Memphis Amps

[Exbass17]

Does anyone know what it is with these things obviously it seems like a common problem anywhere from a Memphis 16-st 500d to a 16-mc500d all the way to a Memphis MCD 4KW replace all blown power and output fets and all they do is the same thing flash green power light when powered I don't get it let alone know where to start has anyone else had these problems seems pretty common for me too stumble across 3 of them

 

[Perry Babin]

It sounds like the supply voltage is dropping when you power them up. The only time that I can remember seeing that is when I power them up through a current limiter.

 

[Exbass17]

Capacitors discharging maybe causing the lack of power? Seems pretty odd I have 3 different models and if I recall most of the problem on all 3 of them was clearly observant in the power fets burned up

 

[Perry Babin]

When using a limiter, the LED will blink on as the amp tries to power up but when it does and the rail caps draw significant current charging up, the voltage drops and the amp shuts down for a fraction of a second. This repeats until the caps get charged. Then the amp will remain on.

What are you using to power the amps on the work bench?

 

[Exbass17]

I currently am using a 12volt 3A power supply but the thing that gets me I have another MCD 4kw that it will power on no problem also if turned up to a certain point the amp will start cutting out from the current being limited

Also I have tried running the Memphis 16-ST500D on a car battery with the same flashing results

 

[Perry Babin]

Did all of the memphis amps flash on the battery or only the 500?

A 3 amp supply isn't enough for many amps.

 

[Exbass17]

I havnt attempted the mcd 4kw on a battery because I figured if the one powers up no problem off my 3 amp power supply then something wasn't right considering I have already dumped over 100$ in on the Power and output fets I am afraid they may burn up

The other 500D I can easily try it real quick but I am pretty confident it will show the same results

 

[Exbass17]

The Mc-500D came on with a red light not even a second later the 10 amp fuses popped on this one alittle different I guess ill have to retrace my steps with this one seems like a straight short somewhere on this amp

 

[Perry Babin]

If there is excessive current draw only after the remote voltage is applied, it's likely the fault is in the audio section of the amp (most likely shorted output transistors).

 

[Exbass17]

I went ahead and removed the
4 - IRF9640
2 - IRF640

Outputs with the same result checked voltage at each power fet coming off the coils without the driver riser board installed they all read constant 12.22 volts if I connect the driver riser board the voltage fluctuates from 11.89 v - 12.22 I even tried a known working compatible driver riser board same results

 

[Perry Babin]

You need to write more clearly.

All of the FETs clamped to the heatsink are power FETs. If you mean power supply FETs, make that clear.

There are inductors (coils) and transformers. If you mean inductors, write inductor. If you mean transformer, write transformer.

There are multiple driver boards. You must be clear which one you're referring to (audio, or power supply driver board).

Repost #10 written clearly.

 

[Exbass17]

I went ahead and removed the
4 - IRF9640
2 - IRF640
Outputs

with the same result checked voltage at each power supply fet coming off the transformer coil without the power supply driver board installed each wire coming off the transformer read constant 12.22 volts if I connect the power supply driver board the voltage fluctuates from 11.89 v - 12.22 I even tried a known working compatible power supply driver board I get the same results flashing grn then red light repeatedly

 

[Perry Babin]

Twist/push/pull on the power transformer when it's trying to power up to see if that makes a difference.

If not, pull the audio PWM/modulator board (behind the RCA jacks) to see if that makes a difference.

 

[Exbass17]

The transformer is solid to the board glued on I also tried tapping around the board without any result

The PWM/modulator board and audio board don't seem to effect the volt fluctuation at the power supply fets when the power supply driver board is disconnected

I am beginning to wonder if maybe the rectifiers or the thermal sensor maybe bad I have current passing straight through the thermal sensor not sure if that is suppose to be that way I am going to compare the parts maybe swap them out with a Memphis mcd1000d I have laying around which I know powers up fine with the power supply driver board connected

 

[Exbass17]

Switched out the YG225N2/YG225C2 Fast Recovery diodes the amp is no longer flashing it powers up but when speaker is connected it pops during amp start then passes some distorted music for a quick second and no more sound the speaker

I swapped out the Power supply driver board/audio board/PWM board with known working boards same versions still no sound

also the speaker makes noise when the amp is not powered just connecting the speaker to the terminals with the remote wire jumpered to the + terminal +/- disconnected

Does anyone know of a good replacement for the Fast Recovery Diodes YG225N2/YG225C2 ?