Teac A 3440 Inermittent Stopping

[dasmax]

Yes its driving me nuts. My a3440 has taken to stopping briefly during record and playback. The deck always re-starts on its own and ony seems to do this when cold, usualy within 5 mins of running, any ideas?. I also would like to get hold of new rec and pb heads + a capstan belt. Oh and if anyone has a clue where to get ics for the matching RX9 DBX unit please let me know as I only have 2 of the 4 channels working. I know the ics are duff because if i move the ics from the good channels to the faulty ones the faulty channels work. Thanks to all in advance.
Darren

[Nickthedentist]

Try these people for ICs: http://www.dalbani.co.uk/index.php

[reel-to-reel-man]

Hello, I have a A3440, they have a thing about the pinch roller must be moved into and out of position for rewind and play, some people do not move this and unfortunately the heads wear quickly. There is a Japanese site where you can get the belts and heads, brand new

http://www.openreel.net/parts_2.html

I have brought from them in the past and the items take about 5 days to get to you, they are very good and they accept Paypal. Your hrad and belts are in stock, 9500 yen works out at £46

http://www.xe.com/ucc/

Remember these are brand new parts hence the price which is not all that bad

As for the switch problem, I have had the switches fail for a past time, they have sprung metal inside which snaps, though the recorder starting again would suggest a dead or failing transistor somewhere, will look into.

[Tim]

If the machine uses optical sensors, don't dismiss the possibility of "holes" in the magnetic layer of the tape, allowing the sensor to see the light the other side. Of course if it happens with different or proffesional "backed" tapes then of course I'll go back to sleep...............

[Bob955i]

Tim: The A-3440 doesn't have optical sensors for transport control - the right-hand tension arm has a microswitch which, if the arm drops due to tape breakage/running out or insufficient tension, stops all motors and disengages the pinch wheel. It's important to note that one shouldn't mix reel sizes as this plays havoc with the tape tension due to the differing hub diameters. The A-3440 has a reel size selector switch for 10.5" reels and 7" reels and it's important that this switch be correctly set for the reel diameter being used as this also determines the appropriate tape tension.

dasmax: The transport switches are all momentary types and are commoned so you might either have a problem with the flipflop circuit that controls the play mode (2 trannies and a couple of caps) or a problem with the supply to the capstan solenoid (also has a couple of trannies in the circuit). It all depends on what the machine actually does when it cuts out, ie, does the pinch wheel disengage and all motors stop, or does the pinch wheel remain engaged but the capstan motor stop?

[dasmax]

Thanks to all for the replys. I am well impressed with the price of parts from the suggested site I think that if I can solve the intermittent stopping fault I may well look at fully overhauling this machine. Its a great piece of kit and even with the slightly worn heads it still sounds great (Thanks for the info on pinch roller position "guilty as charged" I did not do this so the head wear is my own fault). If anyone has a circuit diagram for this machine I would be greatfull for a copy, any info on the callibration would be great to. I am currently using Quantegy 499 tape which works well but seems to have a slightly elivated top end response which I find requires trimming out on playback so It would be nice to set the machine up for this tape. I currently buy tape through studiospares WWW.studiospares.com but would be interested in finding other suppliers as they have had some sourcing problems recently.
Thanks again
Darren

[dasmax]

Thanks bob. The transport drops out to full stop (ie reel motors stop pinch roller drops and tape guides move tape away from heads) in the same way as if the stop button is operated.The tape stays tentioned but the capstan motor keeps going.This only happens for about 2 seconds and then the machine re-engauges and continues. Out of interest the capstan motor on this mahine runs all the time from when the power switch is on, is this correct?

[reel-to-reel-man]

The capstan runs all the time on machines used for quick start, this is normal on the A-4430 machines, mine is the 15/7.5" speed one and it does the same

[Bob955i]

dasmax: Like r2r man says, the capstan runs all the time - as long as the tape tension keeps the right-hand tension arm lifted.

I have the service manual for this machine, if you PM me your email addy I'll scan the relevant sections for you. If you plan on a full realignment, you'll also need a NAB equalisation test tape, a sig gen, an MVM and a scope. If it's just a rebias and rec sensitivity alignment, you won't need the test tape although a pink noise generator would be handy.

[dasmax]

I have a fairly well equipped workshop so the test kit is no problem I dont have a test tape, are these still available?
Thanks
Darren

[Bob955i]

Test tapes are still available, but at a price.

Canford Audio stock a variety of MRL tapes.

http://www.canford.co.uk/commerce/ca...9_3000308.aspx

You can check here for the one you want to use:
http://home.flash.net/~mrltapes/which-cal-tape.html

The one I got many years ago now, is 320nWb fluxivity. The fluxivity is dependent to a certain extent on the tape speed and tape itself and is important because it determines the playback level and the playback level is also dependent on the headroom of the electronics and how hard you want to, or can, drive the tape.

The A-3440 was originally set up to run Maxell UD35 tape but Ampex 499 is higher output and higher bias - if the machine hasn't been recalibrated from new then it'll still be set up for the lower bias tape. As such, 499 will be underbiased and this will give you the treble boost you noted on playback.

Got your PM - will scan the documentation for you ASAP.

