is there any issue with doing this?
the amplifier I have is a crossfire BMF1000D.
the mosfets in the powersupply all have holes in them.
not sure if they're the original fets, but they're IRF3205
http://www.irf.com/product-info/datasheets/data/irf3205.pdf
the amplifier appears to have been repaired before, so these may not be the original fets.
the question is, can I simply replace them with IRF1405's, in the hope that the amplifier will be less likely to fail, due to the higher current handling?
http://www.redrok.com/MOSFET_IRF1405_55V_169A_5.3mO_Vth4.0_TO-220.pdf
the amplifier I have is a crossfire BMF1000D.
the mosfets in the powersupply all have holes in them.
not sure if they're the original fets, but they're IRF3205
http://www.irf.com/product-info/datasheets/data/irf3205.pdf
the amplifier appears to have been repaired before, so these may not be the original fets.
the question is, can I simply replace them with IRF1405's, in the hope that the amplifier will be less likely to fail, due to the higher current handling?
http://www.redrok.com/MOSFET_IRF1405_55V_169A_5.3mO_Vth4.0_TO-220.pdf
Unless the user is abusive, the 3205s will work perfectly fine in that amp. There's no reason to use anything else. As far as I know, the 3205s were the OEM part.
Using higher current FETs generally means that they will be more difficult to drive which could mean that the drive circuit would have to be modified for them to work 'properly'. If the amp has a regulated power supply, it may not be immediately obvious that there is a problem with the drive circuit.
Using higher current FETs generally means that they will be more difficult to drive which could mean that the drive circuit would have to be modified for them to work 'properly'. If the amp has a regulated power supply, it may not be immediately obvious that there is a problem with the drive circuit.
You could have a lot of troubles causing this like intermittently shorted power transformer, Shorted output filters...etc...All of these problems may not be evident on a test bench until you push the amp to full power. Perry's is also 100% dead on about the possible issues you may create when boosting current capacity in a power supply...
still haven't fixed this amp, my stupid desoldering station AND the one I borrowed from work, were both completely and utterly useless.
So, I took it into work last night, and desoldered the old parts there.
Of course, my soldering iron died a month or so ago too, so I might be fixing the entire amp at work
I plan to run this at 0.666 ohm shall see how it goes, only need it for "burps" so with impedance rise, it should be fine!
So, I took it into work last night, and desoldered the old parts there.
Of course, my soldering iron died a month or so ago too, so I might be fixing the entire amp at work
An externally hosted image should be here but it was not working when we last tested it.
I plan to run this at 0.666 ohm
shall see how it goes, only need it for "burps" so with impedance rise, it should be fine!
Still didn't get this amp working!
Came back to it a few weeks ago, found a shorted fet on the output, cut it out of circuit, tried powering it up, and it keeps cycling into protect, with the entire negative rail on the output...
Found another shorted fet, removed it, now it powers up, but the rails start at +-35volts, then start to rapidly drop? I haven't left it on for an extended period, but within 10 seconds, they're down to +-15volts....
Came back to it a few weeks ago, found a shorted fet on the output, cut it out of circuit, tried powering it up, and it keeps cycling into protect, with the entire negative rail on the output...
Found another shorted fet, removed it, now it powers up, but the rails start at +-35volts, then start to rapidly drop? I haven't left it on for an extended period, but within 10 seconds, they're down to +-15volts....
If you want to fix it and need to burp (for how long?) into 0,66ohm..so I´d request for you to change each and every fet (power/amp) do not change something in between. If one of those fets is dead -> you change everyone.
I assume that this amp is rated at 1ohm load so there should be no problem to drive it into 0,66ohm WITH good voltages..voltage shouldn´t drop under 12VDC when burping.
Changing those power fets won´t give you anything more out of that amp, unless you modify the driving side of those power fets (like Perry said before).
I assume that this amp is rated at 1ohm load so there should be no problem to drive it into 0,66ohm WITH good voltages..voltage shouldn´t drop under 12VDC when burping.
Changing those power fets won´t give you anything more out of that amp, unless you modify the driving side of those power fets (like Perry said before).
I wasn't expecting to get more out of the amp, other than perhaps slightly more resilience to voltage drop, that may have been the cause for it to smoke in the first place
Problem now, is I have two switching outputs from the controller board in the power supply section making it to the fets, but the rails just disappear, even though the switching signal is still there... and something on the controller board seems to heat up.
I've removed the controller board, and a few more pads, so I'm going to fit a socket so the board can be plugged and unplugged...
Problem now, is I have two switching outputs from the controller board in the power supply section making it to the fets, but the rails just disappear, even though the switching signal is still there... and something on the controller board seems to heat up.
I've removed the controller board, and a few more pads, so I'm going to fit a socket so the board can be plugged and unplugged...
When you measure the rail voltage, did you use the secondary ground as the reference?
If you want to make the amp less likely to fail with low voltage (if that's the reason it fails), either add low voltage protection or add a power supply to the drive IC that won't drop with rail voltage. Rockford takes 15v from the op-amp power supply. Orion used additional windings to create a supply. Zapco rectified the primary winding waveform to produce voltage above the charging system voltage.
Many times, it's not the low voltage. The voltage drops because the amp is drawing too much current (more than it was designed to draw) and providing more voltage to the amp makes the amp less likely to survive.
If you want to make the amp less likely to fail with low voltage (if that's the reason it fails), either add low voltage protection or add a power supply to the drive IC that won't drop with rail voltage. Rockford takes 15v from the op-amp power supply. Orion used additional windings to create a supply. Zapco rectified the primary winding waveform to produce voltage above the charging system voltage.
Many times, it's not the low voltage. The voltage drops because the amp is drawing too much current (more than it was designed to draw) and providing more voltage to the amp makes the amp less likely to survive.
My opinion: If you do have interest on this -> get rid of those transistors and use fet driver.
With nice fet driver(s) you can find much better power fets to that board and you won´t have to worry about that puke driving. With this and Perry´s ´12VDC allthetime -mod´ you have as realible power as you can with reasonable modifications.
Smarter ones correct me if I'm wrong
E: And the replace fet could be something like this (all the way better than the others mentioned)
http://www.irf.com/product-info/datasheets/data/IRFB4110PBF.pdf
BUT you cannot drive these with those transistors..you need the fet driver.
With nice fet driver(s) you can find much better power fets to that board and you won´t have to worry about that puke driving. With this and Perry´s ´12VDC allthetime -mod´ you have as realible power as you can with reasonable modifications.
Smarter ones correct me if I'm wrong
E: And the replace fet could be something like this (all the way better than the others mentioned)
http://www.irf.com/product-info/datasheets/data/IRFB4110PBF.pdf
BUT you cannot drive these with those transistors..you need the fet driver.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.