Speed of Tascam 464?

[TB__]

I previously owned several Tascam 424 decks which had the choice of ‘normal’ and ‘high’ speed. ‘Normal’ speed, with pitch knob centered, matched the speed we know from the normal cassette standard.

I’m currently repairing a Tascam 464 whereby I assumed that ‘normal’ and ‘high’ would imply the same as with the 424’s, however ‘normal’ turned out to be high speed, while ‘high’ meant even higher speed.

Is this supposed to be the case with the 464, is it a high speed deck by default?

 

[SkywaveTDR]

No, If it has a Normal speed selection then that is what is the typical 1.875 IPS speed and the speed being so far off makes me thing the belt is up on the flange of the motor pulley and is rotating the flywheel way too fast while the servo just tries to keep it stable. It does not check for 3KHz as it has no crystal reference.

 

[TB__]

Thanks Skywave, I’m gutted though to hear that, I was hoping for a simple way to resolve it. As far as I remember the belt runs perfectly centered. I’ll look into it with my - thankfully - techy neighbour.

 

[TB__]

Yup, belt runs centered. Funny thing is that the counter is counting faster at normal speed than high speed??

 

[SkywaveTDR]

How is that possible? Anyway the counter may be tied by opto sensor to the reel table. It has no relation with speed of the tape unless you have a tape in there. If a motor goes too fast then there may be a shorted part in the controller. One guy recently said he put a driver in and got sparks at the motor- the driver needs to be isolated from the case so some actions can damage the circuit inside. From your first post this leads me to believe that the motor was replaced by a motor of the Dual cassette type and they do not work the same. These motors run at 2000 and 4000 RPM and even though the 4 terminals are there it is not wired that same as a Pitch control type motor. People go and put in the wrong parts and then wonder why it does not work. There are a few units that I have had to change a motor and do a modification as the original motor was different and so this is the nature of third party parts.

 

[TB__]

Thanks again. I’ll be checking out that motor!

 

[TB__]

Hi again, it has been a while now.

I have checked the motor, it’s a Mabuchi EG-530KD-2B. It corresponds with what I found in the service manual I managed to find on the Internet.

While having it open today I found out that the motor is running really, I mean really hot. Thankfully my neighbour is assisting me as my tech skills are limited.

He thinks the problem might be with the motor itself or the BA6209 driver chips. I have ordered the chips and I’m looking for that Mabuchi motor but that seems to become a pain in finding...

Meanwhile I was hoping someone reply to the current findings: do you think this would be a next logical step, or are we barking up the wrong tree?

 

[TB__]

I read on the internet that faulty thermistors on the pitch assy can be (part of) the problem.
There's a SDT-02 (20 Ohm) and a SDT-09 (90 Ohm) on there but I haven't managed to find replacement on the internet. I do not know if it's either NTC and PTC.
Anyone?

 

[SkywaveTDR]

When you listen to numbskulls on the internet not only are they barking up the wrong tree they don't even know where the tree is. I have never had to replace a Thermistor in any circuit over the years I have worked on these and I am willing to bet I have worked on more of them over 45 years than they have. If the motor gets hot it is either too highly loaded or too old and something is shorting inside it. I have found that the tiny little brushes they use after a time wear through and break- once one come loose, you have a conductive metal piece floating around in the motor and that will end it. These motors are not 7 watt motors like in Open reel decks so they should not be getting hot. Check the voltage going to it- if correct, what has a driver chip to do with a capstan motor- they are usually used on reel motors or cam motors?

 

[TB__]

Hey Skywave.

Sorry to see you agitated there, but I sure appreciate your informative response. I read on gearslutz that someone had similar problems and after replacing one of the thermistors on the pitch board he stated that all was functioning well again. That’s why I had it on my suspects list.

We took the motor apart. We found that the ring to which the copper end wires coming from the copper coils were soldered, was off center. Factory fault it seems. We have no idea though if it had any causal relationship with the motor (ultimately) running hot. After opening I saw a beveled vinyl washer lying on the bottom of the housing which was broken. This washer apparantly usually rests in top of the commutator, around the shaft, between the leaf brushes and the top bearing (this is the best way I can describe it, as English isn’t my native tongue). This meant that the shaft could move more freely in the housing, which is not supposed to happen.

Anyhoo, we put everything back, but it still ran hot. Conclusion: shorting inside the commutator. Thankfully I found a new old stock motor which will hopefully resolve the issue, fingers crossed.

 

[TB__]

Update: New motor arrived and it works like a charm!