CA-810: Help me with my first bigger project?

[auxym]

Hi

My dad gave me his CA-810 which he is the original owner of. Awesome gift, I have great memories of listening to it as a kid. Good general condition, the usual suspects: burnt lamps and random pops and cracks, I assume from dirty controls.

I plan on doing a full restoration on this one. Cleaning, replacing lamps, replacing all electrolytics, replacing anything damaged. I have general electronics knowledge and experience (including soldering, thru mount and SMD) from a robotics MSc degree, but not a lot of audio stuff past running some DeOxit in my previous amp (80s Sansui) and a small speaker recap and refoam.

So I've been doing a lot of reading in these forums, lots of information for sure. Still, I've got the following questions:

1. Speaker output A has not worked since sometime in the 80s. B works fine. According to my dad's memory, this was caused by a beer spillage incident. Ooops. What am I looking at as a likely issue? Blown output TR? I checked the 3 glass fuses, they tested fine.

2. Full dissassembly looks like it will be more of pain than I thought, lots of desoldering. It looks like there are a lot of wire wrap sorta connections between boards, what's the best way to disconnect those, desolder the pin from the PCB or somehow separate the wrap from the pin? Also, there a bunch of soldered pins connecting the tone board to the main board, covered by grey stuff (epoxy?). Any help with that? General tips for dissassembly and reassembly?

3. On that note, any help on separating the selector shafts to get the tone board out? Service manual says to pull them towards to front of the amp, but they are help on by snap rings which I have yet to be successful in removing.

Many thanks in advance

 

[avionic]

any help on separating the selector shafts to get the tone board out

Should be a plastic coupler sleeve that fastens the extension shaft to the actual switches shaft. These just slide on the extension shaft enough usually to disconnect from the switch shaft. The other end should be the same type plastic coupler.

 

[DRecovery]

Spkr A is nothing serious: the same circuits drive Spkr A and/or Spkr B. Likely the speaker jacks or the switch.

I only have a CA-2010 so I can't help with the other specifics. I will say that the driveshafts I have seen on Yammies were attached by spline alone.

 

[avionic]

peaker output A has not worked since sometime in the 80s. B works fine.

Either a cold solder connection, cracked PCB trace/board or fouled up relay.

 

[avionic]

desolder the pin from the PCB

 

[avionic]

Take a lot of photos and grab a note pad. Knobs have either 1.5mm or 2.0mm set screws. Might have to desolder the meter movements wires to get the front bezel off.

 

[auxym]

Wow, thanks for the quick and great replies. All knobs are off, function board is out. Front panel is almost off, just need to heat up the iron. Next are the main & tone boards I guess.

I'll try and do some probing around the speaker selector switch and outputs. Relay outputs too? Other ideas?

Here's a shot of the grey glue. Apparently the solders for the big power caps are under there. How do I deal with this?

 

[avionic]

I need to see a close up of the topside where that epoxy is. WTF.. Maybe that board was cracked in that area. And this was some kind of repair job.I can't think of any other reason to coat a board with epoxy.

 

[avionic]

Do the large caps look new ? Or OEM ?

 

[auxym]

Not an expert, but the best I can tell is they are OEM. They are marked Nippon Chemi-Con brand. To my knowledge, this amp was service only once, 10-ish years ago, and it was only a controls cleaning job. I'll call up my dad tomorrow and ask him. I understand you wouldn't think this is OEM?

Here's the best shots I could take

 

[avionic]

Well the caps look OEM. I don't see any cracks up there. Its going to make replacing the old caps with new ones a little extra difficult. Chipping the epoxy away from the solder pads.If your so inclined.

 

[avionic]

I'd try a dremel tool* and a steady hand for chipping the epoxy from those cap soldered pads. Don't want to go to heavy handed and damage solder traces. That would be the only area to remove the gray poxy from. I'd leave the rest alone unless theres issues.

*Safety glasses or face shield would probably be a good idea.

 

[auxym]

Thanks avionic, this is super helpful. Sanding away the epoxy sounds like a job for when I'll be waiting for parts.

I had a more detailed look at the schematics, trying to undertstand what is going on with the SPKR A outputs. I have to admit I'm a little dumbfounded:

Probing either (L/R) A+ speaker terminal to chassis GND is 0L when selector is set to B or off, and closed when A is selected. Which makes sense, as when the relay is unpowered, it will go to ground. A- (both L/R) are always closed with GND. All this is what I'd expected as normally functioning, and is the same as the B output. Both A and B are connected to the same LO/RO ouputs from the main board.

Any ideas what to try next? I thought of probing with relay powered, but the doesn't sound like a good idea.

 

[avionic]

. Speaker output A has not worked since sometime in the 80s. B works fine. According to my dad's memory, this was caused by a beer spillage incident. Ooops. What am I looking at as a likely issue? Blown output TR? I checked the 3 glass fuses, they tested fine.

If B works and A doesn't.. Its not a blown output or relay. Wiring or speaker select switch come to mind..stand-by...

 

[avionic]

Yes ..Inspect the wiring around the speaker select switch. Switch might just need a good deoxiting.

 

[avionic]

The spilt beer may have fouled the switch contacts.

 

[Nashou66]

I bet some one put the epoxy there after they got Zapped by the large caps. Has it ever been to a tech?

Nashou

 

[auxym]

Yeah, it's been to a tech once for "cleaning", to the best of my knowledge. Possible he might have put that. Bit obnoxious.

As for the speaker, selector, what's confounding me is that the contacts seem to test good. Anyways, Deoxit is always a good first step. I'll do that and report back.

 

[Karl vd Berg]

I'll post your quote here.

Hey, sorry for reviving an old thread. However, the pictures are dead, and they'd be a great help in disassembly of my newly acquired CA-810. Would anyone still have them by any chance? Or could point me to a similar resource?

Unfortunately the pictures on ImageShack are gone. I have to check if they are buried somewhere in a folder, maybe I still have some of them. I hope you could disassembled your unit.

 

[auxym]

I'll post your quote here.

Unfortunately the pictures on ImageShack are gone. I have to check if they are buried somewhere in a folder, maybe I still have some of them. I hope you could disassembled your unit.

Yeah, I think I've got it figured out. Of course, if you have a .zip you could drop somewhere, I'd still be interested, but no biggie either way. Thanks