Another Akai MG1212.......

Are the record amps on individual cards, one per track?

When you did your swap what cards did you swap?

Some of what you describe sounds like relay issues to me.

And on your power supply board repairs, based on what I saw of the battery leakage damage, I'd strongly consider bypassing the effected solder traces and adding jumper wires instead. Battery acid will eat foil.


Okay...scrap my last post. I think it has to do with the rc/pb cards. Sweetbeats, the cards have 2 tracks per card like a 388. I just finished swapping cards again and the problem did move. So my track 11/12 and 7/8 card seems to have a problem. I pulled them out and looked them over for any visaul problems, but I can't see anything. What I did do though is when I recorded something on track 11 and played it back, I gently wiggled the card and got a audible distorted swoosh kind of sound on track 11 when listening back. Even though no recorded sound made it to that track. Same thing happens with track 7. I'm gonna flip the machine up and see if I can get a glimps of the mother board under neath and see if any of the card connector solder points are bad in any way.

As for the power supply, I was thinking of putting some jumpers on, but the "roadmap" of traces are hard to follow because of the green coating that flaked off. So I don't want to risk connecting any points together in the wrong way.
 
Can you hear the track 7 and 11 relays clicking when you arm those tracks?

Yeah. they click. Not sure if my ears are playing tricks on me but the clicks sound a little weaker than others.

Edit... Yeah it's just my ears. They sound pretty much the same
 
Just discovered something.
I just recorded some speaking on track 11(the bad one). When I played back I got nothing. Until, I gently leaned the rec/pb card for that track over ever so slightly and my spoken words started coming through loud and clear.
Hmmm....
I did flip the machine up and l took a look at the solder points for the card connectors on the motherboard and they all looked good.

I'm wondering if there is something on the card that is loose. Or a bad trace that is connecting when I bend the card slightly.

I'm gonna see if this works for the other bad track.
 
:eek:DEOXIT!!!:eek: To the rescue?????

I decided to give the pins of the card connector on the mother board a good swabbing with long wooden swabs and deoxit. I did this for the so call bad cards. And.....Blamo! I'm getting consistent sound now on tracks 11 and 7. Who knows though. It could be an intermitent problem thats just in it's good phase. Track 11 is still fading a tiny bit but not much. If I very lightly touch the top of the card it, sound goes back to normal.

Is it safe to put deoxit in the female connectors on the cards? Does it have to be totally dry before plugging back in?

I'm hoping this was the problem. Im gonna go over all connectors and give 'em a cleaning.

Here is a picture of the swabs. Not much dirt on them, but it could of been the cause. Time will tell.

IMG_20161222_172314.jpg
 
Solder joints can look good, but unless you get a bright light and some kind of magnifier on them you're not likely to see the break. Point is don't just go off of "they looked okay."

The DeoxIT is fine to jet into female connectors. It doesn't have to be dry, but it's not a bad idea. If I'm in a rush I will usually use an air duster to blow out the excess cleaner using a rag to catch the blow-out. You are using the D5 contact cleaner and not the F5 Faderlube, right?

I was asking about the relays clicking to rule out the higher level issue of a possible malfunction in power getting to the relay coil in the first place to close the relay contacts when energized. If it's not getting power obviously it's not going to work, and power supply always gets addressed first. They're clicking, so they have the potential to work. The next issue is dirty or worn contacts which is the issue we typically have if relays are the problem. Depending on the relay they can be opened up and contacts cleaned, but many are sealed, and regardless, based on my experience, it's a better course of action to just replace rather than repair if relays are a problem. But it sounds like you may be on to at least a significant contributor to your problem.
 
Just doing some more tests....
Not thinking the deoxit was the cure anymore. Still getting the recorded signal cutting in and out. I am really thinking its a connection problem. As stated earlier, if I gently push the pb/rec card over to the left while playing back what I recorded, the signal comes in clear and steady. If I let the card go, it fizzles out and either fades in or out or no sound at all. I think the female connectors on the two cards maybe loose and are losing thier grip, or the solder on the connectors need to be reflowed. Even though by looking at them, they look fine. Shiny with no rings or cracks.

And Im still having the problem of a heavey distorted signal coming through channel 11 monitor while recording to track 10. But this subsides while leaning the card slightly. Gonna get some more solder wick tomorrow and try to reflow the connectors.
 
Please do not use solder wick. Get a vacuum solder pump. Even one of the affordable manually actuated spring loaded ones. You'll thank me.
 
Please do not use solder wick. Get a vacuum solder pump. Even one of the affordable manually actuated spring loaded ones. You'll thank me.

Really? I do have a solder sucker but I find the wick works really well.
Would it be because there is more likely a chance to pull up a solder pad?
 
Sounds as if it is a connection problem. By bending the card you're forcing it to contact.
 
Really? I do have a solder sucker but I find the wick works really well.
Would it be because there is more likely a chance to pull up a solder pad?

Well do you have the kind that is just like a rubber bulb? Those suck. I'm talking about something like this:

IMG_7714.JPG

$5

I don't like the wick because it's not quick and clean, and being quick is crucial. The spring-loaded sucker pulls all the solder away quickly so you minimize the amount of time heat is on the joint, and maximize removal. FYI though if you are just re-flowing joints I don't typically remove any solder...I just melt the existing joint and add just a touch new solder...more than a touch if the joint looked light on solder.
 
The female connectors are on the rec/pc pcb.
I think the smaller of the two is the one that might be losing it's grip.


View attachment 98844


Ohhhhhh I thought the unit was outfitted with card edge connectors. Okay. Well the larger of those two connectors is a Molex assembly I believe and those can be problematic. You may want to see if you can find a way to tweak the sockets in that housing to ensure positive contact. Is there any way you can get me a close up of the sockets on the connector? I'm sorry to ask that when I've got two MG1212s sitting out here in the shop, but the way they are sitting right now it would be a pretty major effort to move things around just to try and open one up...not that I'm not itching to do that with all your awesome exploratory surgery you're doing, but it just isn't in the cards until well after the new year.

[EDIT]

if it is the smaller of the two connectors that would be odd because those are the same used throughout pretty much every Teac unit from the 80s and I've had really good luck with those. But something to watch for is the connector housing losing its grip on the card. I have had good success using cheap superglue to help keep the housing anchored to the card. Let me know if you need more detail.
 
I second the NO solderwick. More than once I've had the solder and wick stick together and pull up a pad. No fun.
 
Well do you have the kind that is just like a rubber bulb? Those suck. I'm talking about something like this:

View attachment 98847

$5

I don't like the wick because it's not quick and clean, and being quick is crucial. The spring-loaded sucker pulls all the solder away quickly so you minimize the amount of time heat is on the joint, and maximize removal. FYI though if you are just re-flowing joints I don't typically remove any solder...I just melt the existing joint and add just a touch new solder...more than a touch if the joint looked light on solder.

Yes. I have one of those. I haven't used it in a long time. Will give that a go when I wake up(hopefully out at the pub)
I always thought it was a good idea to remove the old solder. I'll just give it sone heat. I have a good local electronic supplier close by. Maybe they'll. Have some connectors.
 
Yes. I have one of those. I haven't used it in a long time. Will give that a go when I wake up(hopefully out at the pub)
I always thought it was a good idea to remove the old solder. I'll just give it sone heat. I have a good local electronic supplier close by. Maybe they'll. Have some connectors.

You don't need any connectors...you just need to doctor what's there. And when you have a chance try sending a close up pic of the sockets so I can see if I can ID the style...I may have some more specific guidance once I know what the housing is loaded with.

Enjoy the public house.
 
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