Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: El Scorcho on March 18, 2018, 09:32:21 AM

Title: Marshall 5010 Needs Help
Post by: El Scorcho on March 18, 2018, 09:32:21 AM
Total noob here, with little electronics experience beyond wiring guitars. I just picked up a 1982 Marshall Master Lead 30 combo for 50 Euros, so it's not like I was expecting much. I had a Lead 20 back in my teens that I remember liking alot, but this thing sounds like a moist fart.
   I opened it to clean it out and saw that D2 is missing entirely and D1 is not a diode, but a 2n2 Cap. Someone has tagged the bottom of the chassis with a permanent marker W.A.M Workshop And Music.  Has someone actually done something clever, or really stupid? Even on low gain setting there is an unpleasant 'fizzy'coating. I gave W.A.M the benefit of the doubt and swapped out the Red McKenzie out for a Celestion G12L, which made the moist fart sound like a bit more carefully executed fart, so now I'm leaning toward stupid.
 I've researched the other 5010 posts here, and bought a 500k reverse log to replace the V1, but now I'm wondering if it's worth the bother. Looking at the Schematic, D1 and D2 seem to have something to do with Voltage supply, and I wonder if this mod hasn't burned out something else. The amp powers up and seems to work  - it just sounds more like a 1-knob, particle board starter amp from an old Sears catalogue than a Marshall.
    I'm going to go ahead and replace D1 and D2 with fresh 1N914's, and hope that helps. Is there anything else I should worry about? Like maybe R23/24 and C19/20, which seem to be in the same loop? Would this mod have ragged out the op-amp? What would the point of such a 'mod' be? A poor man's variac?
    Sorry in advance if I'm wasting anyone's time, but certainly would welcome some insight.
   
Title: Re: Marshall 5010 Needs Help
Post by: phatt on March 18, 2018, 09:41:13 AM
Hi and welcome,, please post the schematic or link it,, other wise quoting part numbers means nothing. :tu:
Phil
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 18, 2018, 09:58:42 AM
My alpologies, here's a link

   http://www.drtube.com/schematics/marshall/5010.gif (http://www.drtube.com/schematics/marshall/5010.gif)


Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on March 18, 2018, 11:21:09 AM
On the input to the first opamp/ pin 5, there are two back to back diodes.
These diodes are used to limit the input signal to the opamp. (to prevent damage to the IC)

Why D2 was removed and a cap was installed at D1 I do not know.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 18, 2018, 12:52:19 PM
D1, D2 are only there as protection in case the input signal gets larger than 15v peak.  Unlikely from a guitar.  Removing them damages nothing.  A cap in place of one?  Might be there to squash unwanted oscillation.  I doubt it is the problem, but it surely can't hurt anything unless it is shorted.  Unsolder one end of the cap and lift it from the circuit if you like, that tells you if it is causing trouble.

R23,24 are just power supply parts.  The amp runs on something like maybe 25v plus and minus?  20v?  18?   In any case, too much for the op amp ICs, so those two resistors drop the voltage down to 12-15v, you tell me which.  Does the IC have similar plus and minus power on the corner pins?  C19,20 are just decoupling caps for those 15v supplies.

So it sounds bad?  First, are the two power supplies right at the IC similar voltage, other than polarity?  Pins 1 and 7 of the IC are output pins, is there DC voltage on either?

VR1:  you replaced a 22k pot with a 500k pot???

As to fizzy, have you disconnected the internal speaker and listened to the amp through some other speakers?  Possible rubbing voice coil.

