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Help with RT 707 reading schematic

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That is not exactly the schematic that you need to look at. Although the picture of that board (RWX-152) does come in handy to pin point soldering the connections if need be. What you have posted there is simply the (R) right side 'Switch Board' (RWX-152) that shows exactly what pins (in this case Pins 30 & 34 for the FORWARD LAMP wire leads and Pins 24 & 28 for the REVERSE LAMPS wire leads) on the RT-707.

You need to scroll back up to page #64 (of the Service Manual) and in the section C3 (use the letters and numbers at the edge of the schematic for quick location) located basically in the very middle of the whole schematic, locate PL3 & PL4 26V 35mA x 2, look slightly to the lower left of that and you'll see the symbols for PL3 FWD & PL4 REV lamps.

I would recommend that you follow and use that schematic for actual points, gounding, etc.?

Or as I mentioned before, go the easier route and for $15.99 you can purchase this kit, it's easy and quick without any complicated hassels and it come's out looking terrific!

http://www.wjoe.com/diallamps.htm

Good Luck!
 
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Got to the service manual .
Located PL3 & PL4
I assume , that the line where I drawn the blue line , is the + ?
If it's correct , how can I know by the pins which one is which ? I mean , It doesn't indicate the pins there ...
 

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Supply to anode, cathode to ground. Your blue line is correct, that is the positive feed, big thick black line is your ground rail.
 
Wowwow... Easy on me there :) I'm still a newbie with this
How did you figure "Supply to anode - cathode to ground" ?
How do I locate the things actually on the board itself ?
Thanks
 
omri617 said:
Wowwow... Easy on me there :) I'm still a newbie with this
How did you figure "Supply to anode - cathode to ground" ?
How do I locate the things actually on the board itself ?
Thanks
Click to expand...

A LED is a diode (light emitting diode) , a diode has an anode and a cathode, the cathode goes to ground and the anode is fed from the voltage source. If you were to install in reverse it wouldn't light up, reverse it then it would.

As for locating, the schematic "should" match the board.
 
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The schematic you posted has "PL3" and "PL4" written on it above the lamp symbols as well as "FWD" and "REV" written below the lamp symbols.

The diode is drawn as an arrow, and the arrow point is pointing DOWN, at the "FWD" and "REV" letters on that drawing.

The broad part of the arrow symbol is the "ANODE", the tip part of the arrow symbol is the "CATHODE".

Since the lamps are specified as 26 volt, 30mA , resistors will be needed (series, or "in line" ) with each LED, 1500 ohms or more at ONE WATT, because the resistors will be shedding about 1/2 watt of heat dropping the 26v down to about 2 volts for the LEDS.

Depending upon the LED, this may be too bright, (or not bright enough, i.e. too low of a brightness LED, in that case you need different LEDS) and a larger resistance indicated to dim the LEDs.

Translating this to the board layout drawing you posted in the first post:

thus for FWD: pin 30 to a new 1500 ohm 1 watt resistor, other side of that resistor to anode of FWD LED, Cathode of FWD LED to pin 34

thus for REV: pin 28 to another new 1500 ohm 1 watt resistor, other side of second resistor to anode of REV LED, Cathode of REV LED to pin 24

p.s. I know the calculation calls for 1300 ohms, but you may NOT find that "not so standard" value 1300 ohms in 1 watt easily.
 
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I'm using 2.2 Kohms resistor.
You mean diode D602?

I'm a bit confused because :

"4- Solder the balast resistor to the cathode of the led (in the image is shown the first resistor that I tried). Use a simple tester to know which wire will go to the cathode and which one to the anode."

That's what the guide says.
You said :

pin 30 to a new 1500 ohm 1 watt resistor, other side of that resistor to anode of FWD LED
 
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It doesn't matter to the LED WHICH side of the LED the resistor is soldered to, I choose the HOT (anode) side at 26 volts, so an inadvertent cathode short to ground will not damage the LED, the resistor cuts the voltage down before it gets to the led, otherwise the LED has 26v on one side and 24v on the other side. Shorting 24v to ground will let massive amounts of current burn out the LED.

resistor = "ballast" resistor

THis way, one side of the resistor is at 26v, and in normal operation, the other side of the resistor will be at TWO volts = no damage with shorted anode wires. Just NO LIGHT. with shorted cathode wire, LED light will always be on. when NOT shorted LED light will work normally.

NO DRAMA with accidents, blown fuses, zapped transistors etc... I put some THOUGHT into my circuits and explanations...
 
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