The curve tracer finding a bad op amp... 🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯🤯 I tried searching and experimenting on how to test for a blown op amp and couldn't find squat, this absolutely blew my mind.
I'd like to hear Mr. Carlson speak more about The VOLTAGE Theory and how the voltage ratings affects the AC Signal Electrons pass through the BY-Pass Capacitors.. It's nice to have a Voltage Margin Rating (for shortage) but having that.. it also affects the AC Electrons making their way to the GRID of the next stage in the Amplifier.. I call it the "SWEETNESS EFFECT".. Instead of having (ORANGE DROPS) rated at 600 Volts DC. The OLD TIMERS used Paper Caps for a reason.. AND.. they were mostly rated at 400 volts DC.. For a reason.. I'd like to hear-and-speak, maybe with a demonstration, Mr. Carlson discuss this ASPECT and IDEA..
That device looks so cool. Does it send audio as well as receive? Im curious. Great video.
Surely to discharge you just switch on the amp and not plug it in?
What type of de-soldering setup is that??
Maybe they only repainted the bottom...
Great videos. I have subscribed for a few reasons. One, great video quality. Two, you obviously know your science and how to teach. I watch and i know i will learn something. And three. I have a moderately strong fear of electricity. I have been shocked badly several times over my 50 years and want nothing to do with the workings of electrical things. Lol. So watching your videos is like a horror movie for me at times. Watching this particular video really had me on the edge of my seat. Scary but fun. And final point, my hope is i become less ignorant of the insides of electrical things and not worry so much from watching your video. Actually, interesting video idea. What to be afraid of and not afraid of when it comes to electricity. Sort of a basics of electrical devices. I'm only five videos in. You probably have a video like this. Keep it up. Love the videos.
"You dont wanna heat the joint for too long" That is correct in more than one way :D
Did you consider looking at the output with a scope to see how clean the DC was?
This seems so obvious. I never knew of or thought about this. Blew my mind. Awesome video
I would like to build one of these Only the coil turns etc. Would prevent that Any chance you could reverse engineer that Thanks VA6RDR
you're a beast
Do you have a preference in brand, or a favorite website where you procure standoff terminals?
Do you ever sleep? Great video!
Why didn't that circuit start singing "Daisy.... daisy....." while you were doing this? LOL.
Yikes. You must be so careful. Not all pc boards and foils are the same. On some boards, your method will lift the pads and foils on every device. YIKES!!! I cannot stress my YIKES!!!! enough, to be truthful. YIKES!!!!!
Thorough as ever Mr Carlson, (and well spotted with the LED as point of failure - nice old fashioned neon, perhaps?) I got it with the HT boost :) tho' I'm not sure if EL34's would last long with high voltage screens (triode mode) - I'd try them screen taps, maybe with a switchable 'boost mode' in full pentode. But that'd mean drilling holes, wires and stuff ;) Couple of thoughts... 1- Audiophiles and keen guitarists DO have a tendency to run these things WAY hot. Be interesting to run the distortion test to see if this makes ANY kinda sense 2- Remember an EL84(6BQ5) at such a tiny current has a WAY high Ra and a pure current source will have high supply rejection - so wont really benefit from a negative regulator 3- You're being a little generous to the PI design. heck even in NOS heyday it was hard to find dual tubes that could match within a percent or two, (current production, WAY worse) and these amps originally shipped with 12BZ7's in, a regular TV tube. They're probably using classy resistors at that point is due to the large voltage swing and dissipation figuring expensive/audiophile types would be more thermally stable/sound better ') Thanks for the schematic - I sure WOULD rescue one of THESE tho I'd prob connect the UL taps ;) Oh, and 4-I'd be worried about ripple on that DC LT - half wave and only a modest reservoir. I'd go for a schottky bridge, with a lil bit of resistance (2 stage CrC filter) to drop the excess - its the HIGH freq component that tends to get coupled from the heaters, and this isn't doing much to get rid of it Having said that .. Nice iron, nice amp - and nice lil teardown ;) Pete, Gas Electronics, London
Must admit was waiting for smoke...lol
I'm thinking of moving to Canada (in fact, I'm living in London, On, at my daughter's house). I am an audiophile and would like to know if you make repairs / improvements to audio equipment for the general public? Thanks.
This ampifier is in the aquaman movie... ok techmoan told this.
Thanks so much for a fantastically informative video, Paul. Watching you work is totally mesmerising!
It would be easier for us to find your videos if you name them accordingly to their topic. In this case filament flash. Thanks for proving us with knowledge.
