Ok having problems getting this amp running. Replaced all the IRFZ44N with IRF3205. And the 47 ohm gate resistors with Yageo resistors. They measure 46 ohm should be 47. Replaced 2 PN2907A transistors on power supply section. On channel 5 found 1 blown IRF540 and 1 bad KTC3200 bias transistor. Also do these need matched?
Ok
Powered amp out of chassis it ran for 1-2 min blew 5 amp fuse. Pulled all output transistors from channels 3-6. Put fuse in power line blew fuse in probably 20-30 seconds. I could see smoke come from channels 3-4. I Left channels 1-2 outputs in because these were not used in system they came out of. This amp uses 2 IRF540 mosfets per channel. Kinda weird how that works to me but ok. No compliment PNP channel.
I pulled every semi conductor from channel 3. They all read good on my DCA75. So removed the rail voltage jumpers that feed power to channels 3-6.
Amp Powers up channels 1-2 work properly biased at 6.5 millivolts. DC offset is 3 millivolts and 9 millivolts. Played songs for 30 min on a sacrificial speaker. 6 Ohm rated. Then bridged a 4 ohm Clark's Synthesis transducer for 10 min. Didn't push it. Had 7.5 amp inline fuse on 20 amp. power supply 13.6 volts. It's a pyramid power supply.
Ok
Did I break something having this on out of chassis. And how do you check KIA431a for proper operation.
Can you not power these with output mosfets not attached?
Maybe it cannot idol with the mosfets off a heat sink
Also I have it's twin and I repaired it before I worked on this one.
Exact same thing except all the output mosfets we're good. This amp is giving me fits, the power supply was completely fried. Visibly.
Even the 2907A had a melted case on one of them.
I have only 2 fluke volt meters a DCA75, Hakko de soldering iron. And a hakko soldering iron.
I am thinking of scratching the power traces and working on the channels one by one. Not professional. But in my limited knowledge and just learning. It seems to be the best way to limit me damaging more parts. In my mind.
Thanks
David
Ok
Powered amp out of chassis it ran for 1-2 min blew 5 amp fuse. Pulled all output transistors from channels 3-6. Put fuse in power line blew fuse in probably 20-30 seconds. I could see smoke come from channels 3-4. I Left channels 1-2 outputs in because these were not used in system they came out of. This amp uses 2 IRF540 mosfets per channel. Kinda weird how that works to me but ok. No compliment PNP channel.
I pulled every semi conductor from channel 3. They all read good on my DCA75. So removed the rail voltage jumpers that feed power to channels 3-6.
Amp Powers up channels 1-2 work properly biased at 6.5 millivolts. DC offset is 3 millivolts and 9 millivolts. Played songs for 30 min on a sacrificial speaker. 6 Ohm rated. Then bridged a 4 ohm Clark's Synthesis transducer for 10 min. Didn't push it. Had 7.5 amp inline fuse on 20 amp. power supply 13.6 volts. It's a pyramid power supply.
Ok
Did I break something having this on out of chassis. And how do you check KIA431a for proper operation.
Can you not power these with output mosfets not attached?
Maybe it cannot idol with the mosfets off a heat sink
Also I have it's twin and I repaired it before I worked on this one.
Exact same thing except all the output mosfets we're good. This amp is giving me fits, the power supply was completely fried. Visibly.
Even the 2907A had a melted case on one of them.
I have only 2 fluke volt meters a DCA75, Hakko de soldering iron. And a hakko soldering iron.
I am thinking of scratching the power traces and working on the channels one by one. Not professional. But in my limited knowledge and just learning. It seems to be the best way to limit me damaging more parts. In my mind.
Thanks
David
This is a class AB amp and if operated without heatsinking for the outputs, they're likely to overheat and fail, even at idle.
That is kinda what I thought.
Still trying to figure out why it blows fuses with outputs removed.
I will go through every channel and test the transistors.
With the DCA75. At this point I am grasping straws.
I ordered some Harris IRF540 mosfets. 3200GR not sure of what to order.
