464 Play function not working

[Jack Olson]

I've been sitting on this problem with my 464 for months now and can not figure it out for the life of me. When I press play the heads come up for a second and then retract back to the stop position. I should mention the fast forward and rewind work perfectly fine and none of the led's light up when I press play, and that the tape doesn't start counting when I press play. I just replaced a broken gear C and have checked the belts so those should both be fine. I've scrubbed the tape heads, capstan, and pinch roller with isopropyl excessively. One thing I noticed when I replaced the C gear is that one of the little forks on the contact plate that touches the CAM was all bent up, but I straightened it back out and I think it should be making a good connection. I also cleaned the CAM with isopropyl as it was covered with a sticky residue, now I'm wondering if that was a bad idea lol.

I'm not sure what else could be going wrong at this point, I feel like I've given this thing the full run down to the best of my knowledge. Anyone here have any ideas for anything else I should look at? Thanks in advance, I'm ready to put this frustration to bed.

 

[Laszlo]

Hello,

Probably the machine does not sense that the tape is moving, therefore it stops the play mode. The movement sensing must come from the tacho sensors on the sensor panel. The Sensor PCB is located around the table reels on the side of the motors on the transport body. They are optoelectronical sensors, and they sense the rotating stripes on both table reels. This explains also that the counter does not count, since it gets the signal from the move sensors.
Can be a broken wire, or one of the sensors just got damaged.

 

[-mjk-]

Does the take-up motor start right away?

 

[Jack Olson]

MJK- No, the take up motor doesn't start up when I press play, there's no tape movement at all. I know the play can work as it works fine in cleaning mode, just not when there's an actual tape in there.
Lazlo- An error in the sensor PCB does sound like a likely culprit. I'm gonna tear down the transport and see if I can find anything that looks suspicious.

Thanks a ton to the both of you for the help, I really appreciate it. Can't wait to get this baby running again, I'll keep yall posted with any updates

 

[Jack Olson]

Lazlo - Any advice on things to look for to tell if the tacho sensors are bad? I have the sensor pcb pulled apart now, but everything looks alright as far as I can tell

 

[-mjk-]

MJK- No, the take up motor doesn't start up when I press play, there's no tape movement at all. I know the play can work as it works fine in cleaning mode, just not when there's an actual tape in there.
Lazlo- An error in the sensor PCB does sound like a likely culprit. I'm gonna tear down the transport and see if I can find anything that looks suspicious.

Thanks a ton to the both of you for the help, I really appreciate it. Can't wait to get this baby running again, I'll keep yall posted with any updates

That's your problem. If the capstan motor is running and the pinch roller engages and appears to move tape, if the sensor doesn't detect that the takeup reel is moving, the logic immediately stops to prevent a nasty loop from forming. Once you figure out what's stopping the takeup from working, you'll be well along to getting it running.

 

[Anders]

Hello @Jack Olson. I have the same problem I believe. Did you manage to solve it?
For me, forward, stop and rewind work fine, but pressing play just causes the playhead to appear and then after a second or so, it retracts and the playing stops. I can see signal coming through for a brief second, so it sounds similar to your issue.

 

[SkywaveTDR]

Fast wind functions have nothing to do with the play function as they are entire different. Most likely the grease on the feedback board is hard and stopping the contacts from getting the proper feedback so if the controller doe snot see the function has reached it end state it goes back to stop. Tightening screws is not going to fix this- you need to get in and clean the mechanism from that old damping silicon they used. They seem to always find the worse greases to put in their products and it is almost as if it was intentional with the failures they have had. This one has Lubriplate 105 which never gives me trouble-

 

[SkywaveTDR]

Stop using Isopropyl alcohol. We have not used that for 40 years of my career yet people still have to use it as it comes from a drug store BUT is the wrong product and it does no good in the tape path at all.
IF you do not listen to the guys who used to fix these 8-10 hours a day at the factory service you will continue to have trouble.

 

[SueDonim]

@SkywaveTDR, What's the right thing to use to clean the contact plates?

 

[-mjk-]

He hasn't been here in over a year, unfortunately.