1968 Marshall Model 1986 JMP-50 Bass Amp in Beautiful Original Condition
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- Опубликовано: 22 апр 2019
- In this video we will first examine a really nice, original 1968 Marshall Model 1986 JMP-50 Bass amp, inside and out. Then we will review the circuit to see how it differs from a Model 1987 JMP-50 Lead amp. Finally, there will be a side-by-side audio comparison between this Model 1986 and the Model 1987 featured in a previous video, using a 1958 Gibson LP Jr. and a Marshall speaker cabinet.
Extra features include the opening of two gift boxes from generous viewers and a return to the car show at the War Eagles Air Museum.
If you enjoy advertising-free videos like this one, then please subscribe to our channel and consider becoming a Patreon patron at: / uncledougsvintageamps or making a PayPal donation to: dldcam@aol.com. Also please consider donating any unused tube gear or components, possibly to be featured in future videos. Thanks !!! 
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Once again a classy, tastefull video on not just wonderful vintage Marshall’s and the view/review of chassis, but then hot rods and their innards as well. You are impossible to compete with in many levels. I go to bed thinking about it and wake up with a cup of coffee and breakfast to view your videos....the best way to start the day. Thank you so much🙂
Thanks for your very nice comments, MP. We appreciate your viewership :)
Menu:
00:00 to 11:00 Examination of Amplifier, inside and out
11:00 to 29:35 Circuit Review and Comparison with 1987 (Lead) Model
29:35 to 31:48 Open Viewer Packages
31:48 to 42:00 Audio Demo and Closing Comments
42:00 to 50:19 Car Show
Errors: 1.) I say "EL 84's" at 25:15 and should have said "EL 34's". It has been brought to my attention that they may actually be 6CA7's despite the written designation. Here is a discussion of the differences between the two types of tube: www.marshallforum.com/threads/6ca7-vs-el34.16651/ 2.) I said that the Hunt's capacitor was a "Death Cap", but instead it was connected to the HV fuse (not the AC Fuse).....therefore it probably was a "snubber" to prevent popping when the Stand By switch was opened and closed.
Comments: 1.) Thanks to my good friend, Dean, who trusted me with close to $20,000 in precious vintage equipment, so that this video could be made. 2.) To those who think that the strong bass output of the Model 1986 would be better suited to a 4 x 12" cabinet, where it would less inclined to overpower the speakers.......I agree. 3.) The circuit could have been modified to more closely resemble that of the Lead amp, but why? It was pristine, and any alterations would border on heresy. 4.) The demo was performed at very high volume levels (bordering on the threshold of pain), which was challenging for the microphones, but they tended to compress rather than clip, so the audio is fairly accurate.
Link to previous Marshall video (1987 JMP-50 Lead Amp): ruclips.net/video/k2EKNj4qtu4/видео.html
Really wish I could send you my vintage univox head would make a good video was told that it is pre Marshall when jim Marshall was with univox
the time you spent past present . late 60s early 70s you ever cross paths with Shawn Winklman ..one of the many Drummers Gerri Garcia had ? and another ? did you ever back up J Beck back in the late 60s early 70s ..you just to damn good to be an amp tec .that plays an Axe .
A wonderful video Uncle Doug. I've worked on a few of these over the years, and have never seen one that original and in that good condition. You can tell how much your viewers appreciate your videos by the generous items they send you. Take care, and have a great day and beyond.
Thanks so much, GK. I really appreciate it.
Thanks so much for showing us these iconic Marshall Amps Uncle Doug!! I also want to say thank you for all the time and effort you put into each and every one of your video's. I can't tell you how much I've enjoyed watching and learning from you . Cheers from Ontario, Canada..
You're welcome, Dave. It's really nice to hear such nice comments. Thanks !!
Two thumbs up Doug, another wonderful video, one of your best. Glad you came over to the Marshall camp.
Thanks so much, James. We like it here in Marshalltown.
thanks uncle doug !! have a great day with you and the little 1's!!!!
