Oscilloscopes For Audio 101 - Part 4A Single Ended Tube Amplifier Troubleshooting
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- Опубликовано: 17 фев 2021
- Using just a Tektronix 2246 Oscilloscope to troubleshoot a problem with a DG SE1 Single Ended EL84 / 6BQ5 Amplifier (upgraded magnavox console amplifier).
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It is what I'm looking for Mark. Thanks! Great series!! Can't wait to build one with you.
11:53 discussing the isolation transformer to variac to unit under test and establishing ground for the oscilloscope is the exact content and explanation I came here for. Thank you.
Thanks Mark. Useful tips from grounding probes, dummy load considerations, to standard yet essential diagnostic procedures and thought process. Good stuff. Enjoy all your tube amp segments.
I have a 2247a I bought from a recycling place to Advance my understanding & learning of Electronics . The phosphorus screen works perfect on it however, The rest of it does not work. Since then I've bought a digital oscilloscope. fixing the tektronix 2247a oscilloscope is Way Beyond me!
This is awesome! The level of detail makes the demonstration perfectly clear. Thanks for all of your hard work!
Hi its not very clear for me i tried to measure the cathode bypass capacitor on me preamp with my scope and a signal genérator at 1000 hz and i dont see sine wave on my scope ,maybe i make a mistake .
Im a rf tech for 40 years now retired. You are sure right. HF causes all kinds of connection problems. Very fun videos. Keep up the great work.
Thank you so much for taking the time to make this video series. I have learned more in the time watching these videos than I have been able to learn reading over the last six months, the way you present the information is not just educational but entertaining also. When I read, my mind tends to wander and I have a hard time retaining what I have learned (probably ADD 😂) but your explanations and demonstrations soak right in. Thanks again
This also works for me. I'm waiting for the SS demo. You're showing actual O-scope connect points which is not normally shown in other diagnostic videos. I really appreciate your detail!
Thanks Mark, these are great. Love the troubleshooting especially.
Mark. Great series on O-Scopes! I'm a newbie hobbyist as well as an Extra Class Ham Radio operator like yourself. I plan to specialize in RF (namely vintage HF transceiver) repair work. Would LOVE, LOVE, LOVE to see a part 5 focusing on troubleshooting with the scope this type of gear. I'm fairly certain there are other hams on your channel who would like to see this too. Keep up the great work and please mix in an amateur radio repair every once in a while.
Don't forget the solid state portion. So far the videos have made me more comfortable using a scope. Thank you!
These are great. It's been a very long time since I worked on a service bench and that was all low voltage stuff apart from the mains. Nearly everything was done with a DVM. Learning how to work safely inside old amplifiers and radios is an awesome prospect. :)
Thank you! I can't wait for the push-pull part, as I'm currently trying to diagnose noise in a new build and I recently acquired my very first scope (Tektronics 2220)!
Excelent! - clear and detailed instruction - looking forward to working on the solid state amp :-)
Thank you for the informative video. The schematic walk-thru at the end helped considerably.
Great video. Thanks. I’ve been using scopes for forty years, but I haven’t used them much for tube circuits. This was very useful information. I was a little concerned when you walked through the test points without referencing the schematic, but I was glad to see you went through the schematic at the end. I can see the efficiency of not referring to the schematic if you’re already familiar with the circuit and tube pin outs.
I enjoyed this video very, very much. Hopefully you will do more videos like this, because I know that it will greatly help improve my diagnostic skills. Thank you, for all that you do for us followers of your channel!
Great video I can’t wait to see solid state troubleshooting.
I could not have imagined a better video series to watch. Easy to watch and follow and a little entertaining too.
My real interest right now is loud speaker cabinet resonance using a scope -the Rigol DS1054Z I am about to buy and an accelerometer I have yet to understand what I need to buy. First place I will look next is your channel.
this video series, has been an excellent teaching and learning tool for a green rookie like me.
This is just the kind of videos I was looking for. Perfect for me. Thank you! I will share it!
Very interesting video, this is what i was looking for but the previous videos were also interesting and eye opening.
Thank You!
Excellent video and proper breakdown of exactly what to look for if you have a problem not many others explain what is happening to the signal and what is causing it many thanks. Please make more like this showing faulty signal and possible cause this is where the magic is in oscilloscopes just wish I had some of your knowledge.
Absolutely spot on!! Keep rolling the film!
you are a real Technician . we need more videos how to trouble shoot with oscilloscope.
Very good series, thank you. Going to use these steps in trouble shooting my Lafayette LR400 output stage as it has distortion at half volume
perfect, very educational, thank you for your work, appreciated
Thanks I had to watch it a few times to remember all the steps. Great job.
