Another DD Z1 Problem thread

[dwright27]

Well, got this a few days ago and it powers up, maybe for 20 - 30 seconds at most. Kicks into protect, then completely powers down, and repeats the cycle. No sound, nothing. Board looks clean, except for one part on the Power Supply side of things, which ill throw a picture of in a second.

Really just wanting to know whats wrong and how easy of a fix this is.

ive been quoted $200 and $250 to fix it. but if it will be possible to fix myself then i would rather do that.

[dwright27]

[Perry Babin]

Does it produce audio during the 20-30 seconds?

[dwright27]

Originally Posted by Perry Babin

Does it produce audio during the 20-30 seconds?

nope.

[Perry Babin]

Looking along the entire length of the amp, at the point where the transistors connect to the board , do you see any black soot. You may need a lighted magnifying glass to see down into the tight areas.

Many of these large amps (virtually all manufacturers) have problems with the legs breaking on the power transistors. This can cause all sorts of problems (intermittent and otherwise). Many times, the arcing produces a tiny bit of soot at the point where the legs are broken.

[dwright27]

ive got the board sitting on my lap looking over it. i didnt see any but looking over a second time will hopefully yield something.

if a leg is broke can i just solder it back onto the board?

[dwright27]

also would it be on the power supply side or the output side??

[Perry Babin]

It could be on any heatsink-mounted component.

If you try to tilt the transistors forward slightly, do any seem weak (compare those with the same part number)? If so, they're likely to break soon.

If a leg is broken, it's not good to try to resolder it. When you do, it makes the leg more rigid because the solder reinforces the leg. Since the spring clamps are not very strong, they may not be able to make the transistor lay perfectly flat against the heatsink. If you do resolder it, look very carefully at the transistor/heatsink mating. If the transistor is as little as 0.001 off of the sink at any point, it's VERY likely to fail prematurely. If it's using sil-pad insulators, they're a bit more forgiving but they rely in the pressure applied across the entire surface of the transistor to transfer heat efficiently. If the pressure is weak due to the more rigid leg preventing the transistor from laying perfectly flat, the transistor will still run hotter than it should and is more likely to fail. It's best to replace any that have weak or broken legs. Since you have to have relatively well matched transistors in each group of parallel transistors, it can get expensive but it's the only way to make the amp reliable.

[dwright27]

so how much for you to fix it?

[Perry Babin]

I don't work on those amps. The only person I'd suggest to repair it would be Chris at dB-r electronics.