Become A Super Electronics Troubleshooter!
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- Опубликовано: 14 июн 2024
- In this video, we check out a 135 Watt Fender amplifier. I will talk about things to consider before taking on a job.... To tracing a signal right from the input of the amplifier, all the way to the output. We will use the Forecasting Capacitor Leakage Tester to determine whether to "leave or replace" the capacitors, and much more.
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To learn more about electronics in a different and very effective way, and at the same time support this channel, go to Mr Carlson's Patreon page, click here: www.patreon.com/MrCarlsonsLab
the absolute madman, he actually did it
please teach how to download a copy of your brain into mine, thank you :D
Hello Paul. Really enjoy your videos. Thank you. What is your opinion on whether same spec valves from different manufacturers really make a difference to the sound of audio amplifiers? For instance I have seen vintage NOS Telefunken ECC83/12AX7 valves (similar to those in the Harmon Kardon Citation you serviced recently) selling for £150 or more vs other makes for £10 - £15. Is there really any justification for this large price range? I can appreciate that some valves are more microphonic than others but many claim there are tonal and other subtle differences. Perhaps you could make a short video either debunking or confirming the facts on this sensitive issue. Keep up the good work and excellent content.
Thank you for your input Sharkey. The video would be great. I'm not so sure if people can handle the truth when it comes to this question. I find many want to believe in magic. The video would be controversial, that's for sure.
Hi Paul. Yes I am sure it would be controversial, my belief is that one strong tube sounds the same as another but I don't have "magic" ears like some.
Perhaps you could do a video specifically about matching valves, why and where it is important. ie phase splitters, stereo gain stages and outputs.
I have valve hifi amps but rarely use matched valves in anything but the output stage. I am interested to know what matching tolerances are acceptable especially in phase splitter circuit. Perhaps a demo illustrating the circuit with mismatched tubes vs matched and the problems if any that arise from mismatched tubes. Which characteristics are matched by vendors, ie. In the past I have bought GrooveTubes EL34s in matched quads. GrooveTubes claim to match their tubes for gain AND distortion, How is this achieved, is it just marketing.
Three years ago this was one of the first tube amplifier video I watched, now I work on amps for a local shop and my own customers.
oof
I find myself more and more these days, in a state of awe and wonderment. The fact that resources like this exist, of a quality and depth that would have been unthinkable just a few years ago, for nearly anyone and everyone’s benefit...seriously, what a friggin’ time to be alive!I’ve got to remember not to take it all for granted more often.
I’m light years from being considered a professionally competent engineer. My career certainly has a heavy technical aspect to it, but I also have just an insatiable curiosity when it comes to understanding the world around me.
Thank you for sharing your knowledge.
Thank you for making these videos.
Their value, to me, is inestimable.
I know right?
I don't have a ton of cash so I try to spend what little patreon money I have on people I feel really make a difference. As soon as I saw the first couple of videos I jumped on his patreon.
Paul is amazing, super easy to follow, incredibly thorough and the test equipment that you build in his course are almost beyond belief in their abilities, especially the SIFT capacitor tester / Prognosticator and the Super Probe.
I'm like you and far from being anything more than a Simple hobbyist. These videos and the test gear that you build have me much closer to the "Somewhat Advanced but not a pro" Level...
The resource that is amazing and beyond belief is Mr. Carlson himself. Everything you see around you was once a thought in someones or somethings mind, even the stuff not man made.
I concur.
You are so correct sir. I got really serious about electronics troubleshooting around 1999 or so. I was about 17. I used a lot of Internet newsgroups back then. It wasn't great all the time, but now, it's just amazing what we can do and learn. The funny thing is when I wanted to start learning about repairing power supplies and things like stereos and tvs, everyone said I was wasting my time, that nothing is worth fixing anymore, etc. I didn't listen to anyone. I did what I wanted to do and i'm happy with that. I got such tremendous pleasure out of fixing an old 14" CRT monitor then, and I still do to this day. I don't regret my choice at all. This channel and Mr. Carlson help me get better at this, and i'm grateful to him for that.
I have been working on electronic equipment for several years now and have even taught a rather condensed and relatively advanced electronics course recently. I must say that I've always loved my field as a total science nut, however finding Mr. Carlson's videos has changed everything for me. I didn't expect to find someone so in touch with this world of electronics. This is either formal training as an instructor or the greatest naturally talented instructor I've ever seen, and I've met many great professors and teachers. Mr. Carlson has turned my profession into more of a passion than ever before. Watching Mr. Carlson work is a very humbling experience for me as it shows how much there is to learn as well as how exciting electronics can be!
