Started restoration on my CA-810 !

My 810 has the same transformer hum, especially on startup. Like an overdriven guitar with the whammy pedal all the way down. It's barely noticeable after the first 5-10 seconds after powering on but still worries me a bit.

I'm also inspired here, great job with the IEC mod and speaker terminals. I'd like to do LEDs on my meters someday but that's probably a little above my head at the moment.
 
Excellent work, it was well worth the watch and wait. It must be very satisfying to successfully accomplish a task like that!
 
So then onto the lights : bulbs changed for 5mm "straw hat" (= wider angle) warm white leds. dropping resistors changed to equivalent of 1.8 kOhm.
Since originally there are 2 in series, I put in series a pair of parallel 3.6kOhm 1/2 watt resistors. That gives me 20mA (nominal for my leds) and a heat dissipation of 1.44 watts (IIRC) so I should be fine with four 1/2 watt resistors...
The original sockets were used, if the led's leads are not as flexible as the bulb's, they are flexible enough :)
I took out the blue filter, I like it much more like this.

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The amp has been in use on and off, it has seen maybe 1 month of everyday use.
Lately I noticed the meter lighting has become dull and with a cold light color.
So I opened the light housing and saw that all four of my leds, the warm-white 5mm "straw-hat" were all very dim and blueish :rant: :idea:
I'm not sure what happened here, those leds have a nominal current of 20mA, and that's the number I got with choosing dropping resistors.
At first I thought I had forgotten they are in series and that I had given them 80mA for the 4 of them, but no.
They are in series, so the current in the circuit is the same for all 4, at 20 mA....

So I put in other ones I had, 3mm bright warm-white, with the top sanded off for more diffuseness. And the nice warm even light is back.
I hope those will last longer...or maybe I should hope I did something wrong, since I used the same ones for a Marantz 2325 (function lights) I did for somebody :confused:

Does anybody see if I did something wrong here that would explain the leds going bad ? Maybe it's getting too hot in there ? Most likely not.
 
The amp has been in use on and off, it has seen maybe 1 month of everyday use.
Lately I noticed the meter lighting has become dull and with a cold light color.
So I opened the light housing and saw that all four of my leds, the warm-white 5mm "straw-hat" were all very dim and blueish :rant: :idea:
I'm not sure what happened here, those leds have a nominal current of 20mA, and that's the number I got with choosing dropping resistors.
At first I thought I had forgotten they are in series and that I had given them 80mA for the 4 of them, but no.
They are in series, so the current in the circuit is the same for all 4, at 20 mA....

So I put in other ones I had, 3mm bright warm-white, with the top sanded off for more diffuseness. And the nice warm even light is back.
I hope those will last longer...or maybe I should hope I did something wrong, since I used the same ones for a Marantz 2325 (function lights) I did for somebody :confused:

Does anybody see if I did something wrong here that would explain the leds going bad ? Maybe it's getting too hot in there ? Most likely not.

Did you increase the large 5 Watt resistors to limit the current to the correct value? I believe there's 75 or 80 Volts on it, so the current needs to be dropped with increasing those large resistors. I replaced those in mine and the LED's are fine for almost 2 years.
 
Did you increase the large 5 Watt resistors to limit the current to the correct value
Yes, the resistors were changed (there are two of them for the 4 display lights, unlike the schematic which shows one).
When I do the swap to leds, I start with a high value resistor and monitor the current, changing the resistor to get the proper current.
Here I now have a total of 3.6 kOhm resistance, gives me 20.5 mA cuurent, the leds are rated nominal 20mA, max 30mA.

At first I thought I did something wrong, what else could cause all 4 leds to go bad ? But now I've realised maybe there was just one bad led in the lot that caused the current to drop to the other 3, since they are all in series...
I did not dispose of the "bad" ones yet, maybe I can check if it is just one that has gone bad.
 
Hi Bert, I did the same transformation on my CA-810 several months ago with warm white straw hat LEDs and the lighting has also become very weak.
Hmmmm ça c'est intéressant...
I'll leave the amp in use and report back if there are problems with the new leds. I wonder what is happening here.
What was your source for the straw-hat leds ? Mine were from bright-components.co.uk
 
I got mine from chinese seller on eBay. Probably you got the same make.

I did the LED conversion in order to avoir changing bulbs every 1-2 years… it missed.
 
Got quite a bit more done this weekend :
recap is 100% done, also did the secondary P.S. diodes.
All the transistors with heatsinks got taken off the board, fresh thermal paste and cleanup of the glue.

There was a little surprise in the tone board : C330 (10uf 25V) was factory soldered in with the polarity wrong !7This is a signal coupling cap, I'm not sure what the effect on the sound was........anybody knows ?
And yes I'm quite sure, the schematic and board drawing and silkscreen all show the same proper way, and this circuit is nice and symmetrical for both channels...

