CR-410II is dying

invalidbuffa

Super Member
CA-410II is dying

My CA-410II seems to be giving up on me. I turned it on with no signal present and the speaker relay clicked on as it should, but immediately after there was low static noise (not hum) coming through the speakers and I could see the cones move slowly in and out, then the relay clicked off. Since then when I power on the amp the speaker relay clicks on then immediately off.

Any ideas? I'm going to crack it open this afternoon.
 
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OK now this is weird... I went back and tried it again...it fired right up and has been playing music for the past half hour.
 
Whoops, the model is actually a CA-410ii.

I had an opportunity to open it up today on my bench. It hasn't been recapped but I checked it out with my ESR meter and the power supply caps were fine.

However it was acting strange again... On powering it up, the left VU meter slowly went from zero to max and held until the unit was turned off. Also when I went to check and adjust the left channel idle current the corresponding pot VR407 had no effect on the voltage at TP 1 and 3, (right channel adjustment worked fine).

Any suggestions?
 
What does the DC offset look like? Are the rail voltages balanced?
 
DC offset is about -4mV on the left and -30mV on the right. Rail voltages are within a half volt of +/-40. The idle current adjustment works on the left side now...I just forgot to move my dummy load.

I think I found the source of the intermittent problem... I was pushing down on the PCBs with a dowel and discovered that applying force around the input selector switch on the input/function board reproduced the low static and woofer movement. I bathed the switch in deoxit and reflowed the solder joints on the board but the problem still persists. I suspect the input switch might need to be deep cleaned or replaced.

That still doesn't explain the pegged VU meter... The channel still plays fine.
 
On a whim I swapped the left and right meter driver transistors (2SA844)... Bingo! The problem moves to the right-channel meter.

Can I use an NTE234 in its place?
 
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Thanks- ksa1013y it shall be.

While I'm at it, would it be worth the effort to just recap the whole amp? I've heard of people using Elna SILMIC or nichicon FG in the signal path. Would I also want to replace the mylar film caps (esp. in the phono section)?
 
I just finished one. I used Panasonic FM or Nichicon PW types for power, Nichicon FG for signal/phono etc. Bumped values up where appropriate... also Replaced a couple relay drive transistors and it sounds great. It's the bottom CA series amp, I wouldn't spend the extra for Elna stuff.

you've sorted the static issue? I highly doubt the switch will need replacement.... they're quite robust.
 
you've sorted the static issue? I highly doubt the switch will need replacement.... they're quite robust.

I'm not sure what else it could be, unless there's a hairline split in the trace that I'm not seeing. Manipulating the switch body definitely produces the issue. I'll do some more investigating regardless...

When you recapped yours, did you also replace the mylar film caps?
 
I'm not sure what else it could be, unless there's a hairline split in the trace that I'm not seeing. Manipulating the switch body definitely produces the issue. I'll do some more investigating regardless...

When you recapped yours, did you also replace the mylar film caps?

You might have a bad ground near that switch or jack. Look at the solder joints in that area. Look for a dark ring in the solder around the component lead. Resolder any you see like that.
Note that when the unit is in protect mode, you can't measure the offset at the speaker jacks because the relay is open. You have to measure it at the output stage. The air wound coils are a good place. It is important to know if only one channel has a high offset when it's in protect mode or if it's both channels, or no offset, meaning the fault is in the protection circuit.
 
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Sorry, I forgot to mention the relay has been clicking on normally since moving it into my shop. Maybe I'll just reflow all of the solder joints on the input board...
 
I went back and retouched all the solder joints on the input board, but the problem remained... Decided to use more deoxit in the selector switches, and then blow compressed air into the holes in the switch body. After that the problem went away, but I noticed some new fuzziness in one channel that sounded more like a bad connection than a bad cap. I poked around some more and discovered that tapping the relay would cause the fuzziness to go in and out. Aha!

I desoldered the relay and took the cover off, rubbed fine grit sandpaper in between the N.O. contacts, and sprayed in a couple shots of deoxit for good measure. The relay was reinstalled and I haven't had the issue again since. :yes:
 
I went back and retouched all the solder joints on the input board, but the problem remained... Decided to use more deoxit in the selector switches, and then blow compressed air into the holes in the switch body. After that the problem went away, but I noticed some new fuzziness in one channel that sounded more like a bad connection than a bad cap. I poked around some more and discovered that tapping the relay would cause the fuzziness to go in and out. Aha!

I desoldered the relay and took the cover off, rubbed fine grit sandpaper in between the N.O. contacts, and sprayed in a couple shots of deoxit for good measure. The relay was reinstalled and I haven't had the issue again since. :yes:

You need to replace that relay. There is plating on the contacts to prevent oxidation. Over time the plating wears off and the contacts oxidize. Cleaning only helps for about a month, then the contacts oxidize again.
 
Is this a good replacement?

Omron LY2-0-DC12

I would need to know what the original is. It should have a MFR and part number on it. Failing that you have to measure the voltage on the coil and make a drawing of the pins underneath, showing center - center dimensions on the pins. Then match it up with the data sheet for the relay you are considering.
 
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