Mmats d3500.1 questions for repair

[punch45x2]

Hi guys. Working on a mmats d3500.1 and the unit goes into protect immediately. I have tested all of the output gets and the power supply fets.they all seem ok. Only thing I found was a tlc2274c OP amp that's toasted.i think its u1 but there is a via on the silk screen. Any ways any one knows what it controls. I don't think it's a fet driver. Any help would be appreciated.

 

[Perry Babin]

It's not an FET driver. What happens if you power up through a current limiter. Does it still go into protect, immediately?

 

[punch45x2]

I will try that and get back to ya.

 

[punch45x2]

Ok so it did power to low current mode. Heard a low level his from power supply area and u1 was getting warm [opposite side of the board]. This was at 14.4 v at 1.2 amp. It only powered up using both of the dual power inputs.

 

[Perry Babin]

U1 on the opposite side of the board?

14.4v measured where? If you had a limiter in series with the amp, the voltage at the amp, the voltage was likely significantly lower.

Powering up using both power inputs? Is that something that you didn't do previously?

 

[punch45x2]

I have an xtronic power supply that will limit current to what I set it at. U1 was on the opposite end of the board from power supply section. And I was only trying to power it up on one set of power inputs previously instead of the two.

 

[Perry Babin]

What's the DC voltage across the power supply terminals of U1?

Does using both terminals allow it to power up normally (not going into protect)?

 

[punch45x2]

I ohmed between the two positive inputs and got 0 ohms continuity and on the negative inputs so I assumed they were the same so I was only trying one set of inputs. When I used both the unit powered on not in protect.i will check voltage on u1 tomorrow.

 

[punch45x2]

So input voltage is 14.8 v for u1 probably why it's getting hot. Supply voltage is 14.4

 

[punch45x2]

So I can power from either or power input. Remote wire input just takes like 3 seconds to turn on.

 

[Perry Babin]

In the power/ground terminals, does the metallic part of the terminal lay directly on the circuit board or does it have a layer of clear plastic between the metal block and the circuit board?

 

[punch45x2]

They is clear plastic around them but the metal has standouts to make full metal to circuit board contact.

 

[Perry Babin]

Clamp something rigid like a large hex-key wrench into the blocks (all of them) and see if you can move the terminals (even a tiny bit) by pushing on the wrench. There should be no movement.

 

[punch45x2]

They are solid.

 

[Perry Babin]

They probably won't remain solid. This was a common issue with those terminals and was compounded even more for the ones that had essentially no screw head for their mounting screws.

 

[punch45x2]

So these have fairly large washers on the screws that sandwich them to the board. Do you know if the lm340 in the center of the board controls the voltage to u1. That voltage I think is max of 8 and it's getting 14.8

 

[Perry Babin]

LM340 isn't likely the entire part number. Photo?

 

[punch45x2]

Sorry. Lm340t15

 

[punch45x2]

Did you still want a pic?

 

[punch45x2]

So I ohmed it out and that is the voltage regulator for u1. Any idea how to test this one? Do you know what voltage it should be at?