Fixing a BOSS REV3000D amp

[KyferEz]

Thanks for any help... I've divided the post into sections to ease talking about this...

I'm working on a BOSS REV3000D amp (http://ampguts.realmofexcursion.com/Boss_REV3000D/)

1) Anyone know what the rail to rail voltage of the toroidal transformer should be? I'm getting only ~35VAC... Seems low.

2) It's also pulling over 6 amps at idle, so I'm guessing something is wrong besides what I've already fixed:
Replaced all 10 IRFZ44N supply fets
Replaced 4 of the 8 IRF2807 output FETs.
Replaced the HIP4080 output driver chip
All replacement parts were brand new.

3) Test results after above fixes:
3a) The amp makes a high frequency squealing sound; I can barely hear it
3b) The IRFZ44Ns get hot quick (I don't let them get any hotter than I can bear to touch before disconnecting power)
3c) The Protect LED comes on, then goes off after a few seconds.
3d) A few seconds later a relay clicks. It looks to be for the output... Update: not happening any more.
3e) Already mentioned over 6amp draw and Supply outputs ~35VAC rail to rail

4) I'm considering removing the rectifier diodes to see what kind of current draw I get then, and to see if the supply output significantly improves, but I don't like to do that sort of thing unless I have to.

Thanks

[brettcoupe]

The Link did not work,
Do you have a schematic?
Thanks
Brett

[luka]

Hi

Link does work.

Hi KyferEz

How did you get this 35Vac?? Hope that you did use scope, if not don't bother to measure it, because there is high freq.
1.) Your supply voltage should be somewhere around +/-100Vdc to get 1200w into 4 ohm load.
2.) 6 amps for idle is too much, so something is wrong.
I don't think that you can get that much power, because HIP4080 has supply voltage of 80V. So if there is 80V then max is 800Wrms.
3.) I think that your amp (not whole amp) is still not working, but if irfz's get hot and you don't use battery as power source, then supply is not working right. If you do have or you can borrow scope, look at gates of fets, to see if they are opened fully when they should be.

For voltage you can only measure DC on main caps that are right after secondarys.

Do rectifier diodes get hot too?

[KyferEz]

1) How are you figuring those supply voltage versus wattage output at 4 ohm?

Never mind, I figured it out, and here it is for anyone who searches for how to do it:
+/- voltage -> 0.707 * voltage = Vrms -->
(Vrms * Vrms) / resistance = Wrms

+/- 100v -> 0.707 * 100 = 70.7 Vrms -->
(70.7 * 70.7) / 4 = 1249.6 Wrms

+/- 80v -> 0.707 * 80 = 56.56 Vrms -->
(56.56 * 56.56) / 4 = 799.8 Wrms

2) I figured something was wrong... And I also figured the amp specs were lying...

3) I have a scope and will do as you say and report back. I've noticed only 5 fets, all on the same side of the primary, get hot fast, so I'll check them first.

3a) opinion on the squealing I'm hearing? Possibly because supply voltage is too low?

Voltage on main caps after secondary: ~ 20 volts DC.

The rectifier diodes do not get hot.

Thanks Luka

[theAnonymous1]

Those amps are grossly overrated and the power output is rated into 1 ohm, not 4 ohm. +-35Vac sounds about right as I have a Class-AB Boss amp rated at 3000 Wrms into 1 ohm and the rail voltage is +-45Vdc.

Also, I used to own a Boss Class-D amp that had a high frequency "whine" on the outputs. There wasn't anything wrong with it other than it being a Boss amp.

Sorry I can't help more.

[KyferEz]

You misunderstood. It's not +/-35volts...

I'm getting +/-17.5volts = 35volts peak to peak (or rail to rail as I said), so yes, something is still wrong.

Also, the whine is NOT emanating from speakers (as none are attached). The sound is coming from the amp itself!

[KyferEz]

Some new info:

I hooked the scope leads to the secondary of the supply. Ground hooked to common, one lead to each secondary winding.

As you said Luka, my 35vac reading was wrong because I didn't use the scope. Have to remember that

This image is of the secondary with power first applied. Looks a little rough, but Ok. Check my next post.

[KyferEz]

This is the secondary output about 2 seconds after power is applied

This is also when the amp starts squealing.

[brettcoupe]

Sorry , Yes Link Works, Some Kind of Internet Issue at home.

Whats the Voltage rating of the output filter Capacitors?
Its usually a good indicator to what the approx max Voltage will be close to.
For 6 Amps Draw. With Not Amps connected you should be able to feel whats getting warm. Its Possible that the SMPS controller Chip is dead and Not Pulling OFF properly causing some minute overlap. Probe each output of the PWM for Waveforms. and Then at the Fet /Transformer Junction to check Fet and Drivers

Else It can Only be Rectififers or Filter caps.
Maybe the Caps have Dried Out or Leaking. Is the DC Ouput clean, Check using a CRO for Ripple.
Cheers
Brett

[brettcoupe]

It looks Like the PWM is being Modulated. Are the Amps Disconnected.?
If So check your Filter capacitors around the PWM and Drivers
Cheers
Brett