How to fix Noise + add Master Volume Fender Bassman 6L6 tube guitar amp

[@Beizeiten78]

Okay, guys, just got the amp back. Insanely awesome! Can’t tell you how much better it’s improved. Sounds absolutely amazing! Terry’s work is A+++++ . Seriously, I’ve dealt with a lot of techs in nearly three decades of playing, and he’s head and shoulders above the rest. Great guy that does great work, can’t ask for anything better.

[@qua7771]

How did it stay in such good condition? Anytime I see one so clean I assume it got stored in a closet, and forgotten for decades before getting rediscovered.

[@l8tapex]

@@qua7771 would you believe I bought one last year same condition with original plastic cover ( still original tubes and aging inside no updates)? Original one owner. I'm like you ,I assume he didn't really play it . It sounds so good Im scared to use it, cause damage and not be able to replace O.E. parts.

[@vintagetubeamplifiers]

@@l8tapex You should really have the electrolytic capacitors and the 2 prong power cord replaced at the very least if you plan to play it as you should. Just save them in a bag as they can be reinstalled should you or someone else wants to return it to original. The tubes will be fine as long as you can measure a few voltages to make sure they're to spec. Unless you want a museum piece, it's all up to you. Good luck.

[@diregremo]

I don't even know why I watch this channel. I don't even work on electronics, but I watch this shit everyday.

[@paulj0557tonehead]

SEE *Trainwreck Pages - Rob Robinette's* and scroll to TYPE 1 MASTER VOLUME. This will be the one D-Lab is doing. EVERY BRITISH 50-200 WATT HARD ROCK/METAL AMP (Marshall, Hiwatt, Sound City, Orange, Laney) [not sure about CLASS-A VOX amps], as well as U.S. amps- Ampeg, Mesa Boogie, Kustom, Peavey,Soldano, Trainwreck(US?), etc....all of these amps sound great with this Master volume.

[@nickvictor7398]

You do great work, however, it's very anti-climatic for us guitar players, not hearing a guitar through the amp. Can you get a cheap guitar and have it tuned to a chord and hang it on the wall for plugging into the amp so that we could hear a guitar through the amp? You could strum the strings and it would be a test signal.

[@paulj0557tonehead]

My old room mate, amp Guru Frank Levi III didn't play guitar either, so he did just that. What non guitar playing amp techs can do now is just buy a LOOPER PEDAL WITH 9 storable loops up to 10 min each ( see below), with total max record time of 40 minutes. Records at 48 Khz, 24Mgb (far better than CD quality). Just have a visiting guitar player make a variety of loops, clean to dirty varieties. *cuvave looper* pro guitar loop pedal 9 loops total 40 minutes recording time unlimited overdubs built-in tuner function led display $50.86.$50.86 from 2 stores Features:The loop pedal with 48K/24bit sampling rate, lossless, uncompressed and professional tone quality.The total recording ... Stompbox · Looper

[@scootertrasher1369]

A master volume is not to limit noise , it's to get preamp breakup at lower volume, ( think Mesa Boogie),why not install a three prong cord and use the obsolete ground reversing switch hole for the master volume pot?

[@Modwiz125]

I learned a lot from this video. Great emphasis on the wiring to the master volume. I agree it is a brilliant modification to this circuit. Thank you, D-Lab.

[@MichaelLloyd]

I like your perspective on cap changing. Normally I hear that ceramic caps are invincible. Nothing is invincible. Very nice workmanship, as always, too.

[@superhet7281]

Excellent job, Terry, as usual. This has inspired me to finally take a look at the “yard sale find” black face Bassman that’s been in my basement for years. I always enjoy your videos, and always learn something. Thanks for sharing.

[@d-labelectronics]

Cool deal man, Thats a great find. Let me know if I can be of assistance

[@shaneschulze6923]

Yàà

[@petegaslondon]

Some "yard sale" LOL - still I shouldn't complain - I found a pretty complete Vox AC30 chassis in the trash once :)

[@stuarticusrobinson9319]

It would have been good to have heard the amp after the modifications to see the difference.

