#173 RF Troubleshooting Tips part 1

I wanted to start a simple RF troubleshooting tip videos. This will be a mini series on troubleshooting and restoration tips.
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[@davidberry7985]

Nice to see a great little transceiver up and working again. Alway very nice to learn something from someone that knows exactly how to trouble shoot faulty circuts. Thank you for the very nice video

[@msaradio7455]

I ALWAYS pick up something when i watch you buddy. Great Job! 73

[@paublusamericanus292]

I think he is the best. if his ifr is working.

[@TheRadioShop]

Thanks Justin

[@mikesradiorepair]

That's the two things that kill these and the President versions of the radio, bad caps and corrosive glue. I have seen these where the glue became so conductive in the PA section it shorted the torroidal transformers out and had no output power. Remove the glue and they work fine. Man I hate that crap. Never thought about using a syringe as a probe body. Good idea. One thing I would recommend in the audio probe position is placing a capacitor in series. Something around .1uf works fine.

[@TheRadioShop]

Yep, about everyone of these I have worked on in the past 10 years have been cap and glue problems. Like you said in your videos, it is nasty stuff. The syringe is a great little tool to make all kinds of probes. Thanks for stopping in Mike

[@PapasDino]

Hmmm, Mike's "favorite" adhesive for electronic circuits! If folks want to move up to a active RF probe I built a "Janielectronics" RF Active Probe for 100KHz - 1GHz PCB into a Sharpie retractable marker...search on eBay for "RF Active Probe + DC Out 100KHz - 1GHz"; cost about $30 and comes from Hungary. Thanks for all the tips Buddy! 73 - Dino KL0S

[@Drekkag]

not to have a stupid question but putting that cap in series on the audio... electrolytic or disc? and also what voltage range are we talking about putting in. want to learn as much as i can so i can maybe fix these hw-101s that are just sitting here by my bench. still learning alot from you and buddy and peter but still need to get the hang of when to use each type of cap. Thanks to all of you guys for all the videos you take the time to post. 73, ad0am

[@mikesradiorepair]

Adam Rennison Anything would work but you will usually see a high voltage ceramic used. If you use a high voltage ceramic it keeps the size down and you can then probe high voltage audio circuits like a audio amplifier tubes output or output transformer. All the cap does is block the DC.

[@josephcote6120]

Great tips on home made probes. Always good to see a new way to do things. For the syringe probe, if you find it needs shielding this would work fine: More solder braid off the ground point, wrap the plunger with some electrical tape, then wrap with foil, then wrap the braid around the foil and some heat shrink tubing over that to hold it together. If clearance is a problem you could shave the "fins" down a little bit first.

[@TheRadioShop]

Thanks Joseph. Great tip on the shielding.

[@321CatboxWA]

Well done ! . I have a HR2510 with a no tx no rec , between your video and the tips added below I'm going to take another crack at it. Thank you for taking the time to share and teach.

[@TheDefpom]

321Catboxnwc - if the no tx/rx is on all frequencies then you should check the Rx and tx transistor switches, they fail sometimes (assuming you already recapped), if it works on some frequencies, such as above 28.000 only, then it is a problem with one of the vco’s on the MPU pcb, I have seen them fail many times, sometimes it is a bad electrolytic capacitor, sometimes a bad surface mount ceramic cap.

[@TheRadioShop]

Thanks, I would really be looking at failed caps on the cpu board. They leak and this eats the trace right off the board.

[@321CatboxWA]

No tx rx all freq . thanx alot, I will come back with my findings .

[@vboutlaw6537]

This type of video is just what I need since I am getting back into radio work after about 20 years of being away. I am going to build an AF/RF probe myself but with different design. Mine will be small but the switching mechanism and all the electronics will be contained in a small plastic box that will simply mount on the shelf in easy reach. Looking for the second video now.

[@TheRadioShop]

Sounds great. Thanks for sharing

[@LarryDeSilva64]

Love the building of the rf probe in a hypo great idea. Then building the switchable AF/RF probe is pure genius. Yes indeed bad caps and that conductive glue always a suspect if you haven't got a broken wire or a cracked circuit board. Glad it was just a bad cap for the culprit this time. Great troubleshooting video thanks for sharing.

[@xraytonyb]

Great video, Buddy! My nephew has a 3D printer. I guess I'll have a project for him now! Seems like everything that was built in this era is starting to suffer from the "glue blight". Thanks for sharing all the good tips!

