Behringer Gx210 schematic

[diydidi]

Hi
I'm in need of a schematic for this guitar amp. It has a weird BTL type output section.
Any help will be much appreciated.

[J M Fahey]

Is it the one with 4 or 6 parallel bridged LM3886 or some similar chipamp?

Short ago a Bass or Keyboard Behringer amp was posted here with such an output stage, maybe it's close enough or even the same.

Of course, it might also be completely unrelated

[diydidi]

No. It has two LM4701's.

[J M Fahey]

Weird.
Just checked and besides having the OBSOLETE stamp all over the datasheet, look like crippled LM3886 cousins.

NOT pinout compatible but I bet you could substitute them with LM3886, you should mount them to the heatsink anyway, not solder pins to PCB (except if some happen to match by chance or be nearby), bend uncompatible ones up in the air, clip them short (say 8 to 12 mm) and add short wires to proper holes.

Functionally they are the same, specially the NFB network, so I wouldn't touch that.

They provide a mute function, which can be disabled by grounding pin 6, I'd do that and forget it.

In general, a solvable problem, and not deserving much time or perfectionism trying to let is canonically as new, I bet customer wants just a properly working amp.

If any, his mind must be rolling about the words "fast" and "cheap"

EDIT: just checked GX210: it has 2 x 30W amps , each driving its own 8 ohms 10" Jensen speaker, so I doubt the BTL connection.

Anyway LM3886 *should* still be usable (lacking access to original chipamps) unless real estate is so tight that it does not fit.

[diydidi]

This chip is not the same as the Lm3886. It only has 9 pins. LM4701T.
See picture.
I can't seem to find these.

[MarkusBass]

Of course, if you go to chinese servers (like e.g. alibaba.com), you will find the chip without any problem.

Mark

[Jazz P Bass]

Hong Kong & China have 'knocked off' these ic's for a while now.

2pcs IC Chip LM4701T 30W Audio Power Amplifier | eBay

2 Pcs 30W Audio Power Amplifier IC Chip LM4701 LM4701T | eBay

Online Buy Wholesale lm4701t ic from China lm4701t ic Wholesalers | Aliexpress.com

Or try emailing Chase McKnight: carepro@music-group.com

[J M Fahey]

This chip is not the same as the Lm3886. It only has 9 pins. LM4701T.
See picture.
I can't seem to find these.

If you get the "originals* (which are fake or best case cloned) , fine, go for it.

If unavailable or clones explode like mini nukes, *if space permits* use a couple LM3886.
Don't care about 11 pins vs 9 pins, you are not a Musician "painting by the numbers" who needs very detailed step by step answers, you're a Tech !!! (and a good one at that )
What you want to match is function.
(Dyed in the wool Functionalist here )

a) A chipamp basically has : +in , -in , +V , -V , and Out legs; it may hav e other auxiliary ones such as decoupling, compensation or mute/standby , but the main ones are the first 5 .
2) both chipamps have the first 5 (duh!) so you match chip +in to PCB +in hole and so on, using short wires.
You don't need to mess with NFB because it will still be wired from Out to -in and from -in to ground.
+ in also works the same, and so on.
As said before, I'd hardwire the mute to be always on, just to minimize variables.

That said, even if they torture you never say I suggested this, maybe a couple TDA2050 (the real ones, not EBay fakes which are relabelled TDA2030) can be used there.
Same size, same power output .
Gosh!!!! they don't have a Mute function!!!! what will I do now??????

Seriously now, if available try a couple TDA2050, matching pins to holes of course.

[diydidi]

Thanks guys!!
Client got back after I quoted him for the repair, saying he doesn't wanna go ahead. AARGHH!!