[@Beizeiten78]

Trust me, it’s awesome. Terry did a fantastic job on it.

[@cannabineros]

my bassman one power tube out of 4 gets hotter then others. all voltages are correct. only missmatch is after PI 318V and 306V. OT is also warm on idle. Sockets look fine. What could it be or it's normal? Thanx

[@thecappy]

Do you know of a good replacement .001uf 1kv ceramic cap? I can’t find a orange drop with 1kv.

[@emitchsr]

did anyone else get blames for a fart at 5:50?

[@brucemillar3015]

QRZ? (What's your call sign ?) de VE3OQ

[@TheRadioShop]

Very clean amp. Also nice troubleshooting and modification. Excellent work as always Terry.

[@butchmcbride6974]

I love you videos and one so much from them thank you for them but shame on you. The first thing you did was bring out your magnifying glass. You got turned on the amp to listen to it just a short time before. You should have shorted out the filter capacitors for safety before doing anything else. We become complacent I know I was a broadcast that you do for 40 years and probably through God's mercy I'm still alive because I often we become complacent. I'm not trying to be critical I really do appreciate the time you take for your videos you provide a wealth of information for people with very little reward thank you for that

[@audiotechlabs4650]

I find it hard to add more than what has already been said in the comments. I had the same Bassman back in 1969. It was 5 years old. It had the 12 inch JBLs in it. I was a fool to have sold it. 1st wife did not understand the worth of the amp. I am going to build a single channel version with 3 band EQ. of this amp. Try to make it as clean a sound as this one. Great video Terry. Brought back some wonderful memories. Thanxz

[@WileECoyotey]

If you want a master volume on an amp .. go buy one with it . Butchering an original model is disgusting and destroys the value of it.

[@PoppysGuitar]

What is that thing sticking out of the back of the amp? Dummy load? Is that home made? How did you make it?

[@bullwhipjohnson8247]

The first place to check for noise in an amp of this age, is the Filter Caps. Under the Dog House. On the bottom of the chasis. That's where you'll find the source of 60 cycle hum.

[@shawneubanks9737]

The fact that he didn't even address these makes me think that they were already recently replaced...

[@fredbach6039]

Boy that brings back memories. At the music shop (a Fender dealership) I worked at I saw a lot of these in rough shape like all the solder connections shaken to death. 100% resolder job. But when looking for upstream microphonic elements you have to have the volume controls UP not off.

[@billygage6899]

I’ve got a vintage 100 watt Carvin I’d like you to fix

[@Beizeiten78]

If anyone is curious, that’s my amp, and I sold those two Ajax coupling caps for $50. People will buy anything vintage.

[@lincolnmicrophonellc]

hahaha that is amazing

[@luthiervandros]

I just did an aa864 conversion to a 66. I couldn’t get those blue moldies out fast enough.

[@markwhitney5667]

@@luthiervandros All this time I thought just the yellow caps were bad.

[@luthiervandros]

@@markwhitney5667 oh I just meant the bad ones lol

[@seanlavery2236]

Whow! I got a stash of like two dozen of em...

[@pneumatic00]

Nice video, Terry! Whatever noise existed after you did the cap replacements you showed---I will GUARANDAMNTEE you that if you replace the 100K plate resistors (4 places in a Bassman--the ones that come together in the "V" shape---with 2 watt metal films---that noise will be 80% reduced. It's pretty much the same as having to replace the electrolytics under the doghouse on 40+ year old Fenders. Gotta get done, except I don't even think about the metal film plate resistors. There's nothing you can do to a Fender amp as cheap as the MF plate R's that will have anything near the effect. The hissing, popping rodent noises...those are the plate resistors. I promise. Any blackface or silverface Fender. 6 places on reverb amps. I have NEVER replaced those resistors without producing a WOW immediate and dramatic noise reduction. $3. Try it, my friend.

[@HeliBenj]

Sorry for the dumb question, are you talking about the preamp and PI plates resistors?

[@williamscaliarini8201]

Have you ever checked out the ken Fisher master volume control. It's much simpler and works just as well !!!!!!

