MTX Thunder 5601

[S Merlington]

Anyone have high res pics of the board around the rectifiers behingd the RCA jacks ??

Also a high res pic of the area around the regualtors C118 is missing and alot of burnt components in that area

 

[Perry Babin]

http://www.bcae1.com/temp/IMG_0370x.jpg

I don't have anything for the rectifiers. What do you need to see?

 

[S Merlington]

REC 102 is missing and the transistor next to it is also missing ..

Need to know what they are..


Also R123 is missing and R320 is misssing in that area

 

[Perry Babin]

R320 is a 0 ohm jumper.

R123 is a 1k resistor.

When I get back to the shop, I'll see if I have one of these in the junk pile for the transistor.

 

[Perry Babin]

http://www.bcae1.com/temp/IMG_3665x.jpg

http://www.bcae1.com/temp/IMG_3664x.jpg

These are from a 4501. They are probably the same. The board is an MVP170

 

[S Merlington]

Anyone know the value of R318 it sits by the TL072 behind the RCA jacks

 

[Randy62]

100 ohms.

 

[S Merlington]

Replaced R320 Thanks..

Anyone know the values of C141 and R260 they are in the power supply section ?

 

[Perry Babin]

10k

I can't find C141 on the photos I have. If no one else can help, post a photo of its location.

 

[S Merlington]

I called MTX and they gave me the value of the cap.. 10mf 25v

Perry,

Ive replaced the following components

Q108,Q109,Q111,R122,R123,R320,R318,R301 and the 10mf 25v cap that sit behind the RCA jacks by the rectifier circuit also replaced the IRF540 and the MUR1620R..

Ive replaced Q106,Q107,Q110,D104,C118 and the IRF540 on the other side by the Rectifier circuit..

Ive replaced D102,C141,R260 and 1 A06 so far in th power supply section..

R406 is defective and i need to check more components in that general area to see if any are defective..


Should i change the TL072 that sits behind the RCA jacks ??

Do you know of anything else i should check before powering this amp up??


Also is this common or do you have an idea why this amp blew so many components ??

 

[Perry Babin]

I wouldn't replace the TL072 without a reason.

The failure of the voltage regulators can cause extensive damage. There is likely damage on the preamp board as well.

When you power it up, make sure all components are clamped. Do not connect the preamp board until you know that the regulators are OK.

With the scope set to 5v/div, place your scope probe on the regulator output leg and power the amp up. If the voltage viewed on the scope goes off of the display, immediately shut down the amp to prevent further damage. Do for both the positive and negative regulators.

 

[S Merlington]

Well Replaced R143, R406,

Im guessing the rail caps are defective also I removed them from the board and can hear the inners rattling around in the cap

 

[S Merlington]

Set scope to 5v div..

And 5us or 5ms ?


Also your talking about the Mur1620ctr and the byw51 ?

 

[Perry Babin]

The two IRF540s near the rectifiers are the regulators. You can check on the ends of R318 and R319 farthest from the IC.

 

[S Merlington]

The trace on the scope stays centerd

Set the scope to 5v div and 5 ms tryed a couple different posistions and it stayed centerd

 

[Perry Babin]

Did you confirm that the power supply was operating?

 

[S Merlington]

I have a nice square wave on the power supply fets (gate leg)

Im getting + - 15 volts of regulated voltage

Im getting -63 and + 56 volts of rail..


But im getting 56.2 volts measured directly across the outputs..

Any idea what might cause this?

 

[Perry Babin]

Post the DC voltage on all pins of the op-amp between R405 and R407.

 

[S Merlington]

NE5532

Pin 1:12.59
Pin 2:13.60
Pin 3:13.81
Pin 4:-15.34
Pin 5:13.72
Pin 6:13.99
Pin 7:14.59
Pin 8:15.46

 

[Perry Babin]

It appears to be defective but since the input voltages are so near the supply voltage, it's not possible to tell definitively.