American Bass XD1800 repair help needed

[jmilch]

I have a American Bass xd1800. I bought it secondhand recently.

When the amp is powered up, it immediately blows the internal 30 amp fuses. All 4 of the fuses blow. After close inspection, the entire inside of the amp is in remarkable. No bulged caps, no burn marks etc.

There is one trace that the coating came off of, about an inch long. Considering where the amp was stored, I wondered if this was just due to age.

I can post the internal picture if that is needed. It does not appear as though anyone has attempted any repair on this amp in the past.

Can someone give me an idea on where to start troubleshooting? Any and all help is appreciated. I can provide any information that may be needed.

Thanks in advance.

[Perry Babin]

Please post at least one photo of the inside of the amp.

[jmilch]

I will post a photo tonight after work. I also found the basic car audio amplifier troubleshooting guide. I may need help locating the actual items to test, but I can follow the testing procedure and see if I can locate a bad transistor.

I just may need some guidance as to which components to be testing.

thanks again

[jmilch]

Here is the inside picture.

[Perry Babin]

Check each large transistor clamped to the heatsink. Measure the resistance between the legs of each transistor in all combinations (leg 1 to leg 2, 1-3 and 2-3). Does any transistor read anything near 0 ohms?

[jmilch]

Ok upon closer inspection (2) of the clamped transistors say irf1010 on them, and there is one on each side of the amp that is apparently blown.

I removed the heatsink clamps and inspected them all.

These seem to be the only 2 that are a problem.

Can I simply order 2 of them and just replace them?

thanks

[nigelwright7557]

With blown fuses it is usually something hefty which has blown.
So it could be bridge rectifier, smoothing capacitors or output mosfets.

Its a case of eliminating each one in turn.

If the mosfets are blown then it could be because of a short on the output, check for this first. Sometimes the output mosfets going take something further back in the amp with them.

MOSFETs usually go short D-S in my experience.

[jmilch]

Originally Posted by nigelwright7557

With blown fuses it is usually something hefty which has blown.
So it could be bridge rectifier, smoothing capacitors or output mosfets.

Its a case of eliminating each one in turn.

If the mosfets are blown then it could be because of a short on the output, check for this first. Sometimes the output mosfets going take something further back in the amp with them.

MOSFETs usually go short D-S in my experience.

So basically after these are replaced, I may have an issue farther down?

The amp was run at too low of an impedance if that could be a cause for these being blown.

It was rated @ 1 ohm and the previous owner said he ran it normally at .5 ohm. One day it was cranked up, and some smoke came out of it, and he set the amp aside.

[Perry Babin]

For power supply FETs, generally all fail when one fails. Even if they look OK, they could be blown.

Remove the two FETs that you know to have failed. Do any of the others read shorted (after removing the defective ones)?

Have you checked the outputs to see if any are shorted?

[jmilch]

I ordered 10 of the irf1010n fets, and i plan to replace both banks. None of the outputs registered as shorted. So i plan to replace the 10 irf1010n's and test it out. Does that sound right?

Sent from my PC36100