[@brich2929]

@D-lab Electronics, can you do a detail video on your setup with the dummy load and the output to your Scope?

[@brich2929]

Terry! @D-lab Electronics I just bought a Tektronix scope and I NEED you to do a video on the above!!!

[@louphillips1329]

I'm planning on installing a master volume control on my Silverface Bassman. I can't find the model number anywhere but the closest schematic is AA371. My amp has 100K grid leak resistors so the 250K pot sold by Triad should not be used - I didn't find this out till after I bought the kit. This isn't mentioned the Triad instructions. See the rob robinette website for the "Frondelli" master volume circuit where this is discussed. I had to order another 100K pot so I can make the modification.

[@paulkielt9301]

Ceramic capacitors are always prone to produce some kind of noise. I replaced all of them inside my amp with polypropylene ones. I believe they sound even better than Orange Drops.

[@WileECoyotey]

The color of the caps mean nothing.

[@matthewsmith8568]

I think I heard some ‘leakage’ at 5:52

[@chrischwaz7788]

Where did you get the lighted magnifier

[@jamesprice6381]

Brother D-Lab, pls try a master X line X the grids of the driver pin 2 n 7 :) U mit be surprised....Even QUIETER than the Dual....n MUCH simpler.................:)

[@jamesprice6381]

ok, Thts a X over amp, not flat lined AB165 at ..........ALL...............The driver n n Bias splitters say it all..Ive had several in like that great sndg amps..ive got 30 years in, store front repair...seen alot of weird stuff too :) WOO, looked CLOSER at DRIVER Thaz a REALLY REALLY rare amp, the POSITIVE FEEDBACK 220Ks form plates of power tubes to plates of driver tube was wild! THAZ where alot of noise comes from as well......Gives a bassier sound 4 sure... Fender fed back CURRENT from the speaker jack BACK to primary side of driver too, That could be a Dumblish manuever as well :)

[@Brandon-youtube]

Love the videos but saying it's "always" good to change caps and that it doesn't hurt value to add a master is nonsense. If it was a collectible amp in 100% original condition that would destroy the value

[@jeffcotton526]

How true! Changing caps is usually always a good thing to do, especially with very leaky or electrically shorted old ones. However, adding a master volume control actually de-values the amp of such great vintage. True Fender enthusiasts cringe at the thought of a master volume on a black or brown face Fender.

[@telerooo5213]

@@jeffcotton526 It's like getting hold of an Old "Vintage" guitar that is unplayable. Do you fix it just to be an all original collectors wall hanger, never to be played, maybe increasing in dollar value or do you repair it to be the played guitar it was built to be in the first place???

[@fve1352]

Wait... how does it sound now???

[@JobyP]

Great Video! I love the thorough ones. It does make me sad tho because I owned a 67 that was just as clean... in fact I think I traded it to a guy in Indiana... Crap... lol...

[@williambarnes7642]

Hello, I've enjoyed several of your videos. A fellow youtuber, Uncle Doug, talked of taking the master volume out of a Fender Twin Reverb. Not an electronic geek so both of your, you and UD, reasons for taking said actions seems plausible. Why?

[@bobbarcus8310]

Kendricks amps charged me $1200 and kept my 63 Bandmaster for a year,shotguned all my caps...,all that was wrong was a old ground wire

[@motoputz3201]

6:57 I just watched a "home movie" of the fender factory from 1957, the narrator spoke of how out of sorts fenders parts inventory was, so the differanct colors would verify this possibly? a must watch video on youtube

[@billmiller7138]

No spilled beer? Bottle rings on top always make them sound better...

[@MrBanzoid]

Good call changing those ceramic disk caps. They have no place in audio circuits! . I've found them to be generally microphonic. Another great vid, thanks.

[@daleburrell6273]

...THAT'S NEWS TO ME-!!!

[@ptwamps3682]

Another great video, thanks! Nice to see a vintage Bassman that hasn't been hacked to death. I've restored a few vintage Fenders that were in a sorry state compared to this one. In addition to what you did, I always swap out the 2W screen resistors on the power tubes. They tend to get baked to death as the heat rises from the sockets and are often way off tolerance. Cheers.