Aside from it not sounding good, do the gain and master controls and the tone controls seem to work as expected?
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 18, 2018, 01:57:24 PM
Thanks Jazz and Enzo for having a look
    I dont have any testing equiptment yet to measure the IC output voltages. I'm just getting into making my own pedals and will have one soon. Just from looking in the amp-which is similar to the Guv'nor pedal, I could see parts were missing from the scematic. I'm glad it isn't a problem, but plan to return it to stock
   The sound quality isn't good-even though the amp works. Replacing the speaker did make a noticable difference in opening up the high end, but there is still an unpleasant and unatural sounding distortion as the note decays.
     I Have the new 500k rev log pot, but haven't installed it yet. I'm waiting on a parts order for the 1N914's. But the preamp and master gain work as expected.
    The low input jack was pushed inside the chassis so it couldn't be used, but is jumpered to the high sensitivity jack.There is no oscillation from the high gain jack. The preamp gain doesn't do much until the 8-10 range, as expected. Not sure if someone tried a jumper mod on the inputs, or if it is stock-on the scematic there is only one input jack.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 18, 2018, 03:25:22 PM
May I suggest not "returning it to stock" until you know that is part of any problem.  It could even be something Marshall did in later production.

Sometimes a change in one place is involved with a change elsewhere.  If we "change back" the one thing we see, we might not change back the other half of the equation that we didn't see.  Then the amp has a new problem on top of the original problem.


It is tempting to start changing parts just to get something going, but it is better to consider each action.

You really need to buy or borrow a good meter at the very least.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 19, 2018, 08:53:22 AM
OK. I resisted the urge to spray hot solder and got a meter to check the IC voltage.

The only two pins that gave me a reading were on opposite corners, I think the + /- Vcc pins.  I got -13.68 and 13.81. The readings fluctuated a little bit measuring them again, -13.87 and 13.78.
Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on March 19, 2018, 11:26:24 AM
Those voltages will work.
The second test is to flip your meter to read Volts AC.
That will measure the 'ripple' of the supplies.
Ideally, it should read zero.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 19, 2018, 12:27:14 PM
I got zero's across all but 1 of the pins. I think pin 8 is the Vcc+, which read 28.8. It gave me alot of fluctuations from 0 to 5, 16, etc, but 2x it gave a stable 28.8 reading.
Title: Re: Marshall 5010 Needs Help
Post by: g1 on March 19, 2018, 02:29:08 PM
Try reversing the probes where you have that funny reading.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 20, 2018, 04:20:21 AM
I reversed the probes, which gave me a reading of zero at the + Vcc pin, and every other pin but the -Vcc, which read 28.8. Switching the probes again gave me 0 across all pins but the +Vcc, which read 28.8 to 29.0.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 20, 2018, 05:33:06 AM
It is unlikely your 13v supplies have 28v of ripple.  Your meter is confused trying to read AC voltage while DC is present.   Two options:  one is to get a more advanced meter.  Two is to put a cap in series with your probe.  Like a 0.1uf or some such.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 20, 2018, 10:02:53 AM
I'm certainly willing to admit I could have set the meter wrong. I just got it in yesterday. I followed the manual and set the dial to V symbols, but aside from that not sure if it's dialed in tight.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 20, 2018, 10:53:48 AM
Things You Can Tell Just By Looking At Her:

I found alot of electrolytic caps on the board that are not the same value as the scematic.

C2 is supposed to be 0.1p, its 2,2u, 125V

C13 is supposed to be 47n, its 100uf, 125V
c14 is supposed to be 2u2, its 100uf 25v
c17 supposed to be 100u, its 100uf 25v
c18 supposed to be 470p, its 22uf 25v

c11 is supposed to be 47n, its a strange looking disk, with 5000 printed on it
c12 is supposed to be 220p, its .047 orange drop

c20 is supposed to be 100p, its 2200uf -35V
C21 is supposed to be .22u, it's 2200uf 25v
Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on March 20, 2018, 11:23:57 AM
I see C20 as the negative rail voltage cap for the ic's.
The schematic shows it as 100uf. (not 100p)
Title: Re: Marshall 5010 Needs Help
Post by: g1 on March 20, 2018, 12:31:49 PM
Your amp is a different revision that does not match this particular schematic.
Do not try to match up parts to an incorrect version of schematic.
You opened it up to clean it.  I assume that means it was all working well.
Do your cleaning and play it to see if it has any defects.
If it is broken try to find the correct schematic revision.

