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SX3800 - Thanks and a Lamp ?

kensn

kensn

New Member
1st post, but have been lurking for a while.

First and foremost I would like to thank Mark "Markthefixer" for the wonderful, time consuming, detailed and helpful posts. It was with these posts I was able to resurrect a SX3800 that my dad purchased originally and passed on to me about 5 years ago. It had seen less than normal use, so when I decided to use it I was very surprised that it had a problem. Seems to have been D207, but I replaced some transistors, eletros, and zeners while I was there.

OK... So I want to replace the Speaker Selector (ac) and Function Selector (dc) lamps with LEDs. I really want to experiment with resistor values to obtain the brightness I desire. I have searched a lot of posts, but being that I just spent some time successfully getting her going I don't want to fry something.

Can someone give me a starting point on values to use, diodes or not(ac), caps or not(ac) and an example of what has worked for them?

Thanks for reading.. sorry for the long post.

Ken
 
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Thanks Teti.. I was looking to use blue LEDs to match the rest of the Flouroscan display. The link did provide the idea that i could breadboard this to experiment with values.

Let's see what else pops up here....
 
I just finished an LED conversion on an SX-3900. I used white LEDs, as I was not interested in changing the color of the button lights. As you probably know, the color is imparted by plastic covers fitted over the light paths, however these covers also serve as light diffusers so you get a nice even illumination with no "hot spots". You could either go with white LEDs and experiment with different shades of translucent blue plastic, or you could just go with blue LEDs and use clear frosted plastic (or even vellum paper) for diffusion.

Be aware that the function indicator bulbs are powered by 12.5VDC while the two speaker system indicators are powered by 8VAC, so you'll need to rectify it to run LEDs for those.

Just for your reference, I used these LEDs for the function indicators, in series with 270Ω 1/4W current limiting resistors.

For the speaker LEDs, I went these, as they have integrated diodes, and may be connected directly to AC current. I also used 270Ω resistors in series with these as well. The end result was similar color and brightness to the original incandescents, which was my goal. If you're going blue, you're on your own, but perhaps you can use the above LEDs/resistors as a starting point. Hope this helps! :thmbsp:
 

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skibjr said:
As you probably know, the color is imparted by plastic covers fitted over the light paths, however these covers also serve as light diffusers so you get a nice even illumination with no "hot spots".
Click to expand...
I was thinking about going with diffused lens LEDs. Don't need spotlights in the listening room. I was hoping to not use the colored covers. I just need to experiment a bit to get the right look.

skibjr said:
Be aware that the function indicator bulbs are powered by 12.5VDC while the two speaker system indicators are powered by 8VAC, so you'll need to rectify it to run LEDs for those.
Click to expand...
The Schematic shows 8v 50ma for all my bulbs and I think I read (who knows been looking at a lot of threads) that the sx3900 did have a higher voltage on these. I will check with meter, have been focused on the 2 AC speaker ones lately. They are reading a hair over 6vdc across the leads.
skibjr said:
Hope this helps! :thmbsp:
Click to expand...
It all helps... Either me or another reader. Knowing the mcd value you used to get the appropriate light level is a good start.

Thanks skibjr


My main concern is the AC ones. Don't want to replace them and have them burn out prematurely due to high reverse voltage and the such.
 
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@Kensn... I will be following your thread for sure. Much interest in this. @skibjr. That looks great. Perfect color match to orig. I have a 3900 as well that I have been thinking about LEDing. The AUX lamp is out and I just re-worked the receiver completely a while back (including new bulbs) and it's seen relatively minimal usage. Don't want to hijack Kensn's thread, but it may benefit him too. Can you post some photos of the inside? Specifically the way to placed the resistors and the speaker LEDs. I'd like to see the way you put those in as they don't look to be 5mm as the others. Thanks.
 
AC lights are the main illumination lamps and the speaker lamps. for the speaker lamps, use a 1n4004 diode for reverse voltage protection, then two resistors - one for each led.

I used high intensity leds that I throttled down to 2mA current, and with the narrow angles of the lenses in the pushbuttons, 6 degree leds are fine.IF you THINK they are hot spotting, scuff the case of the led. The red and green of leds work FINE. White may not habe enough of the spectral components you need, without going to high intensity. You may have too much "blue" in your red and green sources for the filters to nicely handle.

I have done a few of these, but my documentation is based on very high mcd lamps and that 2mA of current. Regular leds are usually intended to run at 20mA.
 
Brent.. the more input the better!!

Thanks Mark...

Last night ordered a couple of different LEDS and some diodes (1n4001 figured they were fine, unless I'm missing something). I will post some pictures of them illuminated when I get them. I plan on breadboarding them with a pot to dial in the intensity I desire.

Gonna be a few days til they arrive....

Thanks all,

Ken
 
Lights In

Received parts and installed lights today. I had ordered a couple different LEDs to choose from. I went with the oval blue diffused lens LEDs. They were a perfect press fit. They do not have the ridge at the bottom of the LED so no sanding was required.

