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Old 12-05-2018, 05:07 AM   #1
roadrash
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Default What kind of diode is this?

I have a diode to replace on a computer disk drive. I had just removed the pcb to allpw access to clean out the masses of dust build up and general cleaning and read errors.
When i put the pcb back in and powered it up I got a feint burning smell and pulled the power. After removing it again I noticed one of the wires (red) on the power connector had come out (badly crimped) and I dont know what happened but it was the only thing I could see that could have caused this (maybe it touched something).
Anyway I could only see signs of a track getting hot and a diode discoloured. It connets to CN4 power input 12v or 5v.
I dont know if any other damage is done but I must replace this diode now but I am not sure what type this is. It looks like a zener but knowing how many there like a avalanche etc can someone tell me please? and any advice would be welcome.
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Last edited by roadrash; 12-05-2018 at 05:24 AM..
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Old 12-05-2018, 08:56 AM   #2
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Default Re: What kind of diode is this?

is it commodore??
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Old 12-06-2018, 05:08 PM   #3
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Default Re: What kind of diode is this?

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Originally Posted by stj View Post
is it commodore??
No its actually a sony single sided 3.5" drive out of a vintage Apricot.
These look a bit differnt to most other zener diodes so I better check. I cant see any identification markings.
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Old 12-06-2018, 05:57 PM   #4
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Default Re: What kind of diode is this?

Don't you have the apricot service manual?
The one I have shows a slightly different drive

Last edited by R_J; 12-06-2018 at 06:39 PM..
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Old 12-06-2018, 06:23 PM   #5
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Default Re: What kind of diode is this?

if one side of it goes to ground it is most likely a zener .
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Old 12-06-2018, 08:09 PM   #6
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Default Re: What kind of diode is this?

You'd have to trace each end of it, where it goes. SN75492 or connector.
The PCB traces are thicker than the nearby small-signal diodes.
I would guess a zener diode probably to lower 12V to less

A model number would help.
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Old 12-07-2018, 05:31 PM   #7
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Default Re: What kind of diode is this?

Thanks for the help the model number is OA-D31V-94
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Old 12-07-2018, 05:53 PM   #8
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Default Re: What kind of diode is this?

something must have changed here, I can't upload the manual https://elektrotanya.com/sony_oa-d32.../download.html

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Old 12-07-2018, 06:10 PM   #9
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Default Re: What kind of diode is this?

I think i got a manual for it actually thanks. Do you think damage went further than that diode?
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Old 12-07-2018, 06:22 PM   #10
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Default Re: What kind of diode is this?

not enough info to tell. what does the red wire do, you said it supplies +5 or +12v? what did it touch when it came out? where is the diode in the circuit?
None of the board layouts or location numbers in the manuals seem to match your drive, so you need to trace what the diode is connected to.

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Old 12-08-2018, 08:18 AM   #11
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Default Re: What kind of diode is this?

Thanks for helping again RJ I am having a lot of crazy hicups here. This was a surprise to me. I had stripped both drives to clean them out. It seemed impossible for anything to go wrong as all connectors were different and all wires were held in clips away from anything else. So a short or getting connections wrong was impossible. I sripped and cheked everthing again but found bothing wrong except when i went to check the ribbon cable i noticed the red power cable was adrift from its plug and the crimp on connector still inside the plug. It was a complete fluke. I have 4 of these drives (2 as spares) from another computer that maybe beyond repair. But I hate scrapping something as rare as these drives are if they can be fixed. Obe side of that diode goes to a black wire on the power connector which is most likely ground -.
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Old 12-08-2018, 09:50 AM   #12
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Default Re: What kind of diode is this?

Looks to me like D2 anode goes to the red wire, pin1 on J2 plug (5volts). You said it goes to CN4, Where does CN4 go? D2 could just be a regular glass diode and not a zener. Maybe a 1S2348 or 1S1555

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Old 12-08-2018, 10:17 AM   #13
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Default Re: What kind of diode is this?

Quote:
Originally Posted by roadrash View Post
I sripped and cheked everthing again but found bothing wrong except when i went to check the ribbon cable i noticed the red power cable was adrift from its plug and the crimp on connector still inside the plug.
You should be able to repair this
You need to find out how to remove the pin out without damaging the pins or the housing

Once you have the pin out of the housing you can try open the crimp where the wire is and re-crimp the wire or put a new wire in it place and reinsert the pin in the housing

Or solder the wire to the pin DO NOT be tempted to solder the wire to the pin while in the housing you will melt the housing I know because I have tried to do this way before

It can be done because I have had to do this a few times before
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Old 12-08-2018, 03:25 PM   #14
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Default Re: What kind of diode is this?

