How to Repair replace tube sockets Marshall 50 watt guitar amp D-lab

Tube amp theater. D-Lab repairs a Marshall JMP 50 watt tube Master combo amplifier. This amp came into the shop with mushy response. The issue was bad 12ax7 tubes and worn sockets. The fix is rather simple, however an oscilloscope was key in finding the fault.

[@rawknotwantnot]

Thx for this instruction! I need to replace two riveted power tube sockets in an old Laney 60 head. Both have arced in their lifetime. Restoration project currently underway.

[@randyaivaz3356]

Used to go to the Pawn Shops in Vegas, in the 70's, Bought a Fender Twin Reverb for $40, Broken, as is, Owmer insisted I couldn't bring it Back. Agreed. Opened it up, pulled Tubes out to Test. Noticed One of the Output Tube Sockets was Different, had been Replaced, also noticed the Keyway was out 180 Degrees. Desoldered the wires, Pulled out the Socket, Rotated Socket 180 Degrees. Resoldered wires. Installed Tubes, Worked like a Charm. Troubleshooting Ever since. I Dumpster Dive, Buy Broken Electronics, Effects Pedals on Ebay. Love Electronics. Good Job on the Repair

[@acoustic61]

I think you have an oscilloscope museum!

[@Bbendfender]

Good job. I always learn something when I watch your videos.

[@AdrianRP1]

Hey, just finished replacing V1's tube socket in my Marshall 2204 using your instructional video as a guide. Piece of cake man...and WOW, did a good sounding amp just get WAY better! The tube was suspect for awhile...humming...and it sounded good...Marshall like, but something was missing...now..holy crap... The preamp control now is far more sensitive...get way more low end frequencies...and volume...(ears ringing badly now) It's more then obvious this preamp tube socket was attenuating some of the juice at that point... Clear, quiet and pure now...and LOUD!

[@soundboy57]

Great and helpful video, thank you! I tend to vacuum up the metal shavings as I go, so they don't end up where I don't want them. I need to do this on a 1988 Marshall head soon. Your video really helps!!

[@audiotechlabs4650]

Terry, another great video! Your sense of humor is priceless. I think we all have a little comedian in us. Hope you keep these guitar tube amp videos coming. You seem to know what you are talking about. Thankz

[@d-labelectronics]

Hello, Yes Sir, I a temp to generate the illusion that I know my stuff. If the audience suspects different, I toss in some stale humor to get them off the scent. Glad you like the vids. I will try to keep new ones interesting. Thanks for your support. TD

[@Mikey-ex4nf]

D-lab Electronics

[@davidparris7774]

Terry I love it! Still using my grandfather's 535A!

[@tubetone74]

You are a great teacher Terry. Thanks for all the great vids.

[@lineshaftrestorations7903]

My tektronix 531 makes a wonderful space heater.

[@bobvecchi7981]

It’s obvious (In hindsight of course) that you did find the culprit and made the repair. I do take some exception to one troubleshooting rule that you violated, if you don’t mind the constructive criticism. I always follow the rule that when you make a change and want to compare the results you should always use the same test equipment so that the results aren’t affected by some inconsistencies between the different pieces of equipment. In your case you used different scopes with different ‘personalities ‘ which could have contributed to the different scope displays seen had the tube sockets not been the culprit. I think it’s a valuable lesson for newbies to learn and adhere to since they will be less experienced in diagnosis and evaluation. Thanks for the great video and learning experience.

[@jasonsnyder8570]

Great video but I'm biased... (sorry I couldn't help myself) it's my amp and It so obvious that it's in the right hands. I saw this was posted and it was killing me not being able to see it until now. I cant thank you enough for taking this on. I've owned this one for 25(ish) years and have never had any problems with it as you can tell by the blue cap cans. When it faltered I discovered how important it was to get it to someone who get's it. T obviously does. Thanks and great video.. PS I hate to own up to it but you were right about the deoxit that was me. Pps Uncle Doug is great I subscribe to you both.

[@edwhite7475]

i have been wondering for a while exactly WHY i needed a scope....besides just being the coolest looking piece of diagnostic equipment...now i know....thank you-

[@cheycasters]

Loved the show Terry!!! Thanks man!

