Marshall Popular model 1930, circa early 70's

Here's an amp you don't see every day, a Marshall Popular 1930 model. It's a 10 watt 2x10" speaker amp. I've probably worked on 4 of these in the last 25 years, they are quite uncommon though not as rare as the really sought after and far more costly 18 watt 1974 model.

These apparently were only made for the European market so you'll need to either buy a step up transformer or replace the power transformer for domestic use. I know. Replacing a transformer is sacrilege. Whatever. Stick the original in a box and put it away until the day you sell the amp.

This came through with a problem all of them seem to have. Noise. Particularly buzz and lots of hiss. This particular amp was, um, 'converted' to an 18 watt model. A 6CA4 tube was added in place of the silicon diode rectifiers, the output tubes are the more desirable 6BQ5/EL84 tubes rather than ECL86 and another 12AX7 tube was added. Nice thing is all the socket holes are already there as these seem to share the same chassis as the 1974 model.

The intention of the job was good, the execution not so good. I did like the normal channel, it broke up immediately as a result of there actually being an extra gain stage.

So first thing to address was the hum. That was easy. change the filter caps and cathode caps. Hum gone. The challenging parts were: dead tremolo and buzzzzzzzzzzz hisssssssssssssssssss. Un-useable at low volumes. Turn it up and rock out and it's heavenly. You stop playing and you want to turn the amp off.

The tremolo usually dies from dead caps. You know, those 3 in a row typically ceramic caps. Tried that and no life. In this amp the cap going to ground on the tremolo stage was a .1 from the factory. I changed that to a .047 and started getting some oscillation. But not good enough. I noticed when the person modded this amp they changed the power supply resistors to higher values. My guess was they were as frustrated as I was about the buzz and this was an attempt to clean it up. I used the stock values and voom voom voom voom. Tremolo is roaring back to life. And....more buzz and hiss than before.

Yes, already tried new preamp tubes. Also changed load resistors, took out gain stage to see if the stock circuit was quiet. Nope. It all comes from the tremolo oscillator / gain stage. Pull that tube or alligator clip the signal to ground and it's quiet like a dead fish.

Also pulled all the pots and sanded the front of the chassis to tighten up the signal grounds. A minor improvement. Marshall used mechanical grounding in those days. Sometimes maybe in certain conditions, corrosion can happen and you get noise.

But that didn't solve the problem. Worked like a charm in other amps. Rats......

Time to resort to the forums. Type in Marshall Popular noise hiss.... Took me a while to find this problem addressed but I did find it. Someone post this question, a discussion followed that got heated and ugly as forums can do. (These amps are crap! No they aren't! Piss off! Moderators shut this down!). One person attributed the issue to hearsay about the phase inverter. Bollocks. But one person said this: "It's a flawed design. There is no gain stage between your guitar and the volume/tone controls thus causing excess noise." My first reaction was "WRONG!" Add gain, you add noise. This makes zero sense to me. And his comment generated no other comments. So being that it generated nothing and I was bored of this amp I figured he was on the right path.

So I tried it. Moved some wires around so it's more like the 18 watt (I've built a dozen of those, they are quiet!) and lo and behold, QUIET! Minimal hiss, no buzz, great sound.

Amp is loaded with the original Ceslestion 10" speakers. Always a bonus. I did wind up swapping out the power transformer just for ease of use. Plus, my client has a nice house with beautiful things. Having a step up is just kind of ugly. Which part did I use? The Mojo 18 watt power transformer. I did add a 100 ohm 25 watt dropping resistor between the rectifier and the first filter stage. This got it from the 350V to 325V range which is close to original.

So my take on these? Stock they really aren't that good. And the price people ask for these is stupid. Modded they are great. The complaints about them, noisy and thin sounding, are well founded. I, like most of us, prefer quiet and full sounding. They have the potential for that. But don't pay $2500-$3k for one. I'd sooner buy an 18 watt clone for what I want and spend the rest on a ticket to Italy. I would love to see more sanity in the vintage market. If these were great out of the box I'd happily pay what people ask. They are a cute little recording and club amp. When you've spent a lot then you buy into the anxiety of "will making it functional make me lose all my money????" To me something is only worth anything if it's useful. Fortunately my client likes things that work and sound awesome over just things to look at. What rocks stays, what sucks goes away. That's just sane. In the end, I really like this amp now. I wouldn't think twice about taking it on a gig. It really does give up a beautiful sound that is right between a Marshall and a good Vox. With my Fender guitars it's good and clear. Humbuckers it goes into full bodied overdrive without ever getting mushy.

-J

1967 Marshall JMP "Bluesbreaker" 4x10" combo. One of the greatest amps of all time!

This was a fun project, and the 2nd most valuable amp I've ever worked on, the first being a Howard Dumble that belonged to a famous guitarist (not all that impressed with that amp, I would sell it and buy 5-10 of these!).

