Acoustic B200H Service Manual?

[bob p]

Anyone have access to the service documentation for the Acoustic B200H head?

I just had one show up DOA, along with a Hartke VX115 cab and a Hartke 2100 (2x12) cab, with all of the drivers blown. (!) I'm betting that this cheap little amp gave out some DC offset and promptly killed all of the drivers.

I'd be interested in hearing if this is a common problem and/or if the B200H heads are unreliable. I'd really love to get my hands on the service docs. It's be interesting to know what kind of protection this head does or doesn't have.

Thanks.

[bob p]

Is this one of those "not serviced in the field" amps?

[Enzo]

According to their web site

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The line is only sold through Guitar Center, and apparently has no service network. Nor available parts. Schematics may or may not be floating around.


Manufacturers' no field repair lists are for warranty repairs. Fender for example publishes schematics and makes many parts available for the items on their list. The list is not about repairability, it is only about what the company is willing to pay for.

[bob p]

GC reportedly bought Acoustic and turned it into a house brand. If GC doesn't have a warranty repair network, then it sounds like *ALL* Acoustic gear is on the no field repair list, eh?

I have heard stories about walk-in warranty exchanges with this amp -- If you take one into GC during warranty they just give you another one. I guess they make no effort to repair them.

It may just be one of those class D "amp on a chip" circuits where there are no discrete components and everything is in one disposable package. When it fails, then the whole amp is toast.

[Enzo]

Seriously, I don't think it has to do with repairability, it is just a matter of cost. The very common Fender FM212R guitar amp combos are do not repairs, but we have had any number of discussions helping people repair them. The cost on these amps is so low, that Fender - or whatever brand - finds it cheaper to exchange than pay me $50 to fix it. Fender at least makes parts available. For all I know, GC has the4se made in China and hasn't bothered to even bring over spare parts. That would not only tie up parts that could be used in production, it also ties up warehouse/storage space, and people to maintain inventory etc.

You may well be correct, it could also be purchased subassemblies from other vendors.

Eventually any warranty will run out, then they will have customers wanting them fixed.

[blakes]

Acoustic B200H Service Manual *

Bob, Did you ever find a service manual? I'm in need of one too. Had a cap explode in the power supply and one next to it is pregnant. Can't see the values.
Does any one know if the B200H is the same amp as used in the B200 combo?

[The Dude]

You won't find a schematic. Even the folks at Acoustic know absolutely nothing about the amp. I have one open in the shop right now. If you can post pics or designation numbers, I can tell you the values.

[bob p]

I never found anything, and just gave up on it. Some of those amp on a stick designs just aren't worth the trouble when they go.

I think a lot of these amps end up getting cheesed when a musician hooks them up to the wrong load impedance. Class D amps don't like that, but people are so used to getting away with mismatches with traditional tube gear, and they're so used to the relative immunity of solid state gear to mismatches, that they don't realize that impedance mismatching is the kiss of death with Class D designs. RTFM.

[The Dude]

FWIW, these aren't class D amps. They use an STK output device that's no longer available (except for fakes). I have a thread going on one here. I'm in the process of fitting a different amp module in the thing as we speak. That thread will be updated when I get the bugs worked out.

[blakes]

Thanks Dude, I use this amp as a backup so I'm not dying. I'll send you a couple pix. Hopefully they just dried up and nothing else caused them to go.

[blakes]

Here's the pix. The center cap blew off the can and the two on each side both look pregnant but the right one is definitely swollen. Thanks for you help.

[The Dude]

Those are (left to right via your picture orientation):

C34: 2,200UF/16V
C32: 1,000UF/25V
C28: 1,000UF/25V

By the way, I just noticed while looking at this. The values are printed right on the circuit board (at least on the one I'm looking at). I would also check those 2 bridge rectifiers right next to the caps for shorts.

[J M Fahey]

And if you look at the other thread, youŽll see this "Acoustic" amplifier is actually a (modern) Kustom 200 amplifier in disguise, schematic should be the same or at least match 95% .

[bob p]

didn't one of those dude-pics say ampeg?

[blakes]

Acoustic B200H Service Manual **

Hey Dude,
Thanks for the info and suggestions and your quick response. Doing a little more digging, I found the service manual with schematics and PCB layout and component lists. The preamp and Power Amp is Revision B which is what I have. The PS is is Rev E but the lay out looks the same and the cap values match what you sent. I found it on another forum. Thanks guys, you've been very helpful. B200 and B200H zip file attached.