If you can, post some pictures of the actual circuit board inside.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 04:09:25 AM
It works-It just has an unpleasant sound. Even on the lower gain input there is a cruddy blanket of harsh fuzz wrapped around what would otherwise be a useable tone. Some of the parts seem a bit 'aftermarket'.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 04:10:58 AM
Here's another obvious replacement.
Title: Re: Marshall 5010 Needs Help
Post by: phatt on March 21, 2018, 08:05:52 AM
It works-It just has an unpleasant sound. Even on the lower gain input there is a cruddy blanket of harsh fuzz wrapped around what would otherwise be a useable tone. Some of the parts seem a bit 'aftermarket'.
That sounds like crossover distortion the output pair may need rebiasing.
Being a budget model it has no bias trim.
Someone here might know what to alter as I'm not sure.

If you want to establish if it's Xover dist;
at a Clean medium volume just pluck One string  only and let it ring out.
Now with your ear close to speaker listen as the note dies away if there is a fizzy edge on the note then it Xover distortion. Often mistaken for a torn speaker cone.
Phil
Title: Re: Marshall 5010 Needs Help
Post by: phatt on March 21, 2018, 08:07:32 AM
Here's another obvious replacement.

The brown goo is glue which is normal.
They often glue large Caps to help stop vibration cracking the solder pads.
and often mistaken for a leaky cap. 8)
Phil.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 11:43:50 AM
 I hooked everything back up to test it like you suggested,and that's EXACTLY whats happening - no matter which input, no matter how clean I dial it in, I still get that farty speaker-fizz.

Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 11:44:45 AM
Thanks Phil!
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 01:58:49 PM
Ok, I found a Teemuk post about biasing. Looking over the schematic again, I'm wondering if D1 and D2 have something to do with It. That might explain why D2 is missing and D1 has been changed to a small value cap.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 21, 2018, 02:13:08 PM
Output transistors are biased by TR3 and associated parts.  D1,2 are nowhere near that, they are at the preamp input.
Title: Re: Marshall 5010 Needs Help
Post by: g1 on March 21, 2018, 02:29:19 PM
And Enzo is speaking of the schematic you posted, not your amp.
You say you have 2 inputs, the schematic is for an amp that has one.  And the schematic shows a DI out and headphone out, do you have that?
Also having a quick glance at your chassis, I see D3 and D4 which I can't find on the schematic.
So do not trust that schematic, there must be another version for your amp.
Suggest you try contacting Marshall and see if there is another version drawing available.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 21, 2018, 02:42:27 PM
Yeah, I have I think the earliest version. The only schematics I can find are dated 1988 to 1990. 2 vertical inputs, but no  DI or headphone out.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 21, 2018, 08:39:19 PM
I am looking hard for a suitable schematic.  I see the "missing" diodes with the cap in place.  They are near the IC.  How about this idea:  The diodes were originally reverse coupled pair in the IC feedback loop for clipping, and they decided to get rid of them, leaving a cap for stability.  MAybe?  I see the diodes have a + sign at opposite ends.

Look on the underside where the diodes were.  Are the two ends wired in parallel?


Your output transistors have 1982 date codes, if that helps.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 25, 2018, 05:00:42 AM
Thanks Enzo! I contacted Marshall about another version of the scematic. They said they have the a schematic, but can't gaurantee what version it is, and will get back to me. I haven't heard anything further. I finally got under the circuit board, and D1 and D2 seem to be linked together.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 25, 2018, 08:36:29 AM
The pic isn't the best. What's going on is that ends + and - ends of both D1 and D2 have been jumpered together on the bottom of the board.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 25, 2018, 08:44:51 AM
If you think there were clipping diodes in there originally, I would be interested in putting maybe a yellow Led on D1, and a pair of germanium diodes across D2 for more asymetrical clipping, but I don't want to start a fire if it's not for clipping.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on March 25, 2018, 12:14:34 PM
Which backs up my thought that they are back to back feedback diodes across an op amp stage for clipping.  And they were later removed, either as a mod or as a production change.  I could be wrong.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 26, 2018, 12:58:38 PM
I got an e-mail back from Marshall. They won't give out a schematic, or even confirm there is an alternate version. If I want it returned to stock, I have to send it to them.
Title: Re: Marshall 5010 Needs Help
Post by: phatt on March 27, 2018, 06:35:47 AM
I got an e-mail back from Marshall. They won't give out a schematic, or even confirm there is an alternate version. If I want it returned to stock, I have to send it to them.

