How to reduce noise Hiss Vintage Gibson EH-125 Tube Guitar amp Part 2
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- เผยแพร่เมื่อ 17 ก.ค. 2024
- Here is part two of the Gibson EH-125 repair. Due to past maintenance, I pretty much had to rebuild the entire circuit. Also to reduce noise to an acceptable level, I changed the configuration of the Volume pot. Yes, this is a slight modification, however if you really intended to use this amp for recording, in its current state, that would not be possible. The Mod is completely reversible. No extra holes, controls, etc. These amps are not high power. The plate voltage is approx 330vdc. So do not expect to play in a rock concert, however the tone is marvelous, so mic'ing it into a larger system would be the way to go. There is also a Tek Tip in the video for increased gain utilizing a 6AC7 tube. An old ham radio trick. Hello all, a fellow TH-camr suggested adding and added .022 cap from the volume pot center term to the inverter tube to block DC. I did this and the pot noise is totally eliminated. If you all would like, I can produce a schematic of the final design. Provide that to you via e-mail. Thanks again everyone for being on my team. Fun to learn as we go. Hey guys! I just added a Tek Tips page to my website. The updated schematic for the Gibson EH-125 is published on that page. So, now you can reference that or use the schematic to construct this cool amp boutique style! See d-labelectronics.com
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Hope you don't mind this tip Terry. You say you cannot play the guitar, that's fine you're a great tech. If you tune to an open tuning you can play an harmonious chord just by strumming, with no frets involved.
This was awesome. Thanks Terry!
A great work as always!
Great job. Really enjoy your work. Thanks.
Terry, thank you for sharing your wisdom with us. Amazing educational video.
You’ve got DC across that VC. Put a .022 on the feed to the inverter off of the VC
Excellent idea, I will give it a try. Should have thought of that! Just installed the cap! The pot noise is gone! You rock. This update may justify documentation? Thanks man
That's exactly what I was thinking. Good job !
Was that .022 in line or down to ground ?
Thanks for the tip on the 6AC7. I've got a couple of those.
I loved hearing a guitar through that amp! An awesome video once again! Thanks D-lab!
Well done Terry, another old amp brought back to life!!
Best tip! Regardless of what happens keep a fresh and positive attitude! Thanks!
Good info on the tube Terry.And a great fix on a olde but goodie..😎🎸👍
Great info, Thanks, Carl
Ahhhh part 2, now I can rest easy. Nice tech tip, too.
Wow Terry you da' man. It sounds absolutely great!🎸 Think it's time for a celebratory drink.🍷👍🏻👍🏻
Replacing the 6SJ7 with the 6AC7 made a huge difference in the Raven that I built. Thanks for the tip
Wish I had half of your knowledge on amps etc......great stuff
Thank you soooooo much for this put.2! Great repair and upgrade mod and....that tech tip is priceless! Go back and look at a tube Manuel and find the amplification factors and get more gain from substitute tubes! That's what it takes to be Terry of Dlab! Thanxz
Love to watch All your work Terry. Btw Nice brown coating on that chassis and transformer, looks very durable, it is offcourse it’s 78 years.
Really interesting stuff Terry I have a couple of old traynor hand wired amps over here in England. The one needs i guess new filter caps there originals in it. Looking at your videos giving me some great tips I'm dying to get in there and see if I can fix her. I'm well aware of the voltage these things hold but I got to start somewhere I wish I got into it when I was younger. Fascinating subject keep up the great work. Cheers Martyn.
I 'gained' a great deal from that... :-) Nice!! Great job!
Young Terry The man! (Ok! Obviously not in the same class as Emi! But he does his best!!)
Can some body teach ol' Terry an E, A and D chord at least? Haha good job as usual Terry.
Thanks
You did a great job Terry.
You tech tip also a great one. What was the approximate out wattage of the final volume?
Thanks
Keep up the good work.
ty for showing us all how to work on these amps what kind of telecaster is that?
Hm MCW tune up signals.
E A D on a 🎸
Is the easyest once you know them
Love ya man
Question: Could you just jump the output of the top 27k to the input of the pot and clip out the bottom 100k resister? That way all 3 inputs would be running in parallel into the pot. Just a thought. Good video so far.
Good stuff Terry.. I cannot tell you how may pieces I work on that have wrong values put in.. people just use what they have laying around. Nice job on that one... I forwarded the email to you on the other address. Pls let me know if you get it... thanks sir
11:59 is that an unsoldered resistor on the plate of V1?
Looks like a new amp. That thing was all wrong :) I wonder how diferent it sounds from an original one.
