JC-120 in need of a lot of love

[laurie]

Thanks!

[The_Doc]

Me too, I really hope it all works given the huge effort you have put in to save it.

[laurie]

Started installing the boards - physical install and basic power and input/output wiring.

The "high" input jacks have both disintegrated

They are mono, SPST switched (Switchraft 12A equivalent). They are the only type I don't have in stock

So the restoration is stalled temporarily.

---------------------------
The next step is to connect each amplifier board to the power rails through 470 Ohm resistors. The resistors will limit the current in case something is wired incorrectly or broken.

I won't make any other connections to the amplifier board - only power.

Once I've confirmed there is nothing unexpected happening, I'll take the 470 Ohm resistors out and power the board with full power.

Then connect an input signal and speaker to check the amplifier is functioning.

Once that is done for both amplifier boards, I'll make the rest of the connections and see how it sounds.

[laurie]

The restoration proceeds (slowly). Boards and jacks reinstalled. Nothing hooked up yet.
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JC-120_6.jpg (267.97 KiB) Viewed 7229 times

[laurie]

I'm having trouble finding a serial decoder that works. If anyone can help - the serial on the amp is 400363.

Any idea about manufacture date?

<bump>

[Pepe]

https://serial-number-decoder.com/roland/roland.htm

[laurie]

https://serial-number-decoder.com/roland/roland.htm

Doesn't seem to work for this serial number.

[Pepe]

I tried it with your serial number and the amp model.

This item could have been made during any of the following periods.
November-1975
March-1984
Notes :120W power, 2 x 12 inch speaker
If more than one date is returned you can narrow it down.
Pre 1979 Jazz Chorus amps do not have a "BRI" switch, post 1979 do.
1979 and later amplifiers have black plastic corners rather than the chrome on earlier ones.
If there is no chorus/vibrato footswitch input on the back then it is 1975/76

[laurie]

https://serial-number-decoder.com/roland/roland.htm

Oh interesting.. I couldn't get a result out of it.

Huh. Tried it again and now it works.

[laurie]

ok so it is 1978 or 1977. Thanks!