help with clif designs cd860hc amp

[stuntstere]

hey guys i am new to this site so please disregard any noob actions from me... alright I have a clif designs cd860hc amplifier.
The problem: When i have it hooked up and turned on it goes into protection mode right away. while in protection mode the amplifier pusles. you can see it dim the lights. there is a huge amount of current being drawn. measured aprox. 180-210 amps during the pulse... it does it with rca's disconnected and speakers disconnected. also when the speakers are hooked up the pulse goes through them. I have visually inspected the board and don't see anything.. I have limited electronics experience. mostly diagnosis of wiring faults in vehicles but willing to learn new things. Any help is well apprieciated. thanks

[Perry Babin]

This is most likely due to shorted output transistors.

If you can post photos of the inside of the amp, it would be easier to guide you through the troubleshooting. If you can provide high resolution photos, email them to me. It will make it easier to see the numbers on the board.

babin_perry@yahoo.com

If you're new to amp repair, read through the basic repair page below.

[Perry Babin]

Check the A1695 and C4468 transistors to see if any are shorted. With your multimeter set to ohms, if you find anything near 0 ohms between the legs of any individual transistor, the transistor is likely shorted. Check with the meter leads across the legs 1-2, 2-3 and 1-3. They generally short 2-3.

[stuntstere]

hmmm. The only pictures i can get are from a crappy cell phone. I will email them to you to see if they even help any. thanks for the help...

[Perry Babin]

The information you provided was good enough at this point. Measure the resistance and let us know what you find.

Do this with no power applied to the amp.

[stuntstere]

I believe I have found three A1695 transistors shorted.. The three are in a row and the first 2 legs are shorted. showed about 6 ohms and the rest were about 300 ohms. Any thing else i should consider to be faulty too?

[Perry Babin]

The driver transistor (medium sized transistor standing near the emitter resistors) driving them or the driver transistor driving the other output transistors in that channel could be defective.

Pull those 3 transistors and check them out of the circuit. It's likely that only one is actually shorted. Reinstall the other two (if they're OK), clamp the transistors to the sink and see if it will power up.

You'll have to replace all 6 of the transistors 2SA1695 transistors in that channel. Check the large emitter resistors connected to the 6 transistors to make sure that all are within tolerance.

[stuntstere]

I am stumped... I pulled the three transistors and diode checked them and they seem fine.. I put the pos on leg 3 and the neg on 1 then 2 and both read about .5 which is fine to me. on the other combos it read OL. To my knowledge this means it is fine.. Am I wrong?

[stuntstere]

I left all three out and hooked it up.... you can hear it pulse but doesn't pull the extreme amperage now... when you listen to it you here it running then it goes tick and the fan slows down like power is being pulled down. then is goes back to normal then tick. P.S.. I forgot to mention it made this ticking sound before too. When it ticked you could see all the lights dim and my subs would pulse with it to. Now it ticks but doesn't go through the subs and it does pull as much amperage now.

[Perry Babin]

On diode check, 0.5v from 2-3 means the transistor is defective.

Check the driver transistors to see if any appear shorted.