[@ptwamps3682]

Actually, just watched another video where you do address the screen resistor issue. Good on ya! I'm new to your channel and still catching up.

[@jasonkirkham550]

I loved seeing that amp. but, more so.. I enjoyed learning a few new things. Thanks Terry.

[@oldguyjammin9732]

Just came across your channel and wondered by chance if you could comment on adding a bright switch to an Orange Brent Hinds Terror head. It’s two foot switchable channels; an amazing dirty channel that’s just right and a “natural” channel that is pretty dark for anything other than Teles or Strats. Some of suggested adding a bright input jack but that would brighten both channels... thoughts? Thanks

[@jamesprice6381]

ive SELF healed NOISY Allen Bradleys using SOLDER gun tip pressed against it.. :)

[@christopherkremer9294]

Orange Drop caps a not very musical, more hifi sounding. Why would you change out the ceramic and P/I caps without checking the old ones? They original caps are responsible for the vintage sound of that beautiful amp. The preamp tubes are usually the culprit. I have many great sounding old Fender amps, all with original signal and coupling caps.

[@davidstorm4015]

fantastic video, thumbs up from me!

[@Spentelectrons]

Even brand new ceramic caps are suseptible to physical manipulation and produce voltage by themself if manipulated. If im not mistaken. Were those actually bad?

[@KenBernaerts]

Great video! Can you apply this master volume mod to an Ampeg SVT VR as well? So you can dial in a "dirtier" tone with preamp volume knob but control the overall output volume with a master volume without sacrificing any of the tone?

[@voxpathfinder15r]

I do disagree a little with the statement that a post phase inverter master volume doesn’t affect tone. When you look at technical sheets of pentode/tetrode power tubes - they display asymmetric compression not to mention clipping that single ended preamp tubes can’t accomplish, save perhaps an ef86 pentode preamp tube.

[@thome1547]

Terry, great video, systematic and thorough trobleshooting

[@kinkfreud2128]

How's about a dpdt relayed to bypass the msster and simultaneously switch an extra gain stage in/out.

[@MM-ib6qh]

Can you recommend a decent, new oscilloscope, easily available via amazon or similar? I used to work on tube amps a long time ago, but starting to get back into it, and just found that my old scope is toast. I was looking at the Hantek DSO2C10, but not sure if that's overkill or? I have a lot to re-learn, but your videos are helping a ton (and inspiring). Thank you!

[@gregorypinkowski7809]

Ceramic discs are always microphoinc; it's the nature of the beast. Piezo effect, and the big disc acts as a large diaphragm. It doesn't mean it's a source of the noise we were hearing. Still great to replace with something better, but it's NOT the problem.

[@charleslambiase5670]

I don't work on apps I play with the two and I use all old Fender Bassman amps as well as Marshall amps from my Bass especially my frettless, I am totally about tone and I'm finding it more now with low volume by the way the Marshalls is in 1970 major you would love to work on that one its stock I loved your video

[@1thess523]

I have a blackstar with a master volume which allows you to run your tubes wide open and still have playable volume levels.

[@gregorypinkowski7809]

Then I'd probably measure or just replace the carbon-comp plate resistors with something better.

[@jeffmitchell9214]

Excellent video. You know how much we love Fender Amps. Thanks Terry.

[@davidallen346]

My rarely used Fender 59 Bassman 4-10' combo amp has very loud Hum and slight popping sound , it sounds exactly like this but way louder , this is like normal tube amp hum. it did have 2 new power tubes and one preamp tube replaced. I took it to this local amp repair guy he hook it up outside you can barely heart it and he goes I don't hear anything wrong here, he ask me if I have dim light switch , bad grounding etc yea I am familiar with that, but I have other tube amps that does not have this excessive loud hum sound maybe after you biased it the humming sound comes on, so he did not want to check the capacitors voltage make sure all working correctly, I already email you about this issue but you are full of clients at this moment. I think i might sell the amp , I can't stand amp with the loud humming sound going on. I bought a brand new Mesa Boogie amp that had the same problem, loud hum took it back to the store and got my money refunded. So I have no idea what's causing the amp to Hum so loud

[@electrolytics]

Hey D-Lab thanks for another video!