144978057_orig2.jpg


These had a softer more dispersed light. (Mouser 941-C5SMFBJFCR0U0351)

I built a full wave bridge rectifier out of 4 1N4001 diodes and used a 1k resistor for each of the AC speaker lights to power the LEDs.
Here is a pic before insulating with electrical tape.

144978057_orig1.jpg


The other LED lights for the DC function indicators I used a 1.8k resistor inline to match the intensity of the speaker lights.

1449780570.jpg


I was really pleased with the results. The pictures are not real true to the color or intensity, the lights are a deeper blue and not as bright as the pictures depict.

1449780574.jpg


1449780573.jpg


All in all very happy with this project. Need to get the case on and hook her up tomorrow.

Thanks All.....

Ken
 
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Thanks for the info Kensn. I am not too sharp when it comes to some electronic terminology or methods. I do like the look of this LED mod though, and want to incorporate it into my 3900. Can you clarify what you mean by this..."I built a full wave bridge rectifier out of 4 1N4001 diodes and used a 1k resistor to power the 2 AC speaker lights."

Can you be more descriptive for my sake? Thank you.
 
SolutionRoom said:
Can you clarify what you mean by this..."I built a full wave bridge rectifier out of 4 1N4001 diodes and used a 1k resistor to power the 2 AC speaker lights."
Click to expand...

My 2 Speaker Selector bulbs had 8vac, without the bulb attached, driving the bulb.
The image below shows how to arrange the diodes to form a bridge turning the ac current into dc current for the LED. The 2 inputs in the image connect to the original bulb wires, the + output goes to the 1k resistor and then to the Anode of the LED and the - output goes to the Cathode of the LED.

diode


Your voltages driving your bulb may vary from mine. I have seen posts on the 3900 and they seemed to be a bit different. I used a 100k pot to find the correct resistance value for the intensity I wanted for the LED.

I connected the center terminal of the pot to the + output of the bridge, and a side terminal of the pot to the Anode of the LED. I checked the resistance on the 2 terminals of the pot and made sure it was turned the direction that showed 100k. Then I powered on the receiver and very slowly turned the pot until the LED came on, and then adjusted the pot until I liked the brightness of the LED. Care must be taken not to lower the resistance too much or the LED will burn out.

With the pot at the position that gave me the light output I wanted, which was less than the max the LED could supply, I turned off the receiver, disconnected the wires from the pot and measured the resistance on the pot where the wires were connected. This is how I determined the resistor value to use.

A higher resistance would lower the light output and lower resistance will make it brighter. There are a number of resistance calculators for LEDs on the web.

Each Speaker Selector LED has it's own full bridge rectifier and resistor circuit.

Hope this helps.

Ken
 
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That indeed helps tremendously. I just did a quick lesson study on YouTube on the various bridge rectifiers. Your explanation then made it crystal clear to me. Thanks again!
 
So you did 2 separate Bridge rectifiers and resistors for each of the speaker selector LEDs? And then what about the function selector LEDs? How were those handled? They are already DC, so only needed a resistor to bring the voltage/current down? And did you only need 1 resistor or one for each LED for the Function Selectors?
 
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That indeed helps tremendously. Your explanation then made it crystal clear to me. Thanks again!
Click to expand...
Glad it helped!!

So you did 2 separate Bridge rectifiers and resistors for each of the speaker selector LEDs
Click to expand...
That is correct.

And did you only need 1 resistor or one for each LED for the Function Selectors?
Click to expand...
One resistor per LED between the + bulb wire and the Anode of the LED. The other bulb wire goes directly to the Cathode of the LED.

Please check your voltages first. Determine if they are AC or DC.

Ken
 
Hey Kensn... One more thing before I place the order and get this project going... Did you leave the standard bulbs in place for the dial lighting? Or replace them with LED too? I'd like to replace all of them while I'm in there, including the dial lights. What would you do with those?
 
Gotta watch this. I have a nice SX-3700 - right now all the lights are working, but it's only a matter of time...

Are your dial lights bright enough that they light the interior of the receiver, very visible through the cooling vents in the dark?
 
SolutionRoom said:
Did you leave the standard bulbs in place for the dial lighting? Or replace them with LED too?
Click to expand...

I did not replace the dial lighting. I may have to someday but they are easy to get to. It might be difficult to get good light dispersion with LEDs for that application. It will take a bit of experimentation to get a good all around glow on the dial I think with LEDs.

Ken
 
MacNoob said:
Are your dial lights bright enough that they light the interior of the receiver, very visible through the cooling vents in the dark?
Click to expand...

I'll let ya know next time I get it powered on... Rearranging the audio tower today to get the SX3800 in place and newly acquired Hitachi HT550 setup.


Yes they are.

Ken
 
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Hey Kensn... Can you post a few photos of the receiver all powered up and done? I'd like to see the final product on an overall scale now that you have the LEDs all in. I did some testing today with the same blue oval LEDs I just got from Mouser. They really are tolerant of low current and go very very dim if passed through higher resistances. Thanks...
 
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