autotek xs1500.1

[DREW028]

Does anyone know the part number is for the power supply FET's?


Also Perry i seen in another one of your post you recommended changing the output FETS to the IRF3710Z?

 

[Perry Babin]

IRFP064N in the power supply.

Only use the IRF3710Z if the output transistors have failed and you need replacements.

 

[DREW028]

2 failed so I guess ill have to replace them all.

Thank You!

This amp also had 2 more added resistors soldered in at locations r37 and r40. Do you know if this modifies the protection for the amp? Also r39 location is empty, should it be?

 

[Perry Babin]

The parallel resistors are OK. R39 should be the same as R38.

 

[DREW028]

With the new output FETs would it be ok to run it with the protection modded?

 

[DREW028]

Have you ever used or heard about avnetexpress? They have the irf3710z for $.58 and a few other FETs i need for cheap.

 

[Perry Babin]

I don't know precisely how the protection circuit has been modified so I can't tell you it would be safe. I'd guess it would not since it failed to protect the outputs.

I don't buy from that distributor. I generally recommend Future, Arrow, Digi-key and Mouser.

 

[DREW028]

Output FETs are out as well as the rectifiers.


Just installed the power supply FEts and everything seems ok.

i see this amp doesn't have a negative rail on the power supply am i correct?

On the outside pins of the rectifiers im reading +32vAC (on both rectifiers). Center leg to the outside legs im reading +15vAC (both rectifiers). Does this sound right?

I haven't gotten the replacement output FETs yet. Hopefully soon, i am very excited to see this amp work. Thank you!

How do i check IC6 and IC5? I downloaded the datasheet but am not sure what reference to ground to use.

 

[Perry Babin]

The amp only has positive rail voltage for the output transistors. I've never needed to measure the voltage the way you did so I don't know if it's right.

 

[DREW028]

No outputs fets, rectifiers in 63.5vDC on center leg (both rectifiers) black probe on amp ground.

 

[Perry Babin]

That sounds about right.

 

[DREW028]

IC3 reading black probe on amp ground outputs not installed:

pin 1: 18.9
pin 2: 12.03
pin 3: .041
pin 4: .025
pin 5: 12.02
pin 6: 6.4
pin 7: 2.5
pin 8: 5.2
pin 9: 5.2
pin10: 15.3
pin 11: 15.3
pin 12: 2.3
pin 13: .024
pin 14: .024
pin 15: 12.2
pin 16: 12.2
pin 17: .024
pin 18: 12.01
pin 19: 5.9
pin 20: 5.9

 

[Perry Babin]

Most of the voltages on that IC are irrelevant without the outputs in the amp.

 

[DREW028]

Ok, thats what i was thinking while looking at the board but wasn't sure. Im still waiting for the replacements to come in.

 

[DREW028]

Got the outputs in today. The amp produces sound. I tested in a small speaker for less than a minute. The only thing was when adjusting the gain the speaker had static. I don't remember if this happened before. Maybe its because the source I'm using?

 

[Perry Babin]

It could simply be a dirty potentiometer.

 

[DREW028]

Good call on the dirty potentiometer.

Only think I noticed is r29 and r27 get hot to the touch. Is this normal? They have to be removed to be test correct?

 

[Perry Babin]

It's normal for large resistors to operate at elevated temperatures. In general, if they're not so hot that they're desoldering themselves, they're OK.

 

[DREW028]

I just picked up a second xs1500.1. These amps have an 80 amp fuse and are rated 1600watts at 1 ohm. Most newer amps have 2 80 amp fuses. Are these really that efficient?

 

[Perry Babin]

Possible reasons that the 80 will hold.

The amp probably won't produce 1600 RMS.

Bass isn't constant so the high current draw through the fuse isn't constant.

The fuse doesn't blow at its rated current. It will probably pass 2x its rating for a short period of time.

Many amps have fuses rated far too high to protect the amp. I've seen far more blown power supplies than I have blown fuses. I generally drop the fuses down at least one step when I repair an amp.