Hi I'm new here and this looks like a great site for information and maybe someone can help me repair an amp I'm working on for a buddy of mine. It is an older Fosgate 801s. Similar to the punch 800s from around the late 90s. The power connectors were missing so I pulled them from another "parts" amp I had laying around and I replaced them. Someone had worked on the amp prior to me and broke a trace to the led. After I replaced the
the connector I hooked it up to my car battery and the led wasnt coming on so I thought it wasnt powering up. This was before I discovered the broken trace for the led. My ground connection slipped off the battery connection and reconnected rapidly a few times and popped a fet in the power supply. I figured no problem change the fet with an irfz44 I had try it again. When I replaced the fet I fixed the led trace so when I hooked it back up the led came on but then it popped all 4 fets on the left side of the power supply. I removed the fets and ordered replacements irf3205 from jameco and installed them. I checked all the resistors and they read
around 52 ohms feeding the left pin of the transistors. checked the other resistors and they read fine, matching the opposite side of the power supply. I hooked up the ground and remote and got 6 volts at the left leg
of the fets on each fet. I thought I was in good shape. I hooked up the power and ground and in drew current but when I hooked up the remote it popped all 4 new fets I replaced. I removed the fets and checked all the resistors again and they are ok. I also checked the pin holes where the fets are placed for dead shorts and there are none. I am somewhat a newbie so please forgive my terminology here, but I could sure use some help here could anyone suggest what for me to try to check next? What would cause the amp to blow the fets only when the remote is applied. I figured it would blow them as soon as the power and ground were connected if it were something obvious. Any help is greatly appreciated. Thanks
Jeff
the connector I hooked it up to my car battery and the led wasnt coming on so I thought it wasnt powering up. This was before I discovered the broken trace for the led. My ground connection slipped off the battery connection and reconnected rapidly a few times and popped a fet in the power supply. I figured no problem change the fet with an irfz44 I had try it again. When I replaced the fet I fixed the led trace so when I hooked it back up the led came on but then it popped all 4 fets on the left side of the power supply. I removed the fets and ordered replacements irf3205 from jameco and installed them. I checked all the resistors and they read
around 52 ohms feeding the left pin of the transistors. checked the other resistors and they read fine, matching the opposite side of the power supply. I hooked up the ground and remote and got 6 volts at the left leg
of the fets on each fet. I thought I was in good shape. I hooked up the power and ground and in drew current but when I hooked up the remote it popped all 4 new fets I replaced. I removed the fets and checked all the resistors again and they are ok. I also checked the pin holes where the fets are placed for dead shorts and there are none. I am somewhat a newbie so please forgive my terminology here, but I could sure use some help here could anyone suggest what for me to try to check next? What would cause the amp to blow the fets only when the remote is applied. I figured it would blow them as soon as the power and ground were connected if it were something obvious. Any help is greatly appreciated. Thanks
Jeff
Did you check for 6v on the other 4 power supply FETs?
Did you do this with the FETs in the circuit? It's more reliable when they're in the circuit.
Did you check the other 4 PS FETs to see if they were shorted? It's VERY rare that only half of the power supply FETs fail.
Are you sure that you're not getting them too hot when soldering them to the insulator?
Did you do this with the FETs in the circuit? It's more reliable when they're in the circuit.
Did you check the other 4 PS FETs to see if they were shorted? It's VERY rare that only half of the power supply FETs fail.
Are you sure that you're not getting them too hot when soldering them to the insulator?
Yes, I did check for voltage on the other fets and it read 4 volts. While the other side read 6 and they were in circuit. I didn't get them too hot because I put artic silver on them and rested them against the Mesha heatsink instead of soldering them down to the aluminum mesha just to see if the amp powered on. The fets on the right side of the power supply are showing no sign of a short as far as I can tell with my Fluke. There deffinately is no dead short between the pins on the fets. And it is odd only one side of the p.s. is shorted but I've seen it happen once before on a BD1500 I repaired. Thank you for your reply.🙂
I think you have a defective PNP driver for the 4 FETs on the side that failed. The voltage should be the same as the other side. The PNP drivers are Q2 and Q3. I don't know which one is driving the FETs you replaced.