Does your Amp look like this?
https://www.ebay.fr/itm/MARSHALL-MASTER-LEAD-COMBO-5010-30-WATT-MOSFET-SOLID-STATE-1986-MADE-IN-ENGLAND-/141778294919

If you can't find a schematic then take clear pictures of the inside,
Both sides of PCB if it's possible. :tu:
Phil. 
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 27, 2018, 01:44:12 PM
Hi, Phil. Mine looks very similar, only the two input jacks are verticle, and there is no line out/headphone jack. I'm not at home, but will get some pics when I get back tomorrow.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 27, 2018, 02:48:33 PM
  I found a short video of one just like mine, with the same ugly crossover distortion. Funny, the horizontal and single input versions seem to all sound great.

Watch "Marshall Master Lead Combo - Fizzy Distortion" on YouTube
https://youtu.be/y1osT39OSjs (http://Watch "Marshall Master Lead Combo - Fizzy Distortion" on YouTube
https://youtu.be/y1osT39OSjs)
Title: Re: Marshall 5010 Needs Help
Post by: g1 on March 27, 2018, 03:27:52 PM
It would be fairly easy to adjust out the crossover distortion, probably just a resistor value change, but you would have to draw out the schematic for the power amp section as the newer schematic uses different components there.

As far as changing the amp back to "stock", it is probably closer to stock than you think.  There seem to be references to the older version as the "red mckenzie speaker" version.  If you could get in contact with someone who has one that would take some pictures of the circuit board, it wouldn't be too hard to figure out which components have been changed in your amp.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 28, 2018, 08:50:19 AM
Top
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 28, 2018, 08:51:04 AM
Bottom
Title: Re: Marshall 5010 Needs Help
Post by: phatt on March 29, 2018, 08:16:07 AM
I listened to the video link, I can't help but note that most of these small SS marshall's had a lot of distortion because that is what the market dictated. Even some Valve marshall's added cross signal Back to back diodes for some earlier crunch/distortion. (same idea as D1&D2 in this amp)
The buyers wanted the distortion. ;)

I've looked over the PCB and it looks stock except that D1&D2 have been removed. This would actually remove some distortion and deliver a cleaner and bigger signal to the power stage,,,BUT as the power stage is a very basic design it may now be distorting even more so :-\ Hard to know cause I've never worked on these Amps. xP

I'm fairly sure;
You could tap into the Volume (VR2) with an MP3 player or other audio signal which bypasses the preamp and hear if the power stage is running clean. If it's clean then the problem maybe in the preamp.
The centre wiper of VR2 is the input to the power stage it connects to C5 which then runs up to the base of TR2.

I doubt this amp was ever capable of super clean so you may not be able to improve it much. 8|
Reinsert those missing diodes (D1&D2) and it would be stock.
Phil.
Title: Re: Marshall 5010 Needs Help
Post by: galaxiex on March 29, 2018, 09:56:39 PM
C2 definitely looks suspicious.
Should probably be a small tantalum cap like C1 and C6.
Also it looks swollen.
Don't know if this would have anything to do with the distortion you are hearing,
but I'd replace it anyway.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 30, 2018, 10:48:39 AM
Thanks for having a look at guys, I really appreciate it! I'll order some parts.
  Phil, do you think I should use the 1N914's in the schematic, or could I go with LEDs?
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on March 30, 2018, 10:52:58 AM
 And, yeah the way C2 is stuck in there doesn't look like a factory job.
Title: Re: Marshall 5010 Needs Help
Post by: g1 on March 30, 2018, 10:01:31 PM
The cap at D1 looks factory to me, it even has the paint on top.  It's solder connections do not look like they have been disturbed.

