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Depending upon where there is access, it may be possible to pack more fish paper between the bobbin and core to restrain its movement. I've had success on some that way.

A "J" or "K" themocouple and meter, and an alligator clip to hold it to the body of the device can provide a fairly accurate reading compared to an IR scanner/gun. The IR scanners are handy for looking around to locate hot spots, but the actual temperature measurements are not that accurate.

As long as you are in the unit, the power supply should be scrutinized.

The headphone jack IS driven by the output transistors, but through dropping resistors to limit power.

I was wondering who would be saddled with moving/merging/linking up all the old threads that would be in a "Test Equipment" forum. That could take someone at least half an hour (per day, for the rest of their lives).

Very nice save on the furniture!

Thanks for the visual reminder of the time delay tubes. I haven't seen those in a long time, but recall a few supply drawers full of those of various values and contact arrangements, from back in the '80s.

If you ever worked inside a substation or even secondary switchgear, you might soil your garments. Bare copper bars are all over the place, and intentionally cross paths to reduce induction and EMI. They are usually pretty low voltage, however, rarely exceeding 345kV.

As a general note, fire inspectors, particularly the municipal/state employees, are not always the most qualified nor insightful in performing their assignments. As in almost every other endeavor, the really good ones don't work for the government, but are in private/commercial industry...

I would agree that the Ametherm line offers more and better possibilities than simply slapping in a generic Amphenol CL-90 like everyone who has done an internet search would do. It does take a little math to determine the best selection, however. As a matter of fact, 10 years ago I suggested...

The 13½V supply is from Q25, the regulator for all the 13V loads. It could be helpful to verify the proper voltages upstream of that. R1 is the 22Ω/5W ceramic resistor mounted to the main heat sink in the unit. Once side of that should have about 52VDC, and the other should have about 26VDC.

Some of the alloys encountered on modern equipment are a real challenge. The advice given above about adding solder is valid. I also keep a welding tip cleaner on the bench to periodically clear the tip and tube. Taking one apart to clear out carbon, slag, and debris always seems to happen...

Decoding their numbers is helpful. That proprietary numbering system doesn't help anyone, and doesn't even help Marantz any more. As for the devices, finding any really high gain bipolars is getting more difficult by the day, and Darlingtons are comparatively uncommon, if you could even use one.

That might work, but the characters silk-screened onto the board might also go away.

If you can live with a 700V rating, something like this might get you close: https://www.digikey.com/en/products/detail/power-integrations/TOP258YN/1657676

If VR302 has no effect, something in that bias circuit may be open. As for the LH1000 version, the schematic also shows "added for LH1000" adjacent to R30, or possibly Q313. That would imply that R39 and/or Q314 would also have been added for the LH1000, but the diagram really isn't...

Well, technically, it's not China, but Taiwan. If you don't understand the difference, it may become a lot clearer in about 7-10 years when the draft notices start going out.

... Unless you live in a place that still allows 15A convenience receptacles, (no, they are not "outlets") you can get up to 20A pretty continuously from a single receptacle.

The 1220s did have a better Ft, but for audio it may not make a noticeable difference. Another alternate could be KSP2907A.

I'm guessing that Paul Klipsch made some of his first speakers at home (through 1948), if that answers the initial question.

The 555A I was in was rock-solid and dead-quiet, and had no such shield: It also bench tested above the minimum factory specs for performance after the upgrades and repairs.

With a cap-coupled output and quasi-complimentary pair operating from a single power supply, balance is more difficult to control. It may help to read through this thread and consider some of the suggested modifications...

Since they followed you home, those are some well-trained speakers. The cosmetics are probably an easy (maybe not fast) fix compared to finding consecutive serialized speakers.

Good guess. I believe there were other companies offering speakers with wood lattice grilles, too. The whole array of Pioneer CS series, Sony SS-870, the aforementioned Sansui types, Altec 890, Coral BX1001, etc. come to mind. Regardless of their origin, I'm guessing that I know the color of...

A little more information might be helpful. What is the tuning meter doing when approaching and passing an FM broadcast? What kind of deflection is achieved on the signal strength meter?