Problem with Tascam Portastudio 464 pitch control

[Enzo]

The belt rides the bare shaft? Or did you pull the pulley off the old motor shaft?

[g1]

I'm going to jump in here with a similar situation, maybe we can figure it out together. I have a 424 MkII that had a dead capstan motor. I got a replacement from Main Electronics, it's the EG530KD2B, probably same one as you need. I installed it and it spins, so good news there. My problem is that the normal speed now runs slightly fast, even with the trim pot adjustment, and the fast speed runs too slow. I have tried two different new motors and they behave the same way, so I am pretty sure it is something in the speed control circuit outside of the motor. Curious to hear about your progress on fixing yours.

Was the bad motor you removed the same part number? Or is there a chance someone used a different motor and modified the pitch control circuit to work with it?
Pitch control schematic is in post #10.

[bsco]

The belt rides the bare shaft? Or did you pull the pulley off the old motor shaft?

No no....I meant when I bought the motor it didn't come with a pulley...You have to use the pulley from the old motor....I am going to install it after the weekend....I'll let you know how it turns out......
Cheers

[dustartist]

Was the bad motor you removed the same part number? Or is there a chance someone used a different motor and modified the pitch control circuit to work with it?
Pitch control schematic is in post #10.

Same part number as the original. EG 530 KD 2B. I doubt that the motor was modified by Tascam, and I am the original owner of the unit.

[dustartist]

Does your new motor have a small hole on the rearend cover plate?

Also, does the new one have the exact same pulley on the shaft?

Are the speed controls just resistors and pots? In which case, can you not extend the adjustment range by changing a resistor in each speed circuit?

My motor has a hole, but there is a black rubber disc inside the back cover covering it, and besides the hole leads nowhere. I saved the pulley off of the old motor, the new one does not come with a pulley. The speed control circuit in the 424 MKII is a bit more complicated than just resistors and pots. There are a few transistors and diodes involved as well. I have the schematic and will try to post.

[dustartist]

I received the motor a few days ago so I never got a chance to install it....I also had to change the belt so the speed might be slightly off in the unit but I won't know till I install the motor....which will be early next week...I will let you know how i make out with it.....the motor that I received does NOT have an adjustment hole in the rear plate of the motor....many of the tape deck cassette motors that I have seen does have this adjustment slot but this particular one that I have does not have that feature....there is a small ckt board in behind this metal rear cover but there is no adjustment pot there...just a transistor and a few support components....I'll let you know how I make out and if you get your issue resolved please let me know...I would be very interested to hear about it.....

Here is the schematic for the 424 MKII speed control circuit board. P1 goes to the high/low switch on another board. That switch also has -5v and a HS line coming in from somewhere. I'll have to try to consolidate the switch schematic into something understandable.

[g1]

Ok, I didn't even catch that we weren't talking about a 464 anymore.
I think BSCO is also working on a 464 so his results won't be of much use to you.

[Enzo]

Oh, that escaped me.

Hi dustartist, welcome. it is bad form to add a separate repair into a thread on another, we get lost figuring out who's problem has what response. And ESPECIALLY when it is a different model altogether. Threads are cheap. Good form is to start a new thread for each repair.

generally the little rubber cover on the hole is an access point for a small "jeweler's screwdriver" to get at a tiny slotted trim pot inside. is there a slit in the rubber hole cover that would allow a tiny screwdriver through?

[dustartist]

OK, we are talking about the same motor though, and how to control the speed of said motor. Both are Tascam Portastudios so they may have similarities in their design, so comparing notes here could be helpful to both of us in making the repairs that we need to. It actually makes more sense to me to consolidate this information in one place, since it really is the motor itself we are talking about in this thread. I will, however, take my conversation elsewhere if it is not welcome here. Thanks.

[bsco]

OK, we are talking about the same motor though, and how to control the speed of said motor. Both are Tascam Portastudios so they may have similarities in their design, so comparing notes here could be helpful to both of us in making the repairs that we need to. It actually makes more sense to me to consolidate this information in one place, since it really is the motor itself we are talking about in this thread. I will, however, take my conversation elsewhere if it is not welcome here. Thanks.

The original motor in my unit has the same number as the replacement one.....and as far as I know it was original....anyway, when I install this next week I will let you know.......
Cheers,
Bernie
P.S. actually, Enzo does have a point there.....the fact that we are talking about the same motor is a good thing....but if we were talking about two different machines, even it they are the same brand, would be very confusing to all the other members who are trying to help us out.....if the problem turns out not to be motor related, then as Enzo suggested, it would be best to just start a brand new thread for the specific problem that you have....Let me know how you make out....
Cheers

[g1]

It actually makes more sense to me to consolidate this information in one place, since it really is the motor itself we are talking about in this thread.

Is it not also possible that there is some other fault with the machine? Then it would not be a motor issue, and it is not related to the model in the original post.

I will, however, take my conversation elsewhere if it is not welcome here. Thanks.

If you can't take constructive criticism, then yes, it would be best you go elsewhere. People are trying to help you here. The forum's most outstanding contributor (who is also a moderator) made a suggestion to you that had no bad intentions. But you, the new guy, want to say how the forum should run.
Try that at forums "elsewhere" and see how it works out for ya.

[Enzo]

Hey dustartist, the very first thing I said was "welcome", there was no hostile intent.

[tomachi]

My unit would only get +/- minor third faster an increase of 18.9% as a percent, so maybe not much change.