D-Lab Basic Training Fender Vibro Champ No output Simple Fix? No, I made a mistake Believe it or not

Well, This was supposed to be a easy cut & dry repair. Nope, Fred mis-guided me. This one got me, because I expected the usual leaking tone caps. Lesson learned for you & me. Always expect the unexpected, especially when it comes to 60 year old electronics. It is performing super now. I incorporated my gain enhancement, so it will actually be better than new for the owner. These repairs are a very valuable resource, showing you the basics that can be applied to newer designs. Please, support D-Lab and I will support you with information that I have learned over the last 40 + years

[@jamiboothe]

Terry, I love your Star Trek references. I guess the problem actually was the dilithium crystal. Now you can restart the warp drive, after being stalled in a decaying orbit around the planet known to contain the sacred crystal.

[@preiter20]

Thank you Terry for these basic training videos. They are very, very helpful!

[@edwardhannigan6324]

Excellent video Terry..Love the teaching and fault finding. Very clear and more surprises for us all..Great repair and thanks for posting..Ed..UK..😀

[@jamiboothe]

I also love detailed problem solving. Part of problem solving is being wrong initially and taking a logical approach without the emotion of failure getting in the way. Spock, in the Star Trek original series, always figured out the problem by using logic based procedures.

[@williamland3772]

Hey, Fred's back!!!

[@kendavis8046]

Always entertaining, sir! And educational to boot!

[@xiantor]

Mr. Terry, I just wanna say thank you for sharing your knowledge and expertise

[@theoloutlaw]

Ahhh, the beauty and the surprise of electronics! Nice video Terry!

[@alexdeleon7135]

Well done! This issue had me flummoxed as I watched the meter. Brilliant process of elimination, to deduct the true issue. Thanks for posting!

[@drawbridge611]

Yeah, that was definitely weird. For sure that's not "your typical Fender failure." I think the giveaway was the crunchy volume pot. When dirt isn't the cause, I usually find it's DC showing up at the pot, especially when the pot is also involved in the downstream triode's biasing scheme (here, it's serving as its Rg). That forces the downstream triode into some jacked-up combination of cathode bias and grid bias. I've even seen it take out that downstream triode, causing its grid to short to one of the tube's other two electrodes, probably due to excessive plate current & overheating.

[@thedevilinthecircuit1414]

Outstanding learning opportunity, Terry. You're making me smarter!

[@sandiesjoys9777]

Great video. I learned a lot.

[@orionwarren4244]

Always something new to be learned for the electronic alchemist

[@gregjohnson5194]

Nice job. Love these teaching moments you share with us.

[@DeathCapAmplification]

Good one!

[@electrolytics]

Thanks D-Lab. Always entertaining and informative.

[@jwl9286]

These are the kind of things that drive you crazy. I loved it. Those troubleshooting skills are fantastic. I was sure you nipped it right away with those caps. Never dreamed the other cap would give it up. Either way this is a first class training lesson. The only thing I can't understand is how you were able to use your computer to edit and upload the file with your mouse in the tube caddy. 😮

[@tracyc7813]

To be fair, those kinds of caps rarely fail.

[@infectionsman]

I would have put those coupling caps back in, to save the original mojo of the amp.

[@jmormino5465]

Thank you sir, for another excellent tutorial!

[@danielsaturnino5715]

Good deal Terry. Something to keep in mind in the future. Thank you

[@tebek9208]

Another great lesson learnt. Thanks Terry

[@bradrebar101]

Nice vid Terry, I like these Fred videos. I especially like the 3 watt 6aq5 amp you designed, it sounds excellent!!

[@greggaieck4808]

D lab Electronics your utube videos are awesome

[@zbaby82]

Excellent video.

[@MrMrjauregui]

Great video terry

[@joshuahonel7321]

Great vid

[@barbsblogs1563]

Great repair but it would of been good to see the schematic as you worked though it 👌

[@stevenkimsey7039]

I have a 74 Champ. Never seen a amp technician. 2 prong cord and will deliver a mild shock. I guess it's time for service

[@giulioluzzardi7632]

...the Sherlock Holmes of the amplifier world succeeds again.

[@weschilton]

Wow that was a weird one... I can't believe it killed that pot. That's a shame. But you know, if people had these old amps checked out before something failed, it might have only been one part that needed to be changed instead or 4 or 5.

[@greggaieck4808]

D lab Electronics owners amplifier is cool

[@andyandy4306]

If you want to repair a Adcom GDP500II preamp for a video, get a hold of me and I will send it to you. One channel goes out after a short period. Can send some caps.

[@OIE82]

I was sure it was the dilithium crystals.

[@kornami8678]

Nothing like a 22K ohm capacitor.

[@umajunkcollector]

Terry, have you done a 50s David Bogen tube PA amp? They're kewl, and have much potential for guutar mods.

[@jjsant3250]

Originals are ceramic no? Test those larger caps on your leakage tester! Every one from my '71 Deluxe Reverb tests perfect.

[@kbkman7742]

I also thought the treble caps were always ceramic

[@d-labelectronics]

Yes, this one had been replaced

[@Jah_Rastafari_ORIG]

Can't be dilithium-- hasn't existed since The Burn...

[@benitomgomez3290]

✔️

[@TheTrueVoiceOfReason]

But how did they fit a standard DiLithium crystal into a 250 pf mica cap????? Reconfigured transporter? Specialized replicator programming?

[@bobr8565]

I guess you did not feel it necessary to change out the main filter cap? The fact that it is so old ,might be a good thing to do?

[@d-labelectronics]

This was not a complete repair video, Only concentrated on the main fault. Yes the amp will be completely recapped including the filter

[@riley0187]

I doubt that SM is original, forums are full of those failing..Those two old caps you took out I'd rather they went back in personally..

[@stphinkle]

What class of amplifier is this? A, AB1, AB2, B, C, D, etc?

[@d-labelectronics]

Class A

[@earlgreen3265]

That 250pf Treble Cap doesn't look original.

[@dwightjt]

Ya know terry. Im about as logical at figuring out things as you are and you are excellent. I like you you are the goofiest funniest goofy ball I've ever seen in the world and we have never even met and I hope so yet I would love to hang out with you sometime but I'm so poor I can't even travel you are very fortunate and blessed so may I say God bless you you goofy son of a gun I like your style and Uncle Doug down in West Texas you two have taught me quite a bit the things I would have liked to have learned 40 years ago cuz I love Electronics and the other things I do like playing guitar in a local church choir here in Allen Park Michigan you help me out with understanding a great deal you and Uncle Doug from West Texas you guys are excellent thank you for sharing without charging a f****** profit very nice indeed you and Uncle Doug are angels very nice indeed and I love you little granddaughter she's cute don't get me wrong she's 40 years too young for me and I'm not some kind of jerk but thank you for sharing yourself your knowledge and your family love your wife too she must love you very much what a steal you found a pearl a lovely lady God bless you thanks Terry for sharing so much sorry I can't donate but you are a pleasurable man to listen to goofy son of a gun but a great man your friend. Dwight.

[@simocampo344]

Great vid