Marshall Echohead - can I fix it?

[DWBH]

I got this Marshall, but it's kinda weird.
http://www.youtube.com/watch?v=dpM9BrMlP-E

I've made a video of it.

Perhaps I'll send it for repair, 'cause it's all digital and RAM ROM RUM inside.
However, I might try to crack it open and see if there's some burnt component.

Have any of you guys experienced this type of thing before?

[GREEN FUZ]

Strange problem. I have an Echohead that, while not exhibiting the same issues as yours, behaves very oddly when the battery is low. Random noises, weird feedback etc. It might be worth trying with a power supply before sending it off for repair.

[DWBH]

I have. It's the same thing.
I have plugged a fake 9v adaptor to it (not 9V, but 16v). Might I have fried something?

[DWBH]

Any chance you guys know how much does a "normal" repair job cost?
Or, what's  the maximum you'd pay, or you normally pay for a repair job?

[JasonG]

16v power supply on a 9v pedal is bad news. Contact Marshall and see if they have a list of people in your country who can fix it. After you know how much they charge shop around if you need to.

[drewl]

I think I worked on one of these, pretty cheap construction, I felt if I sneered at it, it would break.
Anyway, check the adapter protection diode, see if 9v is getting to any of the chips.
try reflowing any bad looking pc board connections or check for bad/loose components etc.

[DWBH]

I've already talked to Marshall, and I've already been contacted by their Portuguese represention.
Thing is, they've never seen anything like this really, and they can't really tell me how much would it cost.
About the diode. I found something curious while I opened it up. There's a diode in there, soldered directly to the 9v jack. Not on the pcb. Will check that.

[DWBH]

Here's the diode I was talking about.

Between pins:
1 and 2: 0v
1 and 3: 8.92v
2 and 3: 8.92v


And the usual gut-shot for the curious ones:

[DWBH]

Well, I just checked. No signs of burnt components, no loose components. The switch is working 100%.
And the cost for the repair job is €42, which is like $60. So, a whole lotta love money.
If I can't fix it, I'll probably use the enclosure, which is really good. And there's already a Alpha DPDT in it.

[Ben N]

The diode is a polarity protection diode, to protect the circuit components in case you plugged in a positive ground power supply or reversed the battery.

An observation: The silver Marshall pedals (or at least the ones I have seen, and I have not seen an Echohead, FWIW) have old-fashioned SPDT crappy bypass, meaning that the effect remains connected with the input all the time; the bypass switch just selects whether to take the effect output or input to send along down the chain. (This is why they tone-suck, but that is another conversation.) So it is not at all surprising that whatever you play gets processed, and when you turn the effect on, whatever is currently in the processor will come spilling out. If this theory is correct, then what you have there is not a malfunctioning pedal at all--it is just crappy design. (BTW, I know the switch is DPDT, but the other half is used to switch the LED, IIRC.)

Now that I look at your pictures, though, I see that the secondary board, the one that the switch and the jacks are soldered to, is bigger and a lot busier than the secondary Marshall boards I have seen, with what appear to be a bunch of metal can transistors (or are those electrolytic caps, I can't tell--but not FETs???), so possibly there is a legitimate buffered bypass--if that is the case, then probably there is a problem in the bypass, where the switching element at the input is passing signal to the circuit (main board) even when bypassed--which it should not do.

Well, this may not be helping you much, but you should be able to tell what kind of bypass you have just by pressing the footswitch--if it has a hard click to it, then it is probably a mechanical DPDT, and you have crappy simple bypass. If it just goes down without giving a distinct click as you hit some resistance, then the switch is probably a momentary SPST controlling an electronic switch of some kind.

Marshall effect schematics are pretty horrible, but you may be able to locate one to help with this problem. You might even be able to get one from Korg.

[DWBH]

No, it's really a mechanical click.
And I think it's true bypass, really, because when I disconnect the battery (or adaptor), I can hear my guitar come through.

Korg? Do they have the Marshall schematics?

[Ben N]

On Korg--yes. But there is or used to be a Marshall fx pedal website that might have some info. On hearing your guitar--I think that is possible even with crappy non-TBP, because there is still a straight wire connection between the input, switch and output. Only buffered bypass kills your signal when there is no power. (Somebody correct me if I'm wrong.)

[DWBH]

There's nothing on Marshallamps.com.
I'll email Korg tomorrow.
Now, another thing that's interesting (well, not really), is that when I connect to the second output (spill-over output - this means that after you turn off the delay, it fades, and doesn't stop abruptly), having the effect on or off is practically the same thing. The led changes (from the static red light, to that strange blinking led on the video), but the sound is always the same. It's always repeating and "working", and even there's no bypass whatsoever.

Oh, and the delay doesn't seem to change when I change to other delay modes. It's always very "analogue". However, on the reverse and multi-tap, the sound changes.

Crap.

[DWBH]

with what appear to be a bunch of metal can transistors (or are those electrolytic caps, I can't tell--but not FETs???)

Those would be electrolytic caps. On both boards.
On the smaller pcb there are 3 TL072C

[Ben N]

OK, I'm now officially lost--meaning I actually recognize how lost I have been all along. And I see that the Marshll pedal site is completely changed since the last time I looked. Sorry.

[DWBH]

Oh, and I already emailed Korg, and they said "I am sorry but you have been misinformed as we do not deal with any Marshall product. Please go to www.marshallamps.com for help."

[Ben N]

Sorry. Korg USA does (or did?) distribution for Marshall, but that may be just amps.

[DWBH]

No problemo

[DWBH]

Can I bump this?
I emailed Marshall some time ago, but they haven't replied back.
They told me that if it's broken, I should go to their distributer, but when I asked for a schematic they no longer responded me.
Does anyone have by chance, a schematic?