[@TheRadioShop]

Time to put him to work :-) Yes this glue is becoming a problem in this older gear. Thanks tony

[@lylewatts6370]

That's the probe I have been looking for and thanks for showing me how to make one. Many old rigs need a RF probe for trouble shooting and calibration. Wow Buddy we are on the same page. Now I need to find a syringe for the probe. Thanks again and as always I learn something new.

[@TheRadioShop]

Thanks Lyle. Glad I was able to show what you need. Let me know how yours turns out

[@mrjg1013]

Great! I love watching you... I like it even more now, because I like building things like this, and also beginner troubleshooting which is what I need the most! Thank you very much!

[@TheRadioShop]

Thanks for watching John. I will try and get more like this up soon.

[@maverickmoshe7457]

instablaster...

[@w.rustylane5650]

I really like the volt ohm meter stands you've built for your meters. Those would definitely be handy. Guess I'd better get busy and build me a couple. I also like the way you built the RF probe. Very good ideas.

[@TheRadioShop]

Cool idea

[@geofham8332]

Hi, great stuff thanks for the video and your time putting it out. We can all learn something here. Again thanks.

[@TheRadioShop]

Thanks

[@dancingcomanche3951]

Another great informational video, I so hope you make many more like this. Our Ham Radio hobby has great potential and with people like you offering your time and experience we can only hope to extend and expand this great hobby. 73's de 2E0FME

[@TheRadioShop]

Thank you very much for those kind words. I will do my best to make this an informative series.

[@jeffreyhaynes5774]

Sure looks like you have every piece of test equipment that was made,is there any piece you don't have.Sure makes troubleshooting easier.I wish i had this much test equipment when i was a technician back in the 80's,keep up the good work and videos.

[@TheRadioShop]

Thanks Jeffery. No not much in the way of test gear I do not have. Probably more than both GE and EF Johnsons shop combined that I have worked at. Many years of collecting broken gear.

[@jaybats7865]

Great job Buddy just amazing I really enjoyed it

[@dougmcartin3881]

Some good tips as always Buddy. I've made probes from 3/4" PVC pipe. They have a variety of fittings that can be adapted to many uses. Readily available and cheap. 73 Doug.

[@TheRadioShop]

Thanks for that tip Doug

[@jamesharrison2041]

HI DOUG'''IN YOUR PROBE I WOULD LIKE TO SUGEST ''LINEING THE INSIDE WITH SOME OF THAT STICKY BACKING METAL FILM TAPE'' LIKE USED IN HVAC APPLACATIONS LIKE DUCT WORK''''YOU NEED TO KEEP THE ''R.F''. OUT OF IT''''THANK YOU DOUG'''''JAMES''''HARRISON ELECTRONICS'''OKLAHOMA''73;S''''P.S. I ALSO THOUGHT ABOUT ''P.V.C'''''''73'S

[@dougmcartin3881]

@@jamesharrison2041 Yes good point James. I've also used the aluminum shells of jumbo Sharpie Marker Pens that have gone dry. Stay well 73 Doug.

[@cuban9splat]

Great idea using the syringe for the RF probe. Thanks, Buddy. I always learn something new from your videos. 73 DE K7RMJ Frank

[@TheRadioShop]

Thanks Frank, glad you found it useful.

[@brianoakley1559]

@@TheRadioShop my only concern about the syring is that its not shielded. Wouldnt that be a problem, especially with all the rf noise generation around these days?

[@tlrptg]

a germanium diode works well till 20Vpp of RF before failing. use a Schottky diode for higher RF signals (40Vpp max) or specialized detector tubes (for example the World War 2's LG2) for more than 400Vpp of RF.

[@TheRadioShop]

Great tip. I will cover this also in a future video.

[@worroSfOretsevraH]

You should also show the RF probe in action.

[@old64goat]

Great repair Buddy and I may make a probe but it will not be a syringe...too small for me to work on..LOL BTW, is hot glue conductive over time?

[@TheRadioShop]

Hi Bill and thanks. We need to find you a cattle syringe LOL They are huge! I have tested hot glue that was 5 years old and never seen any become conductive.

[@paulcollins664]

I really enjoyed this Buddy apparently ,I'm going to have a New set of RF & RF/AF probes, what else made it good is my youngest daughter Isabel, found it interesting to , new viewer alert, so we are building probes together, don't worry I'm NOT going to hold you responsible for losing some of my workshop, having been blessed with two daughters I'm pleased to share the space with them both. Paul de M0BSW

[@TheRadioShop]

Great Paul. It is always good to hear about young folks getting interested in the hobby. Hope she sticks to it. we need those future engineers and makers! Glad you two found it useful. Perhaps it is time to build another bench...