[@miguelrichartmellado2834]

Gud job mister. In the end of the video , add one cap. in the Bias pot. Its for stabilicing the negative tension? Thanks for your great chanel.

[@LitesLAB]

Great job Terry! You are a master with the scope! I hear those big ceramics add “character”, it appears that you don’t believe! They work great in pedals though.

[@davidb258]

Great video! Where are you located??? I want to drop off my early 70's Bassman 50.

[@bbmade]

Excellent video! I have two of these heads and the work on the first one is almost done so it was good to see this video. Did you check the filter caps at some point or know they had been replaced with the other electrolytic’s? Really enjoy your videos, always learn!

[@d-labelectronics]

Yes, owner showed me pics of the new installed Mallorys

[@bbmade]

D-lab Electronics. It’s a treat to be able to see these videos and learn. Thank you for sharing your knowledge. Happy Memorial Day.

[@d-labelectronics]

Roger that man, 12 yrs USAF here

[@bbmade]

D-lab Electronics thank you for your service!

[@pneumatic00]

Change the 4 qty 100K preamp plate resistors with 2 watt metal films. The ones arranged in the "V" shape. Massive difference in hiss-pop noise, not subtle at all.

[@jman1428]

how about a schematic for the master volume.

[@andyk295]

Terry Great video. One question-should you terminate the AC lines for the deleted two pronged plug before powering it up ? Thanks !

[@mattdixon333]

That's one damn clean amplifier! Great video, Terry!

[@Beizeiten78]

I’m surprised no one has chimed in about the master volume mod yet. I’ll explain why I added that. I should preface this by saying I’m a purist, when it comes to gear and tones, but there are realities to deal with, and Fender wasn’t perfect. I play with mostly dirt boxes that like to see the amp at the verge of breakup, what the post inverter mod allows me to do is get that at any volume, whether I’m practicing alone, with a band, or at a gig. Power tube saturation is a HUGE part of a killer recorded sound, that’s why guys like Jimmy Page used small amps for recording, so they could run it full bore. For recording, I’d run this amp as loud as I could before the preamp over saturates, but for cleaner sounds, I can definitely use the master volume to record a more pristine tone that doesn’t need that power tube saturation.

[@83roadstar]

I have a Silverface Bassman that I wouldn't mind having a Master volume installed, Terry does a very good job, when He isn't swamped with repairs I may have Him do this.... cheers.... PS. Awesome soldering station Terry!

[@d-labelectronics]

Can do man, How's retirement going?

[@83roadstar]

It really hasn't set in yet,but I am relaxed, chilling in AC ,I can drop the Bassman off whenever it's convenient for you.

[@d-labelectronics]

Maybe next weekend, no AC here at D-lab ; (

[@Tomcatime]

Terry really enjoy your videos. Just wish you could do one on a Guild Thunderbird. I am having trouble with mine. Thanks

[@lincolnmicrophonellc]

I need to see it on a schematic to understand what it's doing.. are we just shunting some signal from output tube grids to ground with the pot?

[@nor4277]

If you have to replace resistors in these amps would the metalize resistors work better I like that you use orange drops caps,pricey but nice.you really do great work

[@jimcole6423]

I need to replace my scope. What would you recommend for repairing amplifiers such as what you work on? Thanks.

[@michaelrockhard2906]

My amplifier is a star force USA amp from the 90s sometimes the gain doesn’t turn on

[@michaelweiss9219]

I had a master volume added to my 65 Showman thinking I might be able to use it at lower volumes with at least a bit of breakup, turned out to be a waste of time, still no breakup even with the master low and the main vol. high...

[@Paulmccarthy6801]

What is your going rate to work on an amp. I just got a 68 Bassman. It has a little hissing noise and it seems like when your playing the guitar it goes a little lower sometimes. Usually when you first turn it on. Let me know thank you sir. Love the videos so interesting.

