LED strobe lamp for Dual 1229 howto

I found a nice schematic for a LED replacement for the neon
strobe lamp for Dual turntables, posted by dualfred on dual-board.de
The lamp on my TT started failing, and I found this works great.



The schematic for the dual strobe is below. The LED lamp is the part shown in the box here -



I wrote up a little howto to help you make your own LED lamp.

Before you go any further, note that the strobe board has potentially
lethal line level voltages. Proceed at your own risk.
If you don't know what you are doing, and kill yourself, don't come back to haunt me or
this board

Here's what you will need:

* A small piece of bare copper clad PCB, size 6mm x 26mm (1/4" x 1 1/16")
Double sided board is ok, but make sure to cut the copper
continuity on the reverse side.

* Two super bright surface mount LEDs, as per your choice of color.
5mm through hole LEDs are too tall to fit into the Dual strobe box,
so I had to salvage a couple of SMD LEDs from a broken torch.
White LEDs are working fine, though I may change them to orange
later.

* One Diode - 1N4004, 1N4007 or similar

* One Zener diode - 75V, 1 watt (1N4761)
I had a 68V, 1W (1N4760) on hand, and it works fine for me, so
there is some tolerance here, if you don't have the exact value.

* Two faston PCB type terminals

* The usual diyers tools - soldering iron, clippers, dremel...

Let's get started -

1) Using a dremel or a xacto knife, cut the copper (on both sides,
if you are using double side board) of the PCB as shown.

2) Solder the two LEDs. I used a PLCC-2 type LED. The cathode is
marked by a notch on the package. Both LEDs are in parallel, so
the cathodes go the same way.



3) Solder the 1N4004 diode as shown, anti-parallel to the LEDs.
This is to protect the LEDs from high reverse voltage. Note
where the banded end goes, as in the pic.

4) Solder the zener diode as shown. The zener helps to get a
sharp pulse of light. Again, note the orientation of the banded end.

For the metal tabs at the end, I dremeled them out of
a couple of faston PCB terminals and soldered them to the ends
of the LED lamp PCB

Now, your LED lamp is ready, and should look like the one in
the pic in this listing (have a limit of 6 pics, hence the reference) -

http://cgi.ebay.de/Ersatz-Dual-Stroboskop-Glimmlampe-LED-Typ-orange-/270746598643

To get more brightness, I replaced the 0.068uf cap on the
Dual Strobe PCB with a 0.1uf, 400V AC rated cap, and also
changed the 2.7K resistor to a 1Kohm, 1/2 watt one.

In case you are wondering why the pics look a little wierd, it's because I forgot to take pics
while making the lamp, so had to create these pics using an image editing tool.

I also made an eagle layout, and can attach the file if someone
wants it. Attaching the schematic, pcb, polarity of the components
and a pic showing where to cut the faston terminal using a dremel.

Very nice work. Thanks for the post and the great pictures and tutorial.

The LED's should be run in series, not parallel. Other than that, looks cool.

Thanks, EW.
Actually, I made it first with just one LED, and it was bright enough for me.

If someone needs two LEDs (in series), just refer to the images
in this post - minor changes in the dremel cut pattern
and the placement of the components.

A word of caution on the component layout -
The clear window in the strobe box is not too big, so
take care not to place the two LEDs too far apart
(my photoshopped pic shows them too far and I am too lazy to redo it),
and also the LEDs need to be placed closer to one end (the left side of my pcb)
so that they will both be within the visible window.

EchoWars said:

The LED's should be run in series, not parallel. Other than that, looks cool.

Click to expand...

I was wondering why running the leds in series is better than running them in parallel? I can think of a voltage drop to reduce the voltages across the two LEDs in series. Otherwise, connecting two leds in parallel to a power source lights up both leds (just wondering)!

Don't know for sure, but I would think in series would guarantee both LEDs get the same current. If they weren't identical, in parallel one could be brighter Also, they may have a positive temperature coefficient, so the brighter one would have a shorter lifetime... My 2 cents.

sregor said:

Don't know for sure, but I would think in series would guarantee both LEDs get the same current. If they weren't identical, in parallel one could be brighter Also, they may have a positive temperature coefficient, so the brighter one would have a shorter lifetime... My 2 cents.

Click to expand...

yes, exactly! anyways the LEDs these days are suuper bright...even 1 should do fine

Well since you revitalize a zombie - thread: Meanwhile you can get the complete LED - array as plug-and-play - device in blue, green or orange - from Dualfred aka Alfred Langer himself: https://www.dualfred.de/Drive/Electronic/LED-Strobe-225321or-en.html

quadtech said:

yes, exactly! anyways the LEDs these days are suuper bright...even 1 should do fine

Click to expand...

I needed to replace the bulb in my 721. The original bulb is still working but it seems that the mercury inside the bulb is covering some area on the glass. Anyhow, removing and inserting the bulb 180 degrees helped but not as good as original.
I was thinkering with other solutions when I realized that I had a 704 that I was using for parts. The bulb was still good so I moved it over to the 721.

The bulb on the left has a clear glass. The glass on the bulb to the right is partially covered with the mercury that was inside the bulb. The lighting improves by rotating the bulb by 180 deg inside the socket. It makes it useful again to adjust the pitch.

I searched for replacement neon bulbs. There are some available at a reasonably low cost but none are axially leaded. It would require some effort to fit them into the holder.

The LED solutions above are the best way to replace the burnt bulbs today. When I get a chance I will give it a try and report back with my findings.