😢started learning electronics in the mid 70s from a tv repair man who was also an electrical engineer also tought me math that i could never grasp in school learned mor in 3months of working with him then i did the entire time in school you remind me much of him in my 60s now cant see for sheit but love whatching your videos makes me really miss my electronics
The Bob Ross of electrical and electronic videos. Calm, exceptionally knowledgeable, very well produced videos. Nicely done, Mr. Carlson.
Thanks Jim!
Was an owner/operator of an electronics repair shop, did warranty and non-warranty repairs for some major manufacturers of radio/tv for almost 40 years. I still learn from watching the workflow of others. Enjoy your videos... loved the Hammerlund restorations. Keep up the great work... Rich
This is great, it brings me back 50 years
Thank you Paul for sharing this Patron video, because of it, I was made aware of snubbers in a bridge rectifier, then doing some research, learned of their value.
Cheers,
Adriel
Your warning about high voltages reminded me of a time in High School Electronics class when we were dissassembling old computer monitors. One student was gone when the teacher explained how to properly discharge the tube capacitor. There he was taking the monitor apart. We asked him if he discharged the tube. He looked confused. We explained the high voltages inside. He carefully put his screwdriver down and slowly backed away from the workbench.
Hah, that's... a surprisingly sober and proper reaction. ;)
BOY you are the tech EVERYONE WANTS....methodical...thorough....detailed.....you're TERRIFIC.
VERY experienced. So great....THANKS Paul....(UNCLE DOUG....TWO OR THREE others.... such good tutorials.). Perfect for me. Your a GIFT really. Thanks again!
uncle doug doesnt even know how to wire safety grounds properly. Id recommend psionic audio and brad's guitar garage for other experienced amp techs
Your advice on dealing with a musician client… you my friend are a true pro and total gentleman. SPOT ON!
You, along with Uncle Doug, DLabs and The Guitologist, are by far some of the best channels on youtube for troubleshooting vintage gear.
Props to all of you.
Invaluable information.
Smithii I second that
I am gonna check those out, I would also add.
EEVblog, Louis Rossman, Ave, this old Tony and Electroboom for some high voltage comedy.
Thanks so much for including me in your list of preferred channels, S :)
@@UncleDoug Who are you uncle Doug?
I will check you out.
Hi @@UncleDoug I just watched your current limiter protection video and I have one question. What does it matter the black wire or the white wire for the bulb? I thought AC was AC and both sides were in effect the same?
electricity is fascinating and channels like yours and electroboom make things simple enough for an ignoramus like me to understand. Thanks for teaching mate.
New subscriber
I cannot understand for the life of me, why anybody would give a thumbs down to this or Doug. His knowledge and clarity of explanation there of, combined with his mannerisms are no less than 1000% professional and thorough. His videos are gold!
I have given him a thumbs down for the fender reverb amp video. He recommended an illegal, unsafe modification to earth wiring that I could not approve of. Don't be mesmerised by his 'dulcit tones'. He is not a god. He is very good, but not omnipotent!
Your teaching is a generous gift Mr. Carlson. Even at 70 I'm playing and learning. Thanks.
You're very Welcome!
I always smile when Paul says: "bad things happen..." because we all know what it means in electronics...
For such a seemingly young fellow, you seem to have knowledge way beyond your years. Most thorough and comprehensive videos I've ever watched, and they are great.
Yes maybe worked with an old timer ?
That's exactly my thoughts.
I'm here as a musician that uses tube electronics that is quite interested in them, except I usually sit right around 40 to 150 hz, as a bassist. It's funny you say that about the master volume twin reverb, Fender actually made them less prone to distortion(not that a regular 85 watt Twin is pleasurable to be around at that volume), I had read that it was due to a shift to ultralinear output transformers. I've never been able to drive a UL 70s Fender amp to the point of overdrive that wasn't painful to be in the same building with. Even as a bass player, running my 8 ohm UL Studio Bass(200w, "enough") into a 4 ohm load it was still hearing damage volume at power tube breakup. Incredible amps, these are.
