Weird 2150sx

[Clipped]

i was changing the fets in the ps..and what i saw freaked me out, there was a smp60n06 fet in place of the 3 leg negative diode inline with the ps fets....and it was working..anyway i took it out and put in a negative diode and it still works..

it looks to be like this from the factory , anyone ever run into this? and why did it work?

[jol50]

Did it really work that way, did it have neg rail voltage? I guess it might depend what voltage was on the gate, if it was AC or DC.

I messed with a bunch of cheap amps I got once, saw a lot of manufacturing defects from bridged solders to parts not installed right or broken during install, left out, etc.

[Perry Babin]

The two TO-220 rectifiers are part of an auxiliary power supply that's used to boost the drive voltage of the power supply drive circuit. The amp would probably work without them in the circuit.

[ppia600]

Originally posted by Clipped
i was changing the fets in the ps..and what i saw freaked me out, there was a smp60n06 fet in place of the 3 leg negative diode inline with the ps fets....and it was working..anyway i took it out and put in a negative diode and it still works..

it looks to be like this from the factory , anyone ever run into this? and why did it work?

I didn't know that smp60n06 existed back when that 2150sx was made.. that is weird.

[Clipped]

the smp60n06 was standard issue in every digital Reference ive cracked open.

the negative diode isnt actually part of the circuit that rectifies DC for the rest of the amp, those are located underneath the board.

like Perry said these are for the power supply drive circuit... but why did it work? is what is confizzling me.

this ebay amp keeps getting weirder everyday, i have to get the heatsink retapped for screws, just blew a bank of fresh fets because they werent tight enough...damn 50 amp fuse didnt blow.

[Perry Babin]

Use helicoils to fix stripped screw holes.

The drive circuit gets voltage from the B+ line initially (before supply starts). If the secondary doesn't produce voltage, the amp will operate off of the 12v drive (like most other amps do).

[ppia600]

Oops I must have been thinking of the earlier series. I could have sworn it was the early 80's orions that had not mosfet. They would get super hot. Maybe the gx series?

[Perry Babin]

The first generation used 2N6488s (or a re-badged transistor with similar specs) in the supply.

[ppia600]

Those must have been the ones. I had to repair my friend's 2375gx (or 2175 I can't remember). It was a huge black amp and when he first got it every power supply transistor was toast. I had to replace all of them including some resistors. I also had to replace half the transistors in both channels. One channel had several of one polarity shorted so just in case he planned on bridging it I also replaced the same polarity on the other channel. (npn for example) It was very nicely constructed and besides the fact that so many transistors were toast, it wasn't difficult to repair. He ran it in stereo with two kicker compention (first series comps) with a huge sealed box we built and actually got a trophy for his class. We were all smiles that day

[Clipped]

heck yeah, and i bet using an old school amp made it all the sweeter...