Yamaha CA-1000 III distortion in left channel and blown fuses

Keep the amplifier separated from the pre-amp ,with the coupler switch, for now. Need to check the voltage on the pre-out center pin.

Ok. I am piecing back the amplifier now since I took it apart to see all the capacitors. I have switched the coupler switch to off. Once I get the new Output transistors I can put the mains back in so I can fully troubleshoot. First, I am going to replace the two capacitors on the function board that are leaking.
 
Ok. the only reason I wanted to get the caps order now is to get them mailed together with the new output transistors to save on shipping.

I did notice the two 100uf/6.3v capacitors on the preamp board are leaking. These could be out of spec.

Right , thats fine just save them for when the amp is totally fixed.

Nashou
 
Here are the two caps in the function board.

I don't think they are leaking. Yamaha used a glue around caps to hold them in place. However that glue is corrosive and eats at
other parts leads that it covers. So removing the caps and cleaning off that glue is highly recommended for the entire unit.
Then if you notice any corrosion on the nearby parts replace them.

While you have the unit open, look at all the white fuse resistors ,like in your pic, and measure them to be sure they are to spec.
Those I have found usually can be open or drift higher than noted.

Athanasios
 
Perfect. Yea, I am used to seeing the glue, but definitely looks like some corrosion. I wont know until I remove them. Is there an easy way to test these white fuse resistors without removing them from the board? Just curious as it does get time consuming.

Thanks.
 
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Those two caps have definitely seen better days. Notice how the plastic sleeving has shrunken down on them.
 
Yea, there are multiple caps that look just like this. Besides it needing some work under the hood, the outside is flawless... the power switch is missing its tab/cover, but I am sure I can find one online.
 
Yep the I missed the plastic covers on the caps shrinking, and man did they shrink!!!

Most of the time you can measure them right on the board . Only if they have a way whacked out reading compared to their markings or the schematics value then lift one leg and measure again to verify.

Nashou
 
I am almost done with the parts list of capacitors and output transistors. For the capacitors lower than 3 uf, can I use Wima MKS2's? I have 4 1/80 on the power amp board and some 1/50 & 2.2/25 on the power amp board.

Also, in regards to the Bi-polar capacitors; the only ones I could find from Nichicon are the "ES" series. Is this correct? I find the data sheets on them, but mouser doesn't carry them.
 
Yep the I missed the plastic covers on the caps shrinking, and man did they shrink!!!

Most of the time you can measure them right on the board . Only if they have a way whacked out reading compared to their markings or the schematics value then lift one leg and measure again to verify.

Nashou

I just checked all 6 of them. The 33ohm resistors were reading right at 33-33.5. The other two that are 390 ohm, however, were measuring around .400k ohms.
 

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I just checked all 6 of them. The 33ohm resistors were reading right at 33-33.5. The other two that are 390 ohm, however, were measuring around .400k ohms.


They all are ok, the .4k is the same as 400 ohm so not too far off.
 
I am almost done with the parts list of capacitors and output transistors. For the capacitors lower than 3 uf, can I use Wima MKS2's? I have 4 1/80 on the power amp board and some 1/50 & 2.2/25 on the power amp board.
The question of MKS suitability could trigger a huge debate, so I will get it first, it's generally frowned upon for signal path situations.
The 1/80 caps look like for noise suppression (please correct me) so anything can be used. I will probably use whatever is handy
like Silmic II, Nichi KW, FG,,,, MKS should be OK

The 1/50, 2.2/25 on the big power supply board? The 2.2/25 (C409,10) is bipolar so UEP or ES
For 1/50 the UPW is fine.

Also, in regards to the Bi-polar capacitors; the only ones I could find from Nichicon are the "ES" series. Is this correct? I find the data sheets on them, but mouser doesn't carry them.
Nichicon ES is their 85C bipolar
Nichicon UEP is their 105C bipolar

Both would be OK, both stocked by Mouser, most people would suggest the UEP
 
I use "EP"'s in the power supply /protect areas. Especially if they are in close proximity to pass transistors.
 
Perfect. Thanks. I just placed my order.

While thinking about the preamp issue I was having, I realized when I tested the preamp out into another stereo, I didn't switch the coupler switch off. Would this affect the amplifier still shutting off as it would still be feeding to the amplifier stage? Which is what we know has issues being the output transistors.

Thanks.
 
While waiting on my output transistors to come in, I was hoping to track down 2 switch caps/covers for two of my front switches. Any idea where I can easily find some or do you know someone I can buy two from?

Also need to replace the meter lamps with some blue or green leds. Who is the best to ask about these?
Thanks.
 
Quick update:

New lamps and all mouser parts came in today. I first focused on the main power amp side that was giving me issues. After changing the output transistors (old ones were definitely bad) and recapping it, I soldered it back in and powered it up. I listened on headphones again using the preamp and power amp couple switch turned on. No blown fuses, no distortion on that channel, and the amplifier did not go into protection mode. Headphones sounded great, but I could tell one channel (the recapped one) was cleaner. I'm going to recap the opposite main power amp tonight and test the receiver with speakers to see how it sounds. I believe the main issue WAS the output transistors causing the distortion and amp to shut off. The full recap will be completed this weekend.

Is it crucial that I change the output transistors on the power amp that wasn't giving me issues? Or is it ok to just replace the ones on the channel with bad parts.
 
Can someone recommend me replacement filter capacitors for this amplifier that will easily fit? I think I am going to go ahead and put some more money into this amplifier.
 
Wanted to update everyone on the amplifier. The whole amplifier was recapped (with the exception of some of the bipolars on the meter boards which were covered by a soldered on metal cover). The amp seemed to perform well after just testing it for 10 minutes but it was getting very hot. I attempted to set the bias today and followed the service manual. The only issue is that the trim pots were replaced with pots that were facing down! So getting these things set has been a pain in the a$$. I noticed the previous bad channel was reading high at 112mv (supposed to be 25mv). I set both last night, but am attempting it again to see how much the bias changed. It was only about 4-5 mv off, so I am going to attempt to reset them now and check it again tonight. Can you recommend some better trim pots I can buy to solder on later to avoid issues in the future? I have noticed the values will dance around for a few seconds before finally settling.

Here are the pics of the upside down trim pots and the finished project as well as a pic of the upside down trimmers:
 

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