changed the caps in this 2150sx to 2200 uf from 1000uf
theres 8 caps total ,when i changed them the rails dropped to
35 ~ volts
i was wondering, if i were to add enough capacitance would it be possible to drop the rail voltage to around 30-32 'ish volts.
and make the amp stable at 2.66 ohms mono? the original rail voltage is around 36 volts...and rated for 4 ohm mono operation.
seems like it would be easier than having to rewind the core.
i also think i would have to change the pre-drivers and drivers to a higher amp rating? (mpsu57/07)
and maybe replace a couple of zeners to maintain regulation.
--------------------------------------------
if not, then do you think this amp could survive 2.6 ohms mono if i put a fan on it?
theres 8 caps total ,when i changed them the rails dropped to
35 ~ volts
i was wondering, if i were to add enough capacitance would it be possible to drop the rail voltage to around 30-32 'ish volts.
and make the amp stable at 2.66 ohms mono? the original rail voltage is around 36 volts...and rated for 4 ohm mono operation.
seems like it would be easier than having to rewind the core.
i also think i would have to change the pre-drivers and drivers to a higher amp rating? (mpsu57/07)
and maybe replace a couple of zeners to maintain regulation.
--------------------------------------------
if not, then do you think this amp could survive 2.6 ohms mono if i put a fan on it?
The caps won't change the no-load rail voltage. If the old caps were far out of tolerance, there could have been excessive ripple causing the meter to read higher.
If you want to lower the rail voltage, you could change the zener diode in the regulator. This would reduce the power dissipation in the outputs so they would be more likely to survive but the power supply would still be taking a beating at 2.6 ohms.
If you use IRF3205s in the supply and fan cool the transformer (and heatsink), it may survive.
The drivers would likely survive especially with air flowing inside the heatsink. I can't remember seeing a driver fail unless a shorted output caused it to fail.
If you want to lower the ratio but are unsure of the ratio you need, you could unsolder the outside connections for the secondary. Then follow the windings back 1-2 turns and tap into the winding there. Scrape the enamel and solder a short piece of wire to exposed copper. The wire would go to the pads where the secondary windings were originally.
If you try this, when you initially power it up, do so with a 10 amp fuse in the B+ line. This will protect the supply in case something isn't quite right.
I doubt that the rectifiers would fail if they are clamped tightly to the sink.
If you want to lower the rail voltage, you could change the zener diode in the regulator. This would reduce the power dissipation in the outputs so they would be more likely to survive but the power supply would still be taking a beating at 2.6 ohms.
If you use IRF3205s in the supply and fan cool the transformer (and heatsink), it may survive.
The drivers would likely survive especially with air flowing inside the heatsink. I can't remember seeing a driver fail unless a shorted output caused it to fail.
If you want to lower the ratio but are unsure of the ratio you need, you could unsolder the outside connections for the secondary. Then follow the windings back 1-2 turns and tap into the winding there. Scrape the enamel and solder a short piece of wire to exposed copper. The wire would go to the pads where the secondary windings were originally.
If you try this, when you initially power it up, do so with a 10 amp fuse in the B+ line. This will protect the supply in case something isn't quite right.
I doubt that the rectifiers would fail if they are clamped tightly to the sink.
i think i will try changing to the 3205's if i can find them over here and using 3 fans, i got this really thin squirrel cage fan that can shoot between the pcb and heatsink aimed at the diodes.
guess i will have to cut a hole in the backplate and mount another fan over the core...and the last one over the heatsink.
anything you think i can do to stabilize the PS? like maybe adding a couple of farads to the B+ to smooth out the supply?
originally i was going to do 6 -12's with 3 -2150sx's, but i may do 9-12's at 2.66 ohms per amp...if i can stabilize it.
on one of the amps (the one you helped me fix) some of the legs on the bottom diodes were literaly melted in half, think this was becase the previous owner had it loaded down below below 4 ohms mono? or just do to bad mounting resulting in bad cooling...
ideally i really would like to keep the rail voltage up...at 2 ohms this thing is a monster...
i wouldnt max the system out everyday, just for maybe 10 minutes at a show...the rest of the time at about half volume.
thanx
guess i will have to cut a hole in the backplate and mount another fan over the core...and the last one over the heatsink.
anything you think i can do to stabilize the PS? like maybe adding a couple of farads to the B+ to smooth out the supply?
originally i was going to do 6 -12's with 3 -2150sx's, but i may do 9-12's at 2.66 ohms per amp...if i can stabilize it.
on one of the amps (the one you helped me fix) some of the legs on the bottom diodes were literaly melted in half, think this was becase the previous owner had it loaded down below below 4 ohms mono? or just do to bad mounting resulting in bad cooling...
ideally i really would like to keep the rail voltage up...at 2 ohms this thing is a monster...
i wouldnt max the system out everyday, just for maybe 10 minutes at a show...the rest of the time at about half volume.
thanx
If the diodes are clamped tightly to the sink, cooling them directly (between the board and sink) won't do much. Keeping the outside of the sink cool will keep the diodes cool.
If you use the squirrel cage to move air over the top of the board (between the board and the bottom cover), it will cool the transformer, filter caps and the drivers in the audio section. You wouldn't need to cut a hole in the bottom cover for a fan.
The filter caps will probably overheat if you drive the amp hard for a long time. If the caps on the B+ side of the filter inductor overheat, an external 1F cap should help keep them cool. If the filter caps on the other side of the filter inductor overheat, you may have to parallel several caps to help them survive.
If you use the squirrel cage to move air over the top of the board (between the board and the bottom cover), it will cool the transformer, filter caps and the drivers in the audio section. You wouldn't need to cut a hole in the bottom cover for a fan.
The filter caps will probably overheat if you drive the amp hard for a long time. If the caps on the B+ side of the filter inductor overheat, an external 1F cap should help keep them cool. If the filter caps on the other side of the filter inductor overheat, you may have to parallel several caps to help them survive.
the filter caps on the B+ side of the inductor are the sideways ones right? i think those need to be changed do to age .
what would happen if i change them from 3300uf to a couple parralled 2200uf= 4400uf, because i cant find the 3300uf sideways caps.
would that be alright?
as for the filter caps on the other side of the inductor, im not really sure which ones those are...the straight row of 8?
what would happen if i change them from 3300uf to a couple parralled 2200uf= 4400uf, because i cant find the 3300uf sideways caps.
would that be alright?
as for the filter caps on the other side of the inductor, im not really sure which ones those are...the straight row of 8?
If I remember correctly, the ones that lay down are connected directly to the transformer and are therefore after the inductor. The two standing up in the middle of the two laying down are connected directly to the B+ power wire. You'll have to follow the traces to confirm this.
The two smaller (2200uf) paralleled caps will work are are likely to run cooler (assuming that the ESR is less than or equal to the original).
The row of 8 are on the secondary side of the power supply. If those haven't been changed, you should change them. I've seen them short and cause the power supply to fail. Since you'll be running the amp hard, the old caps would be more likely to fail.
The two smaller (2200uf) paralleled caps will work are are likely to run cooler (assuming that the ESR is less than or equal to the original).
The row of 8 are on the secondary side of the power supply. If those haven't been changed, you should change them. I've seen them short and cause the power supply to fail. Since you'll be running the amp hard, the old caps would be more likely to fail.
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