DAR PLUS E-I transformer dead How to work out voltage?

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Hi,

I have a Pioneer Powered Subwoofer HTP-200SWP with a Pioneer SA-50 65w plate amp.

The E-I transformer internal (one-time) thermal fuse has blown. I want to get a replacement transformer but I don't know the output voltage. Input is 240v. There are no markings apart from "DAR PLUS 9941" Tried searching on it but no specs came up.

is there a way to work out what the output voltage is?

cheers,
col.
 
look at the voltage rating of the various caps in the amplifier.
Compare the claimed output power into the specified load to other amplifiers of similar capability and see how their supply rail voltages compare to your capacitor voltage ratings.

Eg,
if the smoothing caps and the decoupling electrolytics are all 50V rated then you know that the transformer cannot be 35+35Vac . It must be significantly less.
 
I don't know if my math is right, but from 65W into 4 ohms (assuming there, you should check!), I get about +/-22V DC, which comes out to a transformer of +/-16V AC secondaries. Given that you should probably pick the next higher voltage just to be sure you don't get early clipping, and assuming the capacitors are at least 35V rated, I would go for a 18V secondaries transformer.
 
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the absolute maximum voltage rating of the transformer feeding a 63V smoothing cap is 40Vac.
It is more likely to be 30 or 35Vac.

A +-28Vdc amplifier operating from a 20+20Vac transformer would push out ~35W into 8r0. Your 40Vac single secondary should be able to reach this maximum if designed for maximum power efficiency.
A 3ohm load could demand ~90W to 100W from the same 40Vac transformer.
That is maybe why it failed.
90W into 3ohm is a demanding load for a 1pr output stage. It may have taken out the output transistors and a low power transformer may have then overheated rather than blow a fuse.

You will need to check the amplifier on a temporary supply to see if this amp & transformer are worth repairing.
 
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I used a 36Vac 160VA toroidal and changed the 63v 4700uf cap for a 63v 10000uF one. I also added a bigger heatsink to the output transistors and placed a heatsink on the 12v reg for the preamp. The box design seems fairly good but construction poor, lots of gaps and holes that needed sealing.

Sub is now performing very well.

Thanks for the help.

col.
 
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