30 December 2014, 17:30 | #1 |
Registered User
Join Date: Sep 2009
Location: Norway
Posts: 1,711
|
To all people recapping Amigas
There's no need to use non-polarised capacitors for the audio output part, because the audio is never swinging between negative/positive before it enters the caps. In fact, it's always positive. The caps themselves do the 'DC centering' so that the output swings between negative and positive. Remove the caps and hook up an oscilloscope and you will be amazed. I've ran normal 22µF 25v tantalums in the audio part of my Amigas for a long time.
Another thing: Do not use cheramic caps in the audio circuitry. Cheramic caps can pick up vibrations, kind of like a mic, thus they are unwanted for audio applications. You'd not want to couple unwanted things into your audio, do you? Electrolytics or tantalums are perfect. So unless someone proves me elsewise, I can prove them this: The "Commodore did a capacitor mistake" talk is wrong. |
30 December 2014, 17:39 | #2 |
Registered User
Join Date: Mar 2013
Location: Lahti / Finland
Age: 52
Posts: 449
|
Old thread: http://eab.abime.net/showthread.php?t=67240
|
30 December 2014, 17:42 | #3 | |
Registered User
Join Date: Sep 2009
Location: Norway
Posts: 1,711
|
Quote:
|
|
30 December 2014, 21:10 | #4 |
Registered User
Join Date: Sep 2006
Location: Thunder Bay, Canada
Posts: 4,323
|
what is the minimum voltage rated tantalum that needs to be used, 10v, 16v ?. would it ever peak at 25v?
Also, is +ve towards the Amp ? |
01 January 2015, 12:06 | #5 |
A1260T/PPC/BV/SCSI/NET
Join Date: Jan 2013
Location: Moscow / Russia
Posts: 840
|
Just wondering, when should someone recap the board ?
Is there any signs that show that time has come? Should a perfectly working board be recapped just in case? Could a failed cap break something more important and difficult to replace? |
01 January 2015, 12:39 | #6 |
-
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 43
Posts: 9,865
|
If the caps have leaked, it's time to recap the board.
The biggest reason to do it is that the electrolyte in the caps corrodes the traces and vias, which will lead to the eventual destruction of the motherboard. Corroded traces and vias are consuming and tedious to repair. Many but not all surface mount Amigas will see the caps leak. It's everyone's personal choice whether to do it pre-emptively or not. Some meaningless statistics: I have four A1200 boards here with original caps, none have leaked. Two A4000s with caps that have leaked. Three A600s with leaked caps. |
01 January 2015, 15:43 | #7 |
A1260T/PPC/BV/SCSI/NET
Join Date: Jan 2013
Location: Moscow / Russia
Posts: 840
|
I guess I better keep my main A1200 board as is for now.
Only when things really fail (visually leaking caps) or something else starts to behave abnormally. One thing bothers me however. I wonder if it is related to the two caps near the keyboard connector. I have a piggy back board on top of the chip that drives a PS2 keyboard and recently I have got a problem with the keyboard swallowing first 5 keys pressed after soft reboot. It works fine otherwise, and on power on it works immediately too. Any familiar syndromes ? |
01 January 2015, 19:22 | #8 |
Registered User
Join Date: Oct 2012
Location: Krypton
Posts: 1,214
|
In all honesty anyone with a Amiga needs to recap them regardless of caps leaking or not and its better to replace them when they have not leaked because the electrolyte will not have done any damage to the pads on the board, like I keep saying please replace your caps and use Tantalum capacitors and the worry of leaking will be a thing of the past
The A600s and CD32 seem to be the worst for this problem so don't hang around just get these boards recapped ! And regarding the non polar caps I now replace those with a couple of non polar ceramic caps and you can definitely hear a difference using these as opposed to polarized ones |
