This gem came up in my Ewetube feed at 4am. Love your work, Doug Regards from Vinny in Brisbane

@UncleDoug

2 ай бұрын

Thank heavens you were up to watch it, Vinny. Thanks for the nice comments :)

Another great demo of fault finding and selection of suitable repair materials. After watching Rusty's reaction over a number of videos i don't think he's camera shy. I reckon he's waiting for a proper remuneration deal before he'll stay in front of the camera. Maybe get your people to talk to his people ?

@UncleDoug

8 жыл бұрын

Thanks, Andrew. Rusty is a tough negotiator, but his agent is even worse.....we're still working on his new contract :)

Nice to see Rusty is still with us! Thanks 4 your videos!

@UncleDoug

8 жыл бұрын

+Haroslav Drastic Like death and taxes, Haroslav, Rusty and I are here to stay :)

Thanks for taking us on this journey with you. So much to learn from you.

@UncleDoug

2 жыл бұрын

Thanks, Jim, for joining us and for posting a nice comment.

Wow Back to Back gems! These videos give me such encouragement. Thankz

@UncleDoug

8 жыл бұрын

+Audio Tech Labs You're welcome, ATL :)

Cheers to Rusty and yourself sir...A big thanks for not being afraid to share this information with us in a video format. I greatly appreciate your knowledge.

@UncleDoug

7 жыл бұрын

You're welcome, Jason :)

Dear Uncle Doug, you bring back a multiple dose of memories for me. Many thanks!

@UncleDoug

5 жыл бұрын

I hope they are pleasant ones, Tim. You're welcome.

Awesome repair on this cool PA Doug. Seems Rusty's language skills are improving as well. Looking forward to your next vid, thanks4sharing.

@UncleDoug

8 жыл бұрын

+saturn5tony You're welcome, Tony....glad you liked it.

This is the best way to spend a Saturday watch Uncle Doug & Rusty work their magic. Thank you for teaching us!!!

@UncleDoug

8 жыл бұрын

+Finom1 You're welcome, F1.....glad you enjoyed the video :)

Amazing TS work on finding the issue with the open winding on the output xformer. Thanks for sharing!

@UncleDoug

5 жыл бұрын

Thanks, Vince :)

So happy to see you and Rusty making videos again. You've helped me heaps with learning and fixing amps

@UncleDoug

8 жыл бұрын

+Harrison Hein That's good news, Harrison.....keep up the good work. Old amps need love too :)

@harrisonhein1287

8 жыл бұрын

Will do

Great video. Loved the commentary, especially the part about grabbing a beer and pulling up a comfortable chair.

@UncleDoug

5 жыл бұрын

It's always a good way to begin any conversation :)

Hey Uncle Doug! Great video you are a superb diagnostician Thanx I am glad to see that Rusty has everything under control, as always !! LOL

@UncleDoug

6 жыл бұрын

You're welcome, Wayne. We appreciate it :)

Hey Uncle Doug, great video and, once again, glad Rusty solved the mystery! Very educational, I learn alot from watching you guys work. I hope Rusty isn't pushing you too hard. My Husky Igloo pushes me hard sometimes, but he says it's for my own good, and I guess he's right. Have a great day and keep the great videos coming!

@UncleDoug

8 жыл бұрын

+Dave Bogusky Thanks, Dave, and regards to Igloo :)

Excellent repair. Never give up on anything - locating and repairing the transformer problem is always so satisfying.

@UncleDoug

7 жыл бұрын

Thanks, David :)

My dog Tater says Rusty is one cool dog! These are really interesting videos, and thanks so much for posting.

@UncleDoug

8 жыл бұрын

+Ken Davis You're welcome, Ken, and best regards to Tater :)

I love the Precision and Clarity of your videos!

@UncleDoug

7 жыл бұрын

Thanks, 2R :)

@randolphpatterson5061

7 жыл бұрын

I love the clarity of his videos, too, but I prefer the Jazz to the Precision..

Permatex High-Temp Silicone Gasket, who knew? I learned something today. Thanks Uncle Doug.

@UncleDoug

Жыл бұрын

You're welcome, Thomas.

Great videos for someone like me who is trying to absorb how this stuff all works. Thanks again.

@UncleDoug

8 жыл бұрын

You're welcome, Lefty.