You're welcome, Ken. I will :)
Hi Uncle Doug, you are amazing!!! Thank you so much for sharing your wisdom with us!!!
You're welcome, F1. Thanks !!!
Wow..MUCH appreciated Doug! I purchased a 1986 Bass amp (made in 1974) many years ago when i was 19 years old. As the years past I thought I had screwed up because I bought that not knowing what I really purchased. Boy did I get lucky. I can imagine the guy setting around now wishing he had never sold it to me. I have a 1960A slant cab with greenbacks. Love the sound but Im not 19 anymore....hate the weight of lugging it around. Gotta get a small combo for gigs and practice and keep this jewel for the stadium gigs.
Very nice! Thanks again for the circuit-schematic comparisons. Also enjoyed the car show again.
You're welcome, James.
From the kitties to the coupes a very enjoyable video. I don't know why I was surprised to hear such a difference between the 68 and the 67. I would bet in a two guitar band situation with one sporting the 67 and the other the 68 they would compliment each other and just rock the place like the good ole' days.
Thanks, Jim. I agree......just like mixing ceramic and alnico speakers in a cabinet :)
Hi Doug, another great video and with comparison of diagram and actual layout which helps immensely. I wish we could see under the turret boards of some of these amps to see how connections are made between components. A long long time ago you once apologised for your playing during the sound demo and explained that you suffered from old hands. Well something has changed and I hope that means you have found an elixir of life which you must have, as your playing is great. I think it must be all the warm wishes and gratitude you receive which is in all honesty most warranted.
Thanks so much for all your very nice comments, Allan. I am fortunate that Ollie & Jack have taken over responsibility for the audio demos :)
Your videos are amazing. I used to assemble stage amps (Simms-Watts PA-150) many years ago (1970) before embarking on a career in computer programming - but I always kept my interest in electronics. I'm in the process of designing and building a 100+100 watt stereo unit for high fidelity applications including RIAA correction for the phono inputs and 4X KT88 output tubes (valves on this side of the pond). The 'refresher' information that I have learned from your videos has been indispensable.
Thanks so much, Michael. We're glad to hear that the videos were helpful and informative. Best of luck with your (very ambitious) project.
Thank you for another great Marshall video! Nice comparison and beautiful Marshall cab! What is interesting both amps have the same 1202-118 power transformers, so both have 5V GZ34 winding (in your case the winding is just unused). Despite this 1986 bass was designed for silicon diodes rectifier. :) Also both amps has shared cathodes on V1. So I still wait for split cathode vs shared one comparison. Great you decided to introduce Marshalls on your channel! Marshalls are always welcome! :) Greetings from Poland!
Thanks for all your nice and well-informed comments, Marcin.
Awesome amp & thanks for sharing the car show as well UD!
You're welcome, James.
1986 circuit all the way. Duane Allman and Dickey Betts both used 1986 50 watt Marshall's on Live at the Fillmore East and we all know the juicy killer warm lead tones they had on that album. Just richer and warmer when pushed a bit. I know a lot of guys change the 1987 circuit to the 86. Great video as always Doug.
Thanks 6S. It's interesting that they would go from lead to bass rather than the other way around......but having heard a 1986, I can see why now.
@@UncleDoug Yeah, it was just rich in harmonic content on your demo, nice full rich tone with a hint of breakup when you dug in. The 1987 just is too shrill and ice picky on the treble channel. If you jumper them they tame nicely but I think the the 1986 is so more similar to a Fender bassman and gets that same thick rich throaty sweetness just like it's American cousin.
@@SIXSTRING63 That's a great analysis, 6S. Thanks.
Those Allmans did things their own way :
Allegedly they ran their spkr cabs with No Backs ...
How about supposedly screwing the pick-ups down in to the body, whilst raising up the posts to Deliberately get a more microphonic sound ⁉ (i've never tried it)
@@lazyrrr2411 , I have also heard that Duane Allman had some kind of home built preamp mounted on the side or top of his Marshall amp.
