Im thinking about making a custom faceplate for my OTS FM.  Does anyone have a dimensioned drawing or CAD file of the faceplate? 

I received the replacement LED from eBay and finally got around to making the switch.  Here's my report.
The LED version looks exactly the same on the front panel. it doesn't have a colored lens, just a colored LED. The shaft inside the chassis is longer but not so long that it hits anything.  Pulling the assembly apart reveals a 1.2k resistor in series with the LED lamp on my 12 volt DC version.  The eBay seller offered 24 volt versions which differ I imagine in the size of the series resistor only.  Typically a 5mm LED likes about 2-4V dc and about 20ma.  These values vary depending on color and output of LED.  The two issues at hand are selecting the proper size series resistor to get the proper operating current and adding a parallel diode to prevent damaging the LED from excessive reverse voltage.   Typical LEDs can take 5-6 volts backwards without damage.  We're pushing our luck with our 6.3V AC source.  Since I didn't know exactly what LED I had I did a quick test.  I used a 1N914 diode parallel to the LED but reversed in polarity, this will shunt the negative portion of the AC wave and protect the LED.  I put a 1k trim pot is series with the LED/ diode and found about 480 ohms gave me the correct current and lit up the LED nicely.  Since the closest 1/4 watt resistor I could find laying around was 330 ohms I tried that, it made the LED a little brighter but OK.  The 1/4w resistor and the 1N914 are small enough to both fit within the barrel of the new pilot light assembly.  Remember when soldering up the LED to be gentle with your soldering iron and use a heat sink since its easy to cook LEDs.  Finally product looks great from inside and outside the amp and should be maintenance free.  Hope this helps.

Sure, I ordered a few from eBay.  They look exactly the same but are listed as 12 volt DC.  I'm assuming they have a series dropping resistor to get the proper operating current through the LED from a 12 volt source.  I guess I will have to lower the value to maintain the current with a 6.3 volt source.  Then add a diode to shunt the reverse voltage from the AC.

I'll post my findings but it might take a while, the seller was in China and he put them on the "free shipping" slow boat!

Great! - thanks for the link.

The Mouser item looks exactly the same but its a 6v LED (comes with a series resistor), I think Nick is using a neon lamp to work with the AC supply.
I wonder if I'll still need a parallel diode to keep the LED from flickering and protect it from the reverse voltage.
I guess I'll have to experiment.

thanks again for the info!

I need a new pilot light for my OTS.  I'm having a tough time finding 5/16" 6.3v AC replacement.
Does anyone know of a USA source?  I see a few people have drilled out their chassis and installed a Fender light.  I do prefer the authentic small one.  Has anyone converted to LED?  I guess I would need a series resistor and a diode.

thanks!

The same thought crossed my mind.  Even though an air gap is a fine insulator it's disconcerning to see only a 1/4" clearence.  If you think about it, if you have a short you would want it to ground.  Shorts to ground clear the over current protection quickly, in our case the fuses.  I much rather blow a fuse then become the human fault path! 

It's interesting that your kits had backer boards for almost all the boards.  Maybe Nik doesn't see the shorting issue as a problem.  My guess, based on the two boards that have backers is he is concerned with clearence above, not below the boards.

Henry,

I too would be interested in a head cabinet design for a C-lator too.  Something like the cabinet Nik shows on his site.

Will you offer this option?

thanks

Thanks!  mcinku's photos were helpful.  His HRM layout is a bit different than my FM, its got 3 small boards on the ground and two on the wall by the PT.  It looks like four of his boards, the Relay PS, Bias and the two Relay boards are all mounted without standoffs so I assume they all have backer boards.
So, if I assume the two boards I have with backers ( Relay PS and PAB) get bolted down without standoffs then my 6 short standoffs will take care of the Bias, Channel and FET boards.  The 8 long standoffs are obviously for the PS and Main boards.  Problem solved!

I wonder what was Nik's logic in using the backer boards instead of standoffs?  The Relay PS board is awfully close to the pilot light and voltage regulator, lowering them give you a bit more clearance.   Similarly the PAB board's relay sits just under the three small switches on the front face.  So maybe clearance issues on top of the boards were the driving factor.

thanks again!

Hello,
I'm working on a OTS FM 50 Mod Eagle.  The parts list says the two backer boards supplied are for the Relay PS board and the PAB board.  I assume that the 8 long brass standoffs are for the PS and Main boards mounted on the floor of the chassis.  Then I assume the 6 short standoffs are for the three boards mounted on the sides.  So I'm wondering, why does the Relay PS board need a backer if it's mounted on standoffs?  Also if the PAB and Channel boards don't have standoffs, why don't they both have backers?  I figure I will use longer screws and double nuts to get these two small boards off the floor and keep them from grounding out.  Maybe even get a little crazy and cut a backer for the Channel board.

I very much welcome some good advice.

Thanks

Todd,

Arigatou gozaimasu!

I didn't think of that.  I thought it was only used in series with the other 120 volt coil for a 220 volt input.

Nik might want to update the layout.

Rich

I'm working on my DZ30 build using the March 15 2010 layout on Nik's site.
The diagram shows the 100 volt tap of the power transformer connected to the power switch.
Is this an error?  Should it be the 120 volt tap for the US?
Thanks!