Nice one Doug. I've never been lucky enough to find the broken end of the winding - usually buried down inside somewhere. Thanks for another great video. Cheers, John

@UncleDoug

8 жыл бұрын

You're welcome, John. I figure there is nothing to lose, so I root around looking for the broken lead and am sometimes able to find it.....but not always :)

Thanks for a great documentary on motor boating problem that happen from to time on valve amplifier. Keep up the good works you do amplifiers.

@UncleDoug

8 жыл бұрын

You're welcome, Kevin. Thanks for your nice comments. We will do our best :)

This is one of the most brilliant repairs I've seen you do. I've mentioned it before, but that emphatic tapping on amplifier components you do has brought so much joy to my life. My new wife and I laugh a lot when doing the Uncle Doug Tap. You should patent it. We are big fans and hope to meet you someday.

@UncleDoug

6 жыл бұрын

Thanks so much, Joel. It took many years to perfect "the tap" and I'm glad someone out there appreciates it :)

Hi Doug, still trawling through your videos in my quest for electronic knowledge. Unusual noise and great fix. It's amazing all the things that can go wrong in an amp circuit. I know this is one of your older videos, but enlightening non the less. Good to see Rusty' enthusiasm brimming over. Look forward to anything new in the pipeline..Thanks again for all this knowledge..Ed..U.K..😀

@UncleDoug

3 жыл бұрын

Thanks, Ed. It's always good to hear from you.

Uncle Doug! Glad to have you back! Would love to see a video about some vintage rock amps and getting the perfect overdrive sound.

@UncleDoug

8 жыл бұрын

+Cameron Walker Thanks, Cameron. It's good to be back. Hopefully, some vintage rock amps will show up for sale or repair. If they do, I will definitely feature them in videos.....so stay tuned :)

You're truly the king of amp repair

@UncleDoug

7 жыл бұрын

If it weren't for Rusty's guidance, I would just be an old hack :)

Wonderful demo of preservation, v/s t/s by component replacement. This is great!

@UncleDoug

5 жыл бұрын

Thanks, Chad :)

Hi Uncle Doug (and Rusty) - That was a Masterful diagnostic procedure and your repair was positively surgical - a job equal to any Vascular Surgeon!. Thoroughly entertaining and (as always) extremely interesting. Please keep 'em coming.

@UncleDoug

8 жыл бұрын

+StonyRC Thanks, Stony. Now, if I could only get PAID like a vascular surgeon, Rusty's (and my) menu would definitely improve :)

Great video Doug! And a very unusual problem. Rusty was smart to leave it to you, tell Rusty Q-ball says hey! :)

@UncleDoug

8 жыл бұрын

+Randy Schartiger Thanks, Randy.....glad you liked it. Regards to Q-Ball :)

HA! I actually "guessed" the problem before you got to the conclusion, and I only even mention it because this is a credit to you sir, for teaching me all I know about tube amps! Thanks for another great video!

@UncleDoug

8 жыл бұрын

+Marvio Botticelli You're welcome, Marvio. It looks like the student has progressed beyond the teacher :) Rusty and I are glad the videos were helpful. Thanks for watching.

Rusty the Wonder Dog awesome. the little mouse that chewed on your Transformer not so is awesome I find in vintage well-lit magnification in close-up inspection saves me a lot of call backs thanks another great video

@UncleDoug

8 жыл бұрын

+Bret H I agree with your analysis, Bret. Thanks for watching and commenting :)

I love your videos! Thank you so much for passing down your knowledge to us all... and future generations. I noticed this video has one thumbs down, somebody must have hit the down button by mistake... I can't believe anyone would dislike any of your videos.

@UncleDoug

8 жыл бұрын

+toxicgraphix You're welcome, TG, and thanks for your very nice comments. Rusty and I really appreciate it :)

Wow, that's very interesting, congrats for finding the fault Uncle Doug. I actually didn't know that you could find and much less correct a break in a transformer winding, I really learned several things today. Thank you Uncle Doug...

@UncleDoug

8 жыл бұрын

+Buddy Martin You're welcome, Buddy. The trick is to find the other end of the broken lead. Most of the time, I can, and if so then it's generally fairly easy (not on the eyes) to mend the break. Once repaired, the OPT is generally as good as new.

