New to me 610II - Distortion

Kapco

Active Member
Preamble- I am somewhat newbie to electronics repairs. I know the basics and have fixed a few things in the past. I have limited experience fixing audio equipment.

I picked up a non working CA-610II and decided I would give it a go on repairing it.
When I got it I was told the output transistors were shot.
I opened it up and sure enough a pair of transistors on one side was missing along with a blown 5A main fuse.
I managed to find a set of factory ones and put them in.
I gave it a visual once over, put in a 5a fast blow and switched it on. About 1 second delay and pop goes the fuse. Back to the work bench. I tested a few things (PS caps mostly) but found the rectifier was toast. I replaced the rectifier and figured I was popping the fuse from that.
Put in another fuse and round 2....about 2 seconds after on I heard a small pop near transformer. But fuse didn't blow and everything seemed to be OK.
Checked voltage at output of transformer and seems good.
Music now plays, both channels are very distorted and doesn't seem to have much volume. Deoxit'ed all switches and pots. Distortion no matter which input, regardless of volume, speakers a or b both channels.
I started searching the forums thinking maybe it was biased wrong (understand the principle but not dure how to check it) and came across something someone mentioned in a post...and I think I may know what I did wrong and feeling a bit like an moron.....what does a mica insulator look like for the output transistors ....because I dont recall that. :(
 
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If adjusting the idle current doesn't solve your issue. Start cleaning all of the switches and controls . Need to get the cleaning fluid ( Deox-it ) on the actual switch contacts to do any good.
 
http://sportsbil.com/yamaha/ca-610ii-sm.pdf

Page 8 for the " idle current" bias adjustment procedure.
Be careful when probing test points with power applied. One slip can and will burn up output transistors and/or damage other components. I highly recommend a set of mini grabber test leads. Similar to these.These will " save your bacon".
1RK16_AS01
 
Appreciate all the support.
No...definitely transformer.....in fact I swear I saw a bit of smoke....but transformer seems to test fine.
I guess I'll be ordering up some mica insulators.....and new transistors. I'm assuming they are now shot. Probably can be tested with a dmm?
I'll be getting some of those test leads. I can't count how many times I needed them.
Do you happen to know where I can look up replacement part numbers for these output transistors?
If I recall they are a 2SA745 and 2SC1403 if memory serves correct.
 
Mouser or digikey...
MJ21193G ------- (PNP) -- 2SA745
MJ21194G ------- (NPN) -- 2SC1403
 
I just noticed digikey is out of stock of the MJ21194G
I noticed the MJ21195/6 set has the same specs. Can I use those? Why 2 part numbers for the same thing? Looks like very slight characteristic differences. Sorry...im sure I missed some key data in the spec somewhere...
 
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Well....put new output transistors in with the mica insulators. No difference. Its very quiet and distorted. I cleaned all the switches and pots good so I don't think that's it. I got proper output voltage from the transformer....I guess I'll check the bias and see where that's at.
 
OK...totally confused. I must be doing this wrong.
DMM positive lead on TP1, Neg on TP2 I get -4.3mV
DMM Positive lead on TP3, Neg on TP4 I get -4.6mV
E to TP2 or TP4 is 13.2mV

From what I gather from the manual should be positive values and adjusted to around 10mV. And from E to TP2 or TP4 shoukdvbe zero?
 
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OK...totally confused. I must be doing this wrong.
DMM positive lead on TP1, Neg on TP2 I get -4.3mV
DMM Positive lead on TP3, Neg on TP4 I get -4.6mV
E to TP2 or TP4 is 13.2mV

From what I gather from the manual should be positive values and adjusted to around 10mV. And from E to TP2 or TP4 shoukdvbe zero?
Just adjust to the absolute value. Pay no attention to polarity indication. Adjust your 4.3mv and 4,6 mv up to 10 mv. The SM procedure was written for and analog meter where polarity was important to get the proper voltmeter needle swing.
 
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Adjusting doesn't to anything...the voltage doesn't stay static...constantly bouncing around between 3.7and up to 5.2....doesn't matter ehrte is set trim pots...just keeps moving values with no change
 
Adjusting doesn't to anything...the voltage doesn't stay static...constantly bouncing around between 3.7and up to 5.2....doesn't matter ehrte is set trim pots...just keeps moving values with no change
Both channels ?
 
Yes...both channels do the same...just keep bopping around between 4and 6 roughly.....never steady
 
Preamble- I am somewhat newbie to electronics repairs. I know the basics and have fixed a few things in the past. I have limited experience fixing audio equipment.

I picked up a non working CA-610II and decided I would give it a go on repairing it.
When I got it I was told the output transistors were shot.
I opened it up and sure enough a pair of transistors on one side was missing along with a blown 5A main fuse.
I managed to find a set of factory ones and put them in.
I gave it a visual once over, put in a 5a fast blow and switched it on. About 1 second delay and pop goes the fuse. Back to the work bench. I tested a few things (PS caps mostly) but found the rectifier was toast. I replaced the rectifier and figured I was popping the fuse from that.
Put in another fuse and round 2....about 2 seconds after on I heard a small pop near transformer. But fuse didn't blow and everything seemed to be OK.
Checked voltage at output of transformer and seems good.
Music now plays, both channels are very distorted and doesn't seem to have much volume. Deoxit'ed all switches and pots. Distortion no matter which input, regardless of volume, speakers a or b both channels.
I started searching the forums thinking maybe it was biased wrong (understand the principle but not dure how to check it) and came across something someone mentioned in a post...and I think I may know what I did wrong and feeling a bit like an moron.....what does a mica insulator look like for the output transistors ....because I dont recall that. :(
When replacing the output transistors. Did you check the emitter resistors R521- 524 ---- .47 Ω 5 watt wirewound -- Especially the two connected to the original shorted outputs.

BTW Did you put new thin coat of thermal compound on both sides of the mica insulators ?
 
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Hold the fort !!!! It looks like the alignment procedure test points and/or the silkscreen on the circuit board may be incorrectly marked.
 
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