Incredibly helpful. Keep up the great work!
absolutely fantastic series. Educational and fun! Love it! For my part I'd be also interested in troubleshooting of analogue recording gear. For example reel-to-reel tape machines, analogue outboard effects such as compressors, tape echo, flanger. Anyways, I'm learning a lot here! Thank you so much!
Ty. great video. You are an excellent teacher. Hopefully I can attend a class in the barn once you start having them.
Thanks Mark I have received a wealth of knowledge. I am trying to restore a Sansui. SM 320 looking forward to push pull section
Another really enjoyable and informative video, thank you!
Exactly what I’m trying to learn, thanks Mark.
Yes, I am learning a lot about troubleshooting from this video- Thanks
This is straight forward , great nuts and bolts. Thanks.
Thank you! Excellent video...gives me confidence to use an oscilloscope. 🙏
SUBSCRIBED! Mark you are wonderful at Teaching Troubleshooting. JUST WHAT I WAS LOOKING FOR THANKS BROTHER!
Well done mark thank you you answered something I been wanting to know.for a while now great job
Outstanding. Practical help, much appreciated.
What a fantastic video! Thank you so much. You are an amazing teacher.
glad this video is up, I learned a great deal.
Just found these tutorials, really helpful Thanks
Really good.Greetings from Vienna Austria.
Thia is great stuff. Thanks to you and all those kind people doing this on youtube so we adults can go back to class again. (Loi)
Mark, great video. This is doctor ordered, thank you.
Fantastic, just what the doctor ordered boss!
Great Vid,,, thanks looking forward to the next one.
great video Mark. very helpful to see examples of scope trace while troubleshooting. many like myself who are still learning need help
interpreting what the scope trace is telling us. like what does noise, hum or oscillation look like on the scope. for example what is the
noise floor suppose to be and how to set the scope to check? thanks again for sharing your knowledge and experience
This exactly what I am looking for! Thank you
This is perfect Mark!
Great job! Thank you so much for your hard work!
This is exactly what I am looking for, excellent!
Thanks Mark, very informative.
Very nice description.
Mark,
This is a great series! Your attention to detail is excellent and is very much appreciated. Do the dummy loads need to be non-inductive? I thought that I heard you say that they needed to be, earlier in the series. First, why is that, since the voice coils are inductive? Second, aren't those loads shown in this vid at around 4 minutes wire-wound resistors? Believe me, I'm not being argumentative! I just want to make sure that I understand. I'm getting ready to restore an Eico ST-70 and I can't wait to follow along with your steps on that underrated amp. Many thanks for all you have done for so long! Michael
Very clear explaination.
Thank you.
Excellent!
Thanks Mark!
Excellent video. Thanks
Please don't think I'm being critical but I've been repairing solid state audio for 40 years and they handle open loads no problem. The only issue would be if you had a drive problem like an open base-emitter junction won't show the premature clipping as soon, and if it uses output capacitors the center voltage will appear on the output side of the cap and be slow to bleed off.
Yes this is great. Keep doing it!
Very enjoyable 2 watch. Thx
Great Video! Thanks!
great job!
@ 20:58 I finally understand the bypass capacitor and it’s purpose in relationship with the resistor by the way you just explained after all these years. 🤤🤣 I’m a little slow
If your function generator is referenced to earth ground, and it's connected to the device under test, does that pose any sort of grounding issue even though you have the amp plugged into an isolation transformer? Great video series. You are really helping a lot of us that are interested in learning, but too old to begin a new career. Thanks again!!!!
excellent vid. I have one question maybe you could address. when your signal was floating up and down from the cap I thought of times having an open bottom and florescent noise getting in. The question is,,,,, what do you use for bench lighting and ways to keep other noise away from your work?
nice video sir, thank you. If you can make another video with oscilloscope but to check the power supply quality will be super.
Great video as always! Ty!!! Curious, i believe you said you had the isolation transformer before the variac. Would it make much difference if you used had the variac first ?
Excellent. Thanks!
Mark, Really enjoy your videos. My request to on this series is to show how you can measure THD % with a standard 2 channel Oscilloscope. I know you can buy a THD meter or use a spectrum analyzer. Unfortunately I currently do not own either of these instruments. Thanks .
This is exactly what I needed to see. Can you also include how to correctly bias an amp or choose the feedback resistor value? Finally, when can we start to order the Blueglow OPT’s? I could pre-order 4 right now for other projects I want to start. Thanks for doing this!
Thats way out of scope for an oscilloscope video. For another day...
Very interesting. Thanks
You're doin' good.
I am anxious for part B
6EU7 pin-out 6 & 7 are the plates. Pin 1 & 2 is the filament. Great video, though. Shows how useful an oscilloscope can be to troubleshoot a malfunction.