If it was mine,....think I would have modded it further for contemporary guitar use. Separated inputs with 3 different grid resistors so you could have a choice of hi/low/bright inputs would be useful. And a 6SN7 instead of 6ac7 input tube would make another gain stage after the volume pot available. The Eh-150 was designed & built before R&R was stolen from the black folks....so it needs a kick in the arse.
That turned out to be a can of worms Terry.. Bet you needed a glass (or three), of the pressed red grape afterwards... 🤪
Should a one tube wonder record player smoke if it has no valve in it or do you think it could well have other problems?,I am in the process of
doing up a Philips NG5158 as a novice I just plugged it in to test and there was no sound due to the tube falling out in transit.After finding
the tube rolling around inside and pushing it back in it seems to work fine, I'm just worried it won't last long after the smoking episode.
Any help I would be grateful of thanks John
Record players shouldn't smoke. Very bad for their health...
Nice work Terry...one question, you soldered the AC green ground wire to the chassis; would a nut/bolt with crimped wire connector and shake-proof washer been appropriate? I know the ground lead probably won't get hot enough to melt the solder and disconnect leaving the chassis ungrounded but... 73 - Dino KL0S
Dino Papas Hi Dino, for what i’ve seen it comes to Terry with a 3 prong allready installed (see video 1). Also there, you can see when Terry removed that big rocket cap the ground lug is bolted with lug and a nut and soldered.
@@Retro.Studio Well, that's why I mentioned it since he went to the trouble of doing a nut/bolt for the input tube ground connection. TNX for the comment!
Dino Papas I am more surprised that Terry is not rewire that non twisted filament wires ✌🏼
The 6sj7 now needs to be cathode biased?
is the gain addition running any risk of damaging the speaker?
At 9:27 What is grid noise? Does that mean external interference?
Bad solder in the prior work, maybe RoHS lead free?
Hey Terry. Long time watcher and subscriber. I have an old mid 90's Marshall Valvestate VS100R 1x12 combo amp that has developed that same 60-cycle hum over the years, even on the clean channel, and with the volume all the way down. What is your hourly rate, and are you taking on work at the moment?
If so, I can remove the chassis from the cab, and bubble-wrap it and send it in a smaller box to cut down on shipping costs. The VS amps don't have much resale value in today's market, so I don't want to sink a ton of money into it if the repair is going to be a major one. If that ends up being the case, how much would you charge to rip the old solid-state junk out of it, and convert it to a JCM 900 with 2 individual tone stacks (1 clean, 1 overdrive) with 2 overdrive channels, effects loop, and reverb? That should require about the same number of potentiometer knobs and push-buttons that you could leave in the same places, so you wouldn't have to modify or change anything on the front panel.
I would love to see that point-to-point JCM 900 project. I had a 1980 Marshall lead 2000 head 250 watt 300 watt saturation. So much fun!!!
@@Finom1 If he wants to crowd-fund the costs, I'll send it to him and he can make videos of the build, and send it back when it's done. I don't know what it would cost, but I'm sure it's more than I got right now. I was just curious about it for a future project. It would definitely make a good series...
@@goodun2974 No, they were the first "hybrid" amp. The main power section is all solid-state circuitry, but they use a tube preamp that somehow meshes together with the solid state power supply to get that nice warm tube clean tone, and that dirty tube overdrive sound. They're very decent sounding amps when they work right...Just most were plagued with circuitry problems, bad input jacks, and soldering connections failing, like mine has succumbed to.
When Terry does his conversions, he completely guts the whole chassis, and uses the correct parts to build whatever amp you want it to sound like. So, no worries about the stock transformers and stuff not working...They'll be in the trash bin.
Also, thanks for the input, but I'm not new to this. Been playing guitar over 20 years. I have several amps, just thought this might be a cool project for him to build, and cool amp to have when he's done. I'm not planning on selling it.
Is that an Alpha pot? Weird choice given your usual high quality component use.
Hey Terry,
Is that a Hakko FX-951-66 Soldering Station, and did you admit to your significant other how much you paid for it? it’s a very sexy soldering outfit that I’d love to own but can’t quite justify right now.
Watch out for the very yaks !
If my imaginary band makes it big, id have 4 amp techs.. Terry, the Guitologist, Uncle Doug, and Mr Carlson.
But not me? My feelings are hurt.
@@DeadKoby Hahaha you beat me to it. I was going to say the same, lol!
@@DeadKoby ill check out ur channel
Now with a 6AC7........This amp will go to 11.
where is the negative feed back??
^5 if you read through the comments for tech-tips :D
I want a glass of wine, please.