A little more today, I removed the 1 uF capacitor at the base of Q4, the noise went away and I could inject a signal and the amplifier responded. I also tried the low/high gain switch. Didn’t hear much difference. But Q3 is switching on and off shorting out the 10k resistor. Put the 1 uF capacitor back and removed the 1 uF capacitor at the base of Q7. Again the noise was gone and an injected signal worked. It was louder. Q5 also seems to be working OK. So this leads me to the FET Q10 or the circuitry of it. Maybe tomorrow I can look at this part of the circuit.
This morning, I replaced the removed probe capacitors and replaced the J310 FET. Actually I think I was popping the FET with my soldering iron. There is a small AC voltage on the tip. Apparently the iron is not grounded. I added an external ground and soldered it in. Miracles of miracles, The system is showing signs of proper operations. With the probe covered, it will receive the local radio stations. Placing the probe near my signal generator, I can pick up the 400 cps on the RF carrier. I tried the high/low gain switch and expected more of a change. My old ears do not seem to detect much difference. The next item of investigation is the external batteries. I’m wondering if the radio station reception is coming in that way? Anyway, making progress, slow but sure. Thanks for the help.
Hi, I’m glad you have finally got it going. And yes those FETs can easily get zapped but don’t ask me how do I know this …:)). Tnx. for sharing your troubleshooting process with us all. Well done.
Well…. next I want to learn how to use this probe. And understand what I’m doing with it. On a recent YouTube, Paul tested the oscillator of a 10 transistor radio he was repairing. When the probe was set near the oscillator coil, the amplifier made some noise. What is that noise exactly? In an experiment, I placed the probe near my signal generator and I heard the 400 cps audio on the RF. If I turn off the audio, I heard a similar noise. Is this noise just some junk or static on top of the RF? I’m going through some of the old films that Paul made where he is testing a radio with the probe, hoping I can figure out how to, exactly, use this tool. Thanks.
I opened up a working AM radio and tried the Ultra Probe, but was disappointed. I think I found the oscillator signal, but it was hard to get a continuous signal. In fact it was a whistle that changed in pitch as I moved the probe. And I when I probed into the IF section, I got a local radio signal. I had thought that might be correct but when changing the tuning the radio, the received radio signal did not change. I had expected that I could tune the radio and hear different radio signals on the IF. Is that correct? Next I tried to sense the Audio with the probe, but got nothing at all, but hissing (which was the amplifier itself). So I injected an audio signal directly into the amplifier and the tone was strong and clear. So back to the probe. Well….. maybe more tomorrow. Mike
I believe that I’m back to where I was. One step forward and two back? Apparently, I burnt off the end of one the capacitors I removed. Bringing up a question of, can SMT parts be removed and reinstalled without damage? Anyway, I can sense the oscillator in a radio, but had trouble sensing the 1st IF signal, but the 2nd IF signal was strong. And as I had thought, this 2nd IF signal will be the station that the radio is tuned to. So, if the radio is tuned through the band, this IF signal will have that tuned radio station. I figure that maybe my probe or amp doesn’t have enough gain to sense the 1st IF? So I looked at the probe with my scope and the oscillator signal comes through just fine with some gain (not sure how much is correct, anyone know?), but when I get to the emitter follower Q1 at the end, I have a large sin wave at the base, but the emitter signal is distorted, not a sin wave at all, not much of a follower. So, I’m looking in this area right now. Progress. Maybe more tomorrow.
Well….. I could not stay away. It is way to HOT outside so, I came back to this challenge. The distortion was from having the gain turned up too high. Backing down on the gain pot, the follower produced a nice sin wave. I measure about 8 mV P-P at the FET gate, with the probe stuck into the oscillator coil. And with the gain switch on LOW I get about 4 volts P-P at the probe output. With the gain switch on HIGH, I get about 10 volts P-P at the output. This sure seems like plenty of gain. I found that when using the Audio function of this unit, I need to have the radios volume control up quite a bit, then I can sense audio at the audio output transformer. I also noticed that if the probe tip is banged against something, the amp speaker responds. I bet that I could use this to find bad bearing! I’m beginning to lean toward the idea that maybe my probe is working as it should, I’m just ignorant of exactly how to use it. I need to play around with it more.