The ground pin of the bridge rectifier looks like a bad solder joint that has been arcing.  Suggest you resolder it and see if it does anything for the fizz.  Beyond that, if you can wait a bit I will try to draw out the bias circuit for this version, then we will have a better idea how to adjust it.

Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on March 30, 2018, 11:53:18 PM
To me, that amp appears factory.

Yes, right down to the bad solder joint on the bridge rectifier.:(
Title: Re: Marshall 5010 Needs Help
Post by: J M Fahey on April 12, 2018, 01:48:36 PM
The YT Video you linked to does not show crossover distortion at all but something which scares unexperienced guys a lot:

* tube amps have a *smooth*  and continuous non stop variation from clean to distorted, imagine you are rolling a wheeled cart along a long ramp, you will go from a point to a somewhat higher or lower one with no hitch, going from, say, Volume 5 to 6 or 4 may mean going from 5% distortion to 6% or 4%, no big change (since you are never *really*  clean to begin with) , you can´t find a "frontier" since there´s not a defined one, and your ear accepts it.

* SS amps (*all*  of them by the way) are very very very clean before clipping (say 0.5% or less  :o ) to harsh distorted (10/20/30/50%) as soon as they clip, easy to see on a scope where you see a sharp edge at the clipping point.
Going from clean to dirty now is like hitting a staircase step: very definite, very sharp edge, "your cart bumps" on that edge, it is very annoying.
What the video guy does is play basically clean , rise volume until just the peaks distort, the resulting  mix is as harsh as putting mustard on your candy, you are jumping up down all the time between the top and the bottom of the vertical wall stair step.

* experienced SS amp Guitar players simply do NOT play over the step, they just roll their cart either in the clean area or in the fully distorted one.

Here´s one example of an experienced player testing the Marshall Lead 12, your exact preamp circuit, same gain, EQ, distortion mechanism (which does NOT use diodes of any kind but slams Op Amp against the rails, like a mini SS Powwr Amp driven to 11) .
In fact yours is the improved version, with higher power (same circuit but higher rail voltage, larger transformer and a 12" speaker) plus 2 Factory "Mods" :  they added a single transistor buffer to better drive the power amp and an adjustable presence control.
Of course yours may have some improperly changed parts values , but we have lots of doubts about the circuit.
I am certain circuit is the same (they used it on a ton of same era amps, why would they make a different one for this particular model?) BUT parts designation in the drawing and on the actual PCB might not match, so I ask you to print schematic on a large sheet (even better on 2 sheets and tape them together) and follow it part by part, following tracks where they go, then write actual (PCB) labels and actual part value on the paper one.
Then take a nice sharp picture of corrected schematic and post it here.
If in doubt with some part value write what´s printed on its body, don´t guess (as when you called pF what was actually uF).
That is a killer amp.
Power amp *might* be different, I´m puzzled at the "MosFet" label on front panel because those used TO3 metallic Darlingtons (MJ2501/3001).
They did also make a MosFet one, but those are VERY expensive transistors, justified only on the 100W one, definitely not in a way cheaper 30W one.

This guy ONLY plays amps full blast, with a high output humbucker equipped guitar and if not a combo, plugs them into a Marshall 4 x 12" cabinet.
https://www.youtube.com/watch?v=L-5IaYOvmjQ

To make it clear that even the cheapest cheesiest amps can sound GOOD when properly used (without any silly Mods) here´s:
https://www.youtube.com/watch?v=xwKZd-Vc3os
Title: Re: Marshall 5010 Needs Help
Post by: J M Fahey on April 12, 2018, 02:11:46 PM
Started comparing your PCB and the published schematic and just fron the very beginning I see parts designations will NOT match, so you will have to apply what you see on PCB to the paper version.
Actual *circuit* (who connects to who else and how) must match 99%  :o
Just as an example and the first I checked, you go on: paper shows a single jack connected to one of Op Amp inputs through a 0.1uF cap "&C2" ; your amp has 2 input jacks which are mixed by mixing resistors #R1 and #R2 , 68k each .
I am calling paper circuit parts "&"  and actual PCB ones "#" because plain labels R1, R2, C1, C2, etc. differ on both and can be very misleading.

