MTX 81001, Want to know the value of two parts

[dinoo]

The resistor seems to be good.

Which other locations should i check out?

 

[Perry Babin]

Replace any semiconductors in the circles if you're not 100% sure that they're OK.

 

[dinoo]

I replaced Location Fet401
I also replaced Location D404, r410, Q401, U402, U403.

Then i turned the amplifier onn with a 12V 2A adapter.

Then i about 15 sec i heard something sizzle.

I turned the amplifier off immediately.

After i turned off the aplifier i saw the Elco at Location C408 was hot and distended.

 

[Perry Babin]

It could have been damaged by the previous failure of the regulator OR the regulator is still defective and producing too much output voltage. Connect a meter to the output of the regulator and monitor it as it powers up.

 

[dinoo]

At which location is the regulator?

 

[dinoo]

What are the equavalent parts ?

 

[Perry Babin]

All of the parts that you have been replacing and FET401 make up the regulator.

 

[dinoo]

Do you know what the equivalent part is for location D400?

 

[Perry Babin]

MMBD4148

 

[dinoo]

What do you mean by regulator a few notes above?
At wich location can i find the regulator?
What is the part number?

Sorry for my bad english

 

[Perry Babin]

The 'regulator' is a voltage regulator. The opto-couplers cannot operate from rail voltage. The voltage limit is about 20v. The voltage regulator supplies a safe voltage to the opto-coupler.

There is no one part that makes up the regulator. It's made of a number of parts. I don't have a diagram for the regulator with the circuit board designations in your amp but the diagram from another MTX amp can be seen below.

 

[dinoo]

thank you, still dont understand it fully.

How much Ohms do the R403 have to be measured ?

The Location R403 is a SMD Resistor with code 2619 on it.

 

[Perry Babin]

You're reading the resistor upside-down.

 

[dinoo]

I`m still busy with this amplifier. The problem is still the same the Elco keeps burning.

I readed this topic again and i saw this text.
"Until you get the regulators working properly, I'd suggest pulling the two 3120s and soldering a jumper connecting pins 5, 6 and 7 on each 3120. This will prevent damage to the opto-couplers and the jumpers will keep the outputs from switching on."

I want to know what you ment by:
soldering a jumper connecting pins 5, 6 and 7 on each 3120.
(i know what a jumper is. but i dont know what you ment by pins 5,6,7 on each 3120?

 

[Perry Babin]

The output of the optocoupler swings from the voltage on pin 5 to the voltage on pin 8. Pins 6 and 7 are the output (sometimes shorted on the board, sometimes not). Removing the opto-coupler and shorting pins 6 and 7 to pin 5 keeps all outputs OFF and allows troubleshooting with no risk to the output transistors.

 

[dinoo]

So i have to solder pin 1,2,3,5 and pin 8 on the board, except pin 6 and 7.

I will connect pin 6 and 7 together and solder it on pin 5 ?

 

[Perry Babin]

You remove the 3120 and solder pin 5 to 6 and 7. That's all you do to the 3120.

 

[dinoo]

Oke, and when i put back the 3120 which pins schould i solder to the board ?

 

[Perry Babin]

The 3120s won't go back in until you fix all of the known faults.

This is an old thread. I'm not sure where you are on this amp (repair-wise).

 

[dinoo]

At this moment i replaced all of the following locations beneath 3210 :
D404, r410, q401, d401,c408, c406, d405, d406.
I also replaced fet401 and resistor 407 and 403 seems to be good i think the q403 and d400 is not likely defective.

I also relaced a 100ohm resistor and a zener diode j5 under the 2 coils.

And replaced the optocouplers and when i turn op the amp on low voltage the capacitor c406 is distending.