Quote:
Originally Posted by R_J View Post
Looks to me like D2 anode goes to the red wire, pin1 on J2 plug (5volts). You said it goes to CN4, Where does CN4 go? D2 could just be a regular glass diode and not a zener. Maybe a 1S2348 or 1S1555
Here are 2 puctures of the pcb both sides to make it easier

Sam_sam_sam ive repaired the connector and soldered the wires to the pins (not crimped).
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Old 12-08-2018, 03:37 PM   #15
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Default Re: What kind of diode is this?

Is CN5 connected to the stepping motor? if it is the diode could be a D107 1S2348H as seen on page 69 of the manual
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Old 12-08-2018, 04:27 PM   #16
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Default Re: What kind of diode is this?

The drive looks like a Sony OA-D30V circa 1981, the original 3.5" drive. Used on Apple and Apricots. You have to manually slide the metal disk guard over before plopping the disk in.

I cannot find a service manual or schematic for it, to see what D2 does.

Sony OA-D30V OEM Manual


I notice the FD-3 PCB silkscreen shows a zener symbol for zeners like D1, D10 but D2 is an ordinary diode symbol. One end connects to CN5-2 and CN5 seems to be internal connecting to 12V head stepper motor.

On the OA-D32W schematic, assuming a similar circuit, it would be D107 (1S2348H 65V 0.75A high-speed switching diode) on CN105, so the diode there goes between +12V_switched and +5V.

To smoke this diode... CN5 pin 1 or 2 shorted to GND, stepper motor cable pinched?
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Old 12-08-2018, 06:30 PM   #17
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Default Re: What kind of diode is this?

Quote:
Originally Posted by redwire View Post
The drive looks like a Sony OA-D30V circa 1981, the original 3.5" drive. Used on Apple and Apricots. You have to manually slide the metal disk guard over before plopping the disk in.

I cannot find a service manual or schematic for it, to see what D2 does.

Sony OA-D30V OEM Manual


I notice the FD-3 PCB silkscreen shows a zener symbol for zeners like D1, D10 but D2 is an ordinary diode symbol. One end connects to CN5-2 and CN5 seems to be internal connecting to 12V head stepper motor.

On the OA-D32W schematic, assuming a similar circuit, it would be D107 (1S2348H 65V 0.75A high-speed switching diode) on CN105, so the diode there goes between +12V_switched and +5V.

To smoke this diode... CN5 pin 1 or 2 shorted to GND, stepper motor cable pinched?
Thanks i will check that although all the wires were routed and secured in a way that shouldnt be possible but recently ive seen many impossibilities happen.
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Old 12-09-2018, 05:46 AM   #18
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Default Re: What kind of diode is this?

Quote:
Originally Posted by R_J View Post
Is CN5 connected to the stepping motor? if it is the diode could be a D107 1S2348H as seen on page 69 of the manual
I found the diode and ive ordered some. I stll cant understand how it got pinched. Look at pictures and you will see what mean. The connector is keyed so its nit like it could have been one pin out of line. Another mystery.
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Old 12-09-2018, 06:14 AM   #19
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Default Re: What kind of diode is this?

Maybe someone pressed CN5 too hard and physically broke the glass of the diode. Upon powerup, it shorted and burned ?
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Old 12-13-2018, 01:29 PM   #20
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Default Re: What kind of diode is this?

Quote:
Originally Posted by R_J View Post
Is CN5 connected to the stepping motor? if it is the diode could be a D107 1S2348H as seen on page 69 of the manual
I am still waiting on some of those diodes coming but I noticed another problem with tthese disk drives that I will need to ask your advice about. I have 4 drives in total and when i restored this vintage computer originaly I could only get one car drive to read and boot a disk. Since Ive had the drives apart ive noticed that when the computer boots up and moves the heads to read the disk it also switches the power on to the drives motor (one that spins the disk) but some are not moving. One of them is but only if I give it a nuge to get it moving and it will keep spinning until I remove the power. These are brushless motors and if they are little a/c motors, dont htey need a capacitor to start them spinning? )lioke a a/c induntion motor).
There are some really tiny caps on the circuit board near the motor but not sure if maybe I need to replace them and where I would even start to look for capacitors that small. Whayt do you think? here is a picture.
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