Hi, thanks for the videos about the scope. I really enjoyed it. I am just starting using scope but need some clarification since i am new to it.
Anyway from your videos, you said you plugged the variac from the home outlet first then isolation transformer then the amp.
But how about the audio generator? Area using the isolation transformer for the audio generator too?
I assume the audio generator is connected to home outlet.
Since the audio generator will feed hot and ground to the amp and the scope will read the signal from audio generator that connected to home outlet that having ground reference to it. Thanks
Mark I'm really liking these videos that go over measuring techniques. I began a tube electronics hobby at the age of 65 last year as I approach retirement from an embedded systems engineer career. I've been building up my bench with the help of ebay, and by coincidence or intention I've found myself with much of the same gear as yours! But there is one piece of gear I have that has eluded me, and that is my HP8903B. Frankly I'm a little intimidated by it. There are very few videos available to get a beginner going with the 8903B.
Would it be possible for you to do a future video maybe explaining the basic 5 things everyone with an 8903B should know? What are the essential codes and button pushing sequences one should know to do the basic stuff. There really is very little out there for 8903B and your explanations with the scope are so damn good, I know I'd be able to make my 8903B useful.
Rick
Good video ! I use those same "nice" big leads too when measuring outputs form amplifiers and they are really nice. Have you ever gone around to all your alligator leads and soldered all the wires to the clips ? Factory is just a crappy crimp, bit me once measuring an amplifier :(
Referential images/photos with the probes inserted into the schematics would make it ideal!
I'm curious about the 150K resistor between the 245V line and the 6EU7 cathode. I can see that it would place a fixed bias on the cathode, but wouldn't that bias, slightly reduced by the 10K resistor in the feedback line, appear on the positive output terminal?
I need to test an Same type output transistor amplifier for thump and oscilations so what should i keep in mind.
Hi Mark, Great video series...Just wondered what is that contraption holding amplifier chassis? Where can I buy one or is it homemade?
Thanks! :)
On the 12ax7 feedback, what is the purpose of the 150k resistor between the cathode and b+, scratching my head on that...
Awesome
at 13:30 you mention "on a bridged amplifier you need a differential probe." I will be repairing a crown 5002vz amplifier that is designed to be bridged. will I need a differential probe even if I keep it in stereo mode? or will I need a differential probe regardless?
thanks! awesome info!
I like this in depth tutorial with the scope, but all the ground isolation and isolation transformers still confuse me. I wouldn't be safe because I don't understand it and I would eventually blow up a scope. I have a question concerning bypass capacitors, why doesn't the preamp tube have a bypass cap? I've noticed that in many circuits.
I'm curious about the Dale resistor its rated for 250 watts but what impedance resistance is it ? 4 ohm or 8 ohm ?
Could you bias an electric guitar amplifier sometime? Something like a class A/B Marshall. I'd love to see the sine wave and maybe also a multimeter set to mA or mV as you adjust the bias pot.
Are there any differences in the setup or testing of a pre-amplifier?
Good video but i have a question about the schematic. Why would someone lift up the cathode of the 12AX7 with a 150k Resistor tied to 245V ? Never seen that before.
Yes some practical troubleshooting...also show diagrams of the units.
It's not a big deal, but the volume control is missing from the schematic. Also, what's the part # for the power transformer?
Thank you Mark! What amplitude do you set the function generator to? I guess my question is can too much amplitude cause damage to the amp.
hi, normally around .8 V rms.
Love the Oscilloscope video series! Awhile back I watched the video on the wire cutters and in this video I see them on a rack. Can you share some info about the rack? I'd like to purchase one like it.
Its from a dental supply company. www.pearsondental.com/catalog/product.asp?majcatid=613&catid=8350&subcatid=28321&pid=79542
@@Blueglow Thank you very much!
Hi i tried to measure cathode capacitor on my preamp , but i dont see the sinus on my scope ,can you explain why its dont work on the preamp ,thanks a lot
Hi Mark, this is really fun to look at. I have one comment from the days I did a lot of electronics trouble shooting.
I would always use the half way split method. So after you see the problem on the output, you try to cut the hardware in half (and you can repeat that with complex equipment to safe many steps). In this instance you would go straight to the grid of the output valve. I am assuming you "stepped trough the signal path" to demo it. But you would also split the HW if you where trouble shooting this alone. Is that correct?
That is a good approach. If this video had solely been the fasted way to troubleshoot this issue, I would have started with a DMM and verified the power supply voltages (the first 1/2). Then moved to the audio circuit (other 1/2).
I have a doubt. I want to buy a digital oscilloscope to work on tube radios. How many Mhz minimum? Thanks for your channel. I amanhã learning a lot.
When working with audio why not just leave the scope set to AC coupling?