Hitachi HMA-7500 meter lamps

[JamesDee68]

I am replacing the meter lamps in my Hitachi HMA-7500 power amp. I have the schematic but I can't find out anywhere what the lamps are current rated for. I know they are 12vac per schematic but I can't find the current requirement . I bought 4 axial incandescent lamps 12v @100ma but they seem a bit low intensity.
I don't want to go LED as I like the retro look.
Anyone know the proper specs for this lamp?

 

[chazix]

meter lamps in my Hitachi HMA-7500

On the schematic I have, there's a 4.7 ohm resistor in series with the lamps, and voltages on either end of that resistor differ by 1V. That would indicate about 200mA for ALL FOUR lamps, or 50mA apiece. If you installed four 100mA lamps, they would not be getting the expected voltage, and it's quite possible the resistor was damaged.

I have a hunch you will be happier with an LED retrofit. Go for "warn white" with several individual LEDs on each lamp, and get ones with a diffuser covering if that's available in the form factor you need. Sorry, I don't have a pointer to specific parts.

 

[JamesDee68]

On the schematic I have, there's a 4.7 ohm resistor in series with the lamps, and voltages on either end of that resistor differ by 1V. That would indicate about 200mA for ALL FOUR lamps, or 50mA apiece. If you installed four 100mA lamps, they would not be getting the expected voltage, and it's quite possible the resistor was damaged.

I have a hunch you will be happier with an LED retrofit. Go for "warn white" with several individual LEDs on each lamp, and get ones with a diffuser covering if that's available in the form factor you need. Sorry, I don't have a pointer to specific parts.

Thanks, I will have to verify the voltage at the lamps, to verify that indeed I am getting 12vac, and if not , check the in series resistor, to verify tolerance, and find a lower current 12vac lamps if necessary. Or as you say, go the LED route..

 

[JamesDee68]

On the schematic I have, there's a 4.7 ohm resistor in series with the lamps, and voltages on either end of that resistor differ by 1V. That would indicate about 200mA for ALL FOUR lamps, or 50mA apiece. If you installed four 100mA lamps, they would not be getting the expected voltage, and it's quite possible the resistor was damaged.

I have a hunch you will be happier with an LED retrofit. Go for "warn white" with several individual LEDs on each lamp, and get ones with a diffuser covering if that's available in the form factor you need. Sorry, I don't have a pointer to specific parts.

Actually I measured 11.9V at input to R401 and lamp voltage supplied to lamps is 10.5 V which is not to bad. The resistor isn't getting hot but I can't actually look at it as it's covered in a cloth cover. But I did order LED assemblies to replace the incandescent lamps.