Greetings everyone. I'm hoping someone will know about this vintage 1971 receiver I recently acquired. Specifically how the FM meter indicator lights are supposed to work. The lights do not work. I pulled the meters so I could change the bulbs but strangely there are no bulbs to change. There are only two wires connected to the meters. The tuning meter carries 35V across it. Please see the photos. Thanks for your help.
https://www.screencast.com/t/VVvFZ4Ma
https://www.screencast.com/t/2x4I3pTxkT
https://www.screencast.com/t/2InV0ak8x2
https://www.screencast.com/t/gWQYGgyVAgR
https://www.screencast.com/t/VVvFZ4Ma
https://www.screencast.com/t/2x4I3pTxkT
https://www.screencast.com/t/2InV0ak8x2
https://www.screencast.com/t/gWQYGgyVAgR
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> I pulled the meters so I could change the bulbs
The meter lamps are often not IN the meter but "behind" it, shining through the clear/white case. Basically mounted on mounting-brackets. And covered with light-shields so they do not throw light all back inside the case and out the top vent.
ML4 lights both meters so will be in the thin strip between, to throw light to both.
ML3 will be masked to only throw light at the FM Stereo dot.
The dial-scale on this unit is odd. There's separate light for AM and FM but I can not tell from the manual if they are behind (inside) the drum shining out, or in front bouncing off the scale.
Aside from the leads that DO go to the actual meters, there should be a few more wires in this area. See where they go.
Oh! The power switch is in this area. Terminals are "live" even when off. Do not get shocked!
The meter lamps are often not IN the meter but "behind" it, shining through the clear/white case. Basically mounted on mounting-brackets. And covered with light-shields so they do not throw light all back inside the case and out the top vent.
ML4 lights both meters so will be in the thin strip between, to throw light to both.
ML3 will be masked to only throw light at the FM Stereo dot.
The dial-scale on this unit is odd. There's separate light for AM and FM but I can not tell from the manual if they are behind (inside) the drum shining out, or in front bouncing off the scale.
Aside from the leads that DO go to the actual meters, there should be a few more wires in this area. See where they go.
Oh! The power switch is in this area. Terminals are "live" even when off. Do not get shocked!
Attachments
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Yep, you nailed it. Stereo light is in it's own little rubber boot. The single bulb for the meters is between the two mounted on a rail held in with a single screw. Thanks allot!
https://www.screencast.com/t/5spc82JsY1Y
https://www.screencast.com/t/5spc82JsY1Y
Thanks for your help! I found the bulb for the meters off to the side of them. Mounted to a small rail buy a single screw. The stereo light is mounted in it's own little rubber boot. Schematic and parts list does not show a voltage for the meter bulb. The parts list does say the small bulb is 24V but does not specify what that bulb is. I think it is the stereo light bulb cause it is the smaller of the 2 bulb. I may need to power up and measure for voltage. The photo shows the meter light and single screw holding the rail. Red arrow.
https://www.screencast.com/t/5spc82JsY1Y
https://www.screencast.com/t/5spc82JsY1Y
The schematic shows AM FM and meter connected to a 6.3VAC supply. Stereo does derive from a 24V supply but through a 200 Ohm resistor on the MPX board. This old man's guess is that they are 6V 0.1A "grain of wheat" lamps, though possibly with leads at both ends(?) instead of both at one end.
LEDs have killed the demand for GoW bulbs, but they linger in odd shops.
6V Mini Lamps - Small | Jaycar Electronics New Zealand
6V Blue: SL2683 (blue is the lead color, not the lamp)
Philmore 11-706
Ah-- they turn up in bulk at prices low enough to stock-up for a lifetime:
6 VOLT 60MA, T-1 LAMP WITH 11" LEADS | All Electronics Corp.
10 Grain of Wheat Bulb 6Vdc 3MM Clear 1/8" 7 inch leads 68mA: Amazon.com: Industrial & Scientific
But wait. Someone here may know where to get the "correct" lamps. (May even have a bagful handy.)
LEDs have killed the demand for GoW bulbs, but they linger in odd shops.
6V Mini Lamps - Small | Jaycar Electronics New Zealand
6V Blue: SL2683 (blue is the lead color, not the lamp)
Philmore 11-706
Ah-- they turn up in bulk at prices low enough to stock-up for a lifetime:
6 VOLT 60MA, T-1 LAMP WITH 11" LEADS | All Electronics Corp.
10 Grain of Wheat Bulb 6Vdc 3MM Clear 1/8" 7 inch leads 68mA: Amazon.com: Industrial & Scientific
But wait. Someone here may know where to get the "correct" lamps. (May even have a bagful handy.)
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