I've always wanted one of these. They are quite rare. I don't think any amp has surpassed the early 'plexi' Marshall era in terms of sound and style. Looks do matter and these amps are quite beautiful to look at. And of course, they have a special sound as well. Nothing quite like them. Clear, warm and beautiful overdriven sound when pushed. This amp is essentially a Tweed Bassman with tremolo circuit wise but with a much more present mid range.

When I received this amp it was quite a mess. It had been badly damaged in shipping. Poor packing? Maybe. Marshall combos are tricky to pack properly. These amps can command up to $15k so in my opinion it's best to ship the chassis separately. That is a weak part of these amps, how they are mounted.

It's heartbreaking when this happens. Fortunately, everything was fixable and my client decided not to send it back. The company he bought it from are good people and they payed the bill right away. No insurance battle for my client....

So this amp required quite a bit of gluing and clamping. Plenty of doweling as well. A couple filter cans were damaged and some components became unsoldered. The lovely Mullard 5AR4 tube was destroyed so I found a good deal on a NOS one. We're not going to load up a Rolls Royce like this with cheap new glass. No sir, not gonna happen!

Now the crux of this article. The unreasonable fear of 'originality' and 'collectibility' and what that does to a technician.......

Once I got into this amp, and it was gone through by what I assume is a good tech, I found a few issues. First, the Russian tubes were biased hot. 95ma each. These early models don't have a trim pot for bias. My opinion? Screw your 'originality' and put a trim pot in there! Running this amp this hot could kill the output transformer and possibly the power transformer! I was alarmed at seeing this but I've seen this many times before. The fear to alter something to make it ACTUALLY WORK properly. So I added a 22k trim pot. Took 5 minutes to install. Do it. If your customer freaks out about a change like this, you don't need to sell your amp to that person. He/she is unreasonable.

Had a private audience with George Gruhn last month. His words: "If it's old it's been worked on. Even a Stradivarius has a new fingerboard if it' been played." Enough said! My job is to keep important parts like your priceless transformers safe. In this amp the transformers and speakers are original and that is a miracle at 49 years.

Now the next problem. The speakers. At low volume you could hear this bzzzzzzzt as the note decayed. All 4 speakers were bad. One was not moving at all due to a frozen voice coil, the others were all rubbing. At higher volume one would think "oh this rocks". Inspect each speaker. It's important to do this! And it's worth having these re-coned. I had these done at Speaker Repair Pros in Los Angeles. I don't know of anyone here in New York that I trust to do these. One place I called after the third time the man on the phone said "you can just buy new ones cheaper" I finally said "you just don't get it, thank you for your time...." So off they went to Los Angeles. They did a fantastic job as usual!

So why was this amp sold with 4 bad speakers? I don't know. I attribute that to the same fear I wrote about above. In fact, in all honesty I refused to hear it myself. I was a bit afraid to tell my client he needed to get the speakers rebuilt cause I've dealt with many unreasonable clients who are so afraid their amp will lose all of its value. Bollocks to that! And fortunately my client knows better. He want's an amp that kicks it good, not one that will just be looked at!

I love the old logo on these speakers. Classy as can be.

Link to Speaker Repair Pros. They rock! https://www.speakerrepair.com/

So next was the output tubes. We went for Siemens EL34. This amp was built in the first year Marshall switched to EL34 tubes. My favorite year for the old Marshalls!

Biased this pair at 35ma each. Good safe place to run this amp. I also added a pair of 1k 5 watt resistors for the screen grid. The early Marshall amps didn't have them though curiously enough the JTM-45 loaded with 5881 or KT66 tubes had a 470 ohm resistor in this place. Trouble is when you blast this amp without those resistors in place the tubes draw a lot of current and you can pop a tube. You lose a negligible bit of tone by installing them but, it's worth it for the extended tube life. I think it was fine at one point when you had 800 volt Mullard El34 tubes available, but even the Siemens tubes should have those resistors in place.

The Siemens EL34 is by far my personal favorite EL34. Smooth and creamy, no harsh overtones like modern tubes. They were original equipment in 80's 800 Marshall amps and I've seen them go for over a decade being gigged with on a regular basis. And, amps back then were far more brutal on their gear......

Preamp tubes survived, and they are all Mullard long plate 12AX7. The finest for this amp!

One thing about the old Marshall amps the younger folks don't get is, they are 2 channel low gain amps. They evolved into the metal monsters we know and love or hate. These early ones are just as suitable for a jazz gig. In fact, they sound absolutely beautiful for those who want a nice clean tone. Jim Marshall supposedly hated his tremolo circuit but I found it to sound really nice.

These amps are probably the most guitar friendly versatile amps I know. A Tele, Strat, 335, Les Paul, big old Epiphone Jazz box, all sound great through one of these. The first Marshall I ever bought was a '77 JMP 2 input head. Got it for $200. Back in those days we didn't really have all this "true bypass' goodness. Pedals robbed your tone. But with that amp I didn't miss much. There was so much tone there I could stand to lose some. I was sold. My Fender Super Reverb was sold too. That amp was tough as could be. I wonder who has it now?

Amp sounds nice and tight now and is being loved in a happy home.

-JB

Trace Elliot Velocette. Oh, modern, amps. Why so lazy?

