DD Z1 amp issues

[l7runner]

Ive had an interesting history with this amp. I bought it blown hoping to fix it on my own, but I did not have the skill nor time to finish it. So I sent it to DD for repair.

I get it back and within the first day of wiring it down to 1ohm it goes boom . So I check it out and notice a blown PS FET (IRFP 1405). I pulled it and the one next to it and put in replacements, with new gate resistors.

I powered up the amp using a 15 amp fuse to test it out. Once remote voltage is applied I hear a high pitched squeal/whistle with intermittent crackling coming from the PS section. Sounds to be coming from the transformers but it is hard to distinguish. I push on the transformers but there is no chance in sound.

The protection light comes on for the first 5 sec then goes out, but no green light. It doesn't draw enough current to blow the 15 amp fuse, and nothing gets hot. I tested the out puts with a DMM and none indicated a direct short.

I then tested the IC (SG3525A) with the meter. I have included the results below. Also when I touched the probe to the pin that reads 59 mV the sound comming from the PS section changed (got louder/screetch).

I hope one of you gurus could help me out. Thanks in advance.

[Perry Babin]

Part of the problem could be the low voltage reaching the IC. It's rated to work from 8-40v. What was the DC voltage on the B+ and remote terminals when you measured the voltages above?

[l7runner]

Originally Posted by Perry Babin

Part of the problem could be the low voltage reaching the IC. It's rated to work from 8-40v. What was the DC voltage on the B+ and remote terminals when you measured the voltages above?

Power was supplied using a 12volt battery. So 12V should have been reaching the amp, I will check again.

The same kind of sounds (buzzing/wizzing) were noted when the amp first blew still connected in my car.

I was also surprised to not see ~12 volts at the IC.

[l7runner]

I tested the voltage again, and it was a solid 12V at the B+ and REM leads. But still only ~7.4 V on the pin of the IC. I will study the driver board a little closer to look for any obvious problems.

I also noticed a loud clicking noise after power had been applied for a few seconds. This sound would typically occur when the amp came on (almost like a switch). After the click the amp would go from protect to power (when the amp was working). But now it clicked a few times and still no power.

I believe the parts responsible for this are these little black boxes labeled "Handouk RA-A12S" which are adjacent to where the speaker leads leave from the output section. They are apparently some type of coil encased in a black plastic box. I am not too familiar with amps to know what these are/if they could be the problem. Perhaps some style of solenoid?

I hope I was being clear in my explanation.

[Perry Babin]

Those are relays in the speaker lines. They click when they engage or drop out.

Can you post (or email me) a photo of the driver board for the power supply?

[l7runner]

Here are the best pics I could get of the PS driver board. The speaker leads get in the way. If you want and part #/more info just let me know. Thanks

[Perry Babin]

Does any transistor on that board have a direct connection to the B+ terminal and (on another pin) a direct connection to either pin 13 or 15 of the 3525?

[luka]

wait what? you send it to DD and then it blow again? did you ever call them and talked with them about this?

[l7runner]

Originally Posted by luka

wait what? you send it to DD and then it blow again? did you ever call them and talked with them about this?

Yeah Ive been talking with them...and its a big hassle. They outsource their repairs and it was a very questionable repair (wont get into details). It would probably cost me just as much in shipping it back to DD as it would be to repair myself.

So it is kind of a goal of mine to fix this amp myself...I will see how it goes.

I am having a hard time following the circuit for the PS driver card, it might have to be removed to view it completely (which I don't want to do).

I am going to make some Emails and see if I can come across some schematics for this bad boy.

[luka]

also go to soundpressure.com, since that is DD forum, you might get some extra help you need. I say go for DIY repair, since as you say, all fets are ok(?), so expensive part is intact, now I would say you need to get yourself scope, or you really don't know what is going on in circuit...it would be much more easy to find the problem, but yes, those 7v on SG is WAY low, fets are open, but not with a lot of voltage margin, so good start is there