[@paulcollins664]

On it already Buddy,she has already claimed one of the scopes multimeter and sweep /function generator, we completed two New sets of probes, it was real fun, working with her :)

[@TheRadioShop]

Great to hear Paul. Keep at it my friend.

[@bblod4896]

Fantastic! I'll build one. Thanks Buddy.

[@TheRadioShop]

Thanks my friend!

[@williamcolvin3609]

I have a President Zachary T that was working one day,but would not work with a power mic - the next day I turned on the radio and no transmit at all. I have replaced all the capacitors,all the diodes and the driver and final transistor still will not key-up,The radio works fine in PA Mode push-to-talk work with nice loud clear audio. The Squelch,Mic Gain and RF Gain all work fine. Also when it was working - I was getting 18.2 volts to the Driver and final transistors and the radio was only supplying 13.6 volts to the board which was the reason I out all new caps and diodes in the radio.

[@TheRadioShop]

Hi William. I am not familiar with this radio. But would start looking for a bad solder connection or bridged solder joint.

[@williamcolvin3609]

Buddy - what is the problem with the Cobra 25 LTD Radios made after the year 2000,there is literally truck loads on EBAY being sold 5 lots for $100 and FREE Shipping?

[@TRXLab]

a very nice video Buddy which will definitely help out a starter in electronics...

[@RC-Heli835]

Great video man ! Thanks for sharing!

[@CT1ELP]

I believe the circuit in the two probes is not exacly the same, on the second one you have all the three components in series while the first has just cap and resistor in series with the "hot" line and the diode connecting to the ground. I would like to hear your explain why the difference and when to use one or the other for practical purposes. Thanks and keep up the good work.

[@TheRadioShop]

Great observation. There are many different types of RF probes. Lots of designs out there. Some are more sensitive than others but practically does the same thing. The designs I used were straight from the Heathkit manuals. I will do my best to explain them in future videos. Thanks for the comment.

[@ricktighe191]

It seemed like the diode in the heathkit schematic went from the junction of the resistor and capacitor to ground, but in the build you put the diode in series with the other components. If my observation is correct please explain the operational difference between the two designs.

[@richardmills5450]

Fabulous video. But what are those 3 copper coils for at the rear of the radio?

[@skyboy2410]

Great video as always Buddy!

[@tectalabyss]

Thank you for the great,troubleshooting tips. Buddy. All my best. Bobby

[@TheDefpom]

I would just be recapping the entire radio, they all need it now they are as old as they are. On the hr2510/2600/Lincoln variant I have found surface mount ceramic caps failing on the MPU board too.

[@TheRadioShop]

That correct, replacing all the caps is a must for a unit of this vintage. Those caps on the cpu board cause a lot of crazy issues.

[@johnkaveski7953]

great channel thanks for all the help.

[@Backtothefutureradios]

On the first rf probe, shouldnt the diode be connected at the junction of the resistor and the capacitor? Cheers Larry

[@TheRadioShop]

Not on this particulare probe.

[@jackgraham505]

I was wondering if I could get the CAD file for the Tips you made on your three D printer. Thanks for the great videos you are sharing on KZbin.

[@TheRadioShop]

I will put them on my website this week end.

[@roncrow3965]

As usual good information and great troubleshooting procedure.

[@RC-Heli835]

Man this is awesome stuff! On the audio / rf probe is the switch bypassing all the components except the .0068 cap?

[@albenieallain7251]

Hi Buddy, great videos. Very much appreciated. Do you or anyone out there know how much the IFR 1200S cost ,when new? Just finished building my own "sniffer" probes to use on my newly acquired IFR 1200S.

[@TheRadioShop]

If not mistaken somewhere around 10 grand, plus for add ons.

[@srs26]

Great video! Very interesting and I look forward to the next part! Why did you suspect the capacitor between pin 3 and 1? Why would that be the most likely? Kind regards, Simon, UK M0SYS

[@TheRadioShop]

Hi Simon. Since the IC was running so hot we know there is a problem on the output side of it. If it was on the input side there would be no voltage and no heat. Looking at the schematic the first thing we see is an electrolytic capacitor rated at 10 volts. The output pin has 7 to 8 volts on it. First red flag. The fact is most of the time when an audio device runs hot there is too much load on the output. This capacitor was so leaky it was shorting the output to ground. Hope that helps answer your questions and thanks

[@srs26]

Hi Buddy, I see what you mean, I'm looking forward to the next part! Thanks for the explanation, great videos and very helpful!

