobody works on them it’s a RadioShack 40 channel CB radio with weather channel I bought it off a guy off of Facebook market so if you can help me out
Mike, great videos. I have a question about the oscilloscope. What is the range for working on electronics. I see them for sale with different ranges. I appreciate your advice. I saw some cheaper ones that seemed to be in the lower range ie... khz. Thanks
If you want 2% accuracy or better then you want to multiply the frequency you want to sample by 5. 5 times the frequency gets you 2% or better accuracy with imperceptible distortion of the waveform. In the real world 2 times the frequency is usually all you need if your working on radios. If you only work on HF radios (30 MHz and below) a 60 MHz scope is all you need. The advertised bandwidth of a oscilloscope is the "3dB point". If it's a 100 MHz scope the signal will be 3dB down or 1/2 the amplitude when viewing a 100 MHz signal.
Thanks Mike - this one was more help than either of us could have imagined! I was given a box of CB radios to play with - most of which were dead. One, in particular, is labelled Korinna KSB-18. I found one old source of schematics but they haven't replied. I have been a long time follower of yours and, tonight, this video popped up on my RU-vid feed - and I recognised the board! - OK mine is the 18 channel and this is the 40 - but I now have a digital copy of Sams manual that will assist in getting the thing to transmit again. Many, many thanks from Australia!
Mike this repair and troubleshoot series will be come populair. Good solid information. Fast troubleshooting. Excellent. The advice to buy a simple broken radio got me started and it worked. so it will work for other people. About equipment, fancy stuff does not make a better service man. I love equipment but as you stated a voltmeter and a scoop tackled many problems. Down the road of experience i bought better equipment. Keep it coming Mike i look forwar to it.
i've bought almost all my equipment just never used it yet, watching videos like this will make it to when i finally start doing my own repairs. just picked up an almost complete set of sam's..i got the bk precision dynascan cb service center and signal generator and freq counter. got a 100 mhz oscilloscope
Ive searched google and RU-vid. Came up with NOTHING still.. Can Anyone PLEASE help. Maybe I'm typing it in wrong. I have a midland base station and another mobile cb. When I turn it on NO MATTER WHAT THE VOLUME OR ANYTHING, WHEN I KEY THE MIC IT HUMS OR LIKE A LOUD BEEEEEEEPPP AS LONG AS ITS KEYED. Any help would be appreciated. Even if someone could point me in the right direction.
Sounds like an issue I was having. Apparently different microphone can be wired different than others. You can either get a different mike or you can rewire the one you have. Google cbtrick and you should be able to find your cb and see what wiring it take.
I hope you can answer this. I have a cobra 139 / 23 chan ssb. I have no power to the pa/cb switch. Where does it come from? I can't tell on the schematic.
Thanks for sharing your knowledge with us, Mike. Can you go through bringing the radio back to factory with us? That would be pretty interesting. I Look forward to learning all I can from you.
Very clever and may I ask I do have an Icom 760 and sometime the audio recieve is working normal and okey but there are times when the audio recieve will suddenly drop meaning the audio will become low even on 12 or 3 o'clock volune settings. What can be the problem? I know a ham fellows once said that it might be the relay LY2-0-DC12 parts and I'm looking to avail one just in case. As I was watching your video I was hoping I can get your professional advise about the sickness of my radio. Thank you and will hope for your reply. 73
I found this video while trying to find out why a 10.240 crystal fried. I've never seen this happen before. something created a massive amount of heat to cook the legs right out of the board. ( cobra 21 ltd ) Such a clean looking older radio too. Anyway, I'm not a tech, not even close, but tinker on my own stuff. Enjoyed the plain language run down on how to find problems. Side note: I have a friend, who, if I didn't know was not a radio tech, I would swear that was him voicing this video. You two sound identical!
Hi Mike, can you advise me please, just dug out an old 80ch AM FM SSB cb radio I was given a few years ago, the radio is a Major M588 on the PLL 02A chip, this radio had a bunch of badly done and messy mods which needed removed, I started this a couple of years ago and then we had to move house due to my partner needing to be close to her parents due to illnes, just dug it out again to complete the job, It now has TX but on a different frequency to the RX, RX sounds good (removed open clarifier and put it back to stock replacing the diode and resistor, removed voltage from clarifier) sorted FM Mod to a working version FM TX audio is now good, replaced all VRs on the boards as the tops were popping off, removed a strange 10KC shift mod without transistor and resistors also removed an add on crystal trimmer tagged onto the back of the high band crystal to get the old UK 27/81 channel shift. The problems I have left is that when on USB RX the needle is pegged hard to the end of the meter scale as soon as USB is selected, AM FM and LSB are fine on RX, any idea what to look for to cure this? TX is off frequency on all modes, step one PLL alignment tunes to 10.240 MHz exactly through the recomended 1,000 pF cap and when on step 2 of the alignment of the off-set frequency alignment the max readings I can get from TP4 are around 18.020.04 MHz instead of 20.555 MHz on High band and 17.795.19 MHz instead of 20.330 MHz on Mid Band which has stopped me in my tracks? I have a scope, analog and digital MM and a 7 digit frequency counter which reads true on my amateur radios, here is a link to the schem if needed www.cbtricks.com/radios/major/m588/index.htm Another thing to note is that the NB and ANL switches are now empty and they must have been bypassed when the rig was first modified (these switches were used for mods alone) there is also no PA (wires and rear skt removed) I dont care about these missing functions. Thank you
I was un-screwing the " finals" to put new heat sinking compound behind them because they were dry and one was getting very hot then the radio would not work right. I used a magnetic screw driver and now the radio sound like its off. Is it fixable and worth it. Its a General Lee
Terry Fennell Magnetic screwdriver shouldn't have done anything. What do you mean by "sounds like it's off"? Frequency off, audio distortion in receive or transmit.......