Jack Darr mentioned this in his book, and I had always wondered what it sounded like. Thanks for posting!

@UncleDoug

8 жыл бұрын

+Paul Passat You're welcome, Paul. I have heard it before, when working on radios, but have never encountered the problem with a guitar or PA amp. It generally "putts" at a faster rate, but the sound is unmistakable.

Thanks for another fantastic and informative video. Excellent content and very entertaining .

@UncleDoug

7 жыл бұрын

You're welcome, DT.....glad you liked it :)

You sir have been a huge source of information for us all. Because of watching all your videos over and over again, I am now on my third scratch built tube amplifier! I love the sound so much I sold all my other amps! I hope your shop assistants and yourself are doing great. Keep the videos coming!!

@UncleDoug

5 жыл бұрын

That's great to hear, Miguel. Congratulations on your scratch-building success. We will :)

@vminator

5 жыл бұрын

@@UncleDoug Had a question for you, If I'm using a PT with 120mA HV secondary. Do I need to use a filter choke thats rated for 120mA? or does the filter choke only need to be rated for the current your actually drawing from that secondary? I have a 100mA filter choke I want to use but the PT secondary is rated at 120mA. Would it blow the filter choke?

Some fine troubleshooting here. Well executed repair, too.

@UncleDoug

4 жыл бұрын

Thanks, Aaron.

Great explanation and nice repair job. Thanks for the upload!

@UncleDoug

8 жыл бұрын

+Joop S You're welcome, JS :)

wonderfully done. loved it, thanks

@UncleDoug

7 жыл бұрын

You're welcome. Thanks for the nice comments.

Oh my gosh LOOK at that transformer! That's a keeper, have to frame it! :) You're a master, Doug.

@UncleDoug

7 жыл бұрын

Thanks, Michael.

Thanks for another good video, really like the way u explain things Keep the videos comming😊😊😊

Wow a video to go with my morning tea, and then one to serve as a nightcap ! Great feeling when you can save a transformer, nicely done Uncle Doug.

@UncleDoug

8 жыл бұрын

+Barefeet200 Thanks, BF :)

love to hear troubleshooting thought processes!

@UncleDoug

3 жыл бұрын

It's our pleasure to share them with you, CC.

Great troubleshooting. Thanks for sharing.

@UncleDoug

6 ай бұрын

Thanks. Glad you enjoyed it :)

Another good one from Uncle Doug and his enthusiastic pet. Just wanted to say thank you for the tip about the analog meter. I have a Simpson 260 also, but I largely kept it for posterity. Now I have a good reason to use it, maybe.

@UncleDoug

8 жыл бұрын

+Barnekkid Analog meters can perform tasks that digital meters cannot. They are both very valuable and useful tools. By all means, dust it off and begin using it, BK. You will wonder how you ever did without it :)

Missed your videos.. welcome back Doug.

@UncleDoug

8 жыл бұрын

+Cawfee Dawg Thanks, CD. It's good to be back :)

I've only watched a handfull of your videos and i got to say I'm hooked....keep em coming uncle doug and say hi to rusty for me!!!!

@UncleDoug

8 жыл бұрын

+charlie brown We will, Charlie......and Rusty says "hi" to you all.

Great video, many thanks! Rusty thinks you covered this so well he had no need to contribute.

@UncleDoug

8 жыл бұрын

+SiliconSet Thanks, SS. I guess he always thinks that way :)

Uncle Doug, definitely enjoy your videos. Rusty Too!! 🎸

@UncleDoug

6 жыл бұрын

That's good to hear, GM :)

Nicely done! 👍

@UncleDoug

8 жыл бұрын

Thanks, VonZ :)

Thanks for the video Uncle Doug, give Rusty a hug and a treat from me too. Best wishes always.

@UncleDoug

4 жыл бұрын

You're welcome, Mike. Sadly, Rusty passed away several years ago, but I'm sure he would have appreciated your kindness.

