Purpose of PEB 12V 2 Amp Power Upgrade?

[kl99]

Hi!

 

I am wondering on the purpose of the PEB 12V 2 Amp Power Upgrade which is described on the mainbyte website:

http://www.mainbyte.com/ti99/peb_pow/peb_pow.html

 

Is this mod always required if you want to use 2 half-height disk drives within the PEB?

 

I am planning to use 2 half height disk drives and will apply the 12V FAN mod as well.

 

Sorry, if its clear to everyone else...

[+Lee Stewart]

Hi!

 

I am wondering on the purpose of the PEB 12V 2 Amp Power Upgrade which is described on the mainbyte website:

http://www.mainbyte.com/ti99/peb_pow/peb_pow.html

 

Is this mod always required if you want to use 2 half-height disk drives within the PEB?

 

I am planning to use 2 half height disk drives and will apply the 12V FAN mod as well.

 

Sorry, if its clear to everyone else...

 

I have 2 half-height drives in 2 PEBs and have not had any problems related to the power supply.

 

...lee

[+Ksarul]

Some of the older half-height drives had a pretty high current draw on the 12V line--and would not work well if you had more than one of them in the PEB. Qumetrak 142 drives were notorious power hogs, IIRC. . .

 

The TEAC drives were never a problem, and I'm pretty sure the Epson drives were always OK too. I've never done the 12V mod to any of my PEBs--and all of them have dual drives (TEAC for the most part).

[kl99]

wonderful thx, my disk drives are mitsubishi. i will simply try it without modification. thx again.

[+Ksarul]

The Mitsubishi drives are another of the low-power types. They should work fine. . .

[Omega-TI]

I've been toying with the idea of doing this modification myself down the line. Since the box is 32+ years old, I'm eventually going to have to change out all of the capacitors, so while I'm at it, this modification can be helpful, as my box is getting fairly well populated and because once the machine is open I plan to:

 

1) Install a USB 5v power connector.

2) Use the old fan leads to install a 120v outlet for a low power adapter (my Lantronix UDS-10) so it'll come on whenever I turn on the P-Box.

[am1933]

Similar to Lee's answer above-I have two half height drives in a stock PEB and have never had any problems.

[gregallenwarner]

I too have two half-height drives in a stock PEB with no power supply modification. My philosophy is this: Only one drive is ever active at a time. There's never a time when both drives are spinning their motors simultaneously. There is no need for the additional power capacity.

[Stuart]

But as the MOTOR ON signal on the floppy interface is common to all the drives, don't all the drives spin even though only one is actually selected?

[Omega-TI]

.. don't all the drives spin even though only one is actually selected?

 

I always thought so, now I'll have to check!

[+OLD CS1]

IIRC, _MOTORON line is shared but the _DS# (drive select) lines are what activate the drives.

 

EDIT:

 

Floppy Diskdrive pinout diagram @ pinouts.ru
"The original Shugart interface (from which the IBM PC floppy interface is derived a long time ago) doesnt have separate motor on signals for the floppy drives but it does have a total of four device select lines. I have also seen floppy drives that wont turn on their motors unless the according device select signal is driven low. My guess is that this kind of drives strictly follow the original Shugart standard."

[+Schmitzi]

 

Hi, in one of my PEBs I have two Shugart SA455 HalfHight, no Problems

 

 

 

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