Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ericlen838 on November 18, 2020, 07:25:06 pm
-
I can’t get the light switch to light up.....help please. This amp is a 50 watt Marshall silver jubilee.
-
You need more wires on the switch. Look at this...
https://el34world.com/charts/images/mar_switch.gif
-
Yeah, those lights can be kind of tricky to get to work sometimes. I discovered that they don't work if you put the wires on the wrong connectors...
-
I had trouble getting a rocker switch to light up on a Plexi 50 build a while ago. If you search for it there’s a lot of good info from Sluckey on how it all works with the link he posted above
-
The rockers use a neon, which is internally connected across each side of the switch on the newer 4 terminal switches. In order for it to light up you need to wire it up as intended (DPST), switching both the live and neutral wires. Run the live conductor from the mains fuse to one side, and the neutral conductor to the other side.
However, on the 5-terminal switches which you and stock Marshall's use, I believe that they run one of the legs of the neon to the bottom (5th) terminal......
Edit: sluckey's post below provided clarification. Again, the easiest way forward is to wire it like I mentioned above, and run a jumper from lugs 24 to 26 like he suggests below.
(the neon is connected across lugs 11 & 26)
-
For the 5 lug switch just wire like the above pic but also put a jumper between terminals 24 and 26.
-
For the 5 lug switch just wire like the above pic but also put a jumper between terminals 24 and 26.
So, the neon is connected across lugs 11 & 26. Thanks for correcting that.
-
For the 5 lug switch just wire like the above pic but also put a jumper between terminals 24 and 26.
So, the neon is connected across lugs 11 & 26. Thanks for correcting that.
Functionally, that's correct. But there must be a resistor in series with the neon bulb, so I'm not sure exactly how all that is connected.
-
[/quote]Functionally, that's correct. But there must be a resistor in series with the neon bulb, so I'm not sure exactly how all that is connected.
[/quote]
On the 4-lug switch, one can figure the current limiting resistor is connected internally.
On the 5-lug switch, my "guess" is that there is a 100k-150k resistor wire internally also, and that is why they keep it running off the 120V tap of the voltage selector (unless one is wired inline and enclosed in heat shrink. I can't recall off hand).
-
Yes, NE-2 and resistor both inside the switch body.
-
I can’t get the light switch to light up.....help please. This amp is a 50 watt Marshall silver jubilee.
It doesn't look like a Marshall Silver Jubilee.
What PT are you using?
If it has multiple primary taps, are you using a voltage selector?
-
So, the neon is connected across lugs 11 & 26. Thanks for correcting that.
I have good reason to believe that the lamp is between lugs 11 and 13 on the 5-lugs that Marshall used. If this Mojo switch is truly a mirror image, then the lamp would be connected between lugs 24 and 26.