Love your work!
thanks for showing me something new...i will never need it but all knowledge is useful
It is nice as well to have the opportunity to work with it because it is isolated and does not have any reference to ground. Beautiful thing!
One of the first things I did when we bought these units was to change out the XLRs for brand new gold plated jacks as we kept them functional for any type of use in the field in our portable rental inventory and even for rack mounting. The most common issue with these units is a very simple fix. The PC trace lands surrounding the screw terminals very frequently fractures and simply reheating the terminal block contact and the PC trace land will solve the issue. This is why the repair guys in our industry HATE direct contact to the PCB from all outside world connections. We will frequently cut the terminal block contacts and insert a short piece of insulated wire from the PCB to the terminal block to act as a shock absorber.
I guess I am only who sit there with scope and try to open at zero?
I'm overwhelmed just thinking about disassembling the sheet metal.
Hey, I am an audio guy and those Bumblebee capacitors were NOT very highly revered when they were brand new back in the 1950s. Most RF techs thought the bumblebee Sprague caps were just barely above GARBAGE grade caps. The plastic casings were prone to leaking around the leads allowing the oil to leak out and moisture to get inside. There are some Japanese & Taiwanese film caps that test within +/- 10% of a bumblebee Sprague caps. I pay around 3-5 cents for those Japanese caps. Gibson charges over $150 a pair for their fake Spragues. Why would I pay an extra $149.94?
are you inside a spaceship?
It sounds like this is much more tolerant of high voltages and voltage spikes than an analog solid state meter would be. Is that the main advantage of this over an analog solid state meter? Also I'm assuming if you were measuring any mains voltages with this meter, you would want either the meter or the other device connected to an isolation transformer.
My head is going to pop. You have an incredible amount of knowledge and understanding for this gear. Thank you for the great videos and narration. Absolutely enjoy all your shows Dr. Carlson.
Ok, about a minute and a half in, I am reminded of a similar problem I had with a TEAC back in the 80s. My problem was solder breaks on a daughter board. Let's see if the problem is the same. Play...
Alright, after watching, not even close.
Here I was thinking I wasn't going to enjoy the video. "Am AM transmitter? Meh" but the more I watched, the more I want this thing or to build something similar.
That must have been a nasty zap to push enough current through the 10k input resistors to defeat the input protection in the op amp.
hello you seem to be very knowledgeable about adapters. I need a little help I have LED lights that the adapter keeps burning out the specs are input: 100-240v-1.5a and the output 24v 6A what should I get to hold better. The LED are 120 ft long. I will appreciate any advice
And I would have had the unit working in less than 15 min. Find bad part, replace bad part. presto its fixed.
Someone has already had the cover off of the unit.
Excellent video. I could not think of anything to improve upon. Absolutely flawless. I wish I had a shop like yours and the mental discipline to have all of your superior knowledge. Very enjoyable. Some of the audio purists might say the "flavor" of such a high-end piece of audio gear could be adversely affected. Do you feel that the Motorola opamp is enough to satisfy those types of critics? Thank you.
I have this exact same power amp. I found it a bit "harsh" to listen to. So, I replaced the op amp in the preamp circuit with an L49720 and it's a totally different beast afterward.
Capacitor dielectric is wounded in layers so one pin is connected to the inner layer and the other to the outside and then is the external insulation of the capacitors body.In fact it is not polarity but distance from the ground pin so parasitic voltages are forming only in the measurment circuit when ground is the inner and less if ground goes to the outside but not to a real circuit.So the circuit reveals which physical connector of the two is connected to the inner layer and which to the outer and then it is in your opinion how to place the capacitor in a location of a circuit with uncertain polarity or floating.
I do this type of repair commercially practically every day. I would NEVER attempt using this method. When our customers get their units back they look just like they did when we first built them, no patches, repaired traces or bodges! Its fine if its your own I suppose.
Great video, however, I was hoping to see this product demod. It looks very cool. Thanks for your videos.
I’d like to see a demonstration of the transformer turns checks. I just bought the IG-28 which is the big brother of you Heathkit IG-11
Now I am in a quandary. Don't do enough electronics to motivate a scope but now that I know it is going to bug me endlessly. Busy restoring a 1962 tube receiver, can never look at the caps the same ever again, and there are a bunch of them.
Very very well done 👍 thanks !
Well done for showing inexperienced people how to destroy their vintage machines.