Also checked that yours has Darlington power transistors (MJ2500/3000), the early versions of standard MJ2501/3001 and not MosFets, which further confirms it´s the basic same circuit.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 18, 2018, 03:39:48 PM
Thanks for having a look at my post, I've seen some of your other posts on these Marshalls, and was hoping you'd chime in.  Those Johan Segborn videos on YT inspired me to buy another one. I would LOVE for mine to sound like that. I had Lead 20 years ago that sounded great, but I couldn't hear it very well over a drummer. This particular 5010 has the volume, but an unpleasent sound. What's frustrating is the sound is 'in there', but with a crappy coating that can't be dialed out.
    I've been busy with exams, but I'm ready to open it up again.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 21, 2018, 02:57:22 AM
Here's what I've got so far....
Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on April 21, 2018, 09:03:55 PM
I believe that TR2 is the incorrect transistor.

The schematic calls for a BC212, which is a PNP transistor.

Your notation states that a BC182 is installed in that position.
BC182 is an NPN transistor.

Also, I do not know what is going on there at the LTP (TR4 & TR5) but those two transistors should be the same type & hopefully from the same batch so that there characteristics match.
Title: Re: Marshall 5010 Needs Help
Post by: phatt on April 22, 2018, 08:06:50 AM
You will find that the PCB printing sequence does not line up with the schematic used.
Although they are *Almost the same* there are a some differences.

*Elscorcho* has likely just assumed the PCB numbering is the same as Schematic but if you swap the numbering it makes sense. :tu:

D1&D2 are not at the input they are right before the power amp on the input to VR5 (master volume), maybe Diodes were removed at factory and a cap across the master volume to block excessive treble. Makes sense as the diodes would surely restrict the max volume level. So the cap is likely a factory rethink after pcb's were made. (not uncommon). xP

@ Elschorcho;
As JMFahey has noted it's close but not quite the same. Your best bet is to redraw the circuit. Yes it's tedious but you will learn a lot in the process. 8|

You can use the existing schematic as a guide but don't cheat triple check every connection. (wise to do it over several days)
These are single sided semi translucent PCB's and if you hold them up in front of a strong light you can easy see the tracks while looking at the component side of the board. This allows you to work out where the tracks go. I've done this hundreds of times myself to back track odd circuits that have no schematic.
At the end of it you will have an accurate schematic and a better understanding of how the amplifier works.
You will also help others who may have you model amplifier.

BTW, when you quote components please write down *EXACTLY* what is written on the component. i.e. if it says 273 write that,, don't try to convert it to what you think it means.
A capacitor might read 2u2 or 2.2uF which means the same thing.
just write down what you read as most teck guys will know what it means.
hope it helps,, Phil.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 24, 2018, 06:33:38 AM
Interesting development.

I found the exact same Red McKenzie version of this amp for sale locally, and contacted the seller to see if he would be willing to let me take a picture of the circuit board to compare it to mine. While I didn't expect him to allow it, he was kind enough to send me number of google links, which I DIDN'T expect, one of which provided some very useful insight.

Apparently the Red Meckenzie version uses a JM69 circuit board, and the only available Marshall schematic for the 5010 is a JMP27A board.

One of the links provided by the gentleman was from an auction site where someone gutted his 5010 to convert it to a tube amp, and was selling the old board - which in this case happened to match mine, a JM69.