But I think I will go go channel by channel. My DCA75 tells me that 7 of the 8 outputs are still good. I will find Wich transistors are attached to the gate resistors and pull and test them. I already did once. But maybe I damaged them after I posted it back up. None looked shorted with the volt meter.
I know this is a easy solution
Just not for me.
I have 6 hours into this amp.
Having fun just frustrated I cannot find my solution.i measured resistance from points in the pre amp circuit. They all look the same.
Thank you !
Still trying to figure out why it blows fuses with outputs removed.
I will go through every channel and test the transistors.
With the DCA75. At this point I am grasping straws.
I ordered some Harris IRF540 mosfets. 3200GR not sure of what to order.
But I think I will go go channel by channel. My DCA75 tells me that 7 of the 8 outputs are still good. I will find Wich transistors are attached to the gate resistors and pull and test them. I already did once. But maybe I damaged them after I posted it back up. None looked shorted with the volt meter.
I know this is a easy solution
Just not for me.
I have 6 hours into this amp.
Having fun just frustrated I cannot find my solution.i measured resistance from points in the pre amp circuit. They all look the same.
Thank you !
No they are relatively cool. There are 2 transistors or mosfets that are fairly warm. A complimentary pair.
The rail voltage is 28. Something and 29 volts.
Thanks
David
The rail voltage is 28. Something and 29 volts.
Thanks
David
I don't have a scope.
I have been in the Audio business for a lot of years. Did some factory mandated updates. Added general diodes to change regions on car entertainment navigation units. Replaced capacitors and stuff like that. But bad was bad and new is what I sold.
When amps went bad out of warranty they went in the trash.
I would pull the boards scrap the aluminum.
I kept these because they looked very simple inside.
I never even thought about repairs. Because I thought it was just to expensive. JL had flat rate repairs seemed reasonable. But people didn't seem interested. Had a unit repaired worked for a day burned back up.best yet the units got to old for them to repair.
I didn't know this many people were into and able to repair this equipment. I threw away so many nice amps.
I am almost ashamed. Local shop was quoting over 300 on most stuff I brought in. Sent customers there same thing. I looked at the equipment they had. And figured that is the way it is.
Not untill a couple years ago.
I read some stuff From Hoppe's brain and built input boards for GFA565. Mono block amps.
And did power supply swaps and soft start boards
Actually learned a lot.
I have been in the Audio business for a lot of years. Did some factory mandated updates. Added general diodes to change regions on car entertainment navigation units. Replaced capacitors and stuff like that. But bad was bad and new is what I sold.
When amps went bad out of warranty they went in the trash.
I would pull the boards scrap the aluminum.
I kept these because they looked very simple inside.
I never even thought about repairs. Because I thought it was just to expensive. JL had flat rate repairs seemed reasonable. But people didn't seem interested. Had a unit repaired worked for a day burned back up.best yet the units got to old for them to repair.
I didn't know this many people were into and able to repair this equipment. I threw away so many nice amps.
I am almost ashamed. Local shop was quoting over 300 on most stuff I brought in. Sent customers there same thing. I looked at the equipment they had. And figured that is the way it is.
Not untill a couple years ago.
I read some stuff From Hoppe's brain and built input boards for GFA565. Mono block amps.
And did power supply swaps and soft start boards
Actually learned a lot.
The transistors are clamped to the chassis by the diodes. They appear to be part of the power supply section.
When referring to the parts, give their circuit board designation. You know what you're talking about but we're mainly working blind.
Q45 and Q46 getting extra warm to me
Replaced Q54 Q52 Q47 Q48 Q49 Q50 Q51 Q53 Used IRF3205 Replaced Q1 Q2 with a Philips made PN2907A
Q506 bad it's a C3200GR and I believe Q616 or Q615 output mosfet shorted.
Replaced Q54 Q52 Q47 Q48 Q49 Q50 Q51 Q53 Used IRF3205 Replaced Q1 Q2 with a Philips made PN2907A
Q506 bad it's a C3200GR and I believe Q616 or Q615 output mosfet shorted.
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