EVERYTHING the instructions and any info we could get on antenna, my friends and I did the opposite. That was until we got to the point we were interfering with the neighborhood then the "plug got pulled". Good times.
Just discovering your tube I will stick around !
The cats loved to lounge on the cabinet tops of these energy efficient radios and televisions.
Really fine and interesting video! New data for my little slow and inaccurate brains. Thanks
Hello Paul, one of your Patreons here... ;-) You mentioned an isolation transformer as an absolute must. What size/capacity would such a transformer ideally be? There seem to be so many. I am browsing through models from 500 Watts to 3000 Watts. If you could share any advice, it would be highly appreciated. And thanks for sharing all your knowledge! Best regards from Amsterdam, The Netherlands!
Ignorant question here: Will the changing from the JRC to the Motorola have any effect on the sound? Or are those type of things built to an exact spec that doesn't deviate between manufacturers?
Great video as always. I assume when you say “zapped” you likely meant maybe a static electricity charge hit the input pins?
I have known for years why we need to know which capacitor lead goes to the outside foil, but I am shocked to learn that we cannot trust the factory marking!
These videos are so interesting. Thanks for posting them :)
lmao "japanese phillips?" That is definitely not a thing
@Mr Carlson's Lab If you're talking about JIS, that's not Phillips, that's JIS. There's no such thing as Japanese Phillips. There's just Phillips.
OK. Mr CARLSON, VERY GOOD.
you're using a studio recording microphone... Please let us know when you release your new album~
This is such a common problem...a friend you can't turn down brings it to be repaired AFTER trying everything else. Repairing "repairs" are the hardest type because they are not organic faults which are logical in how they impact operation when something fails on its own. When someone gets into a unit and it is beyond their understanding or ability they frequently resort to modifications or finally giving up and reassembling it wrong that induces illogical defects in operation. A much more in-depth understanding of the system down to detail is needed so it becomes a much harder repair task being the 3rd or 4th person to work on a unit. Most consumer electronics is not subject to that repeated repair attempts because it is cheap and older items ar simply replaced by higher performance lower priced items. Older electronics that ARE repaired multiple times fall into the hobby or specialty fields like amateur radio, guitar amplifiers, electronic test instruments, any professional audio system units, classic car electronics such as radios, dashboard wiring and a few large appliances that have no easy replacement such as custom built-ins. I doubt many people what to restore their 1965 tube TV set but a 1965 amateur radio transmitter or receiver is still a daily user. A Collins S line is still considered modern despite being introduced in the late 1950s for example. I used to collect and refurbish quality test equipment, like most of what you have on your bench since I had use for it and they were the peak of engineering and construction excellence, most were still viable decades later after lab retirement. After being surplused out a piece if rugged HP or Tek equipment might go through a number of hands and any fault the 30-year-old piece could have had started to show up. I had the largest pro audio service center in the US for a long time and so filled 23 tech benches with stacks of classic test gear like yours and as owner, it fell onto me to keep it all going. It was amazing how good that old test equipment was and how little I acquired them for through test equipment monthly swap meets in Silicon Valley in the 70s and 80s. I moved out of the US 19 years ago and slowly, with every return visit back to California I brought back 1-2 pieces of test gear from my storage unit carrying them in my empty suitcases. By 6 years of doing that every 3-4 months I had a pretty complete lab set up in my new adopted home. Now, I have not been back in 6 years. Those old very nerdy test gear swap meet have disappeared, however.
Well how did I miss this one ? Yay. Hahaaaa. Pretty funny in this video Paul. Lol. Some rare subtle Humor. Lol. Love it.
most of the instruments hes got in his ""lab"" is old bugger!
You are very seasoned experience ,Greetings from Vietnam
Greetings and welcome!
Is there an actual difference between ground and chassis? Sry in advance if that is a dumb question.
There is in some instances, it all depends on the designer and internal connections.
very excellent video.
I grew up with vacuum tube radio's and TV's; even my first car had a vacuum tube radio in it. Always had to wait at least 10 seconds before they would work after turning them on. Funny thing, now I have to wait for the computers to boot up in my radios and TV's...I guess things haven't changed all that much after all.
