Adding power indicator light to Fisher tube preamps

I'd like to add power indicator lamps to my pair of Fisher 50PR tube preamps.  They were taken out before I purchased the units.  Some one has suggested that I use a "stereo mode switch with shielded section" in lamp housing so as not to induce added hum in the circuit due to taking the 6.3V (for the #47 bulb) from the transformer.  Is this necessary?  Do I need to take extra precaution or can I use just an ordinary bayonet mount with the #47 bulb? Attached is the schematic for the Fisher 50PR.

Fisher 50PR document 2.

Fisher 50PR document 3.

Fisher 50PR document 4.

You could place a 6,3VAC Bulb across the heater windings... twist the leads tightly and there should be no problem... Biggest problem might be to find room enough for the lamp holder.

Best regards

/John

See the schematic where they used to place the bulb

I have a couple of Fender amp lamps with housings that I could use, but would need to enlarge the hole to about 12mm.  Otherwise, I'll need to search for the correct size housing with lens. Thanks!

Ok , but 12mm is not that big really… I do not know the english word for the tool but it is a stepped drill bit that you use to increase the diameter of an existing or new hole… it is like cone… I would guess 15 USD for a quality one (I might be wrong here about the cost)

Best regards

/John

maybe a fuse and grounded plug also.  You could use a 120v lamp and put it close to the power in.

Ok , but 12mm is not that big really… I do not know the english word for the tool but it is a stepped drill bit that you use to increase the diameter of an existing or new hole

Click to expand...

Thanks John.  Yes I have a stepped drill bit and I think I have decided to use it to enlarge the inside frame hole and mount the Fender amp fixtures that I have .  Now I have a plan, just need to do it.  The outer "Fisher gold colored" panel plate will just sit up against the faceted lens - hopefully.