02 January 2015, 00:18 | #9 |
Registered User
Join Date: Jan 2008
Location: United Kingdom
Age: 46
Posts: 733
|
@kipper2k
A 10V or 16V part will be ample, the audio output is only 2V peak to peak. +Ve to the amplifier output. @thread. Scope trace of Amiga audio output attached. Take a look at this: http://conradhoffman.com/capchecktut.htm The pro-audio guys have more experience than us over many decades. I've replaced 2 audio caps in my A600, The two incorrectly fitted ones in a CD32 and had one A500 fail for TBC reasons, the reset circuit among them. The main reason for the A600 was lack of use. Electrolytics need reforming charges if not used. I'm an electronic engineer, one of my guiding rules is "If it ain't broke, don't fix it", the other is that Murphy's law prevails above Ohm's and Kirchoff's laws |
12 January 2015, 04:43 | #10 | |
Posts: n/a
|
Quote:
The caps in the audio section had leaked, so it was high time that they got replaced. The others around the board looked good, but it's hard to stop once I've got my hot air gun warmed up. |
|
13 January 2015, 02:58 | #11 |
Da Digger :)
Join Date: Nov 2008
Location: Monza, Italy
Posts: 2,822
|
|
13 January 2015, 06:25 | #12 |
Registered User
Join Date: Oct 2012
Location: Krypton
Posts: 1,214
|
|
14 January 2015, 16:45 | #13 |
Registered User
Join Date: Jun 2013
Location: Australia
Posts: 685
|
It appears none ever bothers with the electrolytic in the Amiga’s linear power supply
which are the ones that live the hardest life of the lot of them. If they go near short it will heat up/fry the transformer, if they deform, you’ll get hum through the rest of the computer and wonder why it has issues when you thought you installed new capacitors. |
14 January 2015, 19:46 | #14 | |
Computer Nerd
Join Date: Sep 2007
Location: Rotterdam/Netherlands
Age: 47
Posts: 3,770
|
Quote:
|
|
14 January 2015, 22:10 | #15 |
PSPUAE DEV
|
|
15 January 2015, 00:21 | #16 |
Computer Nerd
Join Date: Sep 2007
Location: Rotterdam/Netherlands
Age: 47
Posts: 3,770
|
|
15 January 2015, 08:11 | #17 |
-
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 43
Posts: 9,865
|
You can only guess, not know. :-)
|
16 January 2015, 00:43 | #18 |
Registered User
Join Date: Jan 2008
Location: United Kingdom
Age: 46
Posts: 733
|
@Thorham
Given enough time and the correct environment, any single component in a system will fail. The probability of it happening depends on numerous factors. With any complex PCB, you need to weigh up the risks of damage during re-work, especially if the person doing it is not experienced enough. Hence, the term, if it ain't broke, don't fix it. If you use your Amiga at least every 2 years for a few hours, and keep the operating environment below 50C, the capacitors and the rest of the Amiga should easily last 40 years. Ian |
21 January 2015, 11:58 | #19 |
Registered User
Join Date: Mar 2013
Location: Lahti / Finland
Age: 52
Posts: 449
|
I know that ceramic capacitors are not recommended, especially in the audio use.
How bad is it? Is there any difference on ceramic capacitors with the audio? |
21 January 2015, 13:05 | #20 | |
Unregistered User
Join Date: Sep 2012
Location: Copenhagen / DK
Age: 43
Posts: 4,190
|
Quote:
So go ahead and use ceramics or electrolytic caps, whatever you have available. |
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Recapping A500 + Light Brick PSU | marty | support.Hardware | 10 | 10 January 2017 06:34 |
A600/1200 psu recapping ! | dlfrsilver | support.Hardware | 8 | 18 November 2014 02:18 |
Recapping Services? | themamboman | support.Hardware | 1 | 13 January 2014 21:16 |
Poorly A600. Recapping in order? | ElectroBlaster | support.Hardware | 3 | 24 September 2013 11:39 |
Do people still buy amigas? | amiga_Forever | Amiga scene | 50 | 25 October 2012 23:33 |
|
|