You explain it all very well. Power supply are new to me, I have been running my HF rigs on a battery bank for several years, and that seems to work well as long as I do not forget to give them a charge once a week. And that is where I have problems, I forget to keep an eye on the voltage and recharge my battery bank, so I end up having my HF rig, Kenwood TS590 shut down in the middle of a CW QSO. It is probably not good for the radio, so I decided to buy a power supply. I purchased a Astron 35 M AP I took delivery of today. I have a three questions I am sure you know the answers. First when I turn the power supply on it is like you drop a hard ball on the table, it goes BANG, is that normal? second I notice the incandescent light in my room dim ever slow slightly when I key down, is that normal ?. and third the supply has a hum, not a overly loud hum I suppose it is the transformer, that must be normal. It is a new unit. Thank you for a very fine video . DE N7KO
@Mr Carlson's Lab Thank you for getting back to me. You know your stuff, wish you lived close buy, I would have you fix an antique signal generator that I picked up at the recent hamfest. I would like to use it for demo purposes teaching Morse Code. Thank you again.
Yes, yes and yes.
"Tips and tricks" I just got that
....or you could just order up an SDR setup for under a hundred bucks, and get way more information!!
Where's the fun in that? SDR= Boring!
sounds like a voltage regulator, to me.
uuuffff old ashly quality design (and anothers audio brands) love... Excellent.
9:07 boy, would have been nice to know which Phillips you used right there.
1:25 ? seriously? if someone is too stupid to have not already written down or photoed their own settings, I would not lose one wink of sleep over that. That would not be one of my steps. I am the type that would have already written that down somehow in a notebook, Word doc, whatever.
wouldnt it be WAY WAY easier to just stick a new 2901 IC on top of any suspect once to see which one has the problem??
oh. I was pretty sure it was an op amp but a friend (a real technician, yes) was showing me that trick - maybe it was with a TTL chip though
It doesn't work like that, but it would sure be nice if it did!
so 'BLUE' is the colour of the tinted plastic is what you're trying to say??? since it's complementary to the orange cathodes?
May I suggest that anytime you’re working with Japanese equipment that you obtain a set of JIS screwdrivers that’s Japanese industrial standard. Those screws may look like Phillips screws but they have a whole different contour in the cross. If we use the proper tool we do a lot less damage to them. Of course that won’t solve cross threading that’s just incompetentcy. A set of JIS tips is costs perhaps five dollars on eBay and a really good quality #2 maybe 15. We I do a lot of carburetor work on Japanese equipment and it is an absolute essential to use the right screwdriver.
man i wish your video had a different face.. and different shirts. your wardrobe is absolutely terrible in every video.. i can't stand looking at your face anymore and hearing you breath in every 30 seconds is terrible as well. The content is good, but man.. i'm so glad you didn't teach me in highschool cuz i woulda skipped every class.
sorry man... just.. get some different shirts?
LOL, you would be the only one. In fact you are the only one, in all my time here (on IT-tvs) that has said such a thing, what does that say about you? I suggest you create some video's and show me how it's done.
Wow, that screen saving mode on that RCA oscilloscope (curve tracer) just killed me. I absolutely love it. Keep up the good work. Cheers :)
It amazes me that someone could know enough about electronics to work on stuff yet doesn't know how the house is wired.
I see it all the time.
I wonder what your electric bill looks like
It's usually a piece of paper with some writing on it, and an amount owing.
What I'd like to know is the cause of the ICs' failure. These will fail again in short order, eh?
sounds like you know more about the radio than the manufacturer
Hi, could I ask a guitar amp question, i have tried several amp forums with no luck, I really like your videos and thought if anyone would know you would. I have a Peavey classic vtx 212, its not the heritage, its part solid state and part tube, 2 6l6gc tubes, I am getting this weird oscillating or vibrating hum, and dont know where to start diagnosing this. its been hard to find a schematic on this amp. playing all strings make horrible distortion added to vibrating hum, I dont have scopes or equipment other than a multi-meter. it powers up and still gets loud. but hum makes it unplayable. i have a video and audio clip but i dont know how to attach it. could i email it to you?. any help would be appreciated
Like the video reminds me as a old retired engineer working on old amps
So you could take a for-parts radio and create a functioning machine. cool.... how do you know all this ?
Right after you opened the cover, I could tell someone's been in there before. The zip-tie at the back which was being crushed by the case cover, as well as the excess of thermal compound spread across the heatsink. Neither of those seem factory.
Excelente explanação sobre as falhas (troca de componentes, calibragem, etc.) e também do funcionamento desse receptor de rádio antigo e super conservado! Vídeo bem feito e muito bem detalhado! Apesar da legenda estar apenas em inglês, qualquer um com um certo conhecimento em eletrônica e, se esforçando, conseguirá entender bastante o funcionamento de um rádio receptor valvulado.