collapse

Author Topic: Marshall 5010 Needs Help  (Read 7184 times)

Jazz P Bass

  • Elite
  • ****
  • Posts: 160
  • Chip Points: 13
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #15 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)

g1

  • Legendary
  • ******
  • Posts: 603
  • Chip Points: 70
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #16 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.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #17 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'.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #18 on: March 21, 2018, 04:10:58 AM »
Here's another obvious replacement.

phatt

  • Legendary
  • ******
  • Posts: 2034
  • Chip Points: 240
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #19 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

phatt

  • Legendary
  • ******
  • Posts: 2034
  • Chip Points: 240
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #20 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.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #21 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.


El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #22 on: March 21, 2018, 11:44:45 AM »
Thanks Phil!

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #23 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.

Enzo

  • Legendary
  • ******
  • Posts: 1860
  • Chip Points: 193
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #24 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.

g1

  • Legendary
  • ******
  • Posts: 603
  • Chip Points: 70
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #25 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.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #26 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.

Enzo

  • Legendary
  • ******
  • Posts: 1860
  • Chip Points: 193
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #27 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.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #28 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.

El Scorcho

  • Regular
  • **
  • Posts: 33
  • Chip Points: 2
    • View Profile
Re: Marshall 5010 Needs Help
« Reply #29 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.

 

* User Controls

 
 
Welcome, Guest. Please login or register.
Did you miss your activation email?

* Recent Posts

Ibanez TSA30 - buzzing by theaterguy
[November 11, 2019, 07:25:24 AM]


Intermittent loud crackle from Fender Deluxe 112 Plus by traxcontrols
[November 09, 2019, 01:23:37 PM]


So you need a preamp - here are your options by flester
[November 07, 2019, 05:03:55 PM]


Burned up cap by Den.
[November 07, 2019, 03:43:24 PM]


Acoustic 220 quieter volume than expected by DrGonz78
[November 07, 2019, 03:23:10 PM]

* Sponsors