How to repair Bias Electro Harmonix MIG-50 Tube Guitar amplifier
ฝัง
- เผยแพร่เมื่อ 28 ส.ค. 2024
- Happy 57th Birthday to D-Lab! Yep, its my day. So, I was given a hall pass for shop operation. This amp interested me, What a great design. Unfortunately, it is a PCB based unit. Repair efforts were minimum, since the owner had already replace all of the tubes. As usual, check solder connections. The bias was a bit of a mystery. However, with a bit of assistance from the factory, I was able to get the proper bias info. Fun project. I would highly recommend this amp as a good starter. Very simple, well constructed machine.
Thank you all for the Birthday wishes. Love you all and thanks for being part of the D-Lab Family!
Shoot me your intake address and I’ll send you a five pound spool of that solder
In the manual of the new MKII version, it mentions improvements in many sections of the amp, including the power supply. Perhaps they went on and fixed the bad soldering job?
Happy belated Birthday, Terry. Amazing and very interesting video!
This video has saved me hours of research. I love my EHX MIG-50 and now I know exactly what to do when I need to swap out the tubes. Subscribed! Thanks man.
Happy bday! 🎂🎉. The EHX MiG-50 is a “assembles in usa” reissue of the Sovtek Mig-50 made in Russia. Mike Matthews moved EHX to Russia in the 80s and made tubes and amps under Sovtek name. He brought EHX back to us later. But I bet you remember those old green Russian tank big muffs 😄
"Tower, this is Ghost Rider requesting a flyby" - EH circus boards are a lot more entertaining than Fenders!
So we talked about prostate solder joints and your Johnson still works. Gotta love electronics sense of humor from a real pro. Happy birthday Terry!!
From Leo: I have heard multiple comments where players do not like the sound of the MG50 chassis. If they come with the output tubes at less than 1/2 bias current, making that adjustment should really make the tubes more responsive. Happy birthday!
Ha! The solder spindle I inherited from my dad is Kester but it doesn't say what type it is. I'm sure he bought it back in the 80's or possibly the late 70's. I think this spindle will last the rest of my life. Don't worry, Terry, I don't solder often; I know my limitations. 😛
Happy Birthday, D-Lab!
Happy Birthday Terry, your awesome.
Wow 535 volts to the plates is pretty 🔥.. I had an old sovtek 50 watt tube midget back in the 90s That thing is probably close to 60 watts RMS.. Ringed solder joints are the Big enemy of PCB boards and heat is another. I always look especially at those power tube sockets. Good video Happy Bday Terry
I have a Mig 60 and its recommended bias on schematic is 80mv, which is ihe same parallel config as the Mig50, so 40mv per tube. . But I think it uses EL34s so.....but looks like you found the answer from them and yours is 62-65mv. So I'll shut up now. Haha. You're the best! Cheers Komrad! Salute!
Well we now know how to get a broke Johnson up and working without D-Lab.
Try to insert a little blue pill in the input jack.
Finally if you can't turn off your Johnson after four hours pull the plug.
You got a nod for recording track 10 on that CD. Cool!
Happy Birthday, Terry! Many thanks for sharing your knowledge and love of electronics. I'm saluting you with some vintage grape juice in my D-Lab wine glass. (Alas, I'm out of wine..)
Thank for spending your birthday with us...
Happy Birthday
The Sovtek Mig-50 was made in the 90's with Russian style parts. the EH version would be considered a re-issue, and uses "general" electronic parts. If you see the original, the resistors and pots are especially unusual, and may have been soviet surplus.
Happy birthday good sir. I hope you have many, many more. I'll have a drink to your health.
Your friend Megan sounds awesome, much luck to her in her career.
Happy birthday Terry. Another wine job. I mean fine job!
Happy Birthday! And nice video too!
HAPPY BIRTHDAY, Terry! And may you (and Marsha) have many more.
Happy Birthday D-Lab! You still look younger then the equipment you repair.
Happy Birthday Terry, Bless you and your family!!!
Well done Terry!! Happy Birthday!!
HAPPY BIRTHDAY TERRY!
I like to say I enjoyed watching your videos, not only the knowledge you shared but also your calm voice is reassuring.
Happy birthday!
And Happy Birthday Terry I hope you have had a great day
Happy B-day. Love the video
Happy Birthday Terry! Thank you for sharing your vast knowledge with us and wishing for many, many happy returns!
Very nice of you to share the service procedure! Happy late birthday!
Great amp, I have two of those, very clean, the best pedal platform
Agreed..especially for the price.
great video - hope i didn't seem harsh on the vintage show comment, you gave us plenty of detail in this one!