@repairfreak

4 жыл бұрын

Uncle Doug Im sorry to hear this Uncle Doug, he looked like such a nice boy. I love our dogs like children, sometimes I think even more because my dogs don’t disrespect me, lol. All the wonderful creatures need is love, food, water and a warm bed and they are totally content and give back love in such great magnitude. Keep up the great work with your very helpful videos, you have furthered my knowledge considerably, and for this I thank you sir, God bless 🙂❤️

Good find Uncle Doug. I love the old Simpson 260, that one looks just like the ones I used in the Navy. (Back when I still remembered most of the stuff they taught me during my year & a half of Aviation Electricians training. We went in depth on vacuum tubes, etc. Unfortunately I rarely used any of that knowledge in the decades following. I'd even forgotten the resistor "code" about "Bad boys....etc". Perhaps that's why I enjoy these videos so much, I'm forever thinking,"wow, now I remember that.) Youth is indeed wasted on the young.(at least in my case.)

@UncleDoug

3 жыл бұрын

Thanks, BiG........glad you enjoyed it. We do tend to lose that which we cease to use.

Doug: Nicely done. Great piece of deductive reasoning and trouble shooting. This "eaten" transformer would be rare to most people, but with more than three decades of repairing broadcast transmitters and other remote location electronics, I have replaced many chewed on components, removed at least three snakes from blower inputs and scrubbed more than my share of rodent urine from circuit boards.

@UncleDoug

7 жыл бұрын

Thanks, Ross. One of my favorite "de-animalizations" was the removal of a putrid rat's nest, constructed mainly of tin foil, from the chassis of a really nice early tweed Gretsch amp......I shudder to think about the "light show" that might have occurred if I had simply plugged it in, as-is.

Usually I hear the term "motorboating" used to describe something completely different than an amp failure :) Congratulations on the repair.

@UncleDoug

8 жыл бұрын

+kardRatzinger Thanks, Kard. I understand there are several other meanings for the term, but I think you can see why it's particularly appropriate in this case :)

@fortj3

5 жыл бұрын

Absolutely. Usually when I hear motorboating of an amp, it reminds me of a thumper. Sounds a lot like my Yamaha SR400 idling.

I LOVE these old Davis amps, so cool. I have a pair of Infinity speakers to "re-foam" (replace the foam surrounds on the cones) tomorrow, baby steps, lol. Maybe one day I can work my way up to re-coning a speaker...maybe. As always very informative and helpful video! Thanks

@UncleDoug

6 жыл бұрын

You're welcome, Jack. Good luck with your project.

Nice job on a successful repair. I really like the look of these amps. Unusual and cool. I guess they'll join Alamo Amps as the only vintage amp companies I'm aware of from Texas.

@UncleDoug

8 жыл бұрын

+The Guitologist Thanks, Brad. Yes, they are very well-made, attractive, compact, and functional. I would say they are one of the best candidates I can think of for guitar conversion.....and, as you said, one of only two brands I can think of from Texas :)

Very nice explanations like ever.Thank you !!!

@UncleDoug

7 жыл бұрын

You're welcome, Nik :)

So helpful and detailed. Thank you!

@UncleDoug

7 жыл бұрын

You're welcome, ZB :)

I would not know a wizard with more knowledge than you Uncle Doug!

@UncleDoug

3 жыл бұрын

There are people out there who have forgotten more than I know, Tom.......but thanks !!

Enjoy all your videos Uncle D. Keep um comin`! Cheers!

@UncleDoug

8 жыл бұрын

+August Lyons Thanks, August....we will :)

Great video and a very good repair! Got a good laugh at video beginning, sounded like someone knocking on the door! Hi to Rusty!

@UncleDoug

5 жыл бұрын

Thanks, Tony.

Hey there Doug! I'm new to your channel, and I love your vids! I'm a guitar tech looking to get into amp repair and your videos have been a great insight into it! Cheers!

@UncleDoug

2 жыл бұрын

Greetings, Zane. That's great to hear. Best of luck with your new career :)

excellent video. really enjoy your videos.

@UncleDoug

8 жыл бұрын

+John Miner Thanks, John. Rusty and I appreciate the nice comments.

Interesting repair

I bet your fun guy to hang out with ... lol ... I love your sarcasm ... Priceless ... ))) ... Thx for the Knowledge Uncle Doug ... ))) ... Also , Priceless ... ))) ... Blessings to you and your other half ... Say hey to Rusty for me , oh Yea ... Kitty ... )))

@UncleDoug

6 жыл бұрын

Thanks, TA. Sarcasm is like aftershave lotion......a little can go a long way :) But when it's directed at objects and deeds, rather than specific individuals, I tend to like it too......as you can probably tell ;) The pets all say "Hi".