I've learned so much over the last two days watching your videos about tube electronics, easily the best electronics videos on the internet.
Your channel has quickly become my new favorite. So much knowledge and such a good teacher. Lesson #1: RE-CAP EVERYTHING. I've learned so much about capacitor failure from watching your videos. Keep it up Mr. Carlson, you're awesome!
Thanks Nicholas!
Like the butler, the capacitor is nearly always guilty.
I worked as business equipment engineer for many years and I used to service automatic bank dictation equipment I.e. connected to telephone exchanges. The GPO engineer at the exchange told me the painters were in to brighten up the rooms around the equipment. There was racks of lead acid batteries all connected in parallel for power backup if the mains failed! they remarked “it’s safe enough as the total voltage is only 50 volts! They forgot to mention that the total current available was massive (several thousands of amps) There was a huge bang when somebody dropped an aluminium ladder among the terminals and part of the ladder simply melted! Lucky nobody was injured! H S wasn’t very strict in these days! Fraser
Thanks for sharing your story!
I worked on this type of amplifiers in the late '70s. Thanks for the memories.
What an enlightening video!
I was hooked as if I was watching a good detective film. An hour and six minutes flew by in no time.
Please make one about a solid state circuit.
If there is ever a Patreon that i support.. it's this guy. Very informative, great audio, well edited, good cameras, etc ..just an all around wealth of knowledge.
God bless you, you are the best, Your posts are a treasure to whoever wants to learn, thank you millions
You are very welcome!
I want to thank you for reteaching me electronics. Please keep on making more videos as so to benefit a lot of the newbees who have consent to go down this wonderful road of discovery.
You're welcome Mr Victory.
You make things very clear and very understandable to folks like me. I don't know much about electronics but this was fascinating. Thanks for not talking "above" me.
It is a pleasure being part of your Patreon and I appreciate all the knowledge and skill you have shared with so many! Excellent channel and work!
This was excellent! The way you pointed out the signal path in the chassis and how that corresponds to the schematic was what I've needed to know. I've watched others explain about the circuitry, but nothing comes close to this.
Old ground based aircraft navigation transmitters had 250 VDC as low voltage, 750 VDC as medium voltage, and 12,000 VDC as the high voltage with plenty of current. You paid attention really well when you did anything at all, anywhere.
I spent 20 years as a troubleshooter of telecommunications systems. so I am loving what you are doing here!! I am gaining more and more knowledge to start working on electronics myself!!!
Thanks!
Your instructional videos are the finest I've seen on RUclips. Thank you.
tales me back into my tube tv days. LOL. The easy-to-follow technique of illustration keeps me watching these.
While I don't understand much of your commentary, I manage to learn something from every one of your videos. I still have many videos left to watch, and very much look forward to seeing them.
Mr. Carlson is the best at simply and thoroughly explaining electronics! Thank you!!!!!!
Hi Mr. Carlson, I just wanted to say thank you and tell you that your Patreon program has been so informative and valuable to me. It has not only taught the fundamentals of electronic repair but given me and the rest of your patrons the information and even the tools to troubleshoot the circuitry all the way down to the component level. It’s been an amazing bit of information and I can see why so many are joining up. In addition to learning, it’s been a lot of fun and I look forward to every new video. When I saw this video today, it reminded me of that. I know that this isn’t as easy as it looks, you don’t just sit down and knock out these videos, it’s a lot of work. Like I said earlier, I just wanted to say thank you, I’m having a great time! -Buddy
Thanks for your kind comment Buddy! Lots of sleepless night go into these video's. I'm beginning to think, the lack of sleep is "video fuel."
I agree. I became a Patreon months before I planned on starting to build anything because I knew that the information, projects, and teaching was worth much more than what I had to pay to be a member of Paul's Patreon channel. Thanks Paul!! You're the greatest!
What is sleep but a waste of life, sleep less, power nap and get more done, including enjoyment, life's too short, a couple of years ago I was 28.... now I'm 62 OMG where has it gone????
It is always good of you to issue the warning about HIGH VOLTAGE. One time, as a young teen, I had a Motorola 2m VHF radio powered up. Managed to get the b+ across the chest and that really, really smarted. Worst shock I took. Of course, tube gear was the only readily available hobby material in the mid 60's. I did take a number of shocks and drew many sparks. I never got use to either. Later on, I learned to keep my left hand in my back pocket when probing live circuits. For those new to these circuits, make sure your scope probes can take the high voltage as some cannot. Keep the ground clip on ground.