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I cut out some of the bottom of the hot regulators heatsinks, this should give some more airflow and keep them a bit cooler.

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more pics....

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After having given the output transistors fresh thermal paste, the heatsinks are coming back together

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Did some cleaning as well, and could not resist shining up the top cover of the function board and the selector shafts.
Useless but I like things looking good inside as well :D

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I will soon put the transformer back in....I'm a bit nervous here because normally I would do one board at a time, and test in between......
What did you use in place of those 2.2uf 25v bp caps on the protection circuit?
 
What did you use in place of those 2.2uf 25v bp caps on the protection circuit?
As Willy mentions, these are BiPolar, the KL or PW are not bipolar.
I think I used Wima MKS2 film caps (the red square ones)
Panasonic ECW or ECQ will also be fine but they are bigger.

There is a 10uf 50V bipolar somewhere there also, I used a Nichicon Muse ES (the green one you can see)
 
As Willy mentions, these are BiPolar, the KL or PW are not bipolar.
I think I used Wima MKS2 film caps (the red square ones)
Panasonic ECW or ECQ will also be fine but they are bigger.

There is a 10uf 50V bipolar somewhere there also, I used a Nichicon Muse ES (the green one you can see)
Ya I saw the green nichicon muse ES in your pics but I wasnt sure what the red square ones were.Did you use the Wima MKS2 anywhere else in this amp?
 
Ya I saw the green nichicon muse ES in your pics but I wasnt sure what the red square ones were.Did you use the Wima MKS2 anywhere else in this amp
Yes I did, any electrolytic of 2.2 uF and below was replaced with these film caps. All in all nine 1uf and four 2.2uf if my list was correct :D
 
Yes I did, any electrolytic of 2.2 uF and below was replaced with these film caps. All in all nine 1uf and four 2.2uf if my list was correct :D
Was that only the bipolar ones or can I use them in place of the polarized variety?
 
Yes, here all small electrolytics can be replaced by a film cap.
But of course size and price goes up very quickly once you go above a few uF...
 
I'll leave the amp in use and report back if there are problems with the new leds.
So, reporting back as promised :)
The second set of leds I installed also started fading out with a greenish tint within a dozen hours of use.
I'm not sure what's going on, since the current going through was measured at 20mA, nominal for these leds...

So what I did is this : I added a THIRD led for each meter, by inserting the legs in the existing rubber grommets, and cutting the trace at the back. seee photos.
I then cut down the current to 9mA, with two 3.6kOhm resistors (in series here)
It looks just as good and as bright, I hope it will last longer like that.....

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Another thing that annoyed me from the start with this amp was the (mechanical) buzzing from the transformer. The whole amp was vibrating slightly and the hum could be heard easily from my listening position.
So I thought, what the hell, what does one do to get rid of vibration ?
Here is my solution, and it works wonderfully well, a tiny buzz only is heard when you put your ear right on top of the cover, within a few centimeters of the transformer.

I would NOT recommend this if you plan to ship the amp at any time, since the transformer can move around slightly, and a hit could send the heavy thing to damage something within it's range of movement...

4 silent-blocs, diameter 8mm, length 15mm. The secondary metal plate beneath the transformer was taken out. Like this there are still a few mm clearance to the top cover.

Not being sure of the consequences of the transformer case not being grounded anymore, I ran a wire to keep the ground.

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Another thing that annoyed me from the start with this amp was the (mechanical) buzzing from the transformer. The whole amp was vibrating slightly and the hum could be heard easily from my listening position.
So I thought, what the hell, what does one do to get rid of vibration ?
Here is my solution, and it works wonderfully well, a tiny buzz only is heard when you put your ear right on top of the cover, within a few centimeters of the transformer.

I would NOT recommend this if you plan to ship the amp at any time, since the transformer can move around slightly, and a hit could send the heavy thing to damage something within it's range of movement...

4 silent-blocs, diameter 8mm, length 15mm. The secondary metal plate beneath the transformer was taken out. Like this there are still a few mm clearance to the top cover.

Not being sure of the consequences of the transformer case not being grounded anymore, I ran a wire to keep the ground.

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Great, thanks! The transformer of my CA-810 is also humming loudly. I will try this!

About the LED's: I have exact the same problems with diffuse LED's in my B-2 and CA-810. Running respectively on 15 mA and 20 mA. They start to fade slowly and are completely dull after a month's use. I went back to the seller and he said that while you limit the nominal current, the peak currents in 'vintage audio gear' can be much higher. These peak currents would only be visual with a scope. So he said. Apparently these LED's can't handle those peak currents and will die. I'm not sure about his story.

I use LED's from led1.de for years in my gear (sometimes even at 25 mA) and they never fade, even after years of use.

So I think there might be differences in quality ;)
 
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