I always enjoy your vids UD and Rusty.

@UncleDoug

8 жыл бұрын

+Greg's Garage Thanks, Greg :)

@ThaUltimateDragon

8 жыл бұрын

+Greg's Garage Hey Greg! Cool to see you here.

@GregsGarage

8 жыл бұрын

I love this channel... Sometimes you'll see me post as SkyScraper Guitars too!!! UD &R rock.

@UncleDoug

8 жыл бұрын

Thanks, Greg. Rusty and I have come to really like and appreciate our viewers....like you. What a great extended family we all belong to :)

Awesome Uncle Doug!

@UncleDoug

8 жыл бұрын

+aperioguitar Thanks, AG :)

Awesome repair

@UncleDoug

5 жыл бұрын

Thanks, Tim :)

Hey Uncle Doug, Hey Rusty! Great Video, Love it! 73!

@UncleDoug

8 жыл бұрын

+su pyrow Thanks, SP :)

@supyrow

8 жыл бұрын

You got it good buddy! 73!

Great, as usual. It struck an immediate chord with me, as I have a transistor P.A. amp, which developed the same problem. One minute it was working, with my Fender going through it - the next thing, all hell broke loose, and at a high rate of level! I'm sure you said that the problem on yours was caps, in the power supply? Maybe I'll climb in there and see what I can do, otherwise I'll have to spend some (a lot of) pennies! Keep 'em coming! Ben.

@UncleDoug

8 жыл бұрын

+Ben Morris Thanks, Ben. In my case, it was caused by an open primary winding in the output transformer, but filter caps are a more common cause of the problem.....usually accompanied by a hum. Good luck with the repair.

@benmorris4589

8 жыл бұрын

Thanks, Doug. (When I get round to it)!

I have serviced countless amps over at least 35 years or more and never run into this type of problem. It has always been a bad capacitor in most cases that caused the motor boating, but in the open winding of one side of the tap the sound was distinctively different. Your analyzes of half the active tap does suggest the capacitor is charging and discharging creating that most unusual sound, and after careful thought I have come to the same conclusion you have, and agree with your findings. "Well Done"

@UncleDoug

8 жыл бұрын

+John Cunningham Thanks, John. I've never seen it before in a guitar amp, and it's good to know that I'm not alone. It now seems to perform and behave quite well, so the problem appears to be fixed.

Simply AMAZING!!

@UncleDoug

8 жыл бұрын

+redfishbum Thanks, Bart :)

Nice save Uncle Doug!!!

@UncleDoug

7 жыл бұрын

Thanks, JT :)

thanks for another great video

@UncleDoug

8 жыл бұрын

+otteronbass You're welcome, Otter.

Nice job, I love your dog.

@UncleDoug

2 жыл бұрын

Thanks twice, Ricardo :)

As usual another fine vidio Uncle Doug I like what Ypu did for the output transformer for the amp very logicle choice of methods I was a service technician at a chevy dealership and used high temp silecone Sealers and twopart Fast or slow hardening epoxies For some repairs on things I think I would do the same as you. Wish I had a shop like yours live long and Prosper. Dwight from Detroit,Mi.

@UncleDoug

4 жыл бұрын

Thanks so much, Dwight. Likewise :)

Great Video Uncle Doug !! I was surprised to see how small that wire was on the primary / High voltage side of that output transformer. Nice save !!

@tubical71

8 жыл бұрын

+Donald Filbert The diameter of a tranny coil wire only depends on the current flowing through at first glances. As being this one the wire of the primary coil the current through it is rather small.

@UncleDoug

8 жыл бұрын

+TubiCal Good answer, TC. Thanks.

Very interesting problem, never seen that one before. Nice fix on that OT

@UncleDoug

7 жыл бұрын

Thanks, VC :)

Hey Uncle Doug & Rusty, Good to see you boy's up to your old trick's. Good diagnosis and repair, you are good. I am learning so much from your amp video's I almost feel qualified, not. I hope all is well with you and your's. 80's comin' here in Oregon and looking green with the leave's coming on. Take care, C.

