D-Lab Basic Training Fender Bassman tube guitar amp Low distorted output Lets fix this with Fred
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- Опубліковано 27 лип 2024
- From the tube Caddy of Fred & Fink more basic training. This time we are presented with another Fender Bassman tube guitar amp with low distorted output. In this video you will be asked to consider 3 options. Then we will follow a systematic approach to discover the cause of the fault! Usually the problem can be spotted visually. Lets see if that holds true this time! I hope you enjoy the technical production and stale humor! Thank to all for keeping my shop moving ahead. Please spread the word, subscribe, etc. Check me out on Patreon! / dlab_electronics
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Holy crap, this video couldn’t have been timed any better. Just this morning I received new tubes in the mail for my 1967 Bassman 50, and after installing them I noticed that even though it started working again, the output is low and distorted.
Fred will become the next "Mr. Jingles" (the mouse from the movie "The Green Mile").
The more you explain the scope readings the more I’m learning , Thankyou terry more examples please
I've been repairing amps for some years, but I'm always watching basic traing and other of Your repairing vids. Thanks for Your job! Much regards from polish tube guitar amps freaks!
Fantastic that you have an AMPLITREX! They provide a much more accurate depiction of the tube under test when used in computer mode rather than as a stand alone.
Thanks again and best wishes from Columbus Ohio USA
Nice one Terry..Great to see the signal and the explanation.. Great vid..Thanks again for sharing...Ed .UK..😀
Yay, Fred's back!!!
I KNOW THE COMMENT HAS BEEN MADE BEFORE BUT D LAB SHIRTS WOULD BE GREAT YOU MIGHT BE SURPRISED BY DEMAND 63 K SUBS JUST A THOUGHT
I'd wear one,,,,,for sure! Thanks Terry!
Thanks for the tuition. 👍🏻👏🏻
Thanks, Terry
Disappointed at no Emmy. 🙃
You are wonderful sir. Wonderful.
Cool amp. Great condition. Thanks D Lab!
Your training is great! Thanks appreciate it
Loving this Fred series, Thanks D-lab!
Any chance on doing some Phase inverter scenarios? Explain the difference between using a 12AX7 compared to a a 12AT7 for Phase inverter and the reason for and against etc.
Thanks cheers
,AT is used as it is not a Galn Stage
Get Ol' FRED to da rescue!!
Thanks. Nice lesson.
Great topic and excellent video. Thanks & Cheers!
That's an abundant mouse. I was sure it could pass for a Rat King.
Thank you
and thank you
I have a 5e3 clone that the power tubes are barely warm I can hold onto them what could it be ? I’m thinking maybe a bad solder joint like you should us in a previous Fred video I’m re watching the basic training series I love it keep up the good work thanks again Terry
Must be a Norwegian Wharf Mouse
Sensible steps to assist novices in diagnostics.
Thanks for another interesting video. What is the voltage Vpp of the signal coming from your audio generator unit when you perform the initial testing?
I believe it was set at 100mv
The bad screen resistor went up to 20K homes when a good screen resistor should have been at 470 homes so the bad screen resistor that is at 20K is restricting and giving less current to the power tube and that is causing what type of distortion it look like a symmetry distortion how it would adjust the the width of the positive and negative push and pull maybe you can explain in the comments and get back to me that would help me out a lot but it has something to do with the restriction of current that would that is doing something to the tube to cause it distortion it might be a transconductance thing because transconductance is based on the current verse the voltage of the input and the output of the tube
With the screen resistor being bad would that also make that tube be cooler in temperature ? How would I find this with out a oscilloscope
Hello D-lab, what are your thoughts on using higher screen values (~1k) to protect modern production tubes from overcurrent faults?
I do believe its a good idea. Ham transmitters use screen regulators to protect final output tubes. Examples 0D3, 0C3. They have been doing that for years to protect 6L6 and 6146 tubes. It would be worth exploring.
mouseman mouse house repair
Hi Terry, I am looking at obtaining a LAG55 like yours. What do you think a fair price is for a retired tech like myself at a swap meet or ebay?
I paid $100 for mine
@@d-labelectronics Thanks man, I'll give it a bid and see. Still really enjoying your videos. Besides being reminded of so many little things, there's almost always a new nugget of an idea that I had not considered. Cheers Terry!
Could anyone here tell me what might be causing this issue? New 6L6s installed in a 67 Bassman 50, but only one of them is glowing. The amp still works, but the volume is noticeably lower and the tone breaks up much easier than it used to.
Identical problem the Bassman in this video had. Check those Screen resistors
@@d-labelectronics I swear I’ve learned more from this channel than from years of classes related to electronics. Please keep it up, you’re a national treasure!
Only one “glowing” -- I assume you mean the heater isn’t lit up. Check it in a dark room to make absolutely sure. If you’re certain the heater is dark, then swap output tubes to see if the “dark” tube stays dark in its new position. If it does, then that tube’s probably bad. If, however, after the swap, the other tube that looked fine is dark now, then I’d say you’ve got a problem somewhere inside the amp, in the heater circuit. In the latter case, could also be loose contacts in the tube socket where you’ve determined either tube stays dark. New tubes do occasionally arrive bad, though, so that would be my first suspicion.
@@drawbridge611 I swapped the tubes and now they’re both glowing…. Wtf, this is confusing. The only possible explanation that I can come up with is that maybe the “non-glowing” tube just wasn’t seated properly? Any more ideas, anyone?
@@seanmcdonald4686 It could be a bad socket not making good connection. Or it might be a bad solder joint on the socket.