Gallien krueger MB200 problem

[angelothewolf]

Well apears that we have 27ohm between both inputs and signal GND, on the amplifier board, that is definitely not right, all the amplifier protections are related to the output stage, so is possible to have a problem there. The owner of the equipment tells me that when the fault happens he was connecting a DI in the XLR LINE OUT of the amp and then he pressed some sort of ground lift switch on the DI and the amp stops working.... what do you think?

[Jazz P Bass]

According to the scimpy info on the ICE power board, there is a cap to ground on the signal in.
I would start there & look for any components that are blown shorted.

The info also shows a coupling cap before the main IC, so the damage should not have reached as far as the IC.

[MarkusBass]

I think that the the module has failed. Either you buy a new one (from GK or B&O), or you fix it. If you want to fix it, start drawing a schematic. It seems that on the inputs there are two double protection diodes (I can see it on your photo). They look like BAV99 double diode and maybe they are shorted. If this is the case, you are a lucky guy.

Mark

[angelothewolf]

Ok, thats the thing, sorry for the focus, multiple things apears short there, im measuring 100ohm across one of the diodes and one cap. That 6 pin device between the two diodes is all shorted (less that 2 ohm) i dont know what it is, there are other three bugs (down left) well shorted too. May be some kind of fuses. I think im gonna take out that diode and cap to measure it right. there are multiple 100ohm resistors too, so would have to be very lucky...

[MarkusBass]

I was hoping for slightly better photo . What is the symbol on the SOT23 component - is it "A7"? Check this out: http://www.fairchildsemi.com/ds/BA/BAV99.pdf
The components at the bottom may be inductors on the power supply rails. It's time to check the datasheet of the module - connectors are described there. I don't know what the 6-pins component is. This may be an opamp, or an analog switch (I would vote for an opamp - maybe voltage follower). I would carefully desolder the diodes and check what else can be done with the module. But you have to start drawing

Mark

[HAMERMAN409]

I think the 6 leg component is a 3 line common mode choke.

[IvanC]

Sorry to bring this back from 2014, but I have a MB200 with the same exact problem and I was wondering if you ever solved this

Thanks!

[J M Fahey]

It´s very unusual that two amps, even if same brand and model, have the exact same problem, or thatb the exact same solution works in both.
Please describe what happens to yours.
And welcome to the Forum.
Also fill Country information, many answers depend on location.

[IvanC]

Thank you for the welcome :-)

I've updated my profile (Mex)

I actually managed to get the amp up and running this morning, Swapped the optoisolator and U7, first with a NE5532 (that's what it had in there) but operation was spotty at best, and then for a TL072 (as shown in the schematic) which apparently did the trick, however, I have some nasty distortion as soon as notes are hit harder than necessary, volume is not really good either, I can also hear white noise coming from the amp when nothing is connected.

[J M Fahey]

Thank you for the welcome :-)

I've updated my profile (Mex)

Cool

I actually managed to get the amp up and running this morning, Swapped the optoisolator and U7, first with a NE5532 (that's what it had in there) but operation was spotty at best, and then for a TL072 (as shown in the schematic) which apparently did the trick, however, I have some nasty distortion as soon as notes are hit harder than necessary, volume is not really good either,

Ok, that´s a beginning, now let´s put some numbers into it [tm]

Download and play (MP3 player, Phone, Notebook) a 440Hz tone https://www.mediacollege.com/audio/t...6bit_30sec.mp3 or a 250Hz one https://www.mediacollege.com/audio/t...6bit_30sec.mp3 .

Tones last 30 seconds so set player to "Loop" or "repeat one" or whatever´s needed so it restarts and you have continuous tone.

A headphone out will give you 100 to 200mV RMS which is perfect to drive the preamp input.

Set all tone controls to 5 or flat, no "enhancers" so no Contour/Bright/Shape/whatever, we want the preamp flst, set Master if available to 10, rise volume slowly until output starts to clip.

If you pay attention you will find a point where output goes from "flute sound" (pure sinewave) to "reedy" (distorted); set up/down volume until it *just* starts distorting.

Measure AC voltage across load and post it here, also stating your load ohms.

**All** amplifiers clip eventually, that´s what defines maximum output power; now if your amp clips above, say, 150W RMS it´s fine; if at, say, 20 or 40W then something is very wrong.

That´s why "I rise volume and it distorts" by itself does not mean much, we need "some numbers"

I can also hear white noise coming from the amp when nothing is connected.

Same thing: *how much* white noise?

Set all tone controls as before, plug your Bass in, rise volume until it starts distorting, set all Bass controls to 0 or unplug cable end from preamp .... how much hiss do you have now?

Is it waterfall/jet engine level or barely audible in a silent room?

Is it audible in a rehearsal situation with a Drummer nearby?

[alansombr]

hello
Hi, can anyone tell me a replacement for IPD400N06N G
icepower tr407

[Jazz P Bass]

It would help to know your location.

USA: https://www.findchips.com/search/IPD400N06N%20G

[alansombr]

looking FDD26AN06A0

[alansombr]

BRASIL

looking FDD26AN06A0

[alansombr]

FDD26AN06A0 FOR fIPD400N06N