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CA-3000 Scary Picture!

dr*audio

dr*audio

Fish fingers and custard!
The CA-3000 is a wonderful sounding preamp. Unfortunately it was made when double sided pc boards were primative technology, and the feedthrus (holes that connect the circuit on one side of the board to the other) go open after awhile, causing intermittant sound. There are 2 boards in the CA-3000 that have feedthrus and the main one has the most of them. To properly restore a CA-3000 you have to remove the mother board and insert a wire through each feedthru and solder it on both sides of the board to make the connection. The other board has only a few feedthrus and is easier to remove to do the soldering. Here's a picture of a CA-3000 with the mother board removed.
 

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feedthru

Yeah, I know, same design flaw that the big Quads have, advantage is the pre-amp does not generate the heat the receiver does, therefore the problem is not so severe....
I may just do a touchup this time, I am in process of restoring the power supply board, finally have all the parts.
Dr Audio, any chance of a before and after picture of these joints?
Casey :scratch2:
 
The Dolby board in the 9090DB and 8080DB has over 60 of those damn feedthroughs. The audio signal goes through that board regardess of switch postion. It causes all kinds of intermittant problems.

- Pete
 
dr*audio said:
The CA-3000 is a wonderful sounding preamp. Unfortunately it was made when double sided pc boards were primative technology, and the feedthrus (holes that connect the circuit on one side of the board to the other) go open after awhile, causing intermittant sound. There are 2 boards in the CA-3000 that have feedthrus and the main one has the most of them. To properly restore a CA-3000 you have to remove the mother board and insert a wire through each feedthru and solder it on both sides of the board to make the connection. The other board has only a few feedthrus and is easier to remove to do the soldering. Here's a picture of a CA-3000 with the mother board removed.
Click to expand...

Great info, Warren. However, I have a question: what gauge is that speaker wire in the picture? That big silver one? :lmao:

Paul
 
nosirrah said:
Yeah, I know, same design flaw that the big Quads have, advantage is the pre-amp does not generate the heat the receiver does, therefore the problem is not so severe....
I may just do a touchup this time, I am in process of restoring the power supply board, finally have all the parts.
Dr Audio, any chance of a before and after picture of these joints?
Casey :scratch2:
Click to expand...

I'll use the macro on my camera tonight and try to take a picture. If that doesn't work I'll take a picture through my microscope. The problem with the feedthrus Sansui used is not the feedthru itself; what they did is they had a hole going through the board in the middle of a pad, and they inserted a ferrule into the hole to make the connection, and soldered it in. A void in the shape of a ring developes around the ferrule over time and the contact with the pad is broken. You can fix it by soldering it, but it could form a gap again with time, so I scrape a bit of solder mask from the traces connected to the pad, run a wire through the hole and solder it to the pad and trace. If the trace runs under the switch and I can't solder to it, I solder the wire to the pad. That is actually good enough, as long as you bridge the gap between the hole and the pad with the wire, and solder it, you permanently fix the problem.
 
Morden2004 said:
Great info, Warren. However, I have a question: what gauge is that speaker wire in the picture? That big silver one? :lmao:

Paul
Click to expand...

I noticed that too. I think it's an oxygen tube to keep it going while under surgery.
 
It's a solder fume filter I made up. Eventually I will rig something up to exhaust out the old dryer vent. (The laundry is now upstairs).
 
Here are before and after pictures. This is actually a good feedthru. If it were bad, it would have an obvious gap where the arrow points.
 

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how scrary is it?

dr*audio said:
Here are before and after pictures. This is actually a good feedthru. If it were bad, it would have an obvious gap where the arrow points.
Click to expand...

looks like ive seen that 1 before.... hope its not a horror story..... :sigh:
 
Its All Good Bro

dr*audio said:
Yep, it's yours. Don't worry, strictly routine work here. :thmbsp:
Click to expand...
I have so much faith in you , if you say its cool, I KNOW its cool.... CANT wait to play the beast...... GONNA rock thru the AR9s..... :banana:
 
Working on a CA-3000 with an intermittent channel. The manual blows to try and follow a signal, and is probably one of Sansui's worst (I'm not terribly familiar with the 3000, which doesn't help).

I'm hoping it's simply dirty switches, but you seem to think this work with the feedthroughs ought to be done anyway. 'Zat right? :scratch2:
 
EchoWars said:
Working on a CA-3000 with an intermittent channel. The manual blows to try and follow a signal, and is probably one of Sansui's worst (I'm not terribly familiar with the 3000, which doesn't help).

I'm hoping it's simply dirty switches, but you seem to think this work with the feedthroughs ought to be done anyway. 'Zat right? :scratch2:
Click to expand...

Intermittant channels on this unit are mainly caused by the feedthrus and possibly the relays (3 of 'em!). The main board and the filter board are the ones with the feedthrus. Just solder them all up and the problem will be gone. Some of the feethrus on the main board are hidden under the tape beneath the Molex sockets. There is also one feedthru that is just under one of the switches, but you can get to it without removing the switch. I start on the top to locate them, the silkscreen shows the traces on the bottom of the board, so you can locate where the feedthrus connect the top and the bottom. After fixing the feedthrus, run a signal into all the inputs, and check all the record outputs. Then run a signal into all each play input and make sure it comes out each record output as you switch the copy switch. Otherwise, if you miss one, you're gonna put it all back together and go, "Doh!" Then when you do the filter board, check the output as you flip the filter switches.
 
Well, I have traced the dropped channel to a bad feedthrough on the filter board. Reflowed the solder, and all seems well.

The feedthroughs on the main board all have wires through the center...they look a lot like your 'after' picture a few posts ago. The ones on the filter board do not look like this...
 
EchoWars said:
Well, I have traced the dropped channel to a bad feedthrough on the filter board. Reflowed the solder, and all seems well.

The feedthroughs on the main board all have wires through the center...they look a lot like your 'after' picture a few posts ago. The ones on the filter board do not look like this...
Click to expand...

I have worked on 2 units that had the wires and still had intermittants through the feedthrus. If they just shoved a wire through and soldered it, it isn't enough. The ferrule that goes through the board is fine, no intermittant there. That's all a straight wire would fix. The intermittant connections are where the ferrule is mashed down on the pads, or on the bottom side where I don't think it's mashed down at all. A break developes between the ferrule and the pad. Look carefully at the motherboard and you will see rings around the ferrules, especially on the bottom. It is best to run a wire through the feedthru and bend it over on both sides so it touches the pads, then solder. Where I have room I scrape the solder mask off the trace and solder the wire to the trace.
 
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