[Top Cap]

Hi Darren, I also have a A3440 with this start stop problem, very intermittent and usually following first Play or Record select of the day. I suspect one of the Flip Flops in the control circuit and when I get time (and find some space on my workbench) I will have a look around the control board with perhaps a can of freezer. The take up arm, for want of a better description, operates 2 microswitches, one is normally open and the other normally closed when the arm is not under tension from the tape. The circuit refers to these switches as the Safety switch. The normally open switch interrupts the supply to the Servo motor so, yes, the capstan should only run when the arm is tensioned.
The normally closed one places a short across the transistor Q712 on the control board. This transistor is connected between the STOP command line and 0V. Note that the 1uF capacitor (C709) in the base of this transistor perhaps pulses the transistor on power up? Just a guess but it makes sense to ensure the machine is in Stop mode when you power the machine. Possibly leaky cap but I am not too sure about this as I would not expect the machine to be able to restart if Q712 had been activated.
I suspect I also have another problem in this circuit in as much as the machine does not always go to Stop after a FF or RWD when the tape runs out and the action of the arm dropping should do this.
Les

[Top Cap]

I am still plucking up courage to start sorting through the control board on my Teac A3440 but study of the circuit diagram produced an initial mystery. I kept thinking how can the machine come to a dead stop then start up by itself because to do this the control flip flops would have to remain SET. If the fault had RESET the flip flops then the machine would stop but never start again. So what causes the machine to start and stop regardless of the flip flops? Now guys I am only going by the circuit diagram at present but it seems to me that this start/stop/restart problem could be caused if power to the left and right reel brake solenoids together with the capstan solenoids was temporarily lost. They are in fact fed from the one supply, each being grounded for operation by the relevant flip flop driver. At first I thought that these were powered soley by Q606 on the power supply board but it did not make sense as its driver is fed from a capacitor and not a supply rail. But after further study the penny dropped, there are two supplies. Solenoids do not need as much power to remain held in as they need to initially energise and I think that is what is happening here. Supply 1 is not capable of energising the solenoids but when play etc. is selected, a pulse via C714 temporarily turns on Q607 then Q606 to place a higher voltage on the solenoid supply rail. This pulse occurs of course at the same time that the solenoids are grounded by the flip flop driver transistors. When the pulse has gone and Q606/607 turn off, the solenoids are held in by the lower supply via the diode. I cannot imagine how else this circuit operates but most annoyingly, it does not explain how the solenoids can all drop out and then come back on. Assuming that I am correct in my original diagnosis, I think I shall try replacing smoothing caps etc. on the power supply board before attacking the control board. Any other ideas anyone?
Les

[Top Cap]

Well I decided to look at the Teac today to fix both the intermittent stop problem and also the failure to stop at tape run out. The control board was at fault on both counts, it is in a position where all sorts of debris can collect onto the component side so the first thing to do is give it a good clean. Just a gentle brush as the components are mounted vertical and are easily pushed over, check that no component leads are touching. The NOT STOPPING problem was the easiest to cure, the 0V signal was arriving ok on the connector J702 pin 2 from the stop microswitch but was then lost. This was due to a connecting pin that is inserted through the board, soldered at both ends to connect the top track with the bottom track i.e. a double sided board. I have had a lot of similar problems in the past with Marconi frequency counters so I went over the whole board and re-soldered each connecting pin, there are quite a few. The intermittent stopping was found by using a can of freezer, shielding components with card and just freezing small sections at a time. I found the 0V that should be on one side of the capstan solenoid, provided by Q721, was drifting up and causing solenoid dropout at about 4V. The machine then went wild with bursts of start/stop before finally stopping for good. Rewind still worked in both directions and STOP was ok but no PLAY function until the frost cleared from the board area around Q701 and Q702. I changed both transistors (2SC1740) for 2SC945 as I had some spares of these and they are actually called up on the schematic. So far all seems ok, no amount of freezing will reproduce the fault so I hope I have nailed it. Having looked at this board I can see that there are a number of possibilites here for the same fault so I do recommend using some freezer to try and highlight where your particular problem area may be.
Les

[TIMTAPE]

Top Cap,
I admire your careful detective work on the PCB. I have had a 3440 from new and it has only given (so far) one problem on that board, a faulty trannie or diode, I cant remember which.
But double sided boards... the problems they can cause with the feedthrough connections.
I used to service Philips dictation machines. The older models were fine but then they brought out the inevitable two sided PCB layouts to accomodate logic control with about 20 feedthrough rivets. We had so many problems with those @#&*! rivets. We used to suspect the heat of the iron created expanding gas bubbles under the rivet and blow out the solder you were trying to sweat onto the joint.
To try and isolate which rivets were faulty the head tech used the approach of measuring for the slightest increase in resistance between sides of the board where the rivets were and then resoldering those ones. There were just so many to do for every machine.
Now you've got me worried my 3440 will do the same as yours did, after 25 years! But at least now I know what things to look for if it does.
I think they are a great machine. The most common fault seems to be the sticking grease that seizes up the pinch roller actuation. The arm on mine was almost frozen solid on the pin.
Best wishes,
Tim

[Top Cap]

Hi Tim, Well the good news is that the rivets Teac used are like long double sided solder pins and very unlike the ones that Philips and I suspect Marconi used. I think I was just unlucky with the STOP circuit on my board. The trouble you described with the dictation machines is exactly that with the Marconi counters but worse was the fact that rivets going virtual open circuit led to the death of many ECL chips on the boards. Two big boards, well over a hundred rivets! It would take sometimes 3 days of concentrated effort to fix some of those damn counters. Oh Yes, the dreaded frozen pin, I had that on my machine here and was a real sod to get free and lubricate.
I have successfully fitted an additional veroboard headphone amplifier in the machine and wired it to channels 3 and 4. The headphone socket was no problem to separate, just cut the track with a craft knife so now we can monitor in stereo. The dual 50k pot I bought from Cricklewood goes in a treat, by the way they also do all the rare jap transistors you find in Teacs etc., well worth a look at their website. There is a very tempting rubber drive belt they have about 110mm by 10mm, not quite as wide as a pukka Teac drive belt but for a quid I think it might be worth a gamble as a spare.
With a decent tape, I like the way you can switch between source and play and not hear any noticable difference in quality especially the top end.
Cheers
Les