hcca 250

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whats the serial number on the bottom of the board?... just want to know which board design came first.

if you can, could you count the number of primary and secondary turns on the transformer?... just a suspicion i have on rail voltages between the two different board designs.

did you ever check the predrivers/drivers?

some of these hcca boards used different part numbers instead of the usual MPSU07/57's...they were green and black full plastic casing...but more than likely function like the MPSU's, but you should double check.

that 2150sx i fixed had like 5 different points that were malfunctioning.
I was measuring the voltage with my ground lead on the negative side of my PSU and the positive to the rail.
I already poseted the serial somewhere on this thred
It does have the big drivers . And the drivers check good.

Today I found one if the leads was broke on one of the 06's in the supply. ( I don't know How I kept missing that) I fixed it and all the fets run cool now. I'm in the process of re assembleing it.
So I will let everyone know how it goes. ( makes me feel like a dumb A$$ that I kept missing something so simple.)

I will take pictures when I get it working and I will send them to you Perry. Do you want a copy too Clipped?

One other thing I took my other 250 apart. And it has a revision B board. the one I burnt was a Revision D. Did they go in order when they made these amps?
Ok I have bad news. I installed all the fets, All the drivers and oneside of the outputs. Now the 317 and 337 regulators get hot along with the fets ( on one side) . but they don't instantly get hot. Right now my idle current is 2.5 amps which I have been told is too high.
Throw another idea out to me Perry.:cannotbe:

Oh and the rail voltage is 26.2 VDC . Sorry had a brain fart.
The regulators feed the op-amps. A defective op-amp or a defective capacitor could be causing excessive current draw. It's also possible that they run hot normally if not clamped to the sink.

Are the regulators able to keep the output at or near ±15v?

Clamp the regs to the sink so they don't overheat.

There are low value resistors between the regs and the op-amps. measure the DC voltage across those resistors. If you find that one op-amp has significantly more voltage across the resistors, it could be the reason the regs are running hot (that op-amp is drawing too much current). In the 2150sx, the 5534s have 2.7 ohm resistors. The 5532s have 33.2 ohm resistors.

The regs are diode-isolated from the rest of the circuit. If you're trying to confirm that a particular resistor is connected to the regulator, you'll have to check continuity to the diode.

In the 2150sx, one 5532 has a direct connection to the diode.

If you pull the regs, does the current draw drop significantly?
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