MTX JH1200 repair

[tobyret2]

Why my tip29 and tip30 can warm up as soon as you install lm317 lm337. Operational amplifiers are not soldered, lm317 337 are cold. Here is my wiring diagram

[Perry Babin]

Did you try increasing the Zener value as suggested in post 30?

[tobyret2]

changed from 15 to 22v. I'll try 30v tomorrow

[tobyret2]

maybe there is an amplifier circuit in which a similar power supply is + -15v?

[Perry Babin]

The preregulators are what's rare. Most amps have low voltage windings to supply about 20-25v to the regulators.

[tobyret2]

I may be wrong, but here is a diagram of the preliminary stabilizers, I made them at 22 volts. Input 80, Zener diode 22. The minimum zener current is 0.001, the maximum is 0.018, we take the average value of 0.0095. I consider the resistor 58 / 0.018 ~ 6.2kOhm. It turns out that 22 volts with a current of 0.0095 A arrive at the base of the transistor. Seemingly 0.0095 x average h21e tip31 (32) c which I put in, which is about 40, at the output I should have 0.38A (this transistor has 3A max) .0.38x22 = 8.4W at 30 max. Either I'm confusing something, or everything should work. The only thing that confuses me is the high h21e of these transistors .. 50 should be the maximum and the Chinese pribluda shows 200+. Maybe that's the whole problem?

[Perry Babin]

The important thing is not to drive too much current through the resistor and diode so they don't overheat. The Zeners are 1/2w. You can use 1w if you want a bit of headroom.

After the voltage at the base is set, only the current that's drawn by the regulators will flow through the TIP transistors.

[tobyret2]

I did + -15v. I wound 2 additional windings on transformers. I threw out the transformers, put 2 diodes instead of them, and instead of zener diodes, capacitors 50v 220mkf and cut the tracks from the collectors. As a result, 24v began to come to lm317,337 and everything worked. But another problem appeared, there is a quadratic impulse, there is sound, but the irf640n burns out very quickly ... maybe there are some guesses about what?

[Perry Babin]

Please re-read and edit what you wrote.

[tobyret2]

I wound 2 additional windings, put 2 diodes and 2 capacitors in front of the lm317,337 and +-15V appeared . All this instead of tip29 tip30 and Zener diodes. lm317, 337 are cold. Now another problem is burn irf640n . I turned it on, checked the pulses on the gates . It seems everything was fine, the amplifier played for 2 minutes and then the hum from the speaker . I checked the meander again and turned it on. Again, the same thing. After 2 failures on 1 shoulder, the meander remained, on 2 direct current . Pre-swing transistors (PZTA42) on the driver Board are intact. There are no burnt resistors . Where to dig I do not know( I do not like that the power in the shoulders is different, can this be due to the fact that the irf640 is not soldered ?