[@ke0ourwilliam982]

Thank you for this Video. I will be waiting for the others.

[@chrisj0]

Cool video, but the second thing you did was hook up the ifr. How would you have done this without the ifr?

[@robertruth3281]

Buddy, I watched this earlier today and all I can say is, it's time to stock up on popcorn and soda..... 'cause this is going to be a great series. Separate question, do you know of the Sencore 42 analyzer? Would that be okay as a starter service monitor?

[@bundylovess]

Nice video buddy big thumbs up 👍

[@TheRadioShop]

Thanks allan

[@kennethkimble9889]

Thankyou helped me a lot!!!

[@richardhartman9418]

Is there any follow up to this video? I was looking for the rest of the series but I'm not finding any. Thanks for all the informative video's. 73

[@sneakysnake109]

Personal opinion because of my being clumsy, but I don't like the idea of that last probe you made being metal and grounded. Thanks for the video, gonna have to make me one.

[@TheRadioShop]

Hi sneakysnake. I do agree with your opinion. The RF probe will work ok in a plastic housing. Although if you are trying to locate a noisy component the 'AF" probe needs to be shielded so you can detect the noise source. Heathkit designed this type of probe many years ago. You can cover the body in electrical tape or a piece of large heat shrink tubing. Thanks for our comment

[@aaronson2540]

Hey Buddy Good Morning..... What's the easiest way to remove that glue that crap gets really hard.... 🤔

[@TheRadioShop]

Hi Aaron. I use alcohol and acetone to remove the glue.

[@williamcolvin3609]

For the Audio Frequency - is a DC Blocking Capacitor needed at the Probe Tip?

[@earlbrown8828]

You are tops Brother thanks !!!!

[@earlbrown8828]

Good Training it's the best

[@dpyles9396]

This is a great video. Thanks!

[@caulktel]

Great video Buddy. What do use to de-solder all those caps? Ive been looking at various de-soldering guns and they all seem to have down sides.

[@TheRadioShop]

Thanks Joel. I use a Pace desoldering station for most of my work. I also have a Unger station.

[@wayner-model5880]

Is there any difference between an RF /AF probe and a standard oscilloscope probe?

[@shartne]

Good video I enjoyed watching it.

[@williamcolvin3609]

Buddy I have a Cobra 29 LTD Classic and it is one full channel off frequency and I cannot find an accurate layout of the board and the adjustments for it. When it is on channel 33 it is actually on channel 34 and I could not find a VC adjustment anywhere on the board to set the frequency did not see a VR7 on the board either.

[@LeeKirkman88]

You could have shown us how to use the rf probe in the radio for beginers.

[@leonardbeaver2486]

great video thanks for the info

[@TheRadioShop]

You are welcome Leonard

[@philparrish6914]

On the radio schematic it called for a 47uf cap but you put in a 470uf. Is there a specific reason for this call?

[@danieljohnson8437]

Excellent

[@williamcolvin3609]

What happens when you change the 1N34A Diode orientation on the first circuit - as that circuit is draw different in some schematics?

[@dondakin1]

Hey there great channel. I have a swan 350 and i am seeing lots of vfo drift and jumping in freq would appreciate if i could get some advice from you. Thanks and 73 don ve2ota....

[@TheRadioShop]

Thanks Don. It is a known fact that Swans do drift. The problem is the VFO oscillator causing thermal drift. In the old days just build or purchase an external vfo and this would solve most of the issues. There are many articles on the net about Swans drift problem. You can go in and clean and rebuild the oscillator and that helps some. But even brand new they drift. Some folks have replaced the variable oscillator with DDS VFO units.

[@dondakin1]

The Radio Shop thanks for the info i suppose i could live with "normal" swan drift but what i am seeing is fast drift like 500 hz over 30 sec and discrete steps in freq like it will jump 1khz i thought it was a mechanical problem in the band switch mechanical input to the vfo i tightened that up and its better but still seems to be a problem perhaps an external vfo is the best idea just wondering where the steps might be coming from thanks again for your thoughts and all your work to create these fantastic videos you are an inspiration to many people. 73 don....

