Phase linear 400 meter lamp replacements

[Barnacle]

I just got 2 Phase Linear 400 Amps and neither has VU meter lamps that work. I would like to put in colored leds instead. What is the voltage and series resistor required to do this replacement?
Thanks

[Barnacle]

Originally posted by Barnacle
I just got 2 Phase Linear 400 Amps and neither has VU meter lamps that work. I would like to put in colored leds instead. What is the voltage and series resistor required to do this replacement?
Thanks

Does no reply mean that nobody knows the answer or I just asked a real stupid question.
Bill

[latala]

Well
At last a phase linear fan ! I have 2 off 400,s myself
firstly measure the voltage across the lamp then detuct 2.5 volts for the led divide the remainder voltage by 0.02 and that will give you the value of resistor that you require ! this will give about 20 ma per led
You may want to rectify the votage with a bridge rectifier as the drive to the lamp is ac
Regards Trev

[Barnacle]

Originally posted by latala
Well
At last a phase linear fan ! I have 2 off 400,s myself
firstly measure the voltage across the lamp then detuct 2.5 volts for the led divide the remainder voltage by 0.02 and that will give you the value of resistor that you require ! this will give about 20 ma per led
You may want to rectify the votage with a bridge rectifier as the drive to the lamp is ac
Regards Trev

Thanks for the lesson

I have 2 PL400s now and a PL4000 preamp on the way--Love the stuff. Also it was built just a few miles from me here in Kirkland Washington. Now I need a McIntosh for pure beauty. Got my Big JBLs with Electrovoice horns a couple weeks ago and with the Phase Linears it blows my video room apart with the sounds of the 60s and 70s. Oh how I missed those old sounds as I progressed through the digital age but finally gained my senses back and went back in time to the good old analog creatures. I want to Bi-amp the phase linears [if possible ? ] for each of the JBLs and use my Quatre 250 for the horns and then set up my Dahlquists with a Tube Dynaco 120 for the easy listening of norah Jones.

[latala]

Wow
That system sounds awsome! Despite some people calling them Flame Linears I have found that with the correct matching equipment they can sound superb.
At the moment I am not using mine but do not intend to get rid of them .
Regards Trev

[Barnacle]

Originally posted by latala
Well

firstly measure the voltage across the lamp then detuct 2.5 volts for the led divide the remainder voltage by 0.02 and that will give you the value of resistor that you require ! this will give about 20 ma per led
You may want to rectify the votage with a bridge rectifier as the drive to the lamp is ac
Regards Trev

What would be the advantage of the bridge rectifier in LED circuit? or would it just not work without being rectified? You confused me a little with the "you may want to rectify" part of the advice.
Thanks again
Get those PLs up and running !

[latala]

As the supply to the lamps is AC youwould only get illumination on 1/2 of ther cycle .Also there is a danger that the led would be damaged by a reverse voltage all though that is unlikely
The brightness would also be affected because of the half cycle operation
Also there could be a flickering effect when you view the light while moving your head because of the speed of the led most lamp filaments are to slow for this effect to show
If you have room you could use 2 leds in reverse parrallel is,e cathode of 1 to anode of 2 and anode of 1 the cathode of 2 this would eliminate all the effects so mentioned without the need for a bridge rectifier
regards Trev

[Barnacle]

Originally posted by latala
As the supply to the lamps is AC youwould only get illumination on 1/2 of ther cycle .Also there is a danger that the led would be damaged by a reverse voltage all though that is unlikely
The brightness would also be affected because of the half cycle operation
Also there could be a flickering effect when you view the light while moving your head because of the speed of the led most lamp filaments are to slow for this effect to show
If you have room you could use 2 leds in reverse parrallel is,e cathode of 1 to anode of 2 and anode of 1 the cathode of 2 this would eliminate all the effects so mentioned without the need for a bridge rectifier
regards Trev

That sounds reasonable
The 2 PL panel meters have 4 LEDs each so I presume that I could use this reverse setup for each pair of LEDs or use a series / parallel combination for the hookup of all 8 lights and no rectifier. If this would work with 8 LEDs a little circuit diagram or explanation would be appreciated.
Thanks

[Barnacle]

Originally posted by latala
Well
At last a phase linear fan ! I have 2 off 400,s myself
firstly measure the voltage across the lamp then detuct 2.5 volts for the led divide the remainder voltage by 0.02
Regards Trev

I went to measure the voltage at the meter lamps and there is none. The supposedly 6v to the lamps come from the transformer and it appears that the transformer secondary is burned out. My next choice is to pick up a dc voltage after the Mains rectifier which is 75VDC and use that for the power to the LEDs with the appropriate resistor. Does that sound reasonable?
Bill

[latala]

I would check every thing out as the 6 v sec burning out seams to be unlikly ?
however if I had to go down the route you have mentioned I would wire all leds in series and then use a dropper resistor between the posative supply and ground
remember though that some blue /white leds require about 4 volts each so 8 x 4 = 36 volts 70 volts from supply - 36 = 34 volts
divided by 20 ma = 1.7 k ohm 1.5 k is near enough
power dissipated by the resistor is 0.68 watts
so in this case a 1.5 k resistor rated at 1 watt would be fine
trust this helps
regards trev