[@billb7735]

thanks for the videos. a few lessons i have learned with this type of thing are: 1. it's easy to overtighten #4 mounting screws on preamp tube sockets and end up breaking them, so i have to take it easy with the nut driver. 2. too much solder on those sockets will leak down in and block the socket. so i put an old tube in there while i solder. 3. it's easy to get aluminum shavings in surrounding tube sockets, so i usually cover them if i have to drill. i've had things lodged in a socket and took a long time to figure out the problem.

[@d-labelectronics]

Roger that man, Great pointers. I hope the viewers take these into consideration also. I find that using cutting oil keeps the metal chips corralled. I always take a small ESD vacuum to the amps before power up if I see contaminates. I'ts always best to be anal around high voltages. Thanks for the comment. TD

[@djfrank59]

Love that Tek 515A. Even with the fan noise, it is to be appreciated :) I've seen so many techs bend the socket contacts inward, but for the most part, it isn't even a temporary fix. it doesn't pay; replacing the sockets is the only way to go. Yes, once in a while, I get a cheapo customer that tries to pinch pennies, but if they insist on a quick fix, I make them sign off as a NO warranty repair. Good video, keep 'em coming :)

[@d-labelectronics]

I have always wanted and old tube Tek scope. Could never locate a clean one. A fellow on the east coast had this one as well as a HP 140A that had never been used! I bought both. So the HP will make a star appearance soon. Thank you for your kind support of my video escapades. I will do my best to keep good ones coming. TD

[@cfh13]

Helpful video ,thanks. i have a mesa 50/50 power amp i got recently and one of the tubes burns a lot brighter than the rest so i need to replace the socket. im awful at soldering so wish me luck,trying to save money doing it myself.

[@stanleygerrick6053]

Dear Terry, Another great teaching video! It's also possible for hair line cracks to develop in older, cheaper socket bases between adjacent pin sockets. I once had an older receiver in which the audio would become very distorted as I turned up the audio gain. I finally found the culprit when I viewed the bottom of the chassis in the dark. A hair line crack had developed between two adjacent pin sockets in the bakelite base of the audio amp tube. As I turned up the audio gain, sparking developed at the crack site. As the gain was turned up more, flames started shooting from then crack! I learned to check tube sockets carefully under magnification! Dr. Stan KZ8G

[@duaneadam]

Great video, thanks for the tutorial.

[@jahbay]

I came across your channel while building a kit amp. I was lucky enough to have a friend help me. He has been an Electronics Tech in the computer industry for 30 years. He opened the door and filled in some gaps in my knowledge. Watching your videos open my eyes and confirmed some suspicions I had. I will be ordering a scope today. Do you have any recommendations in terms of reading materials. I would like to fill in the gaps of my knowledge. Obviously your videos have been a great help. Oh and FYI despite several mistakes the amp did fire and work on the first try. Thanks to you and my friend I have the courage to go forward. The first thing I have to do is learn how to discharge capacitors properly. I am sure there's a video on it. what are the pieces of test equipment would I need? I see you have a tube tester and a variac. Those seem to be a repeating theme. I digress, any help would be appreciated especially from my fellow KZbinrs. Rock On....

[@harryconover289]

Great tube tester I want one I have six now to cover all the types I need to check

[@jamieostrowski4447]

I love that oscilloscope!

[@bartmeijer1059]

Hoi, again a verry interesting Vid! I like that vintage scoop you used THE first time! Thanks !

[@d-labelectronics]

I just purchased the Tek 515A scope. Wanted a tube model for the vids. It works like a champ. That scope originally sold for $800.00 in 1957!

[@yrulooknatme]

800 dollars in 57... ain't that like a million these days??? lol

[@tedcabana]

This guy's like a master surgeon, but better!

[@theanthonyrw]

You are the man my friend...

[@MarionBlair]

I wish I knew what you know! That's awesome.

[@ki4dbk]

Great video!!!

[@dr.danamplifiers1753]

Your video and work is awesome. Question. When you hook up the scope where are you hooking the probes to? Are you going across the positive tip and negative tip of the speaker out? Of course you have a dummy load installed. I've used scopes For other work however not as of yet for amps. Would I be ok to hook up the amp In play mode to my 16 ohm dummy load and then take the + and - leads to the corresponding bus wires on the output jacks? Thanks for the awesome video. It is great! You're a real pro and I really enjoy your video. Keep it up. People appreciate this kind of stuff!!