Ok, I checked Q2 and Q3 with with my ohm meter. Q2 gave a resistance of 636 ohm between the rear 2 pins.(The ones on the rear of the component) This also made Q1 appear to give the same reading between it's 2 rear pins. I removed them both and only one was at fault. Due to my inexperience I removed them both at the same time without reading the
part numbers on the components. I thought maybe they were the same as
Q1 and Q2 on some other parts punch amps I have from the same era. But I was wrong I think. I messed up, lesson learned though. With both Q1 and Q2 removed, the pads where there was resistance now has none so
it was probably the Q2 that was at fault like you suggested. I noticed, one of the drivers read a number starting with a 2 while the other started
with a 1. Do you know which one of the 2 would begin with the number 1
and which would begin with the number 2. Probably now that I think about it, the Q2 which was probably the one at fault like you suggested is the one with the number 2. I'll check again which component gives the bad
reading in a little bit when I get some coffee in me. lol. My next question is would I be able to replace the bad component with one off my parts amp? They are very different in size. This is a punch 801s and the amp I'd be pulling it from is like a punch 150.1. My new Fets, 10 Irf3205, arrived yesterday I stole them for $8 shipped from ebay. Way cheaper than the 4 I payed $16 for from Jameco last week. lol. I don't want a repeat of the fets blowing once I replace them again. What else should I check for and what precaution could I take to prevent them from shorting again when I
try to power them up again? Thank you so much for help, I'm learning alot
from this site and especially your posts. 😀
part numbers on the components. I thought maybe they were the same as
Q1 and Q2 on some other parts punch amps I have from the same era. But I was wrong I think. I messed up, lesson learned though. With both Q1 and Q2 removed, the pads where there was resistance now has none so
it was probably the Q2 that was at fault like you suggested. I noticed, one of the drivers read a number starting with a 2 while the other started
with a 1. Do you know which one of the 2 would begin with the number 1
and which would begin with the number 2. Probably now that I think about it, the Q2 which was probably the one at fault like you suggested is the one with the number 2. I'll check again which component gives the bad
reading in a little bit when I get some coffee in me. lol. My next question is would I be able to replace the bad component with one off my parts amp? They are very different in size. This is a punch 801s and the amp I'd be pulling it from is like a punch 150.1. My new Fets, 10 Irf3205, arrived yesterday I stole them for $8 shipped from ebay. Way cheaper than the 4 I payed $16 for from Jameco last week. lol. I don't want a repeat of the fets blowing once I replace them again. What else should I check for and what precaution could I take to prevent them from shorting again when I
try to power them up again? Thank you so much for help, I'm learning alot
from this site and especially your posts. 😀
Check your driver transistors, make sure your getting a voltage of around 4 - 5 volts at the gate pads where the fets go on all 8 fets. If your getting higher voltages then, it may be blown (driver circuit). Or check the channels one may be shorted causing the power supply to fail again.
ebay is not a good source for semiconductors. There are too many sellers selling counterfeit semiconductors that will not perform as well as the genuine parts.
Arrow has genuine 3205s for $0.56 each.
IRF3205PBF for International Rectifier | Arrow Electronics Components
With only the ground and remote connected (no B+), measure the DC voltage on the gate pads for the power supply FETs. You should read 4-5v (as was previously stated). This is best done with the FETs in the circuit but can be done before you install them.
Arrow has genuine 3205s for $0.56 each.
IRF3205PBF for International Rectifier | Arrow Electronics Components
With only the ground and remote connected (no B+), measure the DC voltage on the gate pads for the power supply FETs. You should read 4-5v (as was previously stated). This is best done with the FETs in the circuit but can be done before you install them.
Yeah I think they are counterfeit after comparing them to other IR fets. Are there any tell tell signs of know counterfeit fets? On another note it was my Q1 component that failed. The PNP driver you were dead on with that one. On this amp Q1 and Q4 appear to be PNP. Q2 and Q3 seem to be npn. Ok, here is my main concerning question. I'm using a PNP driver off an old punch amp that only had 2 P.S. fets. Will this be ok since I'm going to be powering 4 fets now? My instincts are telling me not likely but I dont have a full understanding of semi conductors yet. So I was hoping to get lucky. Thanks for your help.
Q1 and 4 are NPN. Q2 and 3 are PNP.The top terminals of the PNP drivers are directly connected to ground.
They generally use the same drivers for all of these old amps. The ones from the smaller amp should work assuming that they're intact and aren't damaged when you remove them.
The counterfeit FETs sometimes look precisely like the originals. It's sometimes difficult to tell if they are not performing properly unless there are obvious signs (excessive current draw, running hotter than normal...) or if they fail prematurely.
They generally use the same drivers for all of these old amps. The ones from the smaller amp should work assuming that they're intact and aren't damaged when you remove them.
The counterfeit FETs sometimes look precisely like the originals. It's sometimes difficult to tell if they are not performing properly unless there are obvious signs (excessive current draw, running hotter than normal...) or if they fail prematurely.
*Post removed by moderator and this one edited to reflect the change, at member's request.*
I got the PNP and NPN drivers installed and they are now giving me the 5volts that I was looking for. I installed the 3205s and powered up the amp with a 10 amp fuse inline on the B+. It popped the fuse and I know that amps dont idle over 10 amps so there must be some other issue going on. I did notice that the fets were reading 8 ohms from leg2 to leg 3 after I checked them with my ohm meter making sure none were doa before i installed them. Well of the 10 I received some were giving above 20 ohms. So... I'm familar with the irfz44 and it always reads zero when I check them. Is it normal to have the 8 ohm reading on new uninstalled 3205? I know the ones reading above 20 gotta be faulty for sure if that is the case. Whats my next move here. What else needs to be checked out. now since I have the q1 and q2 taken care of?
