CPCWiki forum

General Category => Amstrad CPC hardware => Topic started by: cpcbaio on 12:30, 19 February 13

Title: (Solved) My floppy drive not work
Post by: cpcbaio on 12:30, 19 February 13
Hi, I have a CPC 6128 and the drive is not working or emit any noise.he measured voltages and the white connection is 5v but not is 12 V, the red wire is fine soldier.
In the main board of CPC is 12 v fine.
can someone tell me where I need to check the 12v they have to get to the drive?.
Thank you very much.
Title: Re: My floppy drive not work
Post by: Bryce on 12:41, 19 February 13
Hi cpcbaio,
      welcome to the forum. I'm not sure where the white wire is that you are talking about, but this is what you should have on the 4 way connector to the drive:

Red wire = 12V
Black wires = GND
Yellow wire = 5V (Orange on some versions)

Bryce.

Edit: Oops, sorry, had them the wrong way around :(
Title: Re: My floppy drive not work
Post by: cpcbaio on 12:49, 19 February 13
Hello, I refer to the connector white that is conected to the floppy drive.
My conector have this four wires:
Orange: 5V
Black wires: GND
RED: 0,7 v I think this wire should be 12V, or not?.

Thank you.
Title: Re: My floppy drive not work
Post by: Bryce on 12:58, 19 February 13
Yes,  the red wire should have 12V, the connection is more or less a direct connection to the 12V input, there are no components between the input and the red wire. Have you checked the connection from the 12V input (white connector beside 5V input socket) to the red wire. You should get zero ohms between these two points (see picture below).

Bryce.




Title: Re: My floppy drive not work
Post by: cpcbaio on 13:16, 19 February 13
thank you Bryce, for your help, I measured continuity  with a multimeter in the two points and the multimeter tells me that there is no
 ::)

but the transistor (A950Y) that is in the picture, near the imput send voltage to  the drive floppy?
Title: Re: My floppy drive not work
Post by: Devilmarkus on 13:43, 19 February 13
I measured continuity  with a multimeter in the two points and the multimeter tells me that there is no
 ::)

Then there is your reply:
If you already measured both points shown in the image above, your source power is missing.
That can be the monitor or the power supply you are using.

If you got little power here, then perhaps a transistor is short circuited. ~1cm near the power plug is a transistor.
You should check it and replace if needed.
Title: Re: My floppy drive not work
Post by: robcfg on 13:46, 19 February 13
I'd check also the 12v cable to the monitor. It happened more than once that the cable was faulty...
Title: Re: My floppy drive not work
Post by: cpcbaio on 13:59, 19 February 13
the monitor sends the 12 v perfectly, I had checked.
Then, Can be the transistor that I said before?, A950Y

Title: Re: My floppy drive not work
Post by: Bryce on 14:27, 19 February 13
I just re-checked the schematics and it looks like the 12V really is switched through a transistor (Q303). But it's in a "Darlington pair" configuration (one transistor turns on another transistor) so either Q302 or Q303 could be broken.

Check the following to find out which transistor is broken:

With the CPC turned on, measure the voltage at on the bottom pin of Q303 (marked with an "E") - It should be 12V - If not, the connection from Monitor has a problem.

Now measure the voltage of the middle pin of Q303 - It should also be about 12V - If not, one of the transistors has died.

Now measure the voltage on the bottom pin of R321. It's probably about 1.5V or less. If it's more, then Q302 is most likely the problem.

Also check whether either of the transistors are getting hot.

Bryce.
Title: Re: My floppy drive not work
Post by: cpcbaio on 17:45, 19 February 13
I check the transistors with a multimeter and this is the results:

pin "Emisor" of Q303 = 11,84 V
middle pin Q303 = 03,9
pin bottom of R321 = 03,4

Q303 seems to be the problem, right?
Title: Re: My floppy drive not work
Post by: Bryce on 18:03, 19 February 13
Yeah, sounds like Q303 isn't switching. The modern part equivalent for this part is called 2SA950 and it shouldn't be too difficult to find (although it's a Japanese transistor).

Here's the part: SA 950 - Transistor 2SA 950, Si-P, 35V,0.8A,0.6W,120MHz bei reichelt elektronik (http://www.reichelt.de/2SA-Transistoren/SA-950/3/index.html?;ACTION=3;LA=2;ARTICLE=15735;GROUPID=2898;artnr=SA+950;SID=11USOiiH8AAAIAACCtx94c47def666a9d8e07ea732f66382bd655)

Unfortunately, the fact that this has died, might mean that there is a short circuit on the 12V part of your drive. I'd measure the resistance across the 12V pins of the drive (while it's disconnected), just to be sure it's ok. Otherwise the new transistor might die immediately too.

Bryce.
Title: Re: My floppy drive not work
Post by: cpcbaio on 18:13, 19 February 13
Hello, How do I measure that?, pins of the connector white?,

Title: Re: My floppy drive not work
Post by: Bryce on 18:25, 19 February 13
Just remove the white 4 pin connector from the Drive and measure the resistance between the pins where the red and black wire are usually connected.

Bryce.
Title: Re: My floppy drive not work
Post by: lynwen on 19:58, 19 February 13
But it's in a "Darlington pair" configuration (one transistor turns on another transistor) so either Q302 or Q303 could be broken.
WOW just had a blast from the past I remember Darlington pairs from my college days
Title: Re: My floppy drive not work
Post by: Bryce on 11:17, 20 February 13
Well to be more exact, the configuration in this case is actually a "Sziklai Pair", because it uses opposing transistors (1x NPN, 1x PNP), but I don't usually go into that kind of detail here, bacause A - you don't need to know that to fix the CPC, B - This is a retro computer forum and not an electronics class :D

Bryce.
Title: Re: My floppy drive not work
Post by: cpcbaio on 16:35, 20 February 13
I ordered transistor in a store.
When I receive it, I will tell you how it work my floppy drive again,
 ;D

Thank you.
Title: Re: My floppy drive not work
Post by: cpcbaio on 00:48, 08 March 13
I had changed transistor for other similar: BC636. And now my floppy drive, works.But new need a new belt.
Thank you very much.  :-*