U.D. this is above and beyond.. Thanks for sharing your analysis of these beauties!
You're welcome, CD :)
That jumped-channel tone is TO DIE FOR....That JMP-50 is is in my top five greatest amps of all-time! 🎸
I would have to agree, Mike, now that I have had a chance to actually hear them in action.
And thanks for continuing to do the schematic to amp explanation. I really appreciate those.
You're welcome, Sean.
As always, The standard of these video's and the content are second to none......all my favorite things covered :)
Thanks so much, Harb :)
Uncle Doug, you have become a true Marshall guy in last two weeks! Congrats!😁
It's feast or famine when it comes to Marshall amps. None for seven years, then three in a month (there is one more yet to come).
@@UncleDoug But you are almost a Marshall expert already, I must say, after seeing your very good 1986 vs. 1987 circuit comparison and analysis. 👍
Hi Doug... these Marshall overviews are interesting to this Fender Freak... I feel that I can always learn something from them. Keep it up.
Since they are based so closely on the Bassman circuit, it's sort of like they are familiar, Bill, even though I have only worked on two, so far.
@@UncleDoug Just twins from seperate mothers...
It was a great video.... what a treasure of gear, amps and guitar! Very enjoyable, thanks UD!
Thanks, K. We all benefited from the generosity and trust of the friend who loaned all the gear for the video.
Another awesome Uncle Doug Production!
Btw Doug, your playing is improving very nicely 😎
Thanks, John. It's because I turned the demo duties over to Jack & Ollie. They are a godsend to my amp demos :)
Love the 1986 model sound ! And nice to see such a clean circuit, thanks for this video.
Thanks, Erik. Most viewers preferred it. You're welcome.
Fantastic circuit comparison Uncle Doug..!! Both of those JMPs sound fantastic.! Hartley Peavey told me a few funny stories on how he and Jim Marshall argued on who built amp circuits first. Thanks for the great content with added car show..!!
You're welcome, Mr. G. Thanks so much :)
Good punch and clairity on the 86. Thanks for the vid Uncle Doug, great stuff.
You're welcome, PG. Thanks !!!
Good Stuff Uncle Doug always look forward to the next video!! Thank you sir!
You're welcome, CD. Thanks !!!
Very nice Comparison and I wish I had you component sniffer 👍 I love those old Marshall Amps 👌
Thanks, Meik :)
Doug, If only we had teachers like yourself at my school I may have learnt a thing or two. Great job as usual
Thanks, Mark :)
Doug-you are the Best-all my questions answered meticulously !!!!
Thanks, David. We do our best to help our viewers.
Always impressively educational and entertaining. Thanks UD!
You're welcome, FWR.
Thanks for another great video Uncle Doug..
You're welcome, Dave.
Nice tour through the amp, thank you. Beautiful cars!
Thanks, Andrew :)
Chesus! So early I can still hear feedback from someones Woodstock performance. Cheers Uncle, great video. Michael
Thanks, MBR :)
Very nice! I am really learning from these comparative videos, thanks.
That's good to hear, Alan. You're welcome.
I love seeing you do Marshalls! Thanks! I love the 1987!
You're welcome, GL.
I dont know how to read a schematic, but i found myself enjoying every detail. Thanks again for another fun hour!
(Ps... i did catch one little mistake-at one point you called the EL34’s “EL84’s” , but we wont hold that against you!)
Glad you enjoyed it, BP :)
That is one lovely looking Marshall amplifier you have there Douglas. Whenever you spot a Hunts capacitor, serve an immediate eviction notice upon it. I remember how trashy Hunts capacitors were when they were new. Treat them like you would treat vermin.
Sprague capacitors have always been a favourite of mine, though I’m very impressed with IC capacitors.
I enjoyed watching this video, just as much as I enjoyed watching your last Marshall amplifier repair video ...thank you sir.
Regards, Phil.
Thanks so much, Phil. In this case, the Hunt's were successfully evicted.