@cassvirgillo3395

8 жыл бұрын

***** Hey Sceaming deal, Yes, very nice . I'm just outside Willamina, so not to far from Lincoln City. I've seen some nice day's at LC. Will take the winter's for the summer's. Thanks for commenting. Be good, C.

@BrianOfAteionas

8 жыл бұрын

+Cass Virgillo Hey fellow Oregonian! The weather was perfect here in Portland today. Good day for beers, music, and top it all of with a super cool Uncle Doug video. What could be better?

@cassvirgillo3395

8 жыл бұрын

BrianOfAteionas Hey Brian, I couldn't agree more. Happy 1st. Uncle Doug is my favorite channel. I'm getting part's together to build a Fender 5F1 Champ as seen in his 2 part video series. Take care, C.

@UncleDoug

8 жыл бұрын

+Cass Virgillo It looks like you Northwesterner's are having a nice chat. Thanks for all the nice comments.....Rusty and I really appreciate hearing from you all.

@cassvirgillo3395

8 жыл бұрын

Uncle Doug Hi Uncle Doug, I've never had so many reply's to one comment. Be good, C.

Oh man, do I wish I still had that old Sunn Sentura II. After doing a bit of work on it ...tone stack and adding a bypass cap to brighten it up after a bit it developed a ticking noise in the audio. As I say if I still had that amp, it would be interesting to see just hwat caused it. The amp worked but it had that tick motor boating instead of a lower frequency thump. As always another fine video and Rusty as usual makes a great producer.

@UncleDoug

8 жыл бұрын

Thanks, John. Rusty and I appreciate the kind words :)

impressive! You are truly the Man

@UncleDoug

8 жыл бұрын

+Steve Dewitt Thanks, Steve :)

my first guess, was that a capacitor was installed backwards. Your videos are always enjoyable another 10 out of 10

@UncleDoug

8 жыл бұрын

+Is1amization by Immigration Thanks, I by I. I too initially suspected a filter cap as the likely culprit.

another good one, thank's doug,

@UncleDoug

8 жыл бұрын

+PAUL HAMMERSLEY You're welcome, Paul :)

Great surgery on the output transformer and finding the primary coil end (without making the patient any worse). Best ever for me was managing to (accidently?) find, clear and re-insulate a shorted pair of leads on the core of a Twin Reverb II power transformer. Good luck too, an "in kind" rewind by Mercury Magnetics was going to be over $300 (for a $500-600 amp.).

@UncleDoug

8 жыл бұрын

+dennis walsh Thanks, Dennis, and congratulations on your successful (and money saving) surgery :)

great video!

Thanks for the transformer lessen I no very little about them nice save.

@UncleDoug

5 жыл бұрын

You're welcome, Ron :)

I wish dogs could live forever, R.I.P. Rusty. ( I also love your videos)

@UncleDoug

4 жыл бұрын

Me too, Henry. Thanks :)

Hello Doug. What a wonderful treat, to find another awesome video from you, waiting in my email. :) Though Molly is laying on her back sound asleep She sends her regards to You Rusty and handsome Jack. Has always very well done,in both fun and very Educational . I really hope to see more videos from you. All my best. Bobby

@UncleDoug

8 жыл бұрын

+Bobby Tectalabyss Thanks, Bobby, and best regards to Molly :)

Love this video!!! Class dog.

@UncleDoug

3 жыл бұрын

Thanks, Ray :)

Just repaired a 30w double ended amp with a 250mS motorboating fault. Figured it would be a big cap problem what with the low frequency repeat and changed both B+ filter caps to no avail. After much head scratching decided the best option would be to inject and trace a signal. Turned out to be a dodgy phase inverting tube that was causing the problem. Note to self and anyone else who may encounter similar :- Always start with the easiest option when amp fault finding as assumption will almost invariably lead you down the wrong path costing time and possibly money.

@UncleDoug

4 жыл бұрын

Excellent advice, GB. Thanks for sharing it with us.

I love Rusty !!

@UncleDoug

6 жыл бұрын

It's hard not to, Peter. He's a very special guy :)

Great video ,

@UncleDoug

8 жыл бұрын

+Michael Austin Thanks, Michael.

Well, of course, apart from the broken winding! It took me back to the sixties, when we used to use radios as guitar amps, connecting up to the cap of the first valve (detector?).

