I’m working on a Taramps HD5000 that smoked both of the metal film caps at the speaker output terminals.
Taramps used 400v caps in this location. I don’t have any 400v caps in stock. I was wondering if I could go back with 250v caps. I’m not sure what determines what cap values is used in these RC/zobel networks. I’ve worked on lots of these Brazilian amps and have several in the shop at the moment and they are all different as far as the style and value of caps used at the speaker terminals.
Could someone enlighten me a little.
Thanks,
David
Taramps used 400v caps in this location. I don’t have any 400v caps in stock. I was wondering if I could go back with 250v caps. I’m not sure what determines what cap values is used in these RC/zobel networks. I’ve worked on lots of these Brazilian amps and have several in the shop at the moment and they are all different as far as the style and value of caps used at the speaker terminals.
Could someone enlighten me a little.
Thanks,
David
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Drive a signal up to clipping (no load necessary) and look at the ungrounded side of the cap to see what the amplitude of the signal is. It should be a fraction of the output level.
What's the rail voltage in the amp?
What's the rail voltage in the amp?
Rail voltage is 160vdc. So that would give 80vdc potential only each speaker terminal. I drive a signal into it and report back.
The negative terminal has 80 vdc on it with the caps out of the circuit and the positive terminal has 0vdc.
Here are some scope snap shots driving a 60hertz signal in. Just before clipping and at clipping.
Probe is set to x10. Scope is set at max 5v/div time base is 10ms.
The readings are taken at the negative speaker terminal and positive terminal is sitting at ground.
Here are some scope snap shots driving a 60hertz signal in. Just before clipping and at clipping.
Probe is set to x10. Scope is set at max 5v/div time base is 10ms.
The readings are taken at the negative speaker terminal and positive terminal is sitting at ground.
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Are you talking about right here? That is where the two 400v metal film caps go that were smoked. I removed them to bring the amp up to give you the readings you requested.
I can put some 250v polyfilm caps in there and try again with the readings if that helps. That’s the largest non polorized caps I have in stock.
I can put some 250v polyfilm caps in there and try again with the readings if that helps. That’s the largest non polorized caps I have in stock.
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Install the 250v caps.
Are you sure that the positive terminal is at ground? If the negative terminal is at 80v, the positive cannot be at ground.
If neither is at ground, you won't be able to test the RC cap as I wanted you to do unless you use your scope in differential mode or if you have a battery operated or isolated scope.
After seeing that you have only 160v of rail, there is no way that the amp can drive more than that to the caps. The 250 should be fine but 400v may have lower ESR and therefore may run cooler.
The 250 will absolutely be fine in the RC network.
Are you sure that the positive terminal is at ground? If the negative terminal is at 80v, the positive cannot be at ground.
If neither is at ground, you won't be able to test the RC cap as I wanted you to do unless you use your scope in differential mode or if you have a battery operated or isolated scope.
After seeing that you have only 160v of rail, there is no way that the amp can drive more than that to the caps. The 250 should be fine but 400v may have lower ESR and therefore may run cooler.
The 250 will absolutely be fine in the RC network.
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I thought thought that it was strange that the positive terminal was at ground as well. I did some back tracking and found one of the output mosfets was shorted. Which is strange because I tested them last night with my DMM in diode mode and none of them tested shorted. I installed a sacrificial mosfet in for the moment until I get this sorted out.
The rail caps are rated at 200v.
David
The rail caps are rated at 200v.
David