I got the PNP and NPN drivers installed and they are now giving me the 5volts that I was looking for. I installed the 3205s and powered up the amp with a 10 amp fuse inline on the B+. It popped the fuse and I know that amps dont idle over 10 amps so there must be some other issue going on. I did notice that the fets were reading 8 ohms from leg2 to leg 3 after I checked them with my ohm meter making sure none were doa before i installed them. Well of the 10 I received some were giving above 20 ohms. So... I'm familar with the irfz44 and it always reads zero when I check them. Is it normal to have the 8 ohm reading on new uninstalled 3205? I know the ones reading above 20 gotta be faulty for sure if that is the case. Whats my next move here. What else needs to be checked out. now since I have the q1 and q2 taken care of?
PRECISELY how are you checking IRFZ44s to read 0 ohms?
Include lead orientation, meter model and anything else that you think may be relevant.
Include lead orientation, meter model and anything else that you think may be relevant.
Okay, I may have misquoted myself. I am doing a continuity check between all three legs of the irfz44. My fluke is a model T5- 1000. It isn't really the right type of tester for this application but my good one was stolen so this all I have. I check pin one to pin 2 for continuity then pin 2 to pin 3 for continuity and then check pin 1 to 3 for continuity. If there is none it reads zero. I do this while the fet is out of circuit. But I think this meter is for electricians really because it doesn't even give ohm readings above 1k. when it reaches 1k it shows 0. What is a decent priced meter I should be using for working on amps and I'll go buy a new one. Thank you for being patient with me. I really do appreciate your help.
When the meter reads 0, it means that there is a dead short (the same as when you touch the probes together). OL is displayed when there is no significant continuity.
I'd recommend a Fluke 10, 11 or 12. There was a flood of 12s for decent prices on eBay a few days ago. Some are likely still there.
I'd recommend a Fluke 10, 11 or 12. There was a flood of 12s for decent prices on eBay a few days ago. Some are likely still there.
I'm still having issues with this punch 801s.. I've changed The fets, changed the driver transistors, changed The D2 Diode checked the driver resistors and checked for shorted channels. It is still popping 10 amp fuses when I try to hook it up in the car. Any more suggestions please? Thank you.😱
A 10 amp fuse may not be enough for that amplifier. With all of the transistors tightly clamped to the heatsink, try a 15 amp fuse.
Does the fuse blow before or only after you apply remote voltage?
Does the fuse blow before or only after you apply remote voltage?
Ok I tried the 15 amp fuse and it blew as soon as I connected the remote wire. I hooked the ground and power up first to to let the caps charge. after about 10 seconds I connected the remote. It popped the fuse instantly. I was doing some random testing after that and I connected the ground and remote up to recheck my gate voltage. I put my fluke on continuity and it read 3 ohms between ground and power terminals; when voltage isnt applied I get no resistance between the two. The amp led is coming on when I connect all terminals until the fuse blows. Its trying to come on just something else holding it back. Could it be the T94.. chip bad? its pretty much the only thing i havent changed in the ps. How would I check this ic out to see if it is at fault? Thank you
Only way you know that chip is bad.... Check the gate pads on the PS fets. Should be a voltage between 4.5 to 5 volts on each gate pad. All 8 have to be the same if not then it could be the driver transistors failed or that IC failed.
Btw do you think you can post pictures of the board? Driver circuit, power supply section? Maybe there's a piece of solder shorting one of the fets.
You stated that you have no resistance when there is no voltage applied. That would mean that you read 0 ohms with no voltage applied. If the meter remained the same as when the probes are not in contact with anything but air, that would be infinite resistance, not 'no resistance' (0 ohms).
What was the rating of the fuse that blew?
What was the gate voltage when you checked it with no B+ connected?
Did you check the output transistors?
What was the rating of the fuse that blew?
What was the gate voltage when you checked it with no B+ connected?
Did you check the output transistors?
ok on my fluke I hook up black lead to ground and red lead to positive and it counts up to infinity 1 - 0L. I reverse the leads on the connectors I get 0 ohms. not OL but 0 ohms. It blew a 15 amp fuse when I powered it on. Ground positive and after caps charged I applied the remote and thats when it popped the fuse. I did check the output resistors but i will double check them. I did notice D3 is giving a reading of around 975 ohms even with leads reversed. I pulled the diode and the pad it was attached to gave the same reading. I will double check the output circuit. Thanks for the help.
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