[@MichaelLloyd]

Man you're on a roll. Another great video. I'm wondering what the deal was with the missing resistors and possibly odd cap? There are a lot of Fender amp repair videos but I think this was the first Marshall. I picked an old Gretsch up from eBay surprisingly cheap last year. It needed cleaning and power supply electrolytics. When I played it after the rework the amp sounded great. Note that I said the amp sounded great. My playing is a cross between dropping a guitar from the roof of a building and smashing it into an oncoming train (but I enjoy playing when I can). The tubes tested remarkably well so I don't think the amp saw much use. But I digress, I 100% agree on getting a scope. Your videos are always informative and entertaining. You can't beat that with a stick. Thanks for taking the time to make them. If you haven't done so, swing by Uncle Doug's channel, you might enjoy some of the old amps that he's tackled. 73 NE5U Mike

[@d-labelectronics]

Thanks man, This makes me feel pretty good. I try my best to provide straight forward troubleshooting/repair videos. Your input lets me know, I'm on the right track. Thanks again and I will take a look at Uncle Doug. TD

[@DeadKoby]

Uncle Doug is one of the guys who encouraged me to try building my own from parts... rather than a kit. the RTL-1 chassis is made and working... on my channel.

[@nor4277]

Thanks for the info ,maybe they are a good idea on tubes that get very hot,I started seeing them at Ali Exspress, on there tube radio kits.again thank you for the info.

[@locktherock]

Brilliant video, I’ve got exactly that problem...now I’m wondering if a novice soldering iron-er can tackle this successfully🤔

[@roberthurless4615]

At the end I thought I was watching an old episode of The Outer Limits. I'm sure you remember that one.

[@d-labelectronics]

Hello, you got it! That was the effect I was after. I am a big fan of the old 60's shows. I used a SSB transmitter to distort my voice. Have to keep my stage props cheap. I divert most d-lab funds to quality bottles of wine! Glad you like. TD

[@anthonywatson754]

I know this is an older video, but I've been binge watching your videos and was wondering... If you still remember, what was the deal with the missing resistors and caps?

[@chuajsjs2853]

Hi D lab guy... any video on any multi channel amp switching pops diagnose?

[@TheBoss1597]

Hi Terry! Just wonder if it's any drawbacks in using a choke for a tube preamp build?

[@rciancia]

Where did you connect your scope to be able to see that noise when you wiggled the tubes ? Good stuff !!! Love the video.

[@d-labelectronics]

Hello, Appreciate it my friend. I had the scope connected to the speaker terminals for the initial noise check. Later, I connected an non inductive 8 ohm resistor. I had fun with the vintage Tek 515a. Plan to feature it again.

[@larrystevens6282]

Terry, I recently purchased a mint Marshall 8240 amp. The case is wood and all finished like a piece of furniture. Never seen one like this before they are usually always the black vinyl. Anyway....when I switch it on it makes a little hum is that common? The tube in it is a Marshall ECC 83 is that worth changing for a new one?

[@AdrianRP1]

Hey Terry, nice video man! I've got an 86' 2204 with a wore out v1 preamp tube socket. I just got a Belton socket from the Tube Depot...seems pretty stock looking...anyway, what ya think of the Beltons, and um, what size machine screws did you use to secure the new socket with? Thanks!

[@Wizardofgosz]

Those were Beltons he put in. They're the ONLY sockets to use, unless you have a vintage piece and you want to match the existing ceramic sockets or something.

[@drdave337]

What size nut/washer and screw do you use?

[@Cruiseangel72]

Amazing. Can you put a low bass switch on a peavey 700 fire bass?

[@Cruiseangel72]

Ok. But can you doi it?

[@randm7252]

Hello, Just subscribed. I've always been fascinated by electronics but never learned how to repair old tube amps or even owned a tubed guitar amp until recently. I currently own a Mexican made Fender deluxe Hot Rod. Any suggestions on what/how I can start doing mods on? I also have this vintage GAROD tube radio and it appears to have a guitar jack on the side of it. all the tubes are there but never tried plugin it in.

[@d-labelectronics]

Hello, I normally do not mod the PCB built amps. I try to find them with smoked boards, gut them and start over with eyelet boards.

[@bongnp]

What do you use WD40 or hoppies gun oil for?