Great Video Uncle Doug! It was nice to hear/see both amplifiers side by side.. also nice to hear them without all the knobs cranked to 10, with somewhat cleaner tones for Marshall's (also no Wha Wha's or Fuzz's/Overdrives/Distortion to mess with the tone).. I used a stock 72' Superbass with a 68' Basketweave 4x12 for years, and when I purchased my 1st Stratocaster 94' Plus Deluxe, I was surprised at the clean tones it could produce if wanted. Really enjoyed this one Master...
Thanks so much, Tom. I was surprised how clean Marshall amps really are. You have to go to ridiculous extremes to get any "fuzz"......which we did in the demo, especially the 1986 when jumpered.
Lucky you having access to either/both of these gems! If I had to choose I'd say I liked the tone of the 1986 circuit a bit over the 1987 - thanks so much for providing a great comparison!
You're welcome, Brian. Most viewers agree with you.
I wish I could buy stock in you, In the next few months your going to be VERY POPULAR in other words your going to hit the big time my friend. congrats.
Wow, thanks so much, AA. I can't wait. Jack is already shopping for boutique catnip :)
Thank you so much for the informative great video's! I love learning on this channel!
You're welcome, Michael.
Doug! As always is your video's a great inspiration! Keep it up man :)
Thanks, Peder. We will :)
Thanks, Doug! Great stuff, both amps and cars.
You're welcome, GM. Thanks !!
....Thanks Uncle Doug ! Great videos, subject, info and your style ...
You're welcome, Jamie. Thanks !!!
They sound awesome, Nice work, I think the two have a place and value, depending on the sound you are looking for.
Thanks, Hack. That's an excellent observation.
Uncle Doug, you done it up good! Thanks for using the Marshall cab! I strongly preferred the sound of the 1986, I hear a bit of Malcolm Young in that amp.
You're welcome, Darren. High praise indeed......thanks !!!
I spent 2 days watching your videos. I have to tell you that I have learned more watching yours than most of the thousands of all the other ones combined. I don't know if its your style or the material, I think I should have started with tubes. I'm really new at this about a year. and I have had so many Aha moments it felt like you were talking directly to me one on one . I can't thank you enough. Becoming a patreon after this comment.
Wow, thanks so much, Mick. We're really glad to hear that the videos are helpful and look forward to receiving notification of your patronage.
@@UncleDoug Thanks for the quick reply. I sent you a little something through pay pal. with a note, I hope you see it Thanks. Mick
Both your contribution and note were duly received.....and appreciated, Mick. Thanks so much !!!!
Awesome comparison !!!!! Thanks Uncle Doug!
You're welcome, RR1
Another great video Uncle Doug.
You are a very good guitar player as well as teacher. I liked your explanation of the amp at component level. This information is valuable to me with my current Marshall repair. The amp I have is a later model that has had the original board and top caps disabled, and a custom hand wired board put in place to reproduce a late 60’s model Super Lead Plexi.
My amp however is the 100W model using 4 EL34 output tubes.
After listening to both amps in your demonstration Uncle Doug, I would say the 1986 has a warmer richer sound. It sounds like the bridging of the two channels may have given the amps a bit of grit or dirtier sound from what I can tell on my iPhone’s speaker.
🍻 😎 👍 Cheers Uncle Doug !!
Likewise, Mike. Thanks !!!
I had one of these for many years, and it worked equally well for bass, guitar and keyboards
I can see how it would be suitable for such uses, H. Thanks !!
A neatly constructed, well-designed amplifier, which has been well loved and cared for. Having instructed Mil Std 2000, Category "C" Electronic/Electrical Assembly, Wiring, and Soldering, for 18 years, I must say that I have great respect for the layout and construction methods used to build these Marshall Amps.