Great video...that amp does look like it might have spent some time in an attic or a barn...good troubleshooting. My regards to Rusty.

@UncleDoug

8 жыл бұрын

+Jim Lavespere Thanks, Jim. With so much rust, it must have been in a damp location....yet the wooden cabinet is in great shape. Very mysterious.

Uncle Doug, I appreciate your videos and technical expertise. I had a volume fade problem with my Marshall JCM 2000 DSL 50 a few months ago. I am a guitarist,not an amp repair technician so I took my amp to a man referred to me by a friend. After spending 282.00 I brought the amp home and had the same problem. Volume fade and then after a few minutes it may or may not work "correctly". After searching and reading many forums I came across someone who had the exact same problems I was having. I ordered a new $2.95 bridge rectifier and installed it myself. Then I learned that after making such a repair it is necessary to check the bias voltage. I nearly burned up my power tubes. They looked like light bulbs. Max voltage should be 45 ma and mine were around 96ma. A readjustment and my amp has not sounded so good in years. Now if I could only figure out a way to add a separate EQ to the amp and lower the high gain white noise it would truly be what an amp should be. Being able to EQ the clean channel and the dirty channel separately is no brainer and I have often wondered why Marshall didn't include this in the original design. Thanks again for your videos sir .

@UncleDoug

8 жыл бұрын

You're welcome, Troy, and congratulations on a successful repair of your amp. That was a close call on the plate current. I shudder to think what your plate dissipation was at 96mA for each output tube. To reduce your gain and mellow things out a little, you might try experimenting by substituting lower gain duo-triodes (12AT7, 12AU7, 12AY7, etc.) for one of the 12AX7's in your pre-amp.

@troynorris7666

8 жыл бұрын

Ahhh, I was under the impression that my power tubes were burning so hot due to the failing Bridge rectifier that was in the amp originally. After installing a new one that is beefed-up according to the specifications I assumed that was the reason why the voltage changed on my power tubes. 45 milliamps is maximum for my amplifier readjusting the bias after replacing the bridge rectifier has put the amplifier back in correct operating condition. I am an automotive technician by trade so I do understand alternating current and direct current. I am slowly learning the current flow in a guitar amplifier and why components do what they do.

@UncleDoug

8 жыл бұрын

Tubes overheat when the plate voltage and plate current within them is too high. This would not be the result of a failing rectifier or a new rectifier, but because the bias of the tubes is set incorrectly. Biasing involves more than simply adjusting the plate current. You should watch my video on biasing of double-ended amplifiers to see and understand the full process.

Hey Uncle Doug. That's a great lesson again. A thing that caught my attention is your analog voltmeter because I have the same. It needs a bit of maintenance, but my interrogation was about it's power. I was wondering if there was a way to power it other than with the many batteries. I reckon they are powering different parts of the circuit, but perhaps there is a way to simplify the thing.

@UncleDoug

2 жыл бұрын

Thanks, Francois. You could probably wire up a power supply for the Simpson meter......but batteries sure are easier.

Good job.

@UncleDoug

7 жыл бұрын

Thanks, TH :)

+10K on the Simpson 260! Great Detective work! That is indeed a very interesting to find.

@UncleDoug

8 жыл бұрын

Thanks, Mike. Glad you like it :)

@mikedambeck7136

8 жыл бұрын

You are welcome good sir. You and Rusty please keep delivering true Craftsmanship.

@UncleDoug

8 жыл бұрын

We shall, as long as we have encouragement from nice viewers, like you :)

Great repair! I'm trying to track down an intermittent problem on my Pro Reverb - I hate intermittent problems!!

@UncleDoug

6 жыл бұрын

Thanks, CM. So do I......they seem to occur when you are least ready to cope with them.

Indeed sir, the low, but still slightly present voltage would seem to indicate a slight charging of a capacitor then breakdown conduction bleeding (in the rectifier) off the charge and repeating... there would be some induction even with the open winding to build up a charge with very limited current capacity since it’s basically functioning as an antenna at that point... nice find and fix...

@UncleDoug

3 жыл бұрын

Thanks, Robert.

Great Stuff

@UncleDoug

8 жыл бұрын

+Dennis Cochran Thanks, Dennis.