Excellent video, Paul! I actually found your channel just over two years ago when repairing a valve power amp. It's great to see how far your channel has come since then, and see the subscriber count looking so healthy for an electronics channel, with many more subscribers and views yet to come. All the best!
I appreciate Mr. Carlson’s enthusiasm and appreciation for electronics, still so strong after so much experience.
Got a Twin Reverb like this sitting across the room from me that I bought in 1976 except it's an earlier 100w not 135w. Had it modified with a Rivera/Boogie sort of lead channel and used it from Egypt to Japan and points between back in my traveling days. Briefly had a 70w Pro Reverb which should be nearly identical to this Twin Reverb except half power. Now mostly use one or two of my other amps (69 100w plexi. 79 50w Marshall, 68 Bandmaster, a couple of newer Ac30 types) these days. I don't have as many amps as some folks but love them all, especially my Twin Reverb because it was my first REAL amplifier. Great to see Mr. Carlson feature this Twin Reverb amongst the vast array of gear he deals with.
Mr Carlson, You sir are a intelligent man, I'm now old and always wanted to learn electronics, now just to old to start, just enough to learn somethings to help me, The best way for me to learn is to have you show me one on one, Thats how I have learned everything in my life, and reading. I do learn quick ,when someone shows me.. great videos
Mr Carlson, I love it.Fender amps even of this era are like working on an old muscle car .I've owned my share of them my friends play them .They are the sound of rock,jazz,blues and American music in general.
I watched this video a couple of years ago as a fan boy wanting to learn about audio electronics. Since then I have gone through a year of college in EE. Wow! It's amazing how different it is once you learn to speak the language. Thank you for the great videos.
Glad I found these videos, very thorough. Each one yields a wheelbarrow of knowledge. Keep up the good work. You are my new hero Thank you!
Thank you so much Paul. I have watched many, many videos on tube amp servicing and followed along sort of understanding what was being said but the way you explained each step finally made the light come on. (No pun intended). I hope you do more.
Hello, I did watch your entire lesson it was very well presented. You are the best and most comprehensive instructor but I am still a beginner. Thank you so much for all of your great electronics presentations.
That was a very kind description of Kenwood's use of Sony bond at the 24 minute mark!
New subscriber here. Love your videos!
I was working on a 1976 Fender Vibrolux about a year ago for a friend (similar vintage, but smaller amp with roughly 40 watts output, if I recall). I have another friend with the knowledge and test equipment who went through the chassis for me. I was mostly taking it apart and cleaning 40 some years of filth out of the thing. Other than replacing the tubes and cleaning some crackly pots myself, after he was done, my work was mostly a cosmetic restoration. Got it back together, plugged my guitar in, and it sounded great! Just like new! Returned it to my friend. He loves it!
There was one step I found later that we had not addressed, wherein lies my question: adjusting the bias. There is a small nylon screw on the tube side of the chassis which was on or near one of the transformers. The Vibrolux, being smaller, is only powered by 2 6L6s, hence one bias adjuster screw. I believe the Twin, as it has 4 6L6s, has 2 of these bias adjustment screws. Could you do a follow up video, once your amp is back together and running, explaining the importance and/or procedure to this process? Another music/ gear-head friend of mine said that bias adjustment is important and I should get the amp back and have this done. I did go to the trouble of buying a matched pair of 6L6s, but think that bias adjustment may still be necessary. Would love to hear your thoughts on this!
One problem that I saw when fixing Fender amps took me years to finally get to the bottom of. Several Fender amps that I saw would have random "shot noise" that sometimes sounded like lightning interference on an AM radio, sometimes it had random whistles and squeals mixed in. I traced the noises to something in the interstage coupling circuitry. If I squirted the fishpaper and eyelet "circuit board" that Fender used with contact cleaner, the symptom would go away for a while, but would reappear once the cleaner evaporated entirely. Yes, I was mindful of the high voltages while doing that. The few times that I fixed it, I ended up removing certain tie points from the paper and letting the connection float in the air. I learned years later when working with other equipment with high impedance/high voltage connections that after the passage of decades, solder rosin flux residue becomes a noisy resistor. I now know that the original removal of the flux at the Fender factory had driven a small amount of flux into the paper which years later would cause the noises we heard.
