This is a TOTAL MYSTERY....

Replace the open "stop" lamp. And wire a several hundred Ohm resistor across it to prevent future logic issues.

All good fortune,

Chris Hornbeck

**Bugger! Beat me to it. I concur.

Trevor Wilson

Thanks for the tip, but the stop lamp is the very first thing I checked. It is working just fine.

If it were just the stop lamp, the deck would go into the PLAY mode, but then it would immediately stop.

This deck physically cannot go into PLAY mode. The heads only come up as far as the PAUSE position. They never engage the tape, and the pinch rollers never touch the capstans.

This is due to an improper control voltage, but I am going crazy trying to find the point at which the voltage drops. All of the logic board components I have checked so far check out OK.

The two voltage regulators are spot-on. No issues whatsoever. Perfect +12 and -12 DC voltage output from them.

I have found one or two resistors with a positive voltage on one end and a negative voltage on the other, which may or may not be a clue.

Does the Timer Play function work normally?

Mark Z.

Dang! I guess I did hear about lamps on these back in the day...

Oh, well - at least got a free PDF service manual out of it...

;-)

Mark Z.

Mark:

I tried it.

No, the deck cannot enter PLAY mode under any circumstances.

On Wed, 5 Dec 2007 07:14:37 -0500, EADGBE wrote (in article ):

Is there, by any chance, a hardwired remote control jack that needs a dummy plug like the old Revox A77?

Regards,

Ty Ford

--Audio Equipment Reviews Audio Production Services Acting and Voiceover Demos

Guitar player?:

1) was it able to enter play before the bias osc was repaired? 2) is the timer switch in record mode? 3) I think the voltage you are reading at the wiper is the voltage from the pot and indicates what position the cam is in. You need also to read the volatge that the machine is commaning the motor to go to so sometinh is amiss with the circuit around Q430 in fig 2.3.22

4) see fig 2.3.22 what is the voltage at Q430 collector in play and pause. This is an interesting circuit, it looks like the macinh gnerates a voltage for each mode and then the motor moves the cam until it is in the correct position to null the voltage at the op amp...so you have determined that the cam is not moving correctly by reading the pot voltage, but you need to determine is the voiltage wrong becasue the circuit is getting the wrong commmand or maybe it is physically stuck and unable to move to the correct position.

5) The votage on the op amp IC405 input pins 6 and 5 should be "virtually" equal. If they are not equal, then the there should be a voltage on the motor and it should be trying to turn. If they are equal, then the mechinsim is doing what it is told and it is being told to do the wrong thing and the problem is in the command voltage inputs.

6) It looks like the only differnce in the comman between play and pasue is due to the different values of R511 and R514. Make sure the logic signal to them is correct. These different values shoulsd create a differnet input to the op amp and the motor should move and move the cam pot so the voltage on pin 6 and 5 is equal again. This is a big mechanical feedback loop that tries to keep the voltage on pin 6 and 5 equal.

Very nice manual by the way...thanks good luck , let us know what you find.

Mark

**Just a wild thought: Do the pinch rollers move freely on their pivots? If the pinch rollers are jamming....

Trevor Wilson

Gummed up pinch roller arm pivots are so common, these several decades down the road, that a truly serious rework should include removing the rocker arms for washing to remove all the old wax (it ain't grease any more) and relube. Auto wheel bearing grease is great, and easily available.

We're all assuming that the little guy has a good control motor belt (the one that pulls the head bridge up and down), the number one failure of the classic Naks, and that the head bridge moves freely.

Oh, and does the take-up reel rotation sensor lamp still work?

All good fortune, and keep us updated,

Chris Hornbeck

Hello Folks!

I thought you might like to know that I have found the source of the problem with the

582 that is preventing it from going into the PLAY mode.

After a few different theories and electronic testing that produced no real results -- nothing that I could point to and say "a-ha!" -- I have discovered that the deck has a PHYSICAL problem, not an electronic problem.

The electronics are fine. I was only getting weird electronic readings because as many of you may know, the deck's logic electronics are governed by the physical action of the tape transport...the deck controls the transport, and then reacts to the voltages that change on the 10k pot when the transport moves...if the transport does weird things, then the voltages become weird. The pot was not in the right position because the tape transport was not in the right position, and so I got weird voltage readings. I had assumed that something had gone wrong in the logic circuit. I never suspected an actual physical problem until now.

HERE'S THE REAL PROBLEM: The mechanism that moves the tape heads and capstans does not move freely enough. When you press PLAY, the mechanism tries to move to the right position, but something is preventing it from moving far enough. Somehow, it has gotten either jammed or out of alignment, or maybe the lubricating grease has gotten too gummy with age.

The thing that clued me in was observing the arm that is actuated by the main control cam. I'm talking about the main white plastic arm on the front of the transport. One end of the arm travels in the groove on the control cam, and the other end of the arm is attached to the sliding bracket on the bottom of the transport. This white arm was flexing in a rather disturbing way. You could tell that the cam was trying to move the arm, but because the arm's movement was restricted (because the moving part it is attached to is restricted), it couldn't do anything and was flexing under the load being put upon it by the cam.

I can press PLAY and then move the transport into the correct position with my fingers, and the deck does play just fine when I do this. Then, when I press STOP, I have to once again move the transport into the STOP position. So the deck CAN play and stop -- but not without my help.

Incidentally, when I manage to get the deck into the PLAY and STOP positions, the voltage readings on the 10k pot are right on spec.

I must admit that I am at a loss as to how this deck has gotten this way. I had not touched anything in the tape transport. The only things I had done on this deck are the electronic repairs involving the record/erase functions (bias oscillator, etc.)...oh, and I did replace the control motor belt, but only AFTER the new problem started.

This deck was literally MINUTES away from being fully repaired and calibrated when this fault occurred, right out of the clear blue sky. I am hopeful that it won't be too big a deal to free up the tape transport linkage. But I won't know what I'm up against until I start examining the mechanism. I'll let you know what I find.

Lithium grease on the mechanical cams. and check for indents in the cams, Use a dremel with plastic polishing compound to smooth.

--
"I'd rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5

On Wed, 5 Dec 2007 21:22:34 -0500, EADGBE wrote (in article ):

Silicon grease turns to glue at some point. I had that happen with some old consumer decks.

Regards,

Ty Ford

--Audio Equipment Reviews Audio Production Services Acting and Voiceover Demos

Guitar player?:

First replace the control motor belt.

All good fortune,

Chris Hornbeck