I primarily watch youtube channels that revolve around old amps and how to fix them. I've noticed one thing though. When an old Marshall is opened up and we get a look inside, it's nice and clean. An old Fender, it's dirty and grimy looking. Am I the only one who has noticed this?
THANKYOU for your thorough documentation and sharing the xtra pieces of wisdom that you have gleaned from the experts that you have spoken to. I have a 1969 JMP 100w super lead in red tolex (rumored to once have belonged to Thin Lizzy, if the history I was given when I obtained it can be believed) that I am intending to service myself soon, and guys like you are helping guys like me not just be successful in our endeavors but also to prevent us from screwing up what amounts to PRECIOUS "rock and roll cultural heritage heirlooms". We might have POSSESION of these amps for now....but if we can keep from blowing them up, they will one day belong to future generations so that they will know the awesome sound that only these vintage amps can be credited with. Cheers!
What an absolutely glorious sound! It will be interesting for sure to A/B the before and after clips. (I just cannot imagine a better sound than that right now.) Congrats mate, it went to the right guy. Enjoy
Shit. Here we go again. This is going to be a banger Jase! I'll be following closely. Please don't mess with the looks of that beautiful, battle-worn tank.
Looks like a great project for you Jason. It's actually a tremelo chassis from a combo amp. Not sure about the power transformer, the proper 1202-118 Drake would have a B+ of around 430/435v at 120/240v A/C. Looking forward to watching you dial it in.
Nice! Can't wait to see the next video. I recently bought a Marshall 100W from 1973 which has (surprisingly) a turret board and mustard caps. I've kept the 50uF cans that were already replaced, changed the mid pot and the 1st cathode filtering. It sounds pretty good but maybe I can improve it a bit.
Very, very nice. I’ve been following your work for a while, very good job, very nice amps you build. Congrats. Keep doing great stuff man!! Looking to this video I’m thinking if restoration is the right word for what you want to do with that amp. It’s your amp and you do what you want with it, what makes you happy and satisfied. However if it doesn’t go back to original with tremolo and each and every detail in the circuit, it will be a modified amp, which is good also, because, like I said whatever makes the owner satisfied is good. That’s how I see it. I don’t have the hype many people have about old things, collector’s stuff, bla,bla. I prefer a pristine looking and working new thing even when built to old specs. That said, I do respect the concept and people who likes it that way. So, I’ll be looking to see and enjoy the following videos. PD: I’ll be using the relay boards and midi I got from you on one of my designed amps very soon. Thanks for your videos. They are very helpful.
Those 1 ohm resistors look like 1% military metal films.... I bet they are pretty accurate. And if Joey Voltage said 315v, you can take it to the bank. That dude is a wizard. I would suggest keeping the filter caps at 50/50 on both for a 50 watter. If it were a 100 watt amp, lowering the uF on the screens works.
That front panel is....interesting. I make highly authentic Plexi reproduction panels (metalface too) and so I'm very aware of the details of these panels. I don't recall EVER seeing an "authentic" JMP Plexi panel with the large block letter JMP logo before. And I've also never seen that texturing in the gold layer. Makes me suspect it may be someone's recreation since in '69 Marshall had very much settled on the panel graphics and wouldn't have likely changed the logo for a small run of amps. I'd also expect the deterioration of the gold paint to have gone a bit green as the original panels were painted in bronze powder based gold paint. That this has NOT gone green despite the deterioration of the finish also supports my idea that this panel is a poor reproduction. I make plexi repro panels that are made with the original style bronze powder gold so they WILL turn green with time and age just like the originals.
A shared cathode in a '69? Was that a thing in the tremolo models? I thought Marshall had moved to the split cathode in '68 but the only consistency about Marshall during this time is their inconsistency.
Hey! Nice amp! Would you be willing to have a look at some pics of mine? Its a 1969 JMP 50 Tremolo, and I have some curiosities about it, especially because it has a tube rectifier. I was trying to figure out if the tube rec was stock. Its tricky though because where the tube rec is, it looks like there used to be a can cap strap. But the second can cap thats inside (on the side) looks legit. Honestly, it all looks pretty good, but the dang tube rectifier is whats boggling me lol. Dave F said it looks like a mashup of a Black Flag and a JMP 50w T, but Im mostly curious to find out what it started life as, and would just love to get some insight into how its wired currently. Looks like it had some mods at one point that were undone.(some empty 1/4' holes on the back and an empty preamp tube hole. Other than that, fairly nice. Some caps changed, quite a few OG, and the Power Transformer is a MM, but the OP and Choke look OG.
The cleans sound wonderful! Do you feel like a 50 watt is dramatically different in tone than the 100 SLP. I only have 50 watters and one 40wt(Fender). Am planning a 68' 12 series SLP build next.
@@HeadfirstAmps Hahaha Nah keep it stock, lol. But if you don't....being one of my favorite album tones - did George Lynch use SIR#39 on Back For The Attack? I've seen claims that GL used it on that album and the prior Under Lock and Key tour, before Slash "borrowed" it from SIR for AFD and beyond. Thought is was an extra 100k/2.7k/680n stage, with the other triode used for a loop recovery (op-amp send). Schematics used to be over at Caswell's website. Obviously, the trem circuit re-purposed to get the 12AX7 for the job.
Wonder what to do with that can cap, you've got a shared ground on it so using both halves for separate circuits and forcing a shared return current back to their supply is never the best idea. I'd be tempted to mount a 16ufx2 can to the side for the screens and run them in parallel and then use the 50/50uf for the PI and see whether I prefer it at 50uF vs 100uF. The 27K(?) NFB CC resistor on the 8ohm tap, I think Dave F. said Ed had 47K on 4ohm. Did the treble peaking caps in these amps drift up or down, or nothing typically? For my own build i'm wondering if that 820R on the CF is still 820? The amp really does sound excellent right now. Is that normal channel a 820R/330uF cathode?
It is definitely close mic’d. And tons of reverb added. Possibly an eq an compression. It sounds like the power tubes and speaker sounds to be pushed pretty hard. So my guess would be an isolated cab and no attenuator
So,these are just circuits,right?…not magic..So I am wondering is there any sound difference if you build a clone of a specific year model amp,will it sound the same??…..if not,what does it come down to,transformers,old components,component drift,etc??….Just curious how close you can get,building a clone of a certain amp…..or are there things you can’t replicate?…
I mean an amp this old you’re basically ‘paying the iron price’ cause the irons the important thing. I’d be more concerned for the power/output transformers health if it hadn’t had new caps.
