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A-3440 4-track R2R Issues

dr*audio said:
We've got this. Check the relays.
Click to expand...

I've checked the relays on the power supply pcb (4 of them...24v). All check out fine. I did notice something a bit strange that I didn't have happen before. Right before desoldering the relays, I tried it one more time just to get familiar with what was turning/moving inside before I possibly wrecked it with my "work" (LOL). When I hit play, it did the same thing...shut off arm slowly came down to shut off. But then just before it shut off, I heard a relay click inside. Then it clicked a few more times in rapid succession. While clicking, the shutoff arm sprung back up. Ultimately it stopped clicking and the arm came down and shut off.

I took this as a sign that indeed one of the relays was bad. Now I believe there is probably a power issue supplying the relays. Would this be a good assumption? I have no idea how to trace/find it. God I wish I was a technician. LOL. Don't get me wrong. I'm enjoying the process of fixing this thing and learning as I go.
 
Navcom said:
I've checked the relays on the power supply pcb (4 of them...24v). All check out fine. I did notice something a bit strange that I didn't have happen before. Right before desoldering the relays, I tried it one more time just to get familiar with what was turning/moving inside before I possibly wrecked it with my "work" (LOL). When I hit play, it did the same thing...shut off arm slowly came down to shut off. But then just before it shut off, I heard a relay click inside. Then it clicked a few more times in rapid succession. While clicking, the shutoff arm sprung back up. Ultimately it stopped clicking and the arm came down and shut off.

I took this as a sign that indeed one of the relays was bad. Now I believe there is probably a power issue supplying the relays. Would this be a good assumption? I have no idea how to trace/find it. God I wish I was a technician. LOL. Don't get me wrong. I'm enjoying the process of fixing this thing and learning as I go.
Click to expand...
I'll have a look at the schematic. It make take a few days for me to get to it.
 
You're looking for relays K602 and K603. They switch the motors between the big torque resistors and direct to the supply. If the relays are dirty it could work properly for FF and RW but not for play. Also you could try FF and RW using 10 1/2 inch reels of tape. If it doesn't stall out, it has to be the relays or possibly the torque adjusting resistors are open. If it stalls out or slows down it is probably the caps. Having said that, there's no reason not to replace the caps.
 
dr*audio said:
You're looking for relays K602 and K603. They switch the motors between the big torque resistors and direct to the supply. If the relays are dirty it could work properly for FF and RW but not for play. Also you could try FF and RW using 10 1/2 inch reels of tape. If it doesn't stall out, it has to be the relays or possibly the torque adjusting resistors are open. If it stalls out or slows down it is probably the caps. Having said that, there's no reason not to replace the caps.
Click to expand...
Those were two that I tested. They tested fine. I desoldered and tested all the relays on the power supply board and was getting near zero resistance (<.01 ohms). They switched perfect when power was applied with external 24v power supply.

All caps on the power supply PCB, control PCB, and stop PCB have been replaced with new caps. Motor caps (the big dual 7uF cap between the motors) has also been replaced with new caps. I'm using 10-1/2" wheels currently.

I'm going to try to get a video of all operations so it's easier to see what's going on. Thanks!
 
D623 and/or D624 could be breaking down or have cracked solder joints, I suppose. That might give you odd relay operation . . . Q724 and Q725 turn those relays on so that would be a place to check as well.
 

I shot a quick video of what’s happening. There’s a new development. The thing just shuts off immediately now when I hit play. Maybe I didn’t resolder the relays right? Maybe I broke one? Maybe the video has other clues I’m not aware of?

 
dr*audio said:
You're looking for relays K602 and K603. They switch the motors between the big torque resistors and direct to the supply. If the relays are dirty it could work properly for FF and RW but not for play. Also you could try FF and RW using 10 1/2 inch reels of tape. If it doesn't stall out, it has to be the relays or possibly the torque adjusting resistors are open. If it stalls out or slows down it is probably the caps. Having said that, there's no reason not to replace the caps.
Click to expand...
Oh also…I did run the torque resistors back and forth early in this process to see if they did anything. No matter the setting, it didn’t affect the operation.
 
I assume you tested the large resistors already. Have you measured voltages at various points in the right reel motor circuit to see if the supply is there and where you lose it?
 
Richard P said:
I assume you tested the large resistors already. Have you measured voltages at various points in the right reel motor circuit to see if the supply is there and where you lose it?
Click to expand...

the large resistors have been run back and forth and do not appear to have any effect. Unfortunately I’m not experienced enough to know where to test what.
 
With the deck unplugged, measure resistance across each of those large resistors (from 1 end to the other) and from each end to the center tap.
 
Might be different in circuit . . . lift a wire to be sure if in doubt. It occurred to me that the reel size switch might cause issues as well. Clean that and cycle a bunch of times. test it if you can.

Capture2.JPG
 
Richard P said:
Might be different in circuit . . . lift a wire to be sure if in doubt. It occurred to me that the reel size switch might cause issues as well. Clean that and cycle a bunch of times. test it if you can.
Click to expand...

Here's my results...
 

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Navcom said:
I shot a quick video of what’s happening. There’s a new development. The thing just shuts off immediately now when I hit play. Maybe I didn’t resolder the relays right? Maybe I broke one? Maybe the video has other clues I’m not aware of?

Click to expand...
Can you visually verify if the relays are being actuated in play? I think they may not be actuated at all.
 
dr*audio said:
Can you visually verify if the relays are being actuated in play? I think they may not be actuated at all.
Click to expand...

i believe you are right. I can’t hear or see them actuating. The solenoids are activating for the capstan and other stuff but it appears the relays are not. It’s also getting worse and worse. it feels like it’s just dying. LOL!

see my post above about the resistance in the large torque resistors. It appears a couple may be bad. Would you concur?

some good news…I just bought a parts-only second unit that should be here in about a week or so. Figured between the two, I can test components and get a single working unit. It might actually be in better shape than this one!
 
In the second video (but not in the first one you posted a while back, #13) you are running the tape under the pinch roller. It should be threaded between the roller and the capstan.
 
Assuming the "Φ" indicates open circuit then yes, the resistors appear to be bad and need to be replaced . . .

Good catch on the video @Tonoje . I didn't notice that.
 
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