any DIY'ers out there?

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gnarly_d

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Has anyone ever tried to do this? :

I've got an old Tascam Porta One (c. 1985?) -- still in good working order, and still as useful as ever. The thing is, unlike almost every subsequent cassette 4-track, the Porta One cannot record and playback at double speed (3-3/4 inches per second) -- just at the normal sluggish pace of 1-7/8 ips. My question is: how difficult would it be to mod this thing to include the higher speed? Has anyone ever heard of this being done? I know, I know, you're probably all saying, "is this guy nuts?!?!? Just get a VS880", but I have some special plans for this unit... (ask if you're interested).
 
I've never done it on a tascam but I have done it on some other machines. There may be a pot or variable resistor on the pc board that regulates the voltage going to the transport motor. Most of the time, the pot variance isn't a whole lot. Get a copy of the service manual to find out. You may even be able to solder on a variable resistor depending the board design.
 
gnarly_d said:
Has anyone ever tried to do this? :

I've got an old Tascam Porta One (c. 1985?) -- still in good working order, and still as useful as ever. The thing is, unlike almost every subsequent cassette 4-track, the Porta One cannot record and playback at double speed (3-3/4 inches per second) -- just at the normal sluggish pace of 1-7/8 ips. My question is: how difficult would it be to mod this thing to include the higher speed? Has anyone ever heard of this being done? I know, I know, you're probably all saying, "is this guy nuts?!?!? Just get a VS880", but I have some special plans for this unit... (ask if you're interested).
Click to expand...

cassette based recorders typically have a trimpot that electronically controls the speed, as well as a mechanical method whereby there is a motor with a certain size pulley, a belt, and another really heavy pulley (flywheel) connected through the mechanism, where a rubber roller pinches the tape against this shaft.

If you followed any of that, you can engineer your higher speed. Its a matter of making the motor go faster, and/or changing the ratio between the two pulleys that the drive belt runs on. You might be able to find similarly sized motor that spins faster.

One one recorder (not a 4-track), I took out the large flywheel/pulley and put it on my lathe, and turned down a channel where the belt goes. This way the pulley was still large and somewhat heavy (though I removed a lot of material), and used a shorter belt on the new smaller diameter "inside".

It spun faster :)

However, if you remove too much mass off the flywheel, you get more wow/flutter in your recordings.

Hope my ramblings help in some way.
 
I know there's an internal speed adjustment on the PortaOne,

but as the previous members said, you don't get a huge range of adjustment. You may use this adjustment to boost tape speed above 1-7/8"ps, but it may not reach double speed.

There's probably a paragraph in the service manual on adjusting speed on the PortaOne, and since I have the manual, I'll dig out the manual and look into "speed adjustment", sometime later, when I get a chance.
 
Re: I know there's an internal speed adjustment on the PortaOne,

A Reel Person said:
but as the previous members said, you don't get a huge range of adjustment. You may use this adjustment to boost tape speed above 1-7/8"ps, but it may not reach double speed.

There's probably a paragraph in the service manual on adjusting speed on the PortaOne, and since I have the manual, I'll dig out the manual and look into "speed adjustment", sometime later, when I get a chance.
Click to expand...

Another less hassle free method of increasing the speed of a portastudio is to buy a used one that operations the way you want. Just a thought, hope no one minds...
 
mission accomplished

well that was easy. The pitch control pot was only about 2K or so (not much range), and with a meter I discovered that increased resistance increased the speed. So I put a 15K resistor in series with it.... tada, the speed is nearly doubled! The only thing I'm worried about now is damaging my tapes with the Saturn-5-rocket rewind and fast-forward speeds this thing achieves now... but so far so good.

and please, give me a break, frederic. I'm a student... 'nuff said?
 
Nice! Just be aware that tape freq. response will change with the increased speed. Get an AES set up tape run the tones and adjust the freq. pots. I'm not sure if the Tascam has them hard set or serviceable.

Oh, I also forgot... you may need to watch the heat generated by the increased resistence. Components down stream of your new resistor might burn out with the increased juice.
 
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