Wow that's interesting Dobbin! I thought you were gonna say something about leaking electrolyte from a capacitor making the cardboard or elephanthide rivet panel conductive! But flux doing that? I'd never have thought.
You are so kind...such a talented man......you really know how to teach.....God bless you....
Thanks Paul, what a great way to spend my morning while I should be working :)
Really happy Mr C has this up. I bought a Twin Reverb just before Christmas, i have a Princeton a Champ F5 and a Champ 600 which has a PCB not point to point. I think Leo was a genius and so was whomever he employed to drum up the circuits. I would love to see a vintage Radio converted into a Guitar Amp, nothing fancy just a singled ended low wattage Amp made from an early valve/Tube Radio. Bless you Mr. Carlson.
As an EE, Tube Amp repair and modding is a type of meditation for me, and "In the Grid Out the Plate", is my Mantra ! Thanks for cool video !
I signed up today for Mr Carlson's Lab Patreon $20 per month option because need to support quality videos like these - Very Well Done!! I look forward to learning more on your Patreon area.
Great stuff man, you're with no doubt one of the best and most useful channels, keep it up, you're great.
It's nice that you take the time to explain the theory of operation in all your videos. I particularly like the emphasis you put on safety. One of the first things I learned in the Navy is what they liked to call the "left hand rule". Simply put: Put your left hand in your back pocket when working on live circuits. In case you accidentally ground out the circuit through your body, the current travels down the length of your body versus through your chest/heart and out the other arm. It doesn't take a lot of current to stop the human heart. I followed this rule religiously when working on HF transmitters and radar sets. And I still do 'til this day.
Rigorous and thorough. I bet not much leaves you wondering. Here's a thought, I'd love to hear some yarns of occasions (possibly with examples) of times when you've been truly stumped on a troubleshooting mission, even for a short time.
Thanks so much for your excellent tutorial...it was just like watching my father who pass years ago .Explaining to me things in his TV repair shop in the 50-60's...once more.
Your a genius Mr.Carlson, I love your channel and ability to educate the general audience, for me anyways.
Thanks for sharing!
Kind regards Eric Dee
Just love your videos Mr. Carlson. Thanks for suck excellent quality presentations. Your up there in my top ten RUclips presenters.
You have the voice of Dr. Joe Dispenza!
I'm working on a 1951 RCA A-78. I was just trying to figure out tube pin configuration and signal tracing. I had no idea that you would cover these topics in this video before I watched it. Thanks for great video!
mr. carlson is a true genius...wish I could be this good at troubleshooting!
It would be nice to see a Part 2 of this video testing the Electrolytic Capacitors and replacing them, Testing the Output tubes and looking for matched pairs and also Biasing the amplifier.
Thanks
Betcha he does just that!
Totally amazing. And I don't even work with tubes. But there are so much other to learn from your videos.
This video was an excellent campaign to the morning coffee.
this guy is the best viewing i have ever ever ever seen...he is an amazing person.
I just discovered your channel and subscribed immediately!!!! I look forward to checking out your channel & videos and learning much from you!! I see that you are very well respected and want to add my voice to the multitude of those that thank you for sharing your knowledge & wisdom.
THANK YOU!!!! Best regards from your newest fan & follower:
Norman in Montreal, Canada.
Thanks so much for sharing this video with the general public.
Yes excellent, Paul. Very well done, I am learning a lot. Hope to see more. Thanks
Genius...i wish you were my teacher 30 years ago ..i would be much much smarter..thanks
An other excellent video packed full of tips and tricks. Thanks for sharing your wealth of knowledge.
I love your channel! I was in engineering school in 1967 so we still had tubes. Went from that to Polaris fire control in subs. We had transistor gates and 4 k core memory. For large memory it was drum memory, I think 16k. I still fix electronic equipment, but it sure has changed.
Good to see. At this stage you have helped me decide I'm not ready to handle high voltage stuff. A little bit more learning and practice first.
Wow, that was incredibly educational. I have learned so much in this video. Thank you very much.
Absolutely needed this lecture Great stuff, In, out, plate, grid, excellent explanations. You do well and it helps us a ton. Thank You.
I signed up as a Patreon today. Your lectures are so good i wanted more of them. Great job, effort. Thks, can i show you some of my trains? Digital sound, wireless control 3D printed parts on 1947 to 1960 AC Gilbert America Flyer.
