Rockville RX Md3

[bl4ckw1d0w]

I have a Rockville RX MD3 thats heating up the rail caps which leads me to believe there is a drive problem.

I have isolated the current draw to the audio section.

Does anyone have a diagram of the driverboard in the audio section as I am unfamiliar with this one. Is there any other amps that are similar to this one i can scavenge some posts or diagrams to get me started?

KTA1504 and equivalent I dont have in stock. Ive seen them replaced in the power section with MMBTA56 but not sure if these would work in the audio section.

 

[Perry Babin]

Post photos of the audio section of the main board.

 

[bl4ckw1d0w]

See attached.

 

[Perry Babin]

It's essentially the same as the SLA1500. The driver board is a bit different with the 74HCT14 but should be fairly straightforward to troubleshoot, especially if you have clean drive coming off of the driver board.

Without the driver board, is there any current draw or DC offset on the output?

 

[bl4ckw1d0w]

Using a 2ohm limiter i have 3 amps after remote is connected. I have already replaced the rail capacitors. From +speaker to -speaker terminal i have -7 volts. Its the same if i use battery ground.

 

[Perry Babin]

Is this without the driver board?

 

[bl4ckw1d0w]

No driverboard installed.

 

[Perry Babin]

If you can easily remove the driver board without damaging the vias in the main board, remove it and re-check for DC offset.

 

[bl4ckw1d0w]

That was with the driver board removed.

 

[Perry Babin]

Monitor the DC offset and check the DC voltage from gate to source for each FET.

Does one or more of the FETs have more than a fraction of a volt?

Does the DC offset drop to 0v when you're measuring the DCV g-s on any FET or group of FETs?

 

[bl4ckw1d0w]

Rectifiers were in the wrong spot. Amp is working fine now. Stupid mistake.