A very Happy Birthday Terry. Really enjoyed the amp repair. Man that Johnson shirt is awesome! I have to get me some made. Need to start the cosmetic restoration on my two Viking II's soon. But in the mean time got a Apache TX-1 on the bench with no audio. Have a great week end.
Have fun with the Apache :) I want the shirt too :)
Happy birthday to you Teary hope you have a great birthday. I enjoy your videos veary much. Form Donald Hiscock from Vancover British Columbia Canada.
My Johnson (Messenger II black face CB) still works too.
Happy getting older day!
Congratulations on another successful orbit!
Happy Birthday Terry! Hope you had a wonderful day.
Happy Birthday Terry! Thanks for sharing your knowledge!
Happy Birthday, Terry! Always look forward to your videos!
Happy Birthday Mr. D-Lab! Wishing you a happy, healthy and prosperous year ahead. Glad to hear good news about your Johnson as well... :-)
Happy Birthday my friend... I call today Doubler Wine Saturday. Terry, its very hard to be sure, but the right Filter cap looks like the top is slightly bulging. Very hard to be sure so mentioning it just in case. The bias adjustment was very thoughtful by the manufacturer to put there.. that's a good DLAB product enhancement to see make and sell... :P hint hint... Happy birthday bud...
Happy Birthday Terry...Keep the videos coming!!
Many Happy Returns, Terry. Fun to watch your vids.
Yup happy birthday Terry 🎂🍷
Happy birthday Terry, Cheers !!!
Have a very happy Birthday terry...blessings from England UK...:-)
Happy Birthday D-lab!!
Happy belated birtday, Terry. You've inspired me so much with your numerous guitar amp projects. Thanks for that. I've accomplished to build some of them.
Happy Birthday Terry!
Happy birthday Terry, and thanks for the video : another great one and some more to learn for us... I thought birthday gifts were the other way around! 😃
Happy Birthday, D-lab!
HAPPY BIRTHDAY THX FOR YOUR SERVICE SO MUCH CONFUSING AMP TECH ON WEB YOU ARE STRAIGHT TO THE POINT LOVE IT
Happy Birthday D Lab
Happy Happy birthday Terry, just like vino you and your videos get better with age. I hope you have many more also tell Marsha to be extra nice to you, LoL
Happy birthday Terry, and I am glad to hear that your Johnson still works. Ha-ha-ha
Love your videos, actually I fixed a few amps because of your knowledge!!! I just want to say thanks and keep them coming
Happy Birthday, Terry! 🎂
HAPPY BIRTHDAY, Terry! Wish Mine still worked.LOL
Another great video. Happy birthday! Love it when you're working on tube amps.
Happy Birthday Terry, and thank you for another great video.
Happy Birthday Terry!!
happy birthday Terry
Very informative! You rule! Appreciate this so much!
Happy birthday there, Dexter!
(If you'll allow me some constructive criticism, the company in question pronounces their name, 'har-MON-nix')
Well, happy birthday! You are almost a Libra, my own sign. (But to be completely honest, I give no credence to how the stars were aligned when I was born, because that would be just silly.)
Happy birthday Terry! Great channel!
You sir, are a treasure trove of information. Subscribed. Can't wait to watch everything you do.
I really love watching your videos and I have learned a lot, beyond just being satisfied that I could change tubes and bias an amp. You point out what's wrong, why it is causing the problem, and how to repair it and what parts to buy and where to get them. And you are a Godzilla fan to boot! I love Godzilla! But to be honest, I think the best Godzilla movie was the first one, it encompassed all aspects of the human condition against the backdrop of the emerging Cold War, not to mention it was scary as hell! My favorite, ( and yes, I think the most scary scene ) was when Dr. Yamane, with his daughter and his team, with Steve Martin (Raymond Burr) in tow, were on Odo Island, walking up the hill, and Godzilla appears, and as they all start to run, he lets out that vicious, bone chilling roar!
happy birthday to you you old phart .. tnx from another old phart ..jeff
happy birthday my friend
Happy Birthday T-man! Hope you found a nice ‘07 Duckhorn Cab or similar to celebrate 🎉 🥳
Hope you had a great Birthday Terry
Great channel. Great people!! Thank you for your knowledge and entertainment 😎🤘🏻🎸
"FELIZ CUMPLEAÑOS TERRY"
WoW !!!! Happy B-day T-MAN !!!!!! Great Video !!!!!!!!!!!!
Really enjoyed your video love ham radios everything I own is valve including guitar amps keep up the good work. Happy birthday by the way.
Thanks
Great job Terry.