I can hear my friend talk but he sounds off Frequency and he can't hear me at all , and my meter show that I am putting out a signal. It would work untill it got hot and I did that to it
G'Day from DownUnder, Mike, am really enthralled with Your videos. You're Certainly a Specialist!!!, would you have a similar video, Troubleshooting no receive or transmit in a ts820s?, as that I have one of these machines, I can find one relay but not the other . I keep having Mind Blocks and it's driving Me Crazier!!!, I'd appreciate Your input, Thanks
I find those switches and also most ptt switches have little brass rails that the copper clips slide on. They are sometimes black or green with tarnish and only disassembling them and sanding the rails clean will work. Some are not easy to replace (unobtainium) and cleaning them is pretty easy.
hello friend I'm from Colombia I have a radio from the general electric is the 3-5804C turns on but does not give sound has a burned resistance, could I give me the schemes to see what value is that resistance and change it?
Hey Mike I really like your videos and how you do trouble-shooting. I have a question for you... I do not repair Radios but a friend of mine brought in a Cobra 21 into my shop for repair... the question is do you need to have the Antenna plug into the radio when you are trouble-shooting and does SAM's have a manual for that Radio
Good advice, Mike. I've noticed you often refer to some radios as "my radio". I'm assuming that you don't keep them all. Is there really a market for used, working CB's? I do a little repair work, mostly for fun. But, being retired I'm not opposed to making a little money to support my habit.
Hi Mike! Your disrespect for the extra channels was hilarious. Ive got a Cobra 25 doing the same thing as your radio. The last time it worked I picked up the mic and pressed to talk and the needle hung in the middle. Sunday I took it to the CB shop and it worked fine. Come monday morning mounted in the truck it was dead. Theres no squelch noice but the needle moves when the mic is keyed up.
great video mike ! like you say, could fix that with just a meter, always check the basics first ! tbh i think i would just short the switch as who ever uses pa anyway ? lol :)
Iv played with electronics since I was 16, im now 40. I. Still scratch my head at times but a break here and there aways works. Always have a coffee on standby. Works every time :-)
Mike my name is Mike also. Oh my god you are wonderful. I have loved to work on CB almost for ever. I have always want to be taught how, but never found anyone who would. Now I have Thank you so much for spending you time to show us how its done. I will consider helping you out also. Everyone should also. Keep up the great work you are doing. I cherish these videos. Thanks again..................................................
You were saying that you cant mess it up more..well I dont know how many times I did just that, messed it up even more...to the point that it was not worth fixing..or I did not have the money to do it..so I dont know about saying that...it was a very good video, by the way..
Good stuff i like all of your videos i have watched so far , need to know how to use some of the equiment & where to hook what to ? Thanks so much for what you do ! Richard.
I use 3 HP GPS time and frequency reference receivers into Stanford Research Systems distribution amplifiers to feed the 10MHz clock reference input on all my test equipment. They are good for accuracy of 1 X 10 to the -14 after about a week of runtime. They provide several decimal places more accuracy than I could ever possibly need. For the amateur radios I use for satellite work I use a Stanford Research Systems rubidium time standard. Think that one has a accuracy of 1 X 10 to the -11. Plenty enough accuracy for working satellites on 23cm.
@@mikesradiorepair I used a RS components frequency standard for years before the gps it was housed in a quality metal case in a nice blue colour. Never seen another like it either quite rare. But it never let me down. The older stuff was built to last. And i liked it because it was roughly the same size as my Blackstar frequency counter which isn't that big
Family Commercial Lawn Care Service So it transmits but no receive? Did you check transmit power and is your antenna system ok. Coax good and SWR reading OK?
Disassembling the radios without damaging them can be tricky sometimes. I fixed a Motorola cb-555 that required a lot of desoldering, labeling and flipping the thing over many times just to get thing free enough to begin working on it. It's time consuming if it's your first time dealing with some models.
Thanks Mike, great video. I'm right at this point in my hobby. Would you have the number for the Sam's manual for a Cobra 29LTD. I'm starting with a bunch of them and the Cobra 25. Keep them video's coming.