Love the customer mindset; if a customer thinks something is magic, and that makes them feel happy... why break that model of thinking?
Very nice Paul. Thanks! I'm very glad that I am a Patreon subscriber. I was planning on building the Curve Tracer this month and then everything started crapping out on me. I just finished fixing my Sanyo 40" LED/LCD TV that just had some bad solder joints on a few LED's on the first "A" LED strip. Now I have to rebuild the Siemen's Hall-Effect sensor fan motor in my Tek 2465A DV. I might go ahead and start on the Cap Forecaster while I'm waiting on my oil-impregnated spherical bronze bearings to get here. Thanks for all that you do!
I learned from this video. Many thanks for your output. Steve. Cornwall. UK
Glad it was helpful!
I’m a guitar player watching your videos to learn more about tube amplifiers. And yes we think these things are magic .... because they are ! They are how we make our sound. But you can always replace my caps. I know they wear out.
Great content (as usual) Paul. If you ever have the opportunity, It would be great to see a part two on this video and your approach to troubleshooting amp output circuit issues, how you might design/use different loads (reactive versus resistive) to find different problems (low power, oscillation, feedback, AC hum, etc.... ) thanks again!
Thanks for this video. It helped me as I worked on an older Crate Blue Voodoo 6212 combo amp. Your videos are extremely good for building confidence in the repair process. Thank you!
You're welcome Mike!
I MY SELF have built a Marshall 18 watt amp . and also a fender champ 5f1 with my brother. 12 ax7 6v6 I like el 84s tube amps are great. have had a line 6 dig 75 watt spyder 4. Thank you Mr carlson for your great videos.
I've been in the electro game for many years both on domestic and commercial stuff and never met anyone with your experience and knowledge give your apparent age .
i love all the carlson inventions, but that super multi capacitor tester is by far my favorite, i will have to get it at some point!
This is perfect.. I have a pro reverb about the same age that needs a lot of work! Thanks!
Excellent information here !!!! Thanks Paul. Time to get the Leader LBO-501 oscilloscope out and play 👍
You know you are getting old when they start talking about old Fender Amps that are the black tolex. I worked at Fender or at that time CBS Fender Musical Instruments assembling Twin Reverbs and all the others like Quad and Super Sixes. I also assembled all the Speaker Enclosures like the Baseman and Dual Showman. At that time everything was built in the whole plant by piecework another words you were given a standard you had to build in an hour to be equal to your pay. If you built more than that an hour you got a percentage on your hourly pay like a raise. There were like 4 people remember that could that could build at over 200% with zero issues and I was one of them. For instance, a Twin Reverb had a time standard of 9.6 an hour for 100% of of your pay. I could assemble them at 20-21 an hour. So that equaled like over 200% of my hourly pay, which making double your hourly wage was pretty good pay back then. If you did less than 9.6 you still got your regular hourly pay, but you were not going to last long if the company only got that out of you. The only problem was that if you turned in over 200% they would send down the Time Studiers to adjust the standard they really wanted people to only make no more then 150% so us top assemblers would stop working at the 7th hour and just sit around until the shift was over. Boy do I have some great memories of all those guys I worked with and the great times we had together. Glad to see they are still working out there.
Thanks for sharing your story Jeff!
"by piecework another words"?
"were like 4 people"? So they were like people but not actually people? Robots?
GentIlemen, I've been doin tube guitar amp repair for a living since 82. I used to do Fender warranty i n the 90s. I got to know Fender employee,John Fouch. I saw a picture of Nez Pierce leader Chief Joseph from 1890s. The photographer was Johns ancestor.
Jeff thanks so much for Your post, and work. I am sure many of the amps I still see alive and Kick'in ass are the result of Your work ! Fenders are my favorite amps to work on!
Jeff Hook, what you describe is exactly how management operates when I did machining for an aerospace and aeronautics company. If you found a way to beat the time standard, you dare not beat it by too much because you wouldn't get a raise or a bonus; you ---- and everyone else --- would then be expected to make those "extra" parts each and every time!
I seriously enjoyed your video and learn something from your video. Thanks so much for making those excellent video.
Thanks for putting in you time to make this video.
Very much enjoyed this video. Your skills far outweigh mine and that comes from learning and experience, something I hope to also acquire more of with the boost from your excellent presentations.
