Odd Problem with My Tandberg TCD-330

GregPerugini

New Member
Hello;

I am new to this Forum, and I appreciate all help.

I have a Tandberg TCD-330, received from a friend. It seems that all the functions 'Work' in the sense that that the moteos engage the cassette properly for rewind, forward, fast-forward, etc. And when in stop mode, the motors stop turning the cassette. However, in stop it still engages the capstans on both side, effectively spilling the tape because in stop mode it the reels are not turning. I took a video to help better show this (URL below) I am hoping this is an easy fix (bad cap,transistor,whatever) and is an easy fix. Hopefully. Thanks for everyone's help


Greg
 
It's possible the solenoid is being held in the engaged position, which could be an electrical issue. I'd look for mechanical problems with the transport plate bearings and return tension springs, though.

Welcome to AK.

John
 
Thanks John. I will check it out. The head carriage is spring loaded away from the pins. When I put a cassette in lever engages the MS3 spring. The issue seems to be that when the MS3 spring is contacted the head assembly moves moves to the right and engages the pins - That shouldn't occur unless I press play, right? Right now, just the contact with MS3 moves the capstans to the pins, so that even in stop mode (the cassette reels not turning) the engaged capstans pull the tape.

Greg
 
In my 440A , the capstans turn as soon as power is on. This is the way it is designed, and the 330 is very much the same. I have not tried pushing the headbridge the way you do on the video, but have to ask: Have you confirmed that the headbridge and rollers actually move into play position when you insert a cassette, without pushing 'play'? - On my deck this happens only when i push 'play'. I understand that it feels risky to try, but it should be fairly safe if you insert with the tape at the end of the side (A/B). At least, that would limit any damage to a minimum.

What should happen when a casette is inserted is that the upper reel shaft makes a quick wind-up of slack in the tape. Could it be that someone has messed with wiring from the micro switch you trigger (as shown in the video)?
 
Thanks for your reply, Koppa. Yes, my Capstans turn as soon as the power comes on as well. And as you say, the upper real shaft makes a quick wind up of slack for the tape. But the headbridge moves to engage the cassette right away when I insert it. Inserting it engages the M3 spring, and that pushes the headbridge and rollers against the capstan pins, without me doing anything but putting the cassette in. Hence it is in 'stop' mode (and that button is lit), and the reels are not turning, witht he headbridge engaged it pulls tape out of the cassette. This is beginning to look like a circuit problem.

Greg
 
Yes. It sounds as though the logic that drives the solenoid to engage the heads & rollers is faulty. MS3 should only allow the transport logic to be engaged via button input from the controls, not load the mechanism automatically. What are the function LED's doing before/after pressing MS3?

330's use a logic IC array that can be problematic. Let's hope it's something other than that.

Have you had the logic board out of the deck? Any chance you reseated it incorrectly, or another wire pinched during reassembly or possibly reconnected wrong in the process?

John
 
The LEDs switch properly. When MS3 is engaged the top reel spins briefly as it should. When I press the forward, rewind, and play buttons, they light as they should, and the reels turn as they should. But through it all the headbridge has the rubber against the capstans, even when in stop, and hence the tape spills.

I have had that board that has the switches on to check it, and it is seated properly. I cannot say what occurred before it came to me however. The only ones that may of course be a problem would be the green wires out of the MS3, but they are plugged in correctly on the main board.

Thanks again for your help on this, John!
 
I guess next step is to check the solenoid to see if it's being energized prior to pressing Play or Record. Should be a 2-pin connector on the main board A1 a bit inboard of the fuseholder, if you unplug that the mechanism should not engage at all regardless of mode. If there's constantly voltage across that connector when MS3 is closed, check Q301 and Q302 which are right next to the connector. Possible one of those is shorted. if not, check pin 12 of U401 on the logic board - that pin controls Q301 which in turn switches Q302 to control the ground side of the solenoid (other side is fed by 23V line).

If disconnecting the 2-pin doesn't prevent it from engaging, it's a purely mechanical issue which would be pretty weird. Or, someone has hot-wired something.

John
 
OK, I see them. I think you mean J1, right?

Tough to get to them. I have to remove the board with the switches on it to get to them. Can the unit be powered on without that board? In any event, I will try to test Q301 and Q302 and report back. I will also test to see if it the headbridge engages without J1 plugged in.

Thanks again for your help. This unit seems to be very well designed - I have a Akai GX-570dII, and that is much harder to work on.

Greg
 
Yes, J1. Not sure about powering it up without all of the boards in place, I'd avoid that if possible. Don't want to do anything that might damage the logic on this thing, assuming it's not already screwed up.

John
 
OK, I removed Q301, which tests as a PNP, hFe = 152, uF=664mV. The Q302 is a NPN, hFe = 172, uF = 630mV. If these are ok, I will put them back in black. J2 is the two green wires that go to the MS3, not J1. J1 is two red wires.

Greg
 
It was the two red wires on J1 that go to the solenoid I had in mind measuring... if those transistors both check good (sounds like they didn't have any shorts given the data you include above), and there's voltage across the red wires, it's because the logic is turning on Q301/302 when it shouldn't and they're in turn engaging the solenoid to load the head/rollers. That would be a bad thing.

John
 
OK, so I put Q301 and Q302 back in, put it all back together ....without the J1 hooked up.... And it behaves the same way - the heads engage whenever a cassette is in, or the M3 switch is activated. So what does this mean? I checked the red wires to J1, and nothing is going to it in terms of voltage, in stop, reverse, play, or whatever.

It sounds like bad news.

Greg Perugini
 
Shoot, my bad. I was looking at the circuit for the eject solenoid, not the pinch roller solenoid.

Connections on that one are at J21, and there are 4 wires going to it. Control is via Q311/312 and Q313/Q314.

There's a short explanation of this circuit in the TCD-310 service manual, pg. 12. The locator #'s for the transistors etc. are not the same as the 330 and that deck uses manual transport buttons vs. logic IC's but the solenoid circuit functionality is similar. Essentially the deck uses more juice to engage the pinch rollers initially, and less juice to keep them engaged.

That manual is here: http://sportsbil.com/tandberg/tcd-310-sm.pdf

John
 
Yep, I have that manual John, but not in that resolution. Thanks.

Are you sure about those transistors? Q312., Q313, and Q314 are similar in size and shape, but Q311 is fat and squat, and is located a distance away from the others on the board. J22 is near the top, and the wires go to J52 on the another board. Just want to make sure I am checking the proper items.

Given the voltages according to the 310 page 22 stuff, Whatever is giving 13.5V to the + of C316 must be shorted I would think.because when Play and Record is released C316 should have no voltage. When play is pressed it goes through several steps unit we reach step 5, where it gets charged completely. Looks very complicated, but should I test the voltage going into C316 when nothing is pressed? I could also remove those 4 transistors and check them....

Thanks again for your help on this....

Greg
 
You could be right on Q311, but I’d check it for shorts anyway. Should only take a few minutes to check each of those four for shorts in Siri, no need to remove them.

Keep in mind that while the electrical functionality of the solenoid control circuit may be similar, the 330 has logic ahead of those transistors where the 310 had to rely on other means to switch them. I’d check the transistors and then the logic controlling any of them, just go upstream from the bases of the transistor to find those points.

John
 
Well, I think I have the problem. All are checking out normal, EXCEPT, for Q313, which should be an NPN transistor, but is testing out as 2 diodes at 720mV. I have a replacement in my lab I think......I will try it out....
 
That's interesting... what tester are you using? Did it give that result in-circuit, or with the part removed?


John
 
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