I'm not usually one to scream "capacitors", I'm mostly in the 'radio and TV realm' of the restoration hobby/biz; here's the "however": I am of the understanding [my friends from the UK and Australia have told me] that "Hunts Capacitors" are even more notorious than "Black Beauty" and "Bumblebee" caps for shorting. BTW, this is coming from someone who installs 1-amp fast acting pigtails between the selenium rectifier and the power switch, in selenium rectifiers which have no corrosive issues, and test within reasonable parameters, versus the 1N4007/dropping resistor "shotgun" method. I believe there are justifications supportive of both views, by the way...
Thanks so much for your very helpful input, SE. Other viewers have expressed the same (low) opinion of Hunts Capacitors.
It's just a shame I can only give one thumbs up. The rods at the end deserved a good three by themselves!
Thanks, Gerry. I wish you could too. It would help negate the idiot(s) who reflexively (and inexplicably) give a thumbs down ;)
@@UncleDoug I was just thinking the same thing having got to see the rest after my bed so rudley called me last night.
Another Great video Uncle Doug!!
Thanks, BigJoe :)
Outstanding vid!!! Both amps are glorious!. 1987 sounded more open and 1986 abit 'snarky' at first. Funnily enough, i wound up liking this !
Thanks, GM:)
Great circuit and tone comparison. Thanks.
Thanks for watching, Kenneth.
This is wonderful information, Unc! I am poised to go and spend a weekend with Bruce Egnater to do my first amp build. The 18 watt exotic boutique "all red hat and no knickers" build will be a total Marshall-based puzzlement to me. So this video of yours is a great platform from which I can depart as I learn how to not kill myself in the search for tonal glory. I'd buy you some catnip in payment but .... well, postal regs and borders issues... maybe I could send catnip seeds for the kitties.... ???
You're welcome, Ian. I hope it helps you during your amp symposium. Best of luck with your build. Give Bruce our regards :)
Wow! Two plexis in three weeks!! And both at the same time!! I just fell off my chair 😎👍🏼
I know right? I was blown away!
We beat the bushes to find new amps to feature, guys. Nothing is too good for our viewers :)
Both are great sounding amps. It's hard to decide which one I like better!
That's very honest (and diplomatic) of you, MD. Thanks !!!
Uncle Doug testing out the amp playing some Billy Squier. Awesome!
Glad you enjoyed it, NY :)
Thanks, Uncle Dougie. 🙂
My pleasure, ES.
Nice amp comparison, Uncle Doug !
The 1986 bass amp has more of that stiff high tension sizzle, ala "Paul Kossoff playing live with Free" sound then the 1987 guitar Marshall amp.
Another great video !
Thanks so much, Jay. Excellent observation.
thanks a lot uncle Doug ... you rock ..from Quebec
You're welcome, Steeve. Thanks !!
Love the car show vids, too.
Thanks, Sean.
I have two 70’s Marshall’s. I just got the schematics, and learning to read and understand them so I can bias them ( I have training as a electronics tech) so I’ve been watching your biasing videos and especially this one has been (how should I describe...hmmmm. (The clouds are breaking. The sun shining through and a heavenly AAAAHHHHHHHH........) Thank you Uncle Doug.
You're welcome, Joe. Best of luck with your biasing project.
Another great video, really liked the explanation of the differences in the circuits, as audio amplifiers are not my usual repair fodder. Both sounded really good but I liked the sound of the 1986 a little bit better.
Nice to see another update on the feline menagerie, and yes the 2 lazy bums sure do seem to be getting along just fine.
Also nice to see some more of those really nice cars, and yep still really like that Studebaker, too bad the hood was down, would have been interesting to see if the engine was original or had been swapped for a Ford or Chevy.
Thanks so much for all your nice comments, M79. I'll bet both Marshall amps that the Studebaker engine wasn't a stock, original :)
Jack & Ollie, that was some fine guitar playing 😊 From Billy Squier to the recently passed away James Calvin Wilsey; bravo...
Glad you enjoyed the feline concert, Michael :)
Another excellent tutorial! Thank you.
You're welcome, Matt.