Well….. I had to find a subject radio to try the probe out on. I found an old car radio. Exactly it is from my 1966 Chevy, my first new car that I purchased. Anyway, the radio did not work. And after a little time with the probe I found a couple of problems and now the radio seems to work rather well, yet there is still a problem I want to try and repair. When the tuning the set to a spot where there is no radio station, the speaker makes an obnoxious noise. When when I tune to a strong station, the station drowns out the noise. But this noise makes it difficult to find weak stations. So, I need to track down where this noise is coming from. My first shot is to make sure the radio is not picking up something from the room lights, or switching supplies, etal. If that is not the case I want to try the probe to see if I can find what inside the radio is making this noise. Does anyone have any ideas of how to proceed with using the probe to find this rotten noise? Thanks, Mike
Today, I repaired my 1937 Ford radio, using the Ultra Probe. The probe told me that the oscillator, the IF and the detector was working. I heard signals with the probe near each tube. Then when probing around the output tube and the audio output transformer there was nothing. I actually found a couple of problems. The cathode resistor was way out of spec >20% high. The detector tube had an open and the output tube was not working at all. Anyway, the probe helped quite a bit. Thanks, Paul. I have a few other radios I want to work on and I’m hoping the probe will help on these also. Mike
@mike-zahorik Maybe you can share with us how the “machined brass probe” works out for you! I’d be interested in hearing about it. Cheers
Where do I find the kit?
@ferret488 Hi, If you are referring to the ”Ultraprobe” project There ain’t such thing as: “the Kit”. The plans, schematic, PCB layout and the much needed videos are on Mr. Carlson’s lab Patreon page but to gain access to it you must first be a Patreon member. Then, you’ll gain access to all currently available projects. Search the list of available videos and you c pick the project you would like to build amongst which you’ll find the Ultraprobe project too. PS: keep in mind that most of the projects are stretched over more than one video. So, to get the ”whole picture” it is highly recommended that you watch them all and thoroughly. I hope it helps.
Hi! newbie here! I’m kinda lost here… need help please! where can I find the files (PCB, Schematic, Drill, etc…) to start this project? Thanks a lot!
@samplegod Hi, well first of all you can only obtain the needed documentation if you are a contributing member on Mr Carlson’s Lab Patreon page otherwise you cannot. But if you are i strongly suggest that you go to the list of videos where you’ll see a list of numerous videos (probably 232 if i am not mistaken) and start scrolling up and down till you-ll get to the videos that mention the word Ultraprobe in the title. so obviously there are more that 1 videos to watch. The Ultraprobe project extends to a number of videos simply because it has been described first and then explained + some demos and was also built in 2 separate stages: 1 is the base unit and the other is the probe head unit. Also among the videos to watch there is one version in particular for the people who would rather prefer a more aired build such as the Thru-Hole version (but only) the probe head unit has this version (not the base unit !) So anyway, the take is that the project was originally intended to be build as a surface mount style (SMD) the video numbers to watch are 174 – thru to 182. Please note that this interval might be slightly off by one or 2 videos because i only remember the approximate video interval which like i said it might be off by 1 or to but you-ll be mainly be guided by the video titles when you read them. And among the video group you’ll find that some of them have a little attachment file below it but inside the attached file there is an instruction telling you to contact (PM) Mr Carlson from within the Patreon site and ask for the video numbers (attachments) you are interested in. And the bottom line is that you’ll need to ask for attachment from a certain video numbers I my memory serve there will be a bunch of attachments for the Base unit and then a separate one for the drilling of the face plate etc the speaker cutout and then another set/bunch of attachments for the probe head unit build . once you receive them and start building it the videos are crucial to watch because some of them hold some crucial details without which would build might fail. I hope it helps.
PM on the how exactly to contact MCL to ask for the attachments please read this (fairly recent post) https://mrcarlsonslab.com/community/postid/2920/
@ovi4 thanks a lot for the reply!! I browsed before among the related videos in the Patreon page (I am subscriber) but nothing in the video’s attachments besides some Patreon info or whatever… and I got puzzled because in the video description says that there’s some files attached, but there is nothing… I posted some question about it in the MCL Patreon but no one replied me… should I contact Mr. Carlson himself? Thanks for your help!!!