Assuming your reading of 7.5vac is correct, it's no problem for me to fabricate an 8v/60ma/3mm with 20" wires on it, those eBay lamps seem like they won't last long if they're in fact rated 6v. Just my $.02 on this, e-mail me if you need more info, Dave.
I just looked at your picture again, that pointer lamp sure looks about the 4.75mm diameter of my black wire lead lamp, I bet mine is correct!!
(This reply goes back to the pointer bulb for the 2100.)
"Presumed" original pointer bulb
Physical dimensions:
The 4.75mm dia. bulb "may" fit in the pointer housing, but
there is a problem to consider.
For future reference
The pointer itself is what they call a light pipe.
A lightpipe is a kind of fiber-optics.
It is a clear plexiglas or lexan or similar plastic component.
In the Marantz 2100 model, it is either coupled to red lens or dyed red on the top end. Then it is glued to a small black plastic housing which is held in place by four small tangs on the stamped metal pointer/tuner cord assembly plate which slides left and right the "black steel tuner pointer guide track".
When I had to replace the pointer bulb, I had to remove the aluminum face plate, top cover, tuner dial. It is recommended that you insert a piece of cloth, napkin or paper between the pointer (behind the pointer) and the
upper tuner dial plate flange up and around the horizontally oriented flat bare
metal strip which the top cover-to-chassis' two front screws are fastened. - doing this avoids the risk of rubbing the clear plastic pointer against the sharp edge of the that flanged upper edge and the flat bare sheet metal top cover chassis strip. (Warning: IF you nick or scratch the clear pointer, there will be a glow on the dial plate behind that pointer.)
To remove the pointer from the pointer/tunercord assembly plate or "P/TAP":
1) tune the pointer to the middle of the dial plate.
2) insert protective cloth or paper as described above.
3) gently lift the pointer up and tilt back, pushing the P/TAP back and just off the black guide track so it clears the "tuner pointer guide track" or "TPGT".
Note: provided your tuner's cord is in good shape, you should be able to do this without breaking the cord, (something, you definitely don't want to do).
4) With the P/TAP off the track, note the clear plastic track gasket inside of the P/TAP's folded flange. (Do NOT remove it and remember that the plastic has to be on both the top and bottom side of the "TPGT". This allows the P/TAP to slide freely on the TPGT. Without it, the pointer will be jittery as you move the tuner as the P/TAP is snagging on the track.)
NOTE: It is NOT necessary to remove the cord from the P/TAP.
5) Remove the small moulded plastic pointer black box from the P/TAP by gently pulling back two clamping tangs till they just clear the black box.
(Once removed, the light should just come right out.)
NOTE: Those tangs are very fragile as bending metal causes metal fatigue, two light replacements sessions almost guarantees a third service will definitely result in damage of one or more of the P/TAP sheet metal's pointer clamping tangs. See P/TAP Solution Note Below
6) Remove bulb from the housing and reverse the steps above.
P/TAP Solution Note:
I have used a 1.5 40mA bulb wired in series to a 220Ω resistor in the place of the original 68Ω resistor with reasonable success. As of this writing, the bulb has not burned out after approximately 6 hours of service. I am still monitoring this specific fix for durability. Average life of the bulbs are 1000 hours.
Bulb Physical Dimensions:
.15" Diameter.
.20" Long
Note:
a) This bulb is smaller than the original bulb and will easily slide in and out of the black pointer housing's bulb feed-through hole. It CAN be tied securely using very fine wire such as a scrap of insulated 30 AWG. wire fed through the bulb's twisted wire leads and wrapped around the P/TAP and the black box twice and simply twisted on itself, no knots neccessary.
b) This bulb is probably not as bright using a 220Ω resistor as it might be using a 150Ω resistor. My first test used 120Ω and the bulb burned out within 10 minutes. I "think" 150Ω will hold up longer, but how long, I don't know.
180Ω may be the perfect size for this specific combination.
For my second test, I used a 220Ω resistor which is only barely noticeably warm to the touch after 10 mins continuous use. I can pinch this resistor without burning my finger. the previous 120Ω was considerably hotter.
Also, I used a piece of aluminum foil cut from a Coffee Can Seal to form a mirror to help brighten the lamp cavity.
I'll update this reply should there be a reason to do so.
IF this works out, I would recommend using this approach over what was original only because of the fragililty of the small P/TAP clamping tangs which
would be harder to replace than the bulb.
The only other recourse would be to enlarge the pointer lamp housing access hole.
