Flasher Circuit Question

[rrswede]

I have built 3 flasher circuits following Bob Nelson's design. Each is used on 154 Highway Signals with perfect results. Recently I acquired a 262 Highway Crossing Signal that is a semi-combination of a 252 Crossing Gate and 154 Highway Signal. I decided to rewire the device separating the two functions and then connecting the Highway Signal portion to a flasher circuit. Both functions operate, but if I apply more than 8 volts to the Highway Signal, the red lamps start to flash way too fast. Since this flasher works perfectly with a conventional 154 Highway Signal, the problem has to be with the rewired 262.The only differences that I can come up with are 1) the method of grounding the bulbs (device itself vs wire), and 2) the specifications of the bulbs (14v 200ma bayonet vs 14v 100ma wedge). Any suggestions as to a remedy?
Thanks, Swede

[webenda]

Swede, This might help: "Bob Nelson had indicated in his 2003 post that adding additional capacitors in parallel with the original ones would slow the flashing down."

I would like to see the circuit Bob posted (can't find it with search.) If flash rate is independent of voltage or load, as it is with many flasher circuits, taking it apart and rebuilding it may solve the problem (as it did once before.)

[rrswede]

Thank you for the response, Wayne. I did remember Bob's comment regarding additional capacitors in parallel with the original ones to slow the flash rate, but since this particular circuit board properly controls a conventional 154, I figured it should properly control the 262, without needing to be disassembled and reassembled. Tomorrow, I will pull a couple of capacitors off another circuit board and add them to the one in question to see if the flash rate is improved.

 

Here is the original post from 2003. Perhaps after reviewing it you will be able to offer an additional response.

 

"Here's my stab at the simplest possible electronic flasher.  I just tacked one together; and it seems to work fine.  I don't have any way to show you a schematic; but I'll try to describe the circuit.  I will put Radio Shack stock numbers in parentheses.
Get a bridge rectifier (276-1152).  Connect one of the two terminals on each side of the "+" marking to the accessory voltage of the transformer or to the center rail of the track.  Connect the rectifier terminal on the other side of the "+" to an insulated running rail.
Connect the "+" terminal of the rectifier to the positive terminal of a 1000-microfarad capacitor (272-958) and the rectifier terminal opposite the "+" to the negative terminal of the capacitor.  Call the positive capacitor terminal V+ and the negative V- from here on.
Connect the crossing-signal common, terminal 1, to V+.  Connect the emitters, marked "E", of two 2N3904 transistors (276-2016) to V-.  Connect one crossing-signal lamp, terminal 2, to the collector, marked "C" of one transistor, the other lamp, terminal 3, to the collector of the other transistor.
Connect a 3300-ohm resistor (271-1328) between V+ and the base, marked "B", of one transistor.  Do the same with another resistor for the other transistor.  Connect the positive terminal of another 1000-microfarad capacitor (272-958) to the collector of one transistor and the negative terminal to the base of the other transistor.  Then do the same, switching the roles of the two transistors.
If the circuit flashes too slowly for you, decrease the capacitance of the last two capacitors described; increase capacitance to slow it down.  An easy way to cut the speed in half is to put two more 1000-microfarad capacitors each in parallel with one of the existing capacitors.
The parts cost, according to my 2002 catalog, is about $6."

 

Thanks again, Swede

[webenda]

Thank you for Bob's text schematic Swede. I changed it to a symbol schematic so I could see how it worked. I see no reason for it to flash at a higher rate when input voltage is changed. I am stumped

The transistor is rated at 200 mA max. I think I would use a clip on heat sink on the transistors for driving either Lionel grade flasher.

[rrswede]

Thanks again, especially for generating a really nice schematic. I printed it out to replace my handsketch. I did add two capacitors as a test to slow the flash rate down. They did slow the rate down, but at 14 volts, the amount I am using for all accessories, the flash rate remained too fast. I gave up, removed the bi-pin bulbs and sockets, modified the housings, inserted screw type sockets and 14v 200ma bulbs and the unit now works like I had hoped it would. I don't understand why the bulb change would have made such a difference,  but it did.

Swede