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Wounded Acoustic 370

J

joecracker

Apr 14, 2014
7
0
#1
Hello. Newby alert! in more ways than one.
I have come to own an Acoustic 370 Bass amp paired with a EV B215-M Speaker Cab. When being played thru it sounds badly distorted. It also breaks up and fades out when doing a slide. The cab sounds fine under anther amp.

I live in Flint MI. and have been told by many of my musician buds that their is nobody around here that they would recommend to work on it. I think I'm going to poke at it a little bit myself. I've done a bunch of research and youtube watching but they all seem to be in Greek.

I'm just a lowly drummer and know very little about the bass guitar. I've done a little bit of wiring on radios, TVs and guitars but not something this complex. I have a soldering gun and schematic. I also have a multi meter but need to learn how to use it. I would really appreciate any help. Is there "Bass amp repair for dummies"?

Tim
 
#2
Man, sounds like you're in a bit of hitch here...

If you think a 370 is complicated you might want to think about shipping it to a tech if there aren't any good ones local. A 370 is actually a pretty dang simple amp, since it's cap coupled. Honestly, it sounds to me like you're in over your head. I don't want to say don't "dive in", but you'll need much more than a meter to fix it. Meter, scope, signal generator and dummy load at the minimum.

That said, at the very least you can try the monitor outputs on the back to try and figure out what's wrong. Go from those to a known good power amp and try it that way. If it sounds ok, that tells you the problem is in the power amp and not the preamp. At least let you narrow it down. You can also open it up and look for any bad solder joints on the pre and power amp boards.

FWIW, a soldering gun is no good, too much power. You really need an iron. I like the 25W wellers....

I've got a thread going on my 370/301 restore if you want to see. Mine was working more or less when I got it but it needed some help.
 
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#4
I would think that anyone in the area that was factory authorized for major brand repairs (Ampeg, GK, etc.) could easily fix it.
BTW, I had the same rig at one point and it sounded very good.
 
#7
Rickenbackerman said:
Man, sounds like you're in a bit of hitch here...

If you think a 370 is complicated you might want to think about shipping it to a tech if there aren't any good ones local. A 370 is actually a pretty dang simple amp, since it's cap coupled. Honestly, it sounds to me like you're in over your head. I don't want to say don't "dive in", but you'll need much more than a meter to fix it. Meter, scope, signal generator and dummy load at the minimum.

That said, at the very least you can try the monitor outputs on the back to try and figure out what's wrong. Go from those to a known good power amp and try it that way. If it sounds ok, that tells you the problem is in the power amp and not the preamp. At least let you narrow it down. You can also open it up and look for any bad solder joints on the pre and power amp boards.

FWIW, a soldering gun is no good, too much power. You really need an iron. I like the 25W wellers....

I've got a thread going on my 370/301 restore if you want to see. Mine was working more or less when I got it but it needed some help.
Click to expand...

Thanks for the advice. I believe you are right. It's a little over my head. I'll check out your Thread But I think B-string is gonna get the nod.

B-string said:
If you can't find a shop close to Flint contact this group http://www.michupnet.com/index.html Ham operators have a wealth of knowledge, knowhow and are usually more than willing to teach their craft. The soldering gun will turn that amp into a flower pot.
Click to expand...

Thanks much. I think you all are right. gonna find an expert. I'm not in to gardening.
 
#10
Gaolee said:
If you ask questions here: Unofficial Acoustic Control Forum, you will probably get all kinds of answers and information.
Click to expand...

I second that, they got some guys over there that know their Acoustics well. But you have to know which questions to ask.

Lets face it, a 370 from the 70's has 40+ years on the caps. It's very likely that there is one or more dried out or leaky there. I'd do a careful visual inspection first looking for any obvious signs of electronic failure.

In your case, I'd probably have The Beast sent out and lovingly serviced and restored to its PantFlapping BoneKrushing best.
 
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#11
Thanks for the info guys. looks like i'm tracking down a dude. just hope it wont cost me more than its worth. as usual Its the drummer not the bass player who has the job!..... Just kidding!!!! Thank allot. you guys have been a great deal of help. Almost makes me wanna play Bass... almost. 8)
 
#12
First, DON'T have any second thoughts about fixing your 370 Amp. I bought my first one in 1978. It still works, I still Gig with it & it still Kicks Bottom End. Only trouble I've had are Dirty Pots. Lotsa cigarette smoke years ago. The only Mod I've made to it was beefing up the Outputs. It's never let me down and still sounds better than, more than one of, my newer amps (I won't name drop).

I purchased a second 370 recently, (on purpose) that was blown, like I don't have enough projects :) , but I love a good challenge. I found this link:

http://music-electronics-forum.com/t22926/

Looks like some really good guidelines for a rebuild. Sounds like you'd like to try this on your own & you're good with a Soldering Pencil. It's not hard to figure out a Meter.

I'm in the process of procuring all the parts listed. My advice is:

-- DON'T SKIMP on Parts Quality.
-- Beta Match the Output Transistors, meaning you may need to buy a few extras to find a matched set of 6 (info on the Net)
-- Pick up a Variac (to bring it up to voltage slowly after the rebuild).
-- A REALLY good idea would be, if you have access to, is use an Audio Generator & Oscilloscope (to Monitor Input vs Output as you're bringing it up on the Variac)

Don't know what your level of experience is, It's truly not Rocket Science (although a lot of our solid state technology IS a product of the Space Program ;) ). If you've not in a hurry, I SAY GO FOR IT. If you do it yourself, you KNOW the guy doing it, IS doing QUALITY Work.
 
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#15
Sorry. My bad. I should have read the rules a little better. Really? Can't ask what its worth. I have no interest in selling it here. I was looking to trade it to my repair dude of choice locally for services rendered but I get it. Rules are rules. OK. Thanks guys. You've been a ton of help.

PS. If I may be so bold to ask if there is a place I should go ... uh hm...to get get what I need?
 

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