RS1506 odd problem in play mode

[Teeg]

   My spare deck, a well used but generally good-condition 1506, has been packed away for a few years. After taking it out again, it developed a problem where the pinch rollers do not drop onto the capstan while in the play mode. All of the other functions associated with tape handling seem to work, but neither the pinch rollers (and I am going to assume the tape lifters) operate.

 Any ideas where to start looking? Normally the 1500 series decks wont drop the rollers if at least one of the tension arms is not down, and although the arms move freely and 'click', I dont know what this translates to mechanical-wise.

Tj

[ironbut]

Hey Tj,

Since you stated that the machine hasn't been in use for a while, try moving the rollers by hand or switch the "cue lever" on and off. The cue lever should move the rollers within about 1mm to the capstan surface. They should move freely with very little resistance.
If you have difficulty moving the cue lever or the rollers by hand, look at the lifters to be sure they're motion isn't being somehow obstructed. You might remove the headblock to get a better look.

If those seem to be moving freely, it could be the plunger at the top of the machine.

Open the machine back and top cover. Facing the back of the machine, the plunger is just to the right of the transformer box with dominates the top/center of the machine. Try putting the machine in play (with one of the tensioners pushed down) and see if the plunger pushes out and in when the machine is stopped. If the plunger doesn't do this, check all the fuses and try to move the plunger manually. It could be stuck in and a little pushing might free it up.
If you have a service manual, go to the section on the Stoper Position Adjustment. With the stopper plate removed, try moving the plunger by hand. It should take a little force to push it in and spring right back out when released.
There's a pretty good picture of the entire mechanism on the page for Pressure Roller Adjustment. Most of this stuff is totally obscured by the capstan motor and there's little chance that these mechanisms are so gummed up that it would prevent the rollers from moving (keep you fingers crossed on this one).

Well give those things a try and let us know how it goes.

[Teeg]

  That's a great start Steve, thank you. Up until now, neither of my two 1506s have given me any trouble, so I've never had the need to open one up. The deck with the problem makes no noise when the play button is pressed, other than the reel motors starting, so it sounds as if the solenoid that operates that function is doing nothing at all.

  I will tear into it and report back.

Tj

[Tim]

Your "no noise" comment makes me think that your brake solenoids are also not engaging (they should in play mode).  Perhaps your solenoid power supply (usually 24 VDC) is down. Check all power supply fuses.

[Teeg]

  Oddly enough, I removed the rear panel at Steve's suggestion but upon trying it the deck went into play mode just fine. The problem remained intermittent for the first few tries but seems to have worked itself out. I hate when things fix themselves...

 I was incorrect in my previous post regarding what happened when the play button was pressed...I said the reel motors were spinning, but they weren't; nothing at all was happening when you pressed play. For the moment the deck seems to be operating fine, but I'll leave it on the workbench for a few days-I'm somewhat happy that it now works but bothered by what it might have been.

 This was the first time I saw a Technics deck from the inside out. Compared to my Ampex 350 and 440 transports which are simple electro-mechanical creatures, the Technics is crammed full of stuff.

Thanks for your suggestions,
Tj

[ironbut]

Ha Ha! Good deal Tj.

It sounds like it's just a dirty play switch. I've never pulled those things out so I'm not sure the best way to clean them.  You just never know what might have spilled, floated or crawled in behind those guys while it was in storage. You might've punched that button just when something was going to stick it's head out and say "Take me to your leader,.. tape".
Maybe Tim knows the best way to clean those " feather touch" type buttons (I'd like to know myself).

It's not a bad idea to exercise the switches on the left side of the machine and maybe squirt a little DeOxit into the back of those (speed selector and pitch control in particular). They can cause some pretty wacky speed issues.

[Teeg]

  Problem is gone; whatever it was just took some time to work out. I'd like to dig a bit deeper into the cause but that seems pointless unless the situation comes back in the future. This was the first time I've ever had an issue with either of my Technics decks.

TJ

[docb]

Sometimes old electrolytic capacitors need to reform if they have been sitting for a long time. One of the more common issues is the Technics not going into rewind from play or vice versa. Often this is cured by leaving the machine turned on overnight, allowing the caps to reform so they will properly charge. I don't know the circuit off the top of my head, but perhaps there was a similar issue with caps in the pinch roller actuation circuit.