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Great stuff! I appreciate that, Ed. A couple of further notes: 1) I did a paper analysis of the circuitry of the PL30 version of the Tone Amplifier as shown in the schematic. It is the missing RC network that gives the boost to the high frequencies. Without them response is flat at the...

So... It's all back together - and working. There are, however, some interesting discoveries. After putting it back together and performing some initial checks, I began running the Test Procedures outlined in the service manual. Everything checked okay except the Active Equalizer at the...

Got it, Marco. Thanks for the warning. What I would give for an Italian coffee and pastry in one of your bars. Best in the world!

Making progress... Giving each of the boards the treatment, replacing caps and cleaning.

Today I received the Service Documentation sold on EBay. This shows all - the early versions as well as the last. The online (free) documentation is missing a bunch of information and is not recommended. The EBay docs are expensive, but worth it. It has the artwork and schematic of the PL30...

This solves my mystery! And is the perfect answer. Yes, the front panel has an Ambience switch and the front panel is soldered to the main board. Thanks for the pics, Steve K. Appreciate the help. Now I'll be looking for the schematic of that PL30 board, not that it is essential for going...

Photo attached is the current progress... laatsch55: Thanks for your offer. I do believe I'll be after the Tone Amplifier board at least. If you could let me know if you have one I'm willing to purchase it.

Ha ha. Absolutely! I have tons of experience and have tackled more complicated and difficult equipment. Plus I'm retired, so time is not an issue and I have the test equipment - I like projects like this. I get enjoyment bringing equipment like this back to life. The challenge is half the...

Yes, it does work - or at least I can pass a signal through it, both channels. Volume, tone controls, balance and the like all function. It does seem to have a low end roll off. I tested it with my signal generator and scope - a square wave looked reasonable to 10kHz. I'll get more serious...

Yes, yes, and no. It is the joystick version and it is the one NAdude98 posted, but I haven't tried contacting him. This is not a modification I've seen anywhere and I'm sure the purpose was to bypass the Peak Unlimiter and Decoder thereby reducing signal path and reducing noise and...

Indeed. Fairly clean both in and out. Cleaner than a bunch of old radios I've restored from the 30's, 40's, and 50's. I've stripped it down completely - removing all panels - both front and back - for a through cleaning anyways. Front and back look great. Looks like this modification...

I recently purchased this actual PL 4000 and am trying to restore it. The unit has a PL30 in place of the PL03 Tone Amp board and no Decoder board PL06 as shown in the photo, the white wires running from the PL30 to the socket of the PL06. Does anyone have information on this modification? This...

I recently purchased this actual PL 4000 and am trying to restore it (I'm an electrical engineer with many years - too many - of experience). The unit has a PL30 in place of the PL03 Tone Amp board and no Decoder board PL06 as shown in the photo, the white wires running from the PL30 to the...