I did a little research and ARS is now making those caps that are the same size and color as the original LCR caps. The F&T's are great, and their tone is great. I've been using them for years, but the ARS are the same size and color as the originals (the F&T's are much shorter). I will have to try some and see how they perform. Thanks for showing it Uncle Doug.
You're welcome, Bert. Good luck.
ARS is a distributor out of Van Nuys, California. Their labeled capacitors are very good quality and they have the original values available; ie. 50/50, 32/32, 16/16. They even have a 32/16 dual cap. I don't know who makes the caps for ARS but they are very good.
Thank you for the information. I will definitely try a set of 50/50's on a Marshall.
Nice to see Jack is still on the job with the cat scans.
He is a highly motivated sniffer :)
Hey Uncle Doug, really Great videos of recent(not knocking your older videos in bit, I have enjoyed all of 'em!). Wopuld you ever think about doing a Q&A for your subscribers? I'm very Curious about you and what you did for a living. You really remind me of a good friend of my fathers' who lived in Syracuse that worked in the Transmitter Industry back in the 40s & 50s. He was a Ham radio Operator(Like my Dad is) and they were very close as they shared a similar passion in electronics. This is just a suggestion, but I feel that a few of your subscribers might liketo know some more about you :) ...All the best!
I am flattered that you would suggest it, Daniel. Several other viewers have said the same thing, and I am considering it for the future. Of my three previous "careers", only one was related (partially) to electronics. I am relatively a late-comer to this field.
Both are great sounding Marshall amps and I’d be happy to use either of them. There is a slight tonal difference between them but that basic classic Marshall tone is there in both. I’ve seen inside more recent Tube Marshalls and they’re certainly not built like that these days, I guess that they must still be reliable as they’re widely used. I loved the old Les Paul junior, I’d happily watch a video just featuring that. They’re one of my favourite guitars. You’re a very fortunate man to own that and the nice sounding old Telecaster you have.
Thanks so much, Henry. I don't own any of the equipment in the video or demo......it was all borrowed for the purpose of making the video. I definitely agree with your comments and wish you the very best.
Loving both with the P90 equipped vintage Jr. Lester (I think Johnny Thunders would love the geetar)! If forced to choose, I'd take the 1986
I FINALLY had a chance to sit and watch carefully. I have a 1986 Superbass MkII - the 100w monster - assembled in 1979. I acquired it 2nd hand and it was a superb bass amp but not much chop as a guitar amp as it'd stay clean all the way into brain flattening volume territory. I recently had it modded with a Post Phase Inverter Master Volume knob added and a few minor other changes to bring it closer to a Superlead. NOW it sounds great with bass and guitar - it's not as bright and aggressive as a Superlead but it seems there was some non standard stuff in the original circuit - probably a case of using what was on hand as you mentioned. I now know a little more about the beats - thanks!
You're welcome, Ray. Thanks for your input :)
All I can say is, Rusty would be proud !!
Amen! Rest In Peace Rusty
He wouldn't like the noise.....but he would love sniffing those big transformers.
@@UncleDoug Yeah, I know what you mean! Psycho Kitty made it to about 5 on the volume with my floor standing Infinity speakers before she vamoosed. I must admit I never made it to 11 myself, lol.
Both the cats and the wife were hiding out during the demo's.
@@UncleDoug one time I had a mouse take off running from under a folded carpet when I played a single loud chord in my basement at full volume on my Bassman piggyback... Had to laugh.
Both sound great ! As a kid i found a way to play through the family Grundig tube hi-fi ... its all i had, was terribly muddy and distorted . What i think I'm getting at is that we'll play through anything we can get our hands on even if it says bass amp on it 😃 turns out to be a real winner
Thanks, Ken :)
Plexi,s and Pickups ^^ Great video Uncle Doug.
Good catch, SM. Thanks !!!
Another great video !
Thanks, David.