Cheers to you Terry.
Happy Birthday Young Terry! (Must be pushing 30 this year!!) ha ha!
Happy Birthday!
13:20 - Those test-points are a plus. Just make sure you don't short the probes to the chassis!
Happy '39th' birthday :)
Seems like a design flaw doesn't it?
Happy belated, Terry! Looks like a bad wave-solder job. Either they didn't get their flux spray right, or ran the conveyor too fast. The tube sockets would have been masked off for wave with Kaptan tape, and done with selective solder or manually soldered after all of the top layer components went down.
Happy belated birthday! (Im a day late lol still counts)
Good job old man.... :-) (that's a Happy Birthday) :-)
Happy BDay Terry! Enjoy some 14Hands tonight. Keep the Johnson happy! HA
Happy b-day!
Awesome 😎
When they build those pin 8 is the pin they used to adjust where the socket is set for height, and alignment so it's slid around until the socket is where it's supposed to be, and then pins 1-7 are soldered in, but all the flux was cooked off the pin 8s during the initial positioning of the sockets. They SHOULD suck that fluxed up crap solder off pin 8 and resolder it. NONE of those solder joints look acceptable let alone good. The ONLY time I add extra liquid flux is for chassis grounds, and a few select places where I'll use paste to avoid overheating, or for SMD stuff. There is a local boy made good who made amps for Deathlock and other Adult Swim shows, and his first amps were modified Sovteks. Very nicely modified Sovteks!
And why do you need to look up the bias current? Set those tubes up for 60-80% plate dissipation for Watts, and see where the customer likes the sound. Below 60% it gets muddy, above 80% you eat tubes faster. Ohm's Law! NOS Sylvania 6L6GC STR 415s can be biased at 90% or more, but this new Sino/Russian/Slovakian made stuff? NO WAY. 73s KI7AQJ
Happy Birthday! Have some wine ( I'm sure that's already happening) ';^b
Terry, hello and Happy Birthday belated. I thought that bias feature was really neat and thoughtful how the company
put that on the back. I was intrigued they bias both tubes through a single circuit rather than biasing each tube separately.
I do understand cost is involved though. So unless you do some probing and calculations a person won't know if each tube
is truly biased equally. I mean, sometimes tubes aren't matched. Is this a correct assumption? Anyway, it is still a nice feature.
I enjoy your videos and am learning through them and others.Reading books as well to possibly have a small repair shop to
supplement my retirement income when that happens, shortly.
Thanks, Kirk Murphy
Nice job!
HAPPY BIRTHDAY TO MY YOU TUBE LITTLE BROTHER 🎂🎂🎉🎉🎈🎉🎈🎈
Slid that "just about transmitters" in there. I think we all know why you did that! No confusion! Over 500 volts on those plates? That sounds a little excessive to me. 450-475 seems on the high end. That must have been above 70 percent of max! My 60 watt Pignose w/6L6GCs is only435. Great video and T-shirts. Thanxz
I say the power supply caps probably won't give you much trouble but I would still replace the rest of the electrolytics with better quality ones.
I'm betting the schematic you found was for the older ones that were made and distributed by sovtek. The new EHX ones have a completely different layout and I bet they added the bias section.
Happy birthday Terry!
Having been a metal fabricator and welder my whole life, ironically, I had never messed with soldering before. You inspired me to buy a soldering iron and some rosin-core solder to start doing my own guitar pickup swaps. So far, so good. Definitely a learning curve involved, but once you get it figured out, it’s all gravy.
One of these days I need to send you my old mid 90’s Marshall Valvestate VS100R That I’ve had for over 20 years, that has mass-amounts of hum, even in the clean channel, and some of the input and output jacks need replacing or cleaning.
And I want to convert my MIM Fender Princeton 65R 1x12 combo into a tube Hot Rod Deluxe w/ KT77 tubes, and 12AX7 preamp tubes.
What do you think the estimated cost might run for those? I know actual cost will vary, but just wanted to get a rough ballpark number.
Happy Birthday Terry, love Da Johnson’s too!!
Question: because of all the cold and non-existent solider joints and with those being double sided boards why did you not unplug the wires and pull the boards to check both sides?? While I know it’s a huge pain it would be a much better observation and chance to confirm every joint is properly soldiered eliminating bad joints.
HAPPY BIRTHDAY!!
Sovtek made these amps, there is labeled Sovtek Mig50 as well as ElectroHarmonix... But I don't know if at one time they transfer the production in USA?!
I see a Sencore SG-165 in the background. Have you used it on any of your repairs/ restorations? How about a video of it in use? Happy Birthday!