73's de N9ZN - Tampa Fl.
Thank you for this excellent, informed video! One extra safety precaution I always take when working on amp like this that have a standby switch, is to leave the standby in the "up" (play) position until the repair is complete. The standby interrupts the B+ voltage between the rectifier and OT primary/ filter caps under the chassis, so if you try to drain residual HT from the rectifier with the standby off, there's a chance that the caps won't drain properly as the switch interrupts the flow. I always think it's a good idea to touch your drain probes to both lugs on the standby switch as an extra precaution that the HT on both sides of the switch is gone.
Excellent as always. I am trying to fix a modern mixer P.A. that is mostly SMD. Needed some Carlson therapy to stay sane!
Thank you for this video! I am finally getting back into electronics. It is finally time to see what the heck I messed up with my guitar amp build I did way back around 2008. I was young and while I learned a lot, it wasn't nearly enough.
I just hope I don't end up spending a lot on more components. I easily spent $300 or more on parts alone for one of the most simple tube amps ever.
Before starting a project like this, I would have the musician demonstrate all of the functions of the amplifier. I would create a list of what is working and what is not working. With this list I would know if I fixed everything (or broke something, yikes!).
Thank you for your videos Mr. Carlson, you rock!
I feel you have a lot to contribute to people wanting to better themselves in the field. Maybe you could do so with about half the words? I mean, if someone is watching this to figure out how to fix their amp, and they really need a in-depth explanation of how capacitors work, they're probably a bit in over their heads.
18:08 Nice pun... removing the 'cap' from the caps.. In the Fender amp world, this is often called the 'doghouse'.
Killer video from a player who has never ventured to this side of the gear. Now I see why they call these 'big iron'
"They look at these amps like they are magic" You nailed it right on the head - we do tend to look at all of our equipment that way. We guitar players are a strange bunch sometimes.
Or simply a black box. You plug your guitar in, sound comes out. What happens inbetween is none of your business, because "your business is just to shut up and play". That's the mindset of most musicians, and for good reason IMO. Of course the analog synth guys and those kind of people don't fit in this pigeonhole, but you get my drift.
Lol whenever my old tube guitar amps start to sound especially magical, something is about to wear out. Usually a tube but sometimes resistor drift alters things just right for your playing style. I could be wrong but I think old filter caps that are slowing down or wearing out can induce a great sag effect that seems like compression. I know they need to be replaced or something bad will happen but in the meantime.... something good is happening!
I've noticed the subtle sound nuances all disappear as does any talk of playing style when a "guitarist" is instantly disrobed by handing them an acoustic guitar and some music.
@@jjo5917 Hi JJ. Yeah, something good is happening until one day........BANG! A $1000 repair bill!
You are the BEST on RUclips
Excellent instructional video, greatly appreciated.
I've been working on the "CBS" Fenders since the time they were new, and the black face Fenders since the time they were 1st released. Yes on the high flying filament wires. The black faced Fenders had cloth covered solid core wire that took a higher tight twist so they tend to be less hummy. Yes the 'blue molded" poly caps almost never fail.,and yes the mallory filter caps usually have to be replaced, even though often times they "still work",.. the electrolytes dry out. The one error in design seems to be the tremolo cap that You reference at 45:12. since the tremolo circuit tends to oscillate between a cathode follower and a common cathode mode, that cap sees way more than the 25 volts it is rated for, although the current is really low. I usually replace them with a small 200-400 V electrolytics that are now readily available. 10-22 UF. The Fenders are set up to play the output into a shorting speaker jack, when the speaker is not plugged in, which is much better than leaving the xformer open. I ALWAYS plug in a resistor dummy load with a speaker divided off that load, so I can see what is going on, looking at the signal across the load resistor.. Silver face Fenders often suffer from parasitic oscillation resulting from a change to the circuit (by CBS) with the bright switch wired so that the 250 pf cap sees a resistor to ground, creating creating 360 degrees of phase shift at some high freq (20-100Khz). That resistor, though not in any schematic I've seen, is hidden behind the brite switch and a bunch of wires. remove it! Silver face Fenders have a lot of problems created by the "hiFi" engineers from CBS. However the Transformers are better quality, but not necessarily to many guitarists taste. The bias balance control is not as good as a bias control for instance. Nice to see and hear Your excellent analysis , that brings up some things i seldom think about.