[@allanjohnston8049]

Thank you much for the videos I have a fender bassman and a twin reverb I worked on the bassman but not the twin Now I can go back and do them both the right way Thanks again From Canada

[@GuitarosaurusRex]

I noticed you're in Michigan.... we may need to talk.

[@giuseppegraceffa7751]

Excellent work right through.

[@richardbrobeck2384]

I agree Terry those grid coupling caps are known to go bad even in old radios it's just not worth the risk

[@johnplaid648]

Never understood why a tube is installed inverted. The heat rises to the base, socket and connections. I use light bulbs and mount them base down.

[@BlueberryStinkFinger62]

This Amp saw the inside of a home and a Studio..it never saw a Club or any type of hall ..its been only home and studio used..another great video Terry always learn something from you

[@cirenosnor5768]

@Mydickishard - It could have been used on gigs and well cared for including a road case

[@bigbear3694]

Great looking amp

[@thisisitrecords2539]

I like that dummy load you have made, looks like you attached it to a jack, what's the spec?

[@hearpalhere]

Cool video, appreciate the detailed instructions and clear explanations of what is being done. You have a new subscriber! Thanks!

[@hittenzdirten3277]

I suggest using an insulated sleeve when mounting the master volume pot. This might prevent shorting the tube bias to ground if the pots fail.

[@johnsheppard3569]

Hey Terry. What's the blue cap at the bias pot in the final picture?

[@elit3darkness]

My favorite scope!

[@elit3darkness]

Also.. Hako 936... Best soldering station.. Still use it til this day (4-18-2020)

[@kennylittle6998]

hey dlab that amplifier do sound good gkl

[@BenPrevo]

Hi from Dublin -- love your vids -- 2 things I find -- sometimes those carbon screen and grid resistors get baked and cracked and make noise -- also may I respectfully suggest to solder the grounds directly to the chassis -- I has seen bias failures etc die to bad continuity on those lugs bolted on the transformers -- peace

[@tracyc7813]

What is the name of the song and the artist you used in the intro for this video?

[@shckltnebay]

Would that cap issue show up with a speaker plugged in without the scope?

[@electrolytics]

Was something getting microphonic at 1:30-1:50ish. Your audio was a little reverby. Or was that a different mic?

[@d-labelectronics]

Hello, Yes, that was a boom mic. I wanted to capture the hiss+ birdies without background noise in the shop. Good catch

[@hpelisr]

Great info Thanks

[@keithshapiro]

So, is it possible to explain the dummy load, as well as how you're using the scope? Or, if you've got vids already covering that, can you point me to it/them? 🤓

[@keithshapiro]

Found the Dummy head video so there's that

[@thomboy54]

would like this mater volume mod done on my carvin nomad amp

[@Dan79istheman]

Nice one Terry!

[@Beizeiten78]

I’ve watched probably 500 of his videos, but when it’s your amp, man, that’s really cool.

[@d-labelectronics]

Yes Sir, This was a great project, more to do, but coming along nicely.

[@rciancia]

Randall, that amp is amazing. I have a few Blackface Bassmans not in as nice condition as yours, but they are a real workhorse. Anyone in your studio will drool when they see that.. Are you the original owner ? Very cool.

[@Beizeiten78]

Ron C No, I’m not the original owner. The amp is 11 years older than me. Haha.

[@smstiao-tecnologia]

Thank you very much Mr. Terry for this beautiful class, these amplifiers are excellent and deserve this love. 73 by PY2SNN Sebastian

[@guitarsandampsrock7306]

Terry I just fnished my first MV on a Bassman AA864 That I scratch built. Man I love it! This thing ROCKS! Thanks for the awesome instructions!

[@marky2A]

Wow. I wish I'd had this knowledge when I rebuilt my old Wurlitzer juke box amplifier. It worked well for my bass guitar and I understood grid bias, but I could have done so much more. Thank you.

[@paulhoneycutt905]

I noticed that you never popped the dog house to check the filter caps. Why not?

[@Beizeiten78]

Paul Honeycutt They were already replaced and he knew that. It’s my amp.

[@daveogarf]

You da' MAN, Terry! Now the sound matches the incredible looks of this excellent Bassman.