Zooming in on the picture confirms Phatt is correct - D1 is a cap, and D2 is vacant, just like mine. Also, I appear to have a number of factory caps (blue in the pic) replaced with Orange Drops; C 1,4,6,8,9,12, and 16.
Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on April 24, 2018, 11:31:29 AM
Can you post the picture?
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 24, 2018, 01:30:07 PM
I'll go back and find that image, jazz bass. In the meantime, I was on the Marshall forum trying to find out anything I could about the JM69 pcb and not having much luck-until I stumbled across a post about a guy with a similar problem to mine, only with his bass amp. The schematic was for his 5503 30 watt bass amp listed a certain pcb, but his had a JM69 board instead, and the components didn't match. So I ran down that schematic, and found it is much more similar to mine. In fact, the transistor values that seemed out of place on the 5010 schematic match. I think the Red McKenzie version of the 5010  is essentially a bass amp.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 24, 2018, 01:45:07 PM
I tried to post the link to the google image I found of the pcb, but it doesn't seem to work.
https://www.worthpoint.com/worthopedia/marshall-5010-master-lead-combo-pcb-538953534 (ftp://www.worthpoint.com/worthopedia/marshall-5010-master-lead-combo-pcb-538953534)
Title: Re: Marshall 5010 Needs Help
Post by: g1 on April 24, 2018, 02:11:16 PM
That 5503 schematic is not much different, they just call out the transistors differently.  You do not have that many transistors, and you have D3 and D4 in the power amp instead of a transistor for the biasing circuit. 
Also, look at the number printed on TR1 in your amp, is it a FET (2N3819) or a bipolar type (BC184) ?

Here are links to those pics.  They do all show a cap in D2 position and no D1 used.
The orange caps look like the rectangular type rather than orange drops.

https://thumbs.worthpoint.com/zoom/images1/360/0714/09/marshall-5010-master-lead-combo-pcb_360_04439e68e91f9aec21cf34c02ac5c8da.jpg
https://thumbs.worthpoint.com/zoom/images2/360/0714/09/marshall-5010-master-lead-combo-pcb_360_04439e68e91f9aec21cf34c02ac5c8da.jpg
https://thumbs.worthpoint.com/zoom/images4/360/0714/09/marshall-5010-master-lead-combo-pcb_360_04439e68e91f9aec21cf34c02ac5c8da.jpg
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 24, 2018, 03:03:45 PM
In my amp Tr1 is an N3819, though according to the (inaccurate) 5010 schematic it should be a BC184.
Title: Re: Marshall 5010 Needs Help
Post by: g1 on April 24, 2018, 08:15:20 PM
Ok then, if it's 2N3819 then the 5503 schematic is a better match for the preamp.
I am still working on translating a schematic but have no idea when I'll be able to finish it.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 29, 2018, 08:03:22 AM
Ok. Here goes.
Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on April 29, 2018, 12:53:22 PM
The IC is an LM1458.
Title: Re: Marshall 5010 Needs Help
Post by: solidstate2199 on May 02, 2018, 10:25:02 AM
Hi
i havent read the whole topic yet but i know the answer to your 5010
"buzzing background" sound...
this is NORMAL behaviour on the 5010.

What you hear is the Ampsound with gain on 10 as a low volume
background noise.
It is a lets call it "design flaw".

The 5010 is only put to good use with the gain on "10" forget it for cleans and
use it like youre supposed to as a "practice 2203" .

I recall that the background fizz at low gain settings is not all that noticable
at higher volumes...so try the Amp with the Master volume turned at least to 6
and forget about playing totally clean gain has to be at 7 for some hendrixy tones.

Good Luck...the 5010 is a good sounding SS Marshall if used properly
for 80s Hardrock played with a higher output Humbucker.

(all IMO)

(a lot of the 5010s have a problem with oscillations at high gain settings,
i have seen so many with this problem that i think its a design flaw too.
Marshall changed a lot of stuff in their solid state amps of the 80s, lots
of revisions.
Title: Re: Marshall 5010 Needs Help
Post by: Enzo on May 02, 2018, 01:02:58 PM
The huge gain problem is less a design flaw than it is people trying to improve the amp.  In that 5000 series of amps, you might see 1458 op amp.  I recommend getting exactly that to replace them.  people "upgrade" to 4558, 4560. 4580, and then their amps become unstable at gain.

