Jump to content
Why become a member? ×

MXR M80 DI Tech Help Required to Repair (maybe)


Sean
 Share

Recommended Posts

I have an MXR M80 DI that I accidentally powered up with an 18v supply and it stopped working.
It still sort of powers up and the LEDs come on but no sound.

Can anybody tell me what the component is in the photo below? I measured the resistance across it and it's showing open circuit whereas an identical component elsewhere on the board is showing 18 ohm. Is this a power supply fuse? Text on there I can see is GW and IN4 but there's other text underneath that is a continuation of those.

Any advice on what else to look for and how or whether this can be fixed?

Edited by Sean
Link to comment
Share on other sites

1N400x (probably a 4007 or 4009) polarity protection diode. They're pence to buy and easy to replace. My worry is that if it's gone 'open circuit' then it's allowed 18v to go further than just that one component and could have potentially damaged something else.

Link to comment
Share on other sites

It appears to be a diode IN40xx [url="https://en.wikipedia.org/wiki/1N400x_general-purpose_diodes"]https://en.wikipedia.org/wiki/1N400x_general-purpose_diodes[/url] They can be used as a protection method against incorrect polarity connection. The one schematic I can find shows this as D3 - a protection diode. Testing components that are in circuit can give erroneous results - I would expect the diode to show zero resistance in the foward mode and infinite in the reverse bias mode. The 18 ohms you measure with the other diode could be a side effect of the remainder of the circuit.

It can be desoldered with a 'solder sucker' or braid. Component costs pence. Easy DIY job, it may be the cause, it may not.

Schematic here, the only one I can find - you will have to endure the free trial [url="https://www.scribd.com/doc/73304672/MXR-Bass-DI#"]https://www.scribd.com/doc/73304672/MXR-Bass-DI#[/url]

Link to comment
Share on other sites

[quote name='Norris' timestamp='1508180776' post='3390341']
If it's a diode, have you checked it both ways? Swapped the positive and negative leads around? Diodes allow current one way but not the other
[/quote]

Yes. It reads 18 ohm in the one direction, off the scale in the other.
WOuld that indicate that the issue is elsewhere?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...