[@justrockon426]

where do you get your tube sockets?

[@Blaydrnnnr]

Not sure if you answer old posts, but I have a 1986 Marshall 50W 2204 that a thought had a microphonic preamp tube, but after changing it out, I'm still getting noise when I tap that tube. I then swapped the tube with 6 other new ones, and again, its still microphonic. So I swapped the supposedly bad original tube to the next socket, and took the second old tube from socket number 2 and installed it into the microphonic tube socket, and the same socket is still microphonic. So the original tube from that socket, I'm guessing is not really bad, looks like MAYBE the socket itself is microphonic? Any advice would be appreciated. No amp guys around here for over 250 miles so I might be trying this myself. I've done and still do some soldering, but this will be my first attempt at a replacement like this.

[@d-labelectronics]

Hello, Yes, I agree, the socket may be worn/corroded. Can you change it out? If so replace with a Belton Micalex type.

[@Blaydrnnnr]

Thanks for the reply. I think I can. I haven't tried to do one yet, but I have some soldering experience. I've done quite a bit of it. I was planning on doing a cap change on this amp anyway, I already have the standard cap replacement kit from a vendor. I'm not 100% sure thats the problem on this amp. At bedroom levels, is doesn't sound too bad, but the louder I get it cranked up, there seems to be a "rattle" maybe a ringing, hard to explain. At first, I thought I had a bad speaker in the cabinet, but I have 4 different 2x12 cabs to switch through, and it happens through them all. The first thing I noticed ( maybe the biggest clue ) on this thing is this...with nothing plugged in, if I turn up the master volume to say 5, this amp makes a ton of noise. I've changed all the preamp tubes several times, but not the power tubes yet. Some I'm not entirely sure whats going on. Would be VERY cool to see a vid on maybe testing leaky caps? Just to ask, do you have an address to email you? I may want to get more in detail on this thing. I'm a complete novice on tube circuit analysis. But have been wanting to do this kind of work for a VERY long time. Was hoping to do this kind of work once I stop working. Thanks again, hope you have time to try to help me out...

[@nor4277]

I seen the new ceramic sockets ,are they better?

[@d-labelectronics]

Yes, by far they are not affected by heat

[@avhcbeaver2]

Where do you get the sockets?

[@santiagomoreno696]

Probably not where he gets them from, but you can get those from here www.amplifiedparts.com/products/socket-belton-9-pin-crimped-shield-base-micalex

[@simonspeaker]

what brand is your cutter? i look at some xcelite and crescent but it is klein do you use? crescent broke in my hand...

[@minitos1]

I love myself a Knippex cutter

[@pneumatic00]

Those cutters are GREAT (they are flush cutters) and are only $5 at Fry's Electronics if you have one near you. Some are Hakko, some are brand C.H.P. Buy 2 pair. When Terry cut off those rivets, he cut the rivet very close to the tip, it would not have surprised me to see him break the tip off. I have broken those cutters cutting a thick nylon tie-wrap. Yeah, you will break one or two of them but they are much cheaper than Xcelite or Knipex and if you avoid cutting steel, they last very well. They are excellent for trimming toenails as well!

[@yrulooknatme]

I bet that condition gets overlooked often.. I hate removing rivets. I wish you could just place a drop of acid on them and they would just dissolve and disappear.

[@d-labelectronics]

Hello, yes rivets do require some patience removing. I would guess they never expected amps to be around long enough to require changing the sockets. Rivets are cheap and fast to initially install. It was a good project. Hope you enjoyed the vid. TD

[@yrulooknatme]

oh ya i love learning bout amp electronics. thanks for posting your vids

[@DeadKoby]

Those are classic CHINA pre amp tubes.... I can spot those in a heart beat. Want some? they're FREE!

[@d-labelectronics]

Yea man, I thought they were. I have real good luck with the Sovtek 12AX7LPS tubes. Tube depot will give a qty discount.

[@DeadKoby]

The LPS is the one Sovtek 12AX7 I like. The TungSol 12AX7, and JJ 12AX7 are also popular here.

[@Phil_Trujeque]

Awww... looks like a Marshall tube socket repairman couldn't appreciate your video

[@birdsong2552]

8:14

[@TheyreStillOutThere]

I know this video is about 100 years old, but I bet someone squirted WD-40 into those tube sockets.