Hello fellow audio enthusiasts, my first post although I am a memeber her for while now. I have searched this forum thoroughly and found some related data but not conclusive to aid in my problem.
I have on the bench a Cadence ZRS 8000d amp (says "version C") that is not like other ZRS8k's I found on Google. This one looks similar to the Planet Audio VX series amps. This one belongs to a friend and was repaired twice somewhere else but continues with the same problem.
First let me state that I am a "retired" electronics tech with minor experience in car amps. I do have a scope and meters and know my way around schematics although I don't practice every day.
This amp went for repairs because it had blown (leaking/tops opened) rail caps. The originals were 80v 2200uf. The repair shop just did a cap replacement and it measured and worked fine at the shop on a test bench. As soon as it was installed in the vehicle (2 double 4 ohm subs parallel'd @ 1 ohm) and the volume cranked up, the amp started smoking and blew some of the new caps that were installed.
Took it back to the shop and the rail caps were again replaced with new ones but this time with 100v 2200uf (in the pic) because measured rail voltage on the bench was 77v per rail.
Back to the vehicle and everything worked fine for a few days until the amp was used on almost max power for a few minutes and again it smoked the rail caps. Service center can't seem to figure out the problem so I took a look and some readings.
I put in 4 new caps that were left, two in each rail and again measured 77v at the rail. I cranked the power for a few seconds while measuring rail voltage and it climbed to over 110volts and fluctuated with the music well over 77v. When the volume was set to 0, rail voltage went back to normal.
I measured every posible resistor around the TL494 IC and see no signs of anything broken or any other cap leaking. All toroids look gook, no markings, amp sounds great, powwr supply and output mosfets all seem to be in working order, driver board and fan all in working order. Overall the amp is in great shape.
I did read about a similar model with an out of value resistor, I believe it was 150k ohms but this amp does not have it.
Sadly I am not at the shop and not in front of the amp to reply some voltages but can verify any suggestions once I go back there tonight. Here are some board pics of this amp.
I have on the bench a Cadence ZRS 8000d amp (says "version C") that is not like other ZRS8k's I found on Google. This one looks similar to the Planet Audio VX series amps. This one belongs to a friend and was repaired twice somewhere else but continues with the same problem.
First let me state that I am a "retired" electronics tech with minor experience in car amps. I do have a scope and meters and know my way around schematics although I don't practice every day.
This amp went for repairs because it had blown (leaking/tops opened) rail caps. The originals were 80v 2200uf. The repair shop just did a cap replacement and it measured and worked fine at the shop on a test bench. As soon as it was installed in the vehicle (2 double 4 ohm subs parallel'd @ 1 ohm) and the volume cranked up, the amp started smoking and blew some of the new caps that were installed.
Took it back to the shop and the rail caps were again replaced with new ones but this time with 100v 2200uf (in the pic) because measured rail voltage on the bench was 77v per rail.
Back to the vehicle and everything worked fine for a few days until the amp was used on almost max power for a few minutes and again it smoked the rail caps. Service center can't seem to figure out the problem so I took a look and some readings.
I put in 4 new caps that were left, two in each rail and again measured 77v at the rail. I cranked the power for a few seconds while measuring rail voltage and it climbed to over 110volts and fluctuated with the music well over 77v. When the volume was set to 0, rail voltage went back to normal.
I measured every posible resistor around the TL494 IC and see no signs of anything broken or any other cap leaking. All toroids look gook, no markings, amp sounds great, powwr supply and output mosfets all seem to be in working order, driver board and fan all in working order. Overall the amp is in great shape.
I did read about a similar model with an out of value resistor, I believe it was 150k ohms but this amp does not have it.
Sadly I am not at the shop and not in front of the amp to reply some voltages but can verify any suggestions once I go back there tonight. Here are some board pics of this amp.
Sorry if I caused a confusion. The power supply driver IC is KA3525a, output fets are IRFB31n20d, P/S fets are IRFZ46N. The other ICs on board I dont have the #'s but will post as soon as I'm wih the amp.
Here are the amp pics:
Here are the amp pics:
hello ! few months ago have a very similar issue, found faulty lines across the VCC+ to feedback on upc494 try to focus on pin 16,15 of 494 that is the control voltage output for pwm supply. http://circuits.datasheetdir.com/42/UPC494-circuits.jpg
R328 is 150k , measured 147.3k off the board. This is connected to one side of IC 305 (KIA431). the side of IC305 that connects to R328 has -70v, center has -73v and the other side of IC305 has -41v.
R328 has -70 on one side and +73 on the other. All voltages were taken with amp on, green light and idle (no rca's). Rail steady at 73 +/- measurements taken with rail ground reference.
R328 has -70 on one side and +73 on the other. All voltages were taken with amp on, green light and idle (no rca's). Rail steady at 73 +/- measurements taken with rail ground reference.
An externally hosted image should be here but it was not working when we last tested it.
That resistor causes the most common problems with rail voltage but it appears to be OK.
IF the voltage is going too high, you'll have to monitor voltage around the 431 to see where it's varying and allowing the rail voltage to go too high.
You should also be aware that the secondary and output filter inductors short intermittently and can cause all sorts of problems.
If you don't have a diagram for the amp, email me. I have something that should be close enough.
babin_perry@yahoo.com
IF the voltage is going too high, you'll have to monitor voltage around the 431 to see where it's varying and allowing the rail voltage to go too high.
You should also be aware that the secondary and output filter inductors short intermittently and can cause all sorts of problems.
If you don't have a diagram for the amp, email me. I have something that should be close enough.
babin_perry@yahoo.com
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