A-3440 4-track R2R Issues

[Richard P]

K601 and K604 appear to supply power to the right take-up motor when play is pressed. Can you verify they are engaging? I'm not quite sure what the function of K601 is (some kind of boost circuit??) but K604 supplies power to run the motor directly from the transformer through R902 (30 ohm)

 

[Navcom]

K601 and K604 appear to supply power to the right take-up motor when play is pressed. Can you verify they are engaging? I'm not quite sure what the function of K601 is (some kind of boost circuit??) but K604 supplies power to run the motor directly from the transformer through R902 (30 ohm)

I did unsolder all 4 relays and they all checked out. I have not tested in circuit to see if it's activating. What's the best way to do that?

 

[Richard P]

My recommendation is to check diodes D615 ~D624 and transistors Q608/Q609 on the power board (DMM in diode mode) to make sure they are OK. If so, with everything back together, see if K601 and K604 activate when you push play (switch set to large reel). If they activate, check AC voltage between the points 4 and 11 on the connection PCB if you can get to that. If the relays don't energize, we probably need to look at the control PCB starting with Q719.

 

[dr*audio]

My recommendation is to check diodes D615 ~D624 and transistors Q608/Q609 on the power board (DMM in diode mode) to make sure they are OK. If so, with everything back together, see if K601 and K604 activate when you push play (switch set to large reel). If they activate, check AC voltage between the points 4 and 11 on the connection PCB if you can get to that. If the relays don't energize, we probably need to look at the control PCB starting with Q719.

If you can't see them activate, connect your meter across the diodes that are across each relay coil and check for a DC voltage.

 

[dr*audio]

Note: do not ignore K602, it is in series with K604.

 

[Navcom]

Thanks everyone! I’m in other projects till the holidays so not going to get a chance to get back to my bench for a few days. I haven’t ignored the thread! Really appreciate all this!

 

[Navcom]

Hi everyone! I’m back from vacation and back at my 3440. I‘m not having much luck with it but the good news is the machine I picked up before the holidays that was going to be my parts machine is actually in better shape! It had a seized pinch roller and right tension arm, which I was able to free. The thing works great now…for the most part. It works and records/plays back! Rew/FF are a bit anemic but I’m guessing caps are probably at fault. Brakes are great and it records/plays smooth as silk!

only one real issue I’m hoping you guys might have a direction for…..sync mode doesn’t seem to work right. Example: I want to record multiple tracks but one at a time while listening to what’s already been recorded. Example: i record something to track 1. Works great. I can play back and hear it great. I then prepare to record the next track while monitoring track one. Arm track 2, set to sync mode, turn on monitoring for 1 and 2, and hit record. I can hear track one but I can barely hear my playing for track 2…it’s just very faint. When I rewind and play back, it recorded just fine. I just can’t monitor it during the performance. Any ideas what’s going on? Monitor button is selected. Sync mode is selected. I can hear tracks that are already recorded. Just can’t hear my performance.

 

[Navcom]

Since this is heading in a different direction, I think I'll start a new thread as that makes the most sense. Thanks all!

 

[Navcom]

Note: do not ignore K602, it is in series with K604.

Back to this thread as I believe I've discovered something while attempting to get my "parts" unit operational. I swapped out the function PCB from this unit to the new parts unit and I'm having the same issue with it just stopping after 5 seconds. Parts unit has been running mechanically just fine. I even recorded some stuff with it last night and it sounds great...but has another issues I'll mention in a sec. SO, I'm guessing the function pub is the problem with the first unit! Just not sure what part of it. Any ideas where to test? I'm guessing it has something to do with the power, tape speed, or reel size switch. Capacitor issue? I have not replaced the caps on this board yet.

On the second "parts" unit, I'm closer to a working R2R . My only issue here is with track 4. I set it up to record on track 4 and I get meter deflection so I know it's receiving a signal but I can't hear it in the headphones nor does it record to tape. Doesn't matter if it's in source, sync, or play mode. All 4 track monitor switches are depressed and everything is fine on the other channels. I've swapped the function PCB (thus my discovery above), the sinc EQ boards, the channel 4 rec/play PCB, the phone amp PCB, and the OSC and bias PCB's. Still having the identical issue. Any ideas where else to look? I seem to be running out of PCBs. LOL!