Orion 2150GX power draw

[Dr Zeus]

Got this amp on my bench. It fails to power up with a 10A supply, but once I lift the center legs of the rectifiers it appears the power supply section is partially OK. The voltage directly across the lifter rect center legs is ~171vDC. However, the transformer coil gets warm to the touch after about 30 seconds.

I dont have all the latest equipment sometimes, so all I have for testing are 3 power supplys (5A, 10A, 35A) and a car battery. Using the 5A power supply, the amp draws it down to 9 volts with the center leg of rects lifted. With the 10A supply, the amp powers with 13.3vDC stabilized across the power wires. So, this amp idles with about a 5-10A draw and the rect center legs lifted.

I have not yet lifted the PCB out of the sync just because I want to be careful not to hurt any of the TO220s like past experience. I do not see pags where large Rectifiers are usually under the PCB like the 2150SX/2250SX.

[Perry Babin]

171v would be well beyond what this transformer could produce. It's likely an error due to the ripple.

With the power transistors clamped to the heatsink and the 35 amp supply, how much current does it draw (rectifiers in the circuit)?

[Dr Zeus]

I'm back to working on this amp but have not made much progress. Theres definately some wierd things wrong with this amplifier. I still have the center legs of the rectifiers lifted because I'm now wanting to troubleshoot why the amp cannot be turned off via the remote wire. Once powered, I can even disconnect rem and the powersupply is still running full tilt. Also on this amp, there are two silver diodes mounted on top of each other in parallel which after a few minutes run so hot that it made me jump. I thought the heat was coming from the 2w resistor just next to them but it isnt the case.

[Dr Zeus]

Now more wierdum. I re-attached the center legs of the rectifiers and was able to un-cooperativly get the amp to power up and produce +-40rail voltage at the output fets. The way I got the amp to power up may be more to do with my power supply not being able to provide the amp some kind of high-amperate burst to start because it took about 15 power-cycles of my supply to get this amp to stay online. Dont ask me how I figured that one out. With the rectifiers attached REM appears to be working OK as long as I leave the amp powered off for less than 3 seconds else its hard to power it back on again.

Theres no audio output, and it appears there is an upset of DC voltage on some of the opamp outputs. Once I find CT I may be able to further troubleshoot this amp.

[Dr Zeus]

Boy, the more I fiddle with this amp tonight, the more it starts to make more sense. The reason why no audio was heard was because of bad RCA contacts as described on the CD. I lightly moved the center of the RCAs upward and now there is good contact. I was able to have the amp produce clean audio on both channels.

It seems the reason why this amp was no longer used was because of a gain pot in dire need of a cleaning and new wires for the male speaker plug.