[@TheRadioShop]

Thanks Don. This is a shot in the dark but let me say this. The VFO variable capacitor could be causing a lot of that issue. On both ends of the rotor there are ball bearings. These are packed with grease. Over the years this grease becomes dried out and hard. It also contaminates the area and prevents proper grounding. This can cause the frequency to move around a lot. Wash those bearings out with contact cleaner then apply DeoxIt.

[@dondakin1]

I have been working on the swan drift and most of it was eliminated by cleaning the rotary switch entering the VFO in the back ( the band select switch) with a rubber eraser and a little rubbing alcohol, That marginal contact was 90 % of the problem. I also added a fan over the finals and now after a 1 hour warm up. The drift is good for a QSO. It's not 100% stable but it can go for a good long time before needing a tweak. Thanks again for you suggestion it got me looking at the VFO more closely and led to a fix. Loving the Swan.....

[@alessandrozax]

Hi Boss...i'm looking for all parts about "iron probe" such as the tube, but here in Italy it's not so easy to find it. May you help me please !? ...have a nice day '73 .

[@ajw6715]

Without the Germanium diode it would work for IF?

[@ajw6715]

Do you do car radios? I have a bunch of old radios out of 60 and 70 ford mustangs. All have the same problem just a buzzing no stations.

[@fullwaverecked]

I saw Mr. Carlson's lab do an old mustang radio.

[@ajw6715]

@@fullwaverecked I contacted him and go no reply.

[@fullwaverecked]

@@ajw6715 there is a lot of info in his KZbin video on vintage car radio repair. Good luck!

[@goducks11111]

good video

[@frankthetank3342]

Subscribed! :)

[@Budro4764]

What happened with the 25 LTD ??

[@rusty1187]

I always wondered if that 1 khz tone burned out my hearing after all these years....

[@williamcolvin3609]

Hello Buddy - have you heard from Mike in a while,1 month and no new videos or updates. I am trying to find the 36.570 Mhz Mixer Crystal for the upd858 President Radios with no luck.

[@TheRadioShop]

Hi William, no I have not. But I do know he is really busy and have not had much time for anything else. Guess that what happens when you are good at what you do.

[@williamcolvin3609]

I did not know if he was in an area hit by the storm or whether there was sickness or anything that might be wrong - I knew you guy usually kept in touch with each other.

[@davoodzarei695]

♥️👍

[@ericchilton3781]

hi can you use rg8u coax on the rf probe?

[@Stover159]

Hey buddy do you have a patreon account?? I seen a patreon under the name THE RADIO SHOP and was gonna make a pledge of it was yours

[@TheRadioShop]

Corey, Sent you an email. Thanks

[@kennynvake4hve584]

Im making my probe out of an old power detector, the kind you wave around electrical outlets and they light up or beep...

[@TheRadioShop]

Great idea!

[@ojjenkins7110]

Did you fix the IFR?

[@TheRadioShop]

You mean the 1200 FM? No, at the moment I am not ready to spend 250 bucks when there are many other projects in the pipe. I do want to fix it to use on the other bench but will have to wait for now. In this video I was using the Super S which works flawless. Plus I have several other SG's in the shop.

[@ojjenkins7110]

OK I think my 1200s suffers from the same thing :-)

[@buildstoys]

what's wrong with it?

[@johnwest7993]

You might want to mention that you are only replacing electrolytic caps, not all the caps.

[@jamesharrison2041]

BUDDY WE ALL KNOW FROM THE PAST THAT ELECTROLITIC CAPS GO BAD & DONT LIKE THE TEST OF TIME''''MY QUESTION IS DO YOU ''EVER THINK'' THAT WE WILL GET PAST THE ISSUE AT HAND''''''''''A ALTERNATIVE CAP THAT WILL LAST ?.I WOULD LIKE TO SEE LONGER LASTING E-CAPS.

[@ajw6715]

I met AF and I commented to soon as you do cover it. Sorry.

[@denniscornell2747]

The schematic shows the cap tied to the resistor with the diode tied to the junction of the cap and resistor and the other end of the diode to ground. It shows the coax center lead to the free end of the resistor and the ground tied to the other end of the diode. Does it work the way the video showed with the center of the coax going to the resistor where you hooked the diode and the shield to the other end of the diode? I will try it the way in the video and if it needs to be like your schematic I will change it. Thanks for the great videos. [e-mail]