[How to] LED conversion Yamaha CT-600, CT-810 and CA-810 (AC to DC conversion)

Mr. Yamaha

Not so much Yamaha lately...
I had some spare time and recently acquired these units for setting up an office system.

The CA-810 is pretty straight forward and I used the guide as found here: http://www.stereo.net.au/forums/topic/37009-led-replacements-for-incandescent-lamps-in-vintage-gear/

The difference is I used warm white (2700k) LED's with a wide angle of 140 degrees. Also I used two 5 Watt 1.8 K Ohm resistors to replace the original resistors in order to feed the LEDs 25 mA.

The LEDs I use for all my conversion projects do nearly produce the same light warmth and color of the original bulbs. And while in the picture it seems very green and bright, in real life it's that very light green / yellow it should be. Not sure why it always looks so different in the pics.

The CT-600 and the CT-810 were a different story. I know some guys are using the AC voltage to power the LEDs, but I wanted to do it 'right'. So no flickering LEDs and a longer lifespan for the LEDs.

I used a small bridge rectifier and a 100 uF / 50V to smoothen the rectified +. I used this bridge rectifier, but most will do the job: http://uk.rs-online.com/web/p/bridge-rectifiers/2965353/ The Nichicon Muse cap was just laying around.

I tried to make it as good looking as possible with nice shrink sleeves (is that even a word?) and some good soldering. Both the CT-600 and the CT-810 had nice pins to solder the rectifiers on. Pretty solid. Those are the pins where originally the wire leads of the bulbs are soldered on.

First I removed all bulb leads. I cut the 2 AC input legs of the rectifier to the right height (same as the pins they were soldered on). I bent the DC output legs forward in order to solder the cap leads on them. I tied the cap to the rectifier with tie wrap and bent the leads of the cap in line with the leads of the rectifier. NOTE: watch + and - ! Covered the legs with sleeves and soldered the the leads to to each other (cap and rectifier) Some pics:

IMG_0034.JPG IMG_0036.JPG

After that I soldered the AC input leads on the AC leads of the CT's. The CT-600 had 12V AC and the CT-810 had 14V AC. When installed I measured the DC voltages the rectifiers put out. It was 21V for the CT-810 and around 18V for the CT-600. You can calculate the needed resistors here: http://led.linear1.org/1led.wiz. I chose again 25 mA to meet the CA-810 and my LEDs had a forward voltage of 3.2V.

After that I soldered the needed resistor in every + lead. At the CT-600 I chose to solder the resistor just before the LED and in the 810 at the start of the + lead, just after the cap. Why? I was trying which was best, but both has pros and cons.

I used the original rubber meter bulb holders (cut in half) just behind the LED in order to fix the LED properly in the original socket without light bleeding. The soldered the leads on them and some sleeves.

Some pics:

72D9BBDB-0348-497A-B1A4-8B6B80D0C705.JPG D36AC94D-1EBE-4B2F-9F43-61429AE5034A.JPG IMG_0041.JPG A9DD830E-3E75-446A-A684-9E9D2B5FD361.JPG

And the results:
 
Much more elegant than the one I did recently for a friend's Sansui.

I put 4 diodes, a cap, and resistor onto a small piece of breadboard and screwed it to the chassis. Besides ordering the super bright blue LED's, I used what I had on hand.
 
They look fantastic, and in my opinion, better than original. I don't know diddly about electronics, but that looks like some skillful work...well done!
 
Third time in three years that the lights went out, I decides to replace the original incandescent bulbs with LEDs. Even if I normally tend to keep the gear in its original state. Following your guide, Mr. Yamaha, and the original Australian one, the procedure was quite easy in fact.

I chose warm white (2700K) and wide angle (140°) LEDs. I didn’t sand the LEDs and used the original diffusor with the original blue tinted piece in place. I replaced the two resistors with a 2,7kΩ and 1,5 kΩ.

A quick shot made with my phone, you can see that the light is even and significantly brighter than the original, which is welcome. The tint of the light is very close to the original tint. I am very happy about the result.

img_20170109_2358521ds80.jpg
 
Third time in three years that the lights went out, I decides to replace the original incandescent bulbs with LEDs. Even if I normally tend to keep the gear in its original state. Following your guide, Mr. Yamaha, and the original Australian one, the procedure was quite easy in fact.

I chose warm white (2700K) and wide angle (140°) LEDs. I didn’t sand the LEDs and used the original diffusor with the original blue tinted piece in place. I replaced the two resistors with a 2,7kΩ and 1,5 kΩ.

A quick shot made with my phone, you can see that the light is even and significantly brighter than the original, which is welcome. The tint of the light is very close to the original tint. I am very happy about the result.

img_20170109_2358521ds80.jpg
Nice work dksp!
 
I have a CT-810 that has one bulb burned out. Is there a drop in replacement or do I have to switch to LED and do the bridge rectifier and cap mod that you did? Nice work by the way.
 
Old thread but I thought I'd share some info since I just finished working on a CT-810/CA-810 set. As mentioned above, the CA-810 is easy to convert to LED. For the CT-810, I discovered that one reason the 12V / 60mA lamps look so dim is that they are running off 5.9 VDC/7.5VAC in the stock circuit. Yamaha, in it's infinite wisdom, added D604 as a half wave recifier in the lamp circuit which effectively cuts the 14 VAC from the transformer into a hybrid AC/DC voltage. As measured on a DMM I get 5.9 VDC / 7.5 VAC on mine. No wonder the 12V lamps look anemic.

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Adding LEDs is a good idea, but I thought I'd start by making a simple modification to the existing circuit to see what the 12V lamps were supposed to look like with proper voltage, so I added a 220uF / 50V smoothing capacitor to the half wave rectifier circuit (note polarity of the cap. 25V cap would be fine here). This boosted the DC component of the output to 11 VDC with 3 VAC of ripple. Doing this makes the stock, 12V lamps look much better and would provide a better power source for an LED conversion if you head down that path. The 3VAC of ripple would probably be much less noticable on the LEDs than the 7.5VAC from the stock power supply . . .

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Stock 12V/60mA lamps with capacitor added:
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