Had one of these on the ol' desk today, a Trace Elliott Velocette. I remember when these first hit the scene. The crazy 90's "there are no good cheap tubes except EL-84s being made so let's make little boutique sorta VOx sounding sorta Marshall sounding amps" era.

This amp came to me dead. No sound, no lights. Fuse was good, I had a hunch it was an internal fuse or the filament was dead. I haven't seen one of these in years but last one I worked on had a filament line issue.

 All tubes test good, high voltage is good. Yup, too much Bimoze on the filament line.

What's a Bimoze? I really don't know. I just like saying that.

So anyway, these amps are built in the typical modern fashion. With a crappy mother board where most of the components are attached. This includes your tube sockets as well. I never liked this. I'm not opposed to p.c. boards, but come on. Hand wire those tube sockets will ya? It's just better and more reliable. I know, I know. It cuts into profit. I'll shut up.

So the filament line comes off the power transformer into a connector that gets connected to the p.c. board that gets connected to another smaller connector that has wires going to 3 other connectors that connect to each tube. See something wrong with this sentence? It's a run on sentence and I say connector way too many times.


Photo of where the filament line connector meets another connector. Look at all that hot glue..... Got real handy with a razor today. Also notice the heat stains around the smaller black connector.

The underside:

This amp isn't very hard to get apart, that I appreciate. I just turned down working on an amp that I knew would be a nightmare. Life is too short.

More underside:

Hard to tell but wherever there is high current, there are cracked solder joints. This means filament line, high voltage line and speaker. Best to just touch up all of them while you are in there. Also touch up joints on jacks and pots. You can see what I'm talking about if you have a magnifying glass.

Connectors removed:

I wound up hard-wiring where the connector went to connector #2 on the first power tube. Lights on!

But..... after I put the amp back together, the other 6BQ5 tube wouldn't light up. Whack a Mole on such a simple amp! That connector was bad as well. In order to un-solder these connectors you need to remove the tube sockets. Um, EFF THAT!.

So I wound up removing all of these crappy connectors and hard wiring all of the sockets on the other side of the board. Now this little feller makes music. And sweet music it does make. These are really nice sounding amps. Almost has a 'gypsy jazz' quality to it. Warm and dry, cuts nice. They are cathode biased so you may pop in fresh tubes at will.

Speaking if which, one tube did start red-plating. They were just horribly mis-matched so I popped in one that was close. The only sets I have are JJs. Lovely sounding but I popped in 2 sets and they both started red-plating! I don't trust JJ EL-84 for class a operations. They are great for a Blues Jr properly biased but even in this amp, I don't like the risk.

Modern tubes.....bah.

I do like the styling of this amp. It looks like a cross between a vintage British racing car and a French bicycle.

Laziness #2:

Why write the serial number in pen?:

Can you read that? Oh well.

I would love to get one of these and gut it entirely then build a proper amp inside. But even stock, yeah, I would gig with this amp. It's strong point is that sweet, friendly voice it has. More my style then a Fender Pro Jr, which is a similar amp in some ways. I'm a huge fan of cathode bias. The sound produced is infectious.

JB

1978 Marshall JMP 50 watt combo

Yes. That's all I need to say.

These are fantastic amps. This one was blowing the H.T. or high voltage B+ fuse. We had hoped it was one of the 6550 tubes but unfortunately the output transformer was cooked.

When the H.T. fuse pops 9 times out of ten it's just a power tube. Once in a while it's a shorted filter can but every so often it's the output transformer. That makes for an expensive repair. And the sad part is it does tend to hurt the value whether it sounds better or not.

Here's the ultra simple control panel. Gain, Master, EQ and presence. You really don't need any more with an amp that has this much sound. These are known as rock n roll amps but in the right hands can be good with any style. Someone clipped out one of the treble caps, the one on the volume knob. I owned one and clipped out both of them. I don't need that much treble and clipped out you can simply turn up your treble and presence if you need it.

This one has the original speaker intact. A pair of lovely 30 watt "Black Back" Celestion speakers:

So what output transformers do I like these days? I'm a Mercury dealer and I also deal Mojotone as well. For the price you can't beat the Mojo. I believe they are made by Heyboer and they are first class transformers. Friendly right out of the box. The Mercury product is expensive. Very expensive. I like there iron very much but there are only a few things to me that are worth that much more. When I was building amps for people I used their ultra expensive "Radio Spares" iron in a JTM 45 I built and always used their "Radio Spares" output transformers in my 18 Watters. They simply can't be beat in that capacity. I had the pleasure of playing my JTM amp next to a real "coffin logo" '62 model and mine was so close. I sold that amp for about $1300. The '62, granted is ultra rare, but cost around $20,000. So parts makers like Mercury and Heyboer helped me lose my lust for old amps! Why spend all that money if my intent is to enjoy it?

But for general repairs and price, the Mojotone iron can't be beat. I've used many of their transformers with dynamite results. In this Marshall I can say DYN-O-MITE! It's got it where it counts and was a relatively easy install!

JB