Excellent video, the plate resistors were changed on the Amp. It also shows the mixer capacitor was replaced at one point. From my view a lot of the connections have been heated because the colored marking is missing. RCA never made a 6CA7 Power Tube, they are both Sylvania BIG bottle 6CA7. I agree with the Rectifier comments you made, but on the first video is a JTM50 not an JTM45. I provided a link on you first video.
Thanks for your very detailed visual analysis. I'm not sure where you get the "JTM45".....or the "JTM50", since the title of the video and the label on the plexi face both clearly state that it is a "JMP" 50.
@@UncleDoug Sorry I meant JMP
No problem, Con. I appreciate your interest and input.
Hey! I'm the 6th 69 "Like-er" of this video! Uncle Doug, we need to get you a serious "'80's Hair Band" Doo for all your new vids... It would be a nice way to thank you for yet another wonderful contribution to the world of METAL... :)
Thanks, Brad. I would also need a bunch of random tattoos and some leather pants.
Well, personally speaking, there are no random tattoos... there are simply never enough... thanks for another great video.
By random, I mean jailhouse tats that are poorly done, impossible to decipher, and meaningless.
Uncle Doug,
I so much appreciate your videos. I don't know why but your voice makes me feel that everything will be okay. I don't even understand what you are saying many times! I don't care! Thank you, Uncle Doug!
You're welcome, DK. I appreciate your kind words. Best wishes to you and yours.
Another fantastic vid. UD Rocks!
Thanks, UB :)
I came for the amp, and stayed for the cars. And glad I did at that.
So are we, Curtis :)
Man I love the look of these era JTM45, 1959,1987/86 Marshall amps. I know the JCM 800 is a great sounding amp, but they look cheap when compared to these older ones....just my opinion. Keep up the good work Uncle Doug, I’m enjoying my education from Uncle Doug’s amp tech University. (UDAT University?) You have the rare gift that all great teachers possess, & you take pride in your work as a true craftsman should.
That's great to hear, VK. Thanks !!! Glad the videos are helpful.
OK THIS IS EPIC again, thanks UD!
Thanks so much, K :)
The 1986 sounds to have a bit more heart, beef, and soul, the 1987 with an element of twang, but still a great overall platform. Thanks for making tube tech analysis understandable for laymen to grasp, your on-bench reviews of the widest variety of tube amp circuitry, and of course the entertainment and cat factors!
Thanks so much, Eric :)
A dream amp right there, in amazing shape!
Thanks, Bob. It really is pristine.
Both sound terrific! I’m not sure I don’t love the ‘86 best, really well rounded, bassy tone
Thanks, Ralph. Most viewers agree with you.
Nice. This is the amp that Malcolm used to get a different space in the mix to Angus who only used about 30 dozen superleads. 20 years ago they would have called you. I think they have all the rest of them
Thanks, OC. It could be :)
You have some "Wicked Games" going on there UD!! I really like the 86 circuit better myself. I am really enjoying these circuit run down videos also! Thanks so much! Say hi to Jack and the rest of the kitty entourage for me! edited to add I LOVE the Marshall speaker cab! It's also funny how something marketed for one thing ends up going in a completely different direction sort of like the "Jazz" Master that practically none of the Jazz players used but became the voice of Surf Guitar!
You're welcome, Jack. You're right about things working better for applications other than what they were intended for :)
Another beauty of a Marshal! And a great run-through! The output tubes were both manufactured by Sylvania, despite their differing labels. They are the coveted "big bottle" 6CA7s. All sorts of relabelling went on back in the day. The screen grid resistors are likely not original. And 32uF + 32uF value preamp filter caps would have been correct for those amps; the schematics you have are later.
Also, the tube-rectified EL34 amp in the previous video is no doubt original. EL34 amps with tube rectifiers are well-documented, even though a lot of Marshall guys aren't even familiar with them. It is also much rarer than this one!
Wow....thanks for all the detailed info, Ogo. I hope the owner of the two amps sees this.
much informative video...thanks for uploading
You're welcome, Abdul.
