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Old 20 November 2020, 00:15   #21
solarmon
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Quote:
Originally Posted by redblade View Post
off topic: Is their a Arduino Floppy Test project? Or Amiga/PC is best?
Amiga Test Kit is the best IMHO.
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Old 20 November 2020, 10:48   #22
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@redblade
I agree with solarmon. It allows also the head alignment of floppy drive. Although not an easy task.

@solarmon
If I do not know the specifics of the original transistor is a serious problem to find the right replacement. There is the risk of burning some other component.
In my case, we know that 5v is the current to the emitter. Could you test with a multimeter in DC mode the current on the other pins? I mean with turned on drive.
What replacement would you suggest exactly? I mean specifics of voltage, ampere etc.
A link would be appreciated (also ebay or other place) from you or some other user that is reading this topic... and I see that there is a great number of people interested in our experiment :-)
Thank you.
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Old 20 November 2020, 12:32   #23
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I'm no electronics engineer, but if I were to try the replacement myself I would search for a "SOT223 PNP transistor" - like this one:

https://docs.rs-online.com/b07c/0900766b812e0bba.pdf

which seems to have the required pinouts.

I wouldn't personally worry about the current draw - this is only driving a small motor.
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Old 21 November 2020, 18:04   #24
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Seems like I was mistaken. It is not an SOT-223 package. That is too big.

The TR9 component is about 4.5mm wide and an SOT-223 package is 6.5mm wide. Well, the one I had purchased is that size.

I need to figure out the correct package type for this TR9 transistor.
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Old 21 November 2020, 18:08   #25
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I think it is an SOT89-3 - that has matching dimensions - 4.5mm (A) x 2.5mm (B):

https://en.wikipedia.org/wiki/Small-outline_transistor

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Old 23 November 2020, 21:10   #26
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You can do a quick test to see if the transistor is good by connecting its base pin to ground through a 330 to 680 ohm resistor. (This would simulate the IC activating the motor). From your diode checks it's either faulty or a Darlington type transistor. Black lead to base should give you about 0.7 volts with red to collector (middle pin and tab) and 0.7 with red to emitter for a normal transistor or double for a Darlington type.

It looks like a BCX51 in SOT-89 package would be a good fit. https://eu.mouser.com/ProductDetail/...SJT0cBeA%3D%3D
Edwin

PS.
If you have some time or motivation to do so, I suggest editing your diagram and post and change the a/b/c labels to e/c/b respectively for the benefit of future generations.

Last edited by wolfchild; 23 November 2020 at 21:17. Reason: Fix link
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Old 15 December 2020, 14:10   #27
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So I ordered some 2SA1213 - Toshiba Silicon PNP Epitaxial Transistor - SOT-89 transistors:

https://www.ebay.co.uk/itm/202190729415

and took the (working) TR9 off one of my Citizen drives.





The replacement 2SA1213 transistor seems to be working as expected and the drive still works in terms of he motor stopping and starting based on the motor signal.
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