How to troubleshoot preamp tube amplifier microphonics Dynamic test device Example Fender Super amp

[@carlmoren3953]

Good morning, Terri. I maintain valve amplifiers in my city Avare São Paulo Brazil. This kind of service is running out here. I'm one of the few in my area. I've always wanted equipment like that. but what Mr. Montou thought was amazing! Congratulations and thank you so much for the lessons. Awaited the scheme of this wonder

[@guitarslinger8633]

Hi Terry, Thank you for taking the time to explain all the different issues you come across. I may have one that you haven't seen. I have a stewmac 81' Brit hand wired JCM 800 clone that I built and it has developed a problem that I cannot figure out. First off, it worked fine for awhile and then this problem showed up. Every time I play an "A" chord whether fingered or barred the amp goes into the atmosphere with a low "A" frequency feedback that just takes over. I can turn every pot down and the feedback remains. I literally have to shut it off to stop it. Turn it back on and it's fine, no noise or anything. I play another "A" chord and it's lift-off!! I can play around this problem but it has severely limited my song selection! Anyway I first checked for microphonic tubes and found nothing. I then checked voltages at the filter caps, pins 1&6 on the gain tubes (V1&V2) and voltage to the inverter tube (V3). Other than being a little high (20-30 vdc) in each case it seems consistent. I then replaced the power transformer on a long shot and the voltages still stayed a little high. I am now looking at the choke and negative feedback circuits. Any advice?? Also I have tried different speaker cabs with the same result.

[@rockettcrawford890]

What a great concept for testing preamp tubes.

[@tomk1tl39]

Great little gadget...I have an old Heathkit phone patch unit collecting dust.....I'll wait for the final presentation 🙂

[@jasonkirkham550]

Well done Terry !

[@karlschwab6437]

I used that Heathkit phone patch many years ago and had some interesting phone patches. But now, that same Heathkit piece of equipment is about obsolete as they come. It is interesting how you "recycled" one. 73, de Karl, KO8S

[@craign8ca]

I was wondering what you'd be using a Heathkit phone patch for. Built one of those back in the '70's. N8CA

[@zbaby82]

Cool. A lot of us need something like this. All of my amps use 12AX7 and EL34 tubes only.

[@wadereynoldsgm]

Pretty cool. Look forward to more updates. Thanks!

[@K7MD]

Sweet. That little unit is very cool. Great idea Terry!

[@cajuncoinhunter]

That is a nice tube tester , on steroids LOL ...... My neighbor was watching with me and he is amazed , he was brought up in the tube era Radio and Amps also.... We can't wait for the 6 series tube tester to come up in the future....

[@rciancia]

Terry, very cool device as usual. You continue to turn the Tube amp repair space on its ear !!!... well done.. We can now see things we didn't think possible.

[@Finom1]

Bless you for sharing your wisdom with us, Terry!!!

[@gillamb8669]

D-Lab is always full of surprises. Great onesss 👍🤘

[@tschupbach]

Nice! Will be waiting for the schematics, great device!

[@edcataldo7019]

I will live my electronics guru dreams vicariously through you good sir! Brilliant as always!

[@electrolytics]

It's like Edison's Lab in NJ except with guitar amps, radios and wine. A sure fire winner.

[@nnnvp]

Hi Terry, for good perform crt scope line on video - use native manual shutter speed, 1/30 etc 1/30 for 30fps, 1/60 for 60fps for accurate exposure you must use ISO and aperture in auto or manual mode Best regards! Oleg, Russia

[@brunoheidrich]

Thank You,,,Very well done!

[@edwardhannigan6324]

Wow, some cool test stuff in the pipeline Terry..Just so cool..You are the 'Man'...Great video and info..Ed..uk..😀

[@jeffreymcvey2267]

I have that same heathkit chase and wondered what make it into thx! Looking forward to the schematic.

[@cliffgassett6291]

Terry, I would love to know how to get one of your Princeton style kits. Please send a link I am working on my electronics degree and I am employed by a defense contractor. Please help me out. Thanks for the content, it’s always like going to class.

[@mackfisher4487]

An innovative idea Terry

[@gregjanes474]

That's really cool Terry. Can't wait...very interesting. Appreciate the good tech you share with us and Happy New Year!

[@BrendanMConnors]

Great idea!

[@bradc32]

very cool Terry

[@FKinGen]

Hi there. Thanks for making theese great videos. really helpful. Did you solve the nois issue on this Amp? I have the same noise in a VC30 by laney. found microphonic issues on a wire from a preamp tube and on a capacitor or maybe 2. c1 and cx1 i belive. just wanted to hear if you solved yours? Thanks again

[@bobboyle7629]

WOW!! I would LOVE to buy the schematic of that device!! Please let me know when and if that becomes available. Love the channel and many thanks!

[@weschilton]

That's really cool!

[@jenniferwhitewolf3784]

Nice little time saver👍

[@rubenproost2552]

My tube radio did the same crackle crunch pop thing. Turned out to be the on/off switch arcing on one side. Cleaning did not fix it so I tied the wires together on that side of the switch. It doesn't have a hot chassis so no biggie.

[@RicardoSilva-ix5lf]

Hi Terry, thanks for the amazing videos you made so far. Lots of good information and advice. I'm a bit off-topic here but I was considering buying a tube tester. The only problem being the transconductance ones are off the budget and the cheap ones are not good enough. Is there a way to modify an emission one to read transconductance or maybe you could make a schematic of how to generally test vacuum tubes.

[@pjf7943]

I can just the clients face after you charge him for this service..!! LOL! A simple socket cleaning and individual tube swap is the order of the day, as you would have to do that anyway to eliminate the possibility of tube problems.

[@luthiervandros]

We get paid for what we know and for exposing ourselves to risk.

[@pjf7943]

@@luthiervandros What the hell are you blabbering about.??? LOL!

[@laurentboulange9973]

Hi Terry, happy new year to you and your family! Thanks for this brilliant idea... I've had the same exact noise in a customer's amp, and that was a brand new 12ax7. Out of the 5 new Sovteks we had for the repair, two had the same noise... Luckily enough, we only need 3 for a Hot Rod Deluxe, but after checking inside the circuit, I ended up swapping tubes with the ones in my Hot Rod : and voilà! Your build is definitely what I would have need. I have some french 1960s tube intercoms that would be a good host for this! Is the high voltage diode rectified inside? Thanks again, Laurent

[@robertoler3795]

nice job and nice use for a phone patch :) WB5MZO

[@docjeffry]

COOL!

[@BrianGay57]

How much does a rig like that run? The tube testers I have looked at have been quite expensive and seem less useful than your setup. Is there any relatively inexpensive way for an ordinary player to test their tubes?

[@kenpirnar4265]

How long before we can purchase it?

[@d-labelectronics]

I am building a second unit, Then have shake down time. Will keep everyone posted.

[@tubeDude48]

Sounds like a noisy resistor or tube.

[@bradbeasley7669]

KOOOL