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Am I missing something? The schematic for the main output shows the wiper of a 50K pot feeding the output. The P/L 2000 uses an opamp as a buffer betweeen the pot and the output. Depending on the input impedance of the amp and the setting of the pot there will be some phase shift and effect...

The insulators are thin enough to fit inside the core and die cast cradle?

Hate to be a buzz kill, I would have cleaned the board before installing switches and pots. I can't imagine stuffing a board with surface mount.

So what has been done to this amp?

Yea, I learned the hard way with scopes that are grounded through the AC input plug. We used a 2.2 ohm 1/4W resistor on the ground lead. 2.2 ohm as we had a pile of them. That doesn't fix the problem. It just does less damage to the probe.

What's the AC Input voltage?

I bought 4 of the 5 drawer mechanics carts for our Houston UPS lab around 2017. Really good heavy duty construction. They were on sale for under $175 then . List for $269 now. I've got a lot of their stuff. The stuff that looks like flea market stuff is just that. Most other stuff is...

What's with all of the fat holes? They're to big for any IDC (Insulation Displacement Connector) I can think of. Using sockets for opamps? Is there a ground plane? Clad made in Asia?

Other than the possible selector switch issues there is a time delay mute circuit with a fet, Q1, driven by an opamp. You can try pulling the fet. Be advised there may be a turn on thump even if the volume is turned down.

To be precise, in a wye connected 3 phase system, if line to neutral is 240, the line to line would be 415 (240 x 1.732). I'm surprised there is 400 plus volts in a residential panel. I admit to having limited exposure outside the U.S. and no foreign residential expereince. The arc flash in a...

If I recall correctly there is a speaker protection circuit to help prevent speaker damage should an amp fail. Somebody sells a custom version for 400's and 700's on EBAY. I think Sniff uses a similar one on his 700's. As for the cat, I hope the covers are installed over the exposed outputs...

So I feel like pisssing everybody off by saying it amazes me how something 40 plus years old that's full of junk parts still works. How many TV's and microwave ovens lasted that long. Look at all your high priced gadgets in your drawer that failed after a few years. I don't question that...

Hm, residential power with three phase. I don't see an application for it. Is your panel three phase? WYE or DELTA?

It's C111 on the P/L36. Another term to describe the diodes is reverse parallel.

You have to be careful with test gear and ground connections on the C-500. The right channel is inverted and the white binding post is at ground potential.

No, when all else fails, read the manual.

Here is an app note that explains output heat dissipation.. Amplifier max heat.

Yes that one was over tightened. It's also possible that the original transistor was replaced and the silpad reused. Never reuse them. When I install transistors I use thumb and index finger on a nut driver. When the nut driver slips in my hand it's tight. During testing I use a...

I took on a "guy down the street" job last year. What a disaster. Had to trash a full W/O board set. Tracks were blasted off the back planes when outputs were improperly installed. Globs of solder on the boards. Some of the people on this site are true craftsman. You look at the...

At turn on, the amplifier have to stabilize. During the process which takes a few hundred milliseconds, the amplifier dumps DC into the speaker. Not 80 volts, but a significant amount. Once everything is stable there is no (less than 50 millivolts) of DC offset on the output. My relay board...