Thanks so much, Uncle Doug. I always enjoy your videos. ...are you also Tubalcain / MrPete222, by chance? I think you may be! I learned basic machining from that channel and now I'm leaning amp restoration from you, here. God bless you for sharing such amazing instructional videos and helping others learn skilled trades! You've helped my life, business and family through your shared knowledge.
Wow.....you're quite welcome, Rocky. Although I would love to take the credit for being Tubalcain, he does good work, we are two different people.
Such an awesome display of a timeless work of art. Interesting though with the 1986 bass amplifier during the demo and jumpering the guitar would have gone into distortion blocking but it seemed to have worked quite well.
Thanks, Eric :)
Great video! Thanks
Glad you liked it, AB :)
I agree Marshall was transitioning to Diode rectifiers at this point in time. Basically the difference between 86 and 87 is shared vs split cathode at V1. The beautiful thing with turret boards is that you can experiment with both circuits without harming the amps originality but saying that, I myself, would only do that with the replica I built lol. I would consider this a special a special piece and would highly recommend building a replica of this circuit. I actually used push/pull pot at one time where I could switch between shared and split cathode. High drama haha. Sting
Thanks for your helpful and informative input, Sting.
what a gem! Time machine material.
Awesome Channel!
Thanks, Nick.
I managed to squeeze this video in during my bach dinner this evening. Loved the side-by-side comparison of schematic, amp and tone (Jack has stepped up his playing in the past 2 months). Seems silly that I didn't know but I now know why they call it a Plexi. Got a question about the death cap. We call it that because we have grounded outlets, what did they call it back in the 50s? Thanks Doug, I'm off to clean up before my wife gets home.
That's great, Craig. Thanks so much. I don't think anyone even noticed the "death cap" until fairly recently, now that society has gotten all weak and wimpy. In my day, if you didn't get the heck shocked out of you at least once a week, you were branded a sissy :)
I have a Marshall 6100 LM 30th Anniversary It was stored for 10-12 yrs and then I decide to introduce it to my studio and when I turned it on the power came on with no problem, but when I clicked out of standby mode it immediately turned off and the main fuse was blown. At this time I realized that I had plugged into the lineout jack not the speaker out jack. So I corrected this problem and replaced the fuse and again tried with the same disappointing results.
I place it on my bench and did a continuity check of the primary and secondary XFR's the power XFR and Output XFR. In all cases the continuity od each side was good and no short from primary to secondary. The internal inspection was immaculate , I expected to need some compressed air to clean the chassis and it required no cleaning very pristine. Note: that the internal 5amp fuse next to the main fuse was found to be also blown. the other power protective fuses on the main power board were all okay. So no evidence of any burned components and all caps seems to be visually oaky no leakage or inflated tops.
So after watching you videos I concluded that I needed to buy a Euro tube cord only, Blue Tester, and Tripplite IS500 500w 4.6amps, and I built the currently limited circuit and already have a varactor. Based on your very informative and well-prodcued videos I realized that I need some guideance on how I should interconnect all these components. My gut is to place the IS500 first with respect to the power wall outlet then the varactor then the current limited (light bulb). Finally the 6100 which as you have demonstrated that gradually increasing the voltage will possibly recondition the CAPS. When my Blue tester arrives I planned to test CAPS in the circuit.
I know this is New Year's Eve so you probably will see this after the Holiday but I though maybe see by chance. Happy New Years and thank you for the help you provide all of us with these electronic quagmires we seem to always find ourselves bogged down.
My guess is that the electrolytic caps lost their ability to function during the long off-spell. Bringing the circuit up slowly with a Variac is a possible solution, allowing the caps to "re-form". I see no need for an isolation transformer, but would instead use a current limiter between the AC outlet and the Variac, then connect the amp circuit to the Variac, flip the Standby switch to operating mode, and gradually, over an hour or so, increase the voltage in 10V increments, monitoring the PV and PC. The current limiter will monitor the total AC draw and protect both the Variac and the amp circuit from further harm. See if this helps. The other option is to simply replace all the filter caps with new ones. Good luck.