Stick with the 1458 there.
Title: Re: Marshall 5010 Needs Help
Post by: Estomagado on May 10, 2018, 09:32:25 AM
The huge gain problem is less a design flaw than it is people trying to improve the amp.  In that 5000 series of amps, you might see 1458 op amp.  I recommend getting exactly that to replace them.  people "upgrade" to 4558, 4560. 4580, and then their amps become unstable at gain.

Stick with the 1458 there.
1458 is a dual 741. Appaling specs. That's why it works so well with high gain guitar settings. But if you want your amp cleaner, you'd have to upgrade them to 4558s or better, and work on the compensation caps and feedback.

Tubes suck!

Title: Re: Marshall 5010 Needs Help
Post by: El Scorcho on May 13, 2018, 02:20:10 PM
I don't want clean AT ALL on my Marshall, i just want it to sound like a Marshall instead of a cheap practice amp! My old Lead20 sounded great-it just could't be heard over a drummer. It had a sweet sound, wheareas this particular 5010 ( and perhaps the Red McKenzie version in general) sounds like a turd smells. The later versions with the horizontal and single inputs sound really good, and I don't know why mine doesn't- but it really doesn't.
Title: Re: Marshall 5010 Needs Help
Post by: solidstate2199 on May 14, 2018, 05:14:59 AM
I had the 5275; Mosfet 100; Lead 12, Artist 3203 , Marshall 5010, Valvestate 100, JCM 900 Dual Reverb...sorry to say this but good Marshall is not happening with any of those...cut the chase and get real.

(1959 2203 2210 JTM45)x(PPIMV and or Attenuator)=ROCK

Could very well be that your 5010 has a transitional circuit from the
earlier Marshall SS Amps, and i can imagine that sounding not pleasant.

The mid 80s 5010 do a generic
ACDC Sound, nothing more or less.
Title: Re: Marshall 5010 Needs Help
Post by: YANSUEMARTINEZ on September 12, 2019, 11:01:02 AM
I'll go back and find that image, jazz bass. In the meantime, I was on the Marshall forum trying to find out anything I could about the JM69 pcb and not having much luck-until I stumbled across a post about a guy with a similar problem to mine, only with his bass amp. The schematic was for his 5503 30 watt bass amp listed a certain pcb, but his had a JM69 board instead, and the components didn't match. So I ran down that schematic, and found it is much more similar to mine. In fact, the transistor values that seemed out of place on the 5010 schematic match. I think the Red McKenzie version of the 5010  is essentially a bass amp.


Excuse me friend, do you know what the value of the VR1, 2, 3, 4, 5 and 6 pots is? I have the same JM 69 board as the one with the red speaker.
Title: Re: Marshall 5010 Needs Help
Post by: YANSUEMARTINEZ on September 12, 2019, 11:05:39 AM
It works-It just has an unpleasant sound. Even on the lower gain input there is a cruddy blanket of harsh fuzz wrapped around what would otherwise be a useable tone. Some of the parts seem a bit 'aftermarket'.


Excuse me friend, do you know what the value of the VR1, 2, 3, 4, 5 and 6 pots is? I have the same JM 69 board as the one with the red speaker.
Title: Re: Marshall 5010 Needs Help
Post by: YANSUEMARTINEZ on September 12, 2019, 11:12:03 AM
Excuse me friends, does anyone know what the value of the VR1, 2, 3, 4, 5 and 6 pots is? I have the same JM 69 board as the one with the red speaker.
Title: Re: Marshall 5010 Needs Help
Post by: Jazz P Bass on September 13, 2019, 12:12:27 AM
Marshall 5010 schematic:
Title: Re: Marshall 5010 Needs Help
Post by: dazz on March 08, 2020, 12:24:31 PM
Sorry for the necro post, but I figured out the schematic based on El Scorcho's pics of the pcb, so I thought it might help someone out there at some point. Looks like the circuit is almost the same as the published schematic, but without the bright cap and the presence control was moved back in between the two amplification stages. I used the cap values in the published schematic, not sure about those

(https://i.imgur.com/ZcyCP88.png)