Audiobahn a275hct

2fast4u88 · 2010-06-30 9:48 am

Sorry for another thread. I know audiobahn is junk. Either way I got this amp from a friend for free like new. Thing is it won't work. Powers up with the blue led's coming on and the fans but that is it. The vu meters don't work or the white backlight to them. The status light comes on red upon coming on to where it then goes out. I believe it is suppose to turn blue.

Not sure. It just doesn't play sound. No thump from the subs or anything. I tore it apart where nothing is burnt or smell like it so I am at a loss.

Perry Babin · 2010-06-30 4:19 pm

You'll need to post the DC voltage on the 16 pin driver IC. Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage. Have all transistors tightly clamped to the heatsink. You should insert a 15 amp fuse in the B+ line before you begin measuring the voltage.

IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

2fast4u88 · 2010-06-30 9:57 pm

Sorry I'm not to into fixing amps. I can solder new stuff in no problem. What is the 16 pin driver? This morning being bored I kept looking and noticed corosion in a few places. Sorry I don't know the technical names but one of the wire wound things. Had corosion on the left one. Then I am guessing capacitors not the black ones but the big 4 that says audiobahn on them. The one on the left 2nd over was the same way. With the top kind of bubbled along with the other left had a bubble in the top.

Not sure if that would do it or not but I desoldered it. Only take a min to put it back on.

Perry Babin · 2010-06-30 10:44 pm

Please read the Basic Car Audio Amp Repair page (link below).

2fast4u88 · 2010-07-01 2:42 am

Ok will do. Ok I guess what I am talking about is the transformer. It is way bigger than the black caps. Not sure if a good way to tell if they are bad is by the tops are bulged or not. But still reading.

Also I can use a multimeter and such just not sure on all the parts.

2fast4u88 · 2010-07-01 3:20 am

Here is some pics. You can see where I took the I actually guess transformer out. I tried to get a pic of the corosion but I wiped some off. The audio jack piece isn't pictured as it just plugs in. Along with the vu meters just plug in.

2fast4u88 · 2010-07-01 3:22 am

Here is some more pics. Then where it looks to have got hot. Which I am going to guess from to low of ohm's.

Perry Babin · 2010-07-01 3:28 am

The part you removed is a capacitor.

What appears to have overheated?

2fast4u88 · 2010-07-01 3:33 am

Ok that is what I thought well the top is bulged on it and the one right beside of it.

As for overheated. I know the amp never did that when my friend had it. But was saying due to all the melted brown glue on the bottom. Not sure if that is a give away or not. As I thought someone told me that at one time.

Perry Babin · 2010-07-01 3:41 am

The cheap fixative they use around the capacitors breaks down and turns brown. You should remove that fixative. It becomes conductive and corrosive and can cause all sorts of problems.

2fast4u88 · 2010-07-01 3:44 am

Your talking about the brown glue or glue that turned brown right? As it is all over the speaker outputs and the power inputs also. If so what should I use to clean it off?

By the way man thanks for all the help.

Perry Babin · 2010-07-01 3:49 am

If it's all over the board, set your meter to the highest resistance range (if it's not auto-ranging) and touch the probes to the fixative about 1/16" apart. If the meter reads anything other than what it reads with the meter probes open (not touching anything), it needs to be removed. Remove it by picking it off with a pair of needle-nosed pliers or hemostats.

2fast4u88 · 2010-07-01 4:00 am

Hmm.. I will just remove it and see what happens. But there is no way pliers will take it off. As there is going to be no picking to it. Nothing to grab to. I can scrape it off though. Not sure what hemostats are.

Perry Babin · 2010-07-01 4:04 am

Hemostats are essentially light duty locking pliers. They are invaluable when doing repair work.

Hemostat - Wikipedia, the free encyclopedia

The attached image shows fixative that has broken down.

2fast4u88 · 2010-07-01 4:32 am

Yup that is it. I cleaned it all off. Using dull piece of metal to scrap it. Not have the powder all over. What would you clean it with. It was also all over it. Think maybe something to do with it? Should I put the cap back in and try it?

Perry Babin · 2010-07-01 4:38 am

I don't know of any solvent that cuts that type of fixative but acetone may clean up what you can't pick or scrape off.

If it still doesn't power up and remain on, you'll need to post the voltage on that IC.

2fast4u88 · 2010-07-01 4:44 am

Where is the ic at in the pics? Is it the black chip in the middle of the board in the pics?

mike49504 · 2010-07-01 6:58 am

The one circled in yellow is the one Perry needs the voltages off all 16 pins

2fast4u88 · 2010-07-01 9:34 am

Thanks mike that is the one I thought he was talking of. Looks like I will be testing it as it still doesn't work

2fast4u88 · 2010-07-01 10:54 pm

IC#
Pin 1: 102mv
Pin 2: 2.3v
Pin 3: 26.3mv
Pin 4: 100.6mv
Pin 5: .817v
Pin 6: 1.8v
Pin 7: 0v
Pin 8: .245v
Pin 9: 32mv
Pin 10: 34mv
Pin 11: .32v
Pin 12: 7.94v
Pin 13: 2.48v
Pin 14: 2.3v
Pin 15: 2.3v
Pin 16:.45v

I tested it with around 8 volts. It wasn't real steady voltage. So that may be due some of the ones reading a little lower than the other that should be the same. That is if they should be. I will have to dig out on of my old psu to get a steady 12volts in the house.

Audiobahn a275hct

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