wrek

Hi everyone.
My Power switch light burned out on my 50 Watt JCM 800, so I ordered a replacement switch.
On the amp Chassis a label says USA 2205 02/04/86 for the year it was built.
The old switch is a five wire, and the new one is a four wire.

I found this diagram showing how to convert the wiring for the new switch, so it may be useful to anone with the same problem.

http://www.amprepairparts.com/sw491wiring.gif

Thanks.

Update:
I removed the wires from the old 5 pin RED Power switch, one at a time, and "thought" I soldered them one at a time, exactly as shown in the diagram, with the exception being that my amp does not have an orange wire on pin 11. Mine is blue and goes to the transformer.

For some reason, now my standby switch is reversed. When it is in standby, the amp comes on, and turns off when the switch is set to on. I did not remove or rewire the standby switch. The amp works, but there is a hum present that is not what I normally hear when I turn it on.

I think I may have possibly screwed up, but I can't find any diagrams with my wiring colors to be sure. I was thinking that perhaps I inverted the switch, but the diagram on the link above seems to be oriented the same way. The only difference is the second blue wire going to the transformer.

Does anyone have a clear diagram of exactly where the wiring goes from the switch? Maybe my amp was modified before I bought it, or maybe I just wired the switch upside down? (I didn't think it mattered on a 4 pin rocker switch, but I could be wrong).

I am not sure how to upload an image from my documents. The image button here only allows from a URL, so I will just type out how I wired the switch.

Here is what I have on my amp connected to the new switch:

Pin 12 Blue to Mains input Pin 25 Brown to Mains Input
Pin 11 Blue to Transformer Pin 26 Yellow to 3 Amp Fuse

The old switch had the black wire, which I cut and taped.
Blue Brown
Blue Yellow
Black

Any input is appreciated.
Rek

Marshall Amps

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V-man

All I can say is that •I• managed to put one in a few months back. If I can do it, a retarded monkey can.

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RussBert

For the record, I believe Mojo Music Supply carries a 5-pole switch...




Marshall Style Lighted Red Rocker Switch - Mojotone.com

wrek

Hi RussBert,
Thanks for the link to Mojo. I ordered one a few minutes ago.
Now I just have to trace the wiring to see what goes where on the amp.

I should have taken a photo before removing the wires, even though I swapped them one at a time. Normally, this wouldn't be a big deal, but now that I am confused, I don't want to blow up my 1986 JCM 800!

Thanks again,
Rek

wrek

Got any bananas?
I suddenly feel more retarded than a monkey.

wrek

Ok,
I figured out how to upload photos.

Here is a drawing I made, showing my current switch wiring. I have a feeling I inverted the switch wiring, although the switch seems to work properly. Perhaps it has to do with where the switch sends power first?

Note: Do not use this diagram or photo to wire your own switch, as it may be incorrect.


The other photo is my current switch install.

Attached Images

	My Power SW cropped.jpg (40.2 KB, 12 views)
	M (2).jpg (94.2 KB, 18 views)

mickeydg5

I do not know which 4 post switch you have but I believe that the brown and yellow wire may need to be swapped out. Your description are a little confusing as compared to the schematic. The Yellow wire with the fuse should be coming from the mains input, is it not?. But you indicate two other wires coming from the mains input.

You should really trace the wires. The two wires from the PT connect to one side of the switch with the LED while the other two mains input wires connect to the other side. 11/24 (26?) form one side and 12/25 form a second side. You also want your mains neutral flowing to the start side of the PT (blue wire ?).

Another switch is not needed. The correct wiring is however. With a 5 wire switch the side of connection is not as critical and Marshall had it wired differently.

Hope this makes sense.

wrek

mickeydg5 Quote: "The Yellow wire with the fuse should be coming from the mains input, is it not?. But you indicate two other wires coming from the mains input."

Hi mickeydg5,
Thanks for the info. Any help is appreciated.

This is the switch I initially ordered.

MARSHALL JCM 800 900 2000 LIGHTED AMP POWER SWITCH *NEW | eBay

My Amp is definitely wired completely differently than this schematic.
http://www.amprepairparts.com/sw491wiring.gif

On my amp Brown and Blue both are wired directly from the Red rocker switch to the Mains input. I will assume the Blue is Neutral and the Brown is Hot.

The yellow goes straight to the 3 amp fuse.
A black wire comes out of the fuse that goes directly to the mains selector switch. The black is jumpered across two pins on the selector switch.

The other blue wire comes from the transformer.
The OLD black wire came from the mains selector switch.

I have attached a pic of the mains and fuse wiring.

The only wires I removed were directly from the 5 pin switch to the 4 pin switch.

Thanks again,
Rek

Attached Images

M (3).jpg (92.7 KB, 10 views)

jupiter89

I replaced lighted powers switches on two amps that were originally 5 lug with 4 lug. The replacement 4 lug variety do not need the separate black wire for the bulb because it is wired internally. I know nothing about electronics but was able to do it. Here's the link to the thread : How difficult is it for a novice to replace a rocker switch ?



Here is the replacement - notice the black wire taped off since it does not need to be connected to a 5th lug. Keep in mind you are viewing the chassis upside down




this helped me a lot. Correct colored wire to correct small numbers on the new switch:

mickeydg5

I see, your mains fuse is on the PT side of the POWER switch.

If Marshall held true to European colors then your wiring is basically correct. As long as the switch lights in the ON (1) condition the POWER switch is ok.

The power switch has nothing to do with the STANDBY switch. You would have to had physically changed the STANDBY switch to get it to work in reverse.

wrek

I checked my wiring to the diagram and photos Jupiter89 sent, and my wires match, with the exception of not being able to see the wire under his blue on the red rocker sw. On my amp, that wire goes to the transfromer.

Other than that, it seems correct, so I have no idea why the standby is suddenly reversed when I haven't touched it.
I will check with Jupiter89 to see where his wires go.

Thanks for all of your help.

wrek

Thanks for attaching the pics. I really appreciate it.
All of your wiring seems to be wired exactly the same as it is on my amp.
The only wire I can't see on your pic is the one under the blue wire.

Is your's orange or blue?

Mine is blue, and goes to the transformer.
Would you mind checking where that wire goes on your amp, so I can at least see if it goes to the transformer?

Other than that, I have no idea why the standby sw suddenly went in reverse when I haven't touched it. At least I am getting closer to the issue, since your wiring seems to be the same.

I contacted Marshall tech support, but they haven't even replied yet.

Much appreciated.
Rek

mickeydg5

The wire you cannot see at the switch is that blueish-green wire with the green tape on it. You have to look really good at the lug but can see it a little, besides it is the only one left. That looks like a wire that would come off the PT.

wrek

Ok, then if that is the case, my wiring matches it exactly, and yes that greenish blue does go to the transformer. Maybe my standby issue is elsewhere, and not related ot the red rocker sw.

Thanks for your help. At least that confirms the wiring.

wrek

Hey everyone,

I received the Mojo switch today, and wired it up the same way as the other switch, but added the black wire again, It works fine now.

jupiter89

Great ! That wire you could not see on my 4-lug switch below where the blue wire is connected was dark green - almost looked black. In fact if you look at the picture you can see that wire with a small piece of green electrical tape I put on it to differentiate it from the black wire. I believe on some amps that orange may be used in place of dark green.

In any event, glad you got it working !

wrek

Thank you for all of your help, and everyone elses. This forum has proven invaluable. Much appreciated!