Soundstream ref 414s Problem

[Perry Babin]

Did you try to play this amplifier into speakers?

If so, what was the problem?

On the schematic, it looks like the secondary is simply floating (no resistor to tie it to ground).

[mrFrog]

Originally posted by Perry Babin
Did you try to play this amplifier into speakers?

If so, what was the problem?

On the schematic, it looks like the secondary is simply floating (no resistor to tie it to ground).

No I didn't, my h/u suddenly died, took it apart, found some burnt and broken PCB tracks, traced them to the line-outs of the h/u and decided to check the amp's line-in just in case.
I am glad I did since it seems the next h/u might well have suffered the same fate !

Jaime (Jandrelectronics on eBay) has come back to me and made the same suggestion (floating ground). Apparently, only channel 2 is grounded, the other RCA's are grounded via a 1ohm resistor. He's asked me to check a few things (337 and 317 voltage regulators to start with) and will get back to me.

I've also received a useful response from Soundstream

HELLO; THIS IS NOT NORMAL AND THE AMPS NEEDS TO BE REPAIRED. COST TO REPAIR YOUR AMP WOULD BE A FLAT FEE OF $150.00 AND COMES WITH A 90 DAY WARRANTY. IF YOU WANT TO SEND YOUR AMP IN FOR REPAIR, PLEASE GIVE US A CALL AT 1800-724-1377,SO WE CAN ISSUE YOU A RA-REPAIR NUMBER. THANK YOU

So no schematics from them then

[Perry Babin]

Without remote voltage applied to the amp (only B+ and ground connected to the poweer supply), measure the DC voltage on channel 2 shield (or the output shields). The black meter lead should be connected to the power supply ground. If there is 12v present, the transformer is shorted. You may want to twist/move the transformer slightly while checking the voltage because the short could be intermittent.

[mrFrog]

Thanks, I will try that too

[mrFrog]

Originally posted by Perry Babin
Without remote voltage applied to the amp (only B+ and ground connected to the poweer supply), measure the DC voltage on channel 2 shield (or the output shields). The black meter lead should be connected to the power supply ground. If there is 12v present, the transformer is shorted. You may want to twist/move the transformer slightly while checking the voltage because the short could be intermittent.

Tried this to no avail... same with remote voltage applied.
However, and here is the most frustrating thing... the problem has disappeared... on the test bench at least.

All powered up with a lab power supply, bare board on the bench, all checks out fine.
Put the board back into the casing, and all is fine.

Wiggling the transformers makes no difference . Now, I don't know what to do... electronics don't fix themselves... if I put it back in the car, chances are the h/u will eventually fry itself.

I don't want to throw the amp away

[Perry Babin]

I still suspect the transformer. If you pushed on it, you may have made enough clearance between the lead windings and the rest of the windings to break the connection. The problem is almost always between the lead windings (the ones that connect to the board) and the remainder of the windings. The cores are not well supported (particularly in the ones that have the transformers in a cutout) and they cause the enamel to wear through when the windings wrapped around the core rub on the lead windings.

If you can't find the short, I'd strongly suggest that you apply epoxy between the lead windings (where they begin to wrap around the core) and the main body of windings. Try to work the epoxy between the windings. If possible, work an epoxy soaked piece of paper between the windings.

When you reinstall it, I'd strongly recommend that you fuse the shield connections between the amp and the head unit. If the short returns, the fuse will open instead of the traces in the head unit.

You can fuse the shields by using a short RCA extension cable (male to female) and breaking the shields in it. You would use 1 amp fuses to reconnect the shields.

Other than a shorted transformer, there are few things that can cause the amp to burn the head unit's shields. The only other thing I can think of is a speaker wire shorted to ground but that would not have caused you to have DC on the shields after it was removed from the vehicle.

[mrFrog]

Thanks Perry, this all makes sense, I will try and re-insulate the windings and put an inline fuse as you suggested.

Thanks again for your support