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Electronics => Beginners => Topic started by: Nonmi9 on May 16, 2020, 02:22:42 am

Title: Identifying parts for a Compaq Portable 1
Post by: Nonmi9 on May 16, 2020, 02:22:42 am
I've been stumped trying to find the part in the attached picture (best shot I can get without a macro). I think it's a tantalum capacitor, its labeled as 10-15 M(2). All others have a three digit code that I've been able to find and replace.

Thanks in advance.

[attachimg=1]
Title: Re: Identifying parts for a Compaq Portable 1
Post by: amyk on May 16, 2020, 03:15:49 am
10V 15uF or 10uF 15V. What's the voltage of the power rail it's on?
Title: Re: Identifying parts for a Compaq Portable 1
Post by: Nonmi9 on May 16, 2020, 08:19:57 pm
It's on a ISA slot, so ether 5v or 12v. I don't know which one is uses.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: amyk on May 16, 2020, 09:15:44 pm
If it's a 5V rail, then 15uF 10V makes sense; if it's a 12V rail, 10uF 15V.

You'll need to trace it with a DMM.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: tkamiya on May 17, 2020, 12:43:25 am
It's obviously a tantalum capacitor.  Depending on what it is connected to, the exact value might not matter, especially if it's just a decoupling capacitor for voltage supply.  How about if you check to see if they are on voltage supply rail and put 10uF 25V there?  Today's equivalent device is much smaller than back then.  It should fit physically in available space.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: james_s on May 17, 2020, 01:17:48 am
I seriously doubt the value makes any difference, anything from 4.7 to 100uF would likely work fine, in fact for testing purposes the computer will probably work fine with the capacitor completely removed. There is typically a significant amount of redundancy with decoupling capacitors.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: I wanted a rude username on May 17, 2020, 05:40:23 am
Your mileage may vary, but all the tantalum capacitors I've seen have had the capacitance listed first, no matter how it was formatted.

As already mentioned, the exact capacitance is not so important ... whereas I would over-rate the voltage significantly (10 uF, 25 V as suggested), because there was a time when designers weren't as wary of tantalums' problems as we are today.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: Nonmi9 on May 17, 2020, 03:52:13 pm
i've replaced it with a 10uF, 25V, it now won't boot unless the card is removed. I'll have to go though it and trying any others that have shorted. Thank you guys for your help!
Title: Re: Identifying parts for a Compaq Portable 1
Post by: TimFox on May 17, 2020, 07:25:56 pm
Is it possible that the new capacitor was installed backwards (reverse polarity)?  Such tantalum capacitors are polarized.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: Nonmi9 on May 18, 2020, 12:40:12 pm
I checked, I've got the polarity matched up.
Title: Re: Identifying parts for a Compaq Portable 1
Post by: james_s on May 18, 2020, 08:52:33 pm
What was the symptom before? You said now it won't boot unless the card is removed, was it booting previously?