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Offline klx300rTopic starter

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fuzzy sound on 1200
« on: August 19, 2008, 06:34:28 AM »
a bit worried the last few days as my 1200 started to have a fuzzy/scratch type sound coming out of both speakers  :-?  The sound still works on both left & right speakers but the volume level has dropped a bit i.e have to increase volume level higher now

any ideas :-?
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Offline countzero

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Re: fuzzy sound on 1200
« Reply #1 on: August 19, 2008, 06:48:27 AM »
caps caps caps caps ...

capacitors at the audio filter are dying. replace them ASAP, or embrace a mute miggy. There is a good chance you can lose your beloved miggy for good too.
I believe in mt. Fuji
 

Offline klx300rTopic starter

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Re: fuzzy sound on 1200
« Reply #2 on: August 19, 2008, 06:54:40 AM »
Quote

countzero wrote:
caps caps caps caps ...

capacitors at the audio filter are dying. replace them ASAP, or embrace a mute miggy. There is a good chance you can lose your beloved miggy for good too.


AHHHHH :-o  ok starting to calm down a bit.....whew..soldering iron warming up....where do i get the caps ..my MB is revision 1D4
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Offline Castellen

Re: fuzzy sound on 1200
« Reply #3 on: August 19, 2008, 07:05:49 AM »
I've covered this subject in much detail here.

I can supply the SMD electrolytic capacitors you require, or they can be sourced from many electronic distributors.  i.e. Farnell, Radio Spares, Digi-Key.  Feel free to Email me for pricing/availability.
 

Offline countzero

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Re: fuzzy sound on 1200
« Reply #4 on: August 19, 2008, 07:08:59 AM »
any hobby electronics store ?

make sure you take note which value you desolder from which place. Actually you could also track it down through schematics/pictures later, but it will save you lots of headaches.

When buying replacements, the F value should be the same (22pF for 22pF) but you can buy a replacement with higher V tolerance. for example if a cap is 22pF 10V you can put in a 22pF 16V there without worries.
I believe in mt. Fuji
 

Offline davideo

Re: fuzzy sound on 1200
« Reply #5 on: August 19, 2008, 08:05:48 AM »
Quote

Castellen wrote:
I've covered this subject in much detail here.


I'd like to thank you for that information as that allowed me to bring my 4000D sound back to life a few months ago.

Thanks, Dave G  8-)
 

Offline Castellen

Re: fuzzy sound on 1200
« Reply #6 on: August 19, 2008, 09:00:50 AM »
@davideo
No problem, glad it's been of some use to you :-)


@countzero
Many hobby electronics stores don't stock much in the way of SMD components.  Mainly because most hobby electronics involves leaded components, which are easier to use with veroboard or whatever.


The capacitor voltage rating is good advice.  In the case of the Amiga audio circuit, you can also get away with a higher value of capacitance since all the electrolytics are either used for power supply decoupling, or AC coupling/DC blocking.

For example, the reactance of a 22µF capacitor used for audio coupling at 100Hz, Xc = 1/(2 x pi x f x c) = 72 ohms

If you replace it with a 47µF capacitor:
Xc = 1/(2 x pi x f x c) = 33 ohms

Which results in a lower cutoff frequency, i.e audio bandwidth is increased.

In any case, the circuit performace would be *slightly* better at lower frequencies (not that the Amiga's DAC can really do much better), but larger capacitors have a larger physical size, so you'll eventually start running into mechanical problems.

If capacitors of a smaller capacity are used, the lower cutoff frequency of the circuit will increase (reducing audio bandwidth).  In the case of decoupling, the circuit may suffer excess noise if smaller value capacitors are used.
 

Offline Dwyloc

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Re: fuzzy sound on 1200
« Reply #7 on: August 19, 2008, 09:15:02 AM »
Just to say I have had this problem twice on my A1200 as well and the problem has not caused by bad caps in my case.

The first time the problem was caused by a short as a result of my mediator pressing down on the pins for the clockport addon on my IDE-Fix Express Buffered IDE interface.

This time it looks like it is the result of damage to the power connector on my Mediator A1200 caused by fitting a Radeon 9200PCI at the same time as my Voodoo 3 and my BlizzardPPC.

So I just wanted to say that your sound problem may well be caused by bad caps on the motherboard but its not the only think that can cause bad/weak sound from an A1200 motherboard.

So if you have lots of addon like me if maybe worth making sure that none of them are causing your bad sound problem by making contact were they should not.
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Offline darksun9210

Re: fuzzy sound on 1200
« Reply #8 on: August 19, 2008, 11:27:19 AM »
also make sure that your PSU is giving you proper voltages.
i found that a -12V only supplying -4V led to distorted audio, and flakey hard disk/data corruption. :-(
although, i would go with the caps for initial inspection and problem solving :-)

A500, A600, A1200x3, A2000, A3000, A4000 & a CD32.
and probably just like the rest of you, crates full of related "treasure" for the above XD
 

Offline klx300rTopic starter

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Re: fuzzy sound on 1200
« Reply #9 on: August 19, 2008, 02:37:19 PM »
awesome info..thanks :-D should be able to source caps out from local electronic shop
____________________________________________________________________
c64-dual sids, A1000, A1200-060@50, A4000-CSMKIII
Indivision AGA & Catweasel MK4+= Amazing
! My Master Miggies-Amiga 1000 & AmigaOne X1000 !
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***X1000- I BELIEVE *** :angel:
 

Offline klx300rTopic starter

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Re: fuzzy sound on 1200
« Reply #10 on: August 19, 2008, 02:40:04 PM »
some good info Dwyloc! I have a Blizzard 030@50 and a CF card acting as my main dh0 so its possible theres some interference going on somewhere..will have to investigate....though it seems replacing the caps is probably a good idea anyhow once the case is open yet once again ;-)

@Darksun
checked the power supply and its working ok
 :-)
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Indivision AGA & Catweasel MK4+= Amazing
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Offline Dimlow

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Re: fuzzy sound on 1200
« Reply #11 on: September 02, 2008, 04:23:12 PM »
Did you ever get this fixed ? One of my 1200's is now starting to make noises, like there is a ghost in it.


 

Offline klx300rTopic starter

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Re: fuzzy sound on 1200
« Reply #12 on: September 03, 2008, 03:03:38 PM »
@ Dimlow
yes I solved my problem quite easily as it was some interference from my cf card pressing down on the mb when my desktop case was closed...some electrical tape solved the problem...however, I will also be changing the caps when I get some time even though mine look ok for now as it appears to be an inevitable problem for our miggys
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c64-dual sids, A1000, A1200-060@50, A4000-CSMKIII
Indivision AGA & Catweasel MK4+= Amazing
! My Master Miggies-Amiga 1000 & AmigaOne X1000 !
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***X1000- I BELIEVE *** :angel:
 

Offline klx300rTopic starter

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Re: fuzzy sound on 1200
« Reply #13 on: September 15, 2008, 04:36:06 AM »
ok well I decided to replace those nasty caps before I install my long awaited internal flickerfixer/scandoubler from Jens :-D  questions are:
- polarized or non-polarized?
- best make to get
____________________________________________________________________
c64-dual sids, A1000, A1200-060@50, A4000-CSMKIII
Indivision AGA & Catweasel MK4+= Amazing
! My Master Miggies-Amiga 1000 & AmigaOne X1000 !
--- www.mancave-ramblings.blogspot.ca ---
  -AspireOS.com & Amikit- Amiga for your netbook-
***X1000- I BELIEVE *** :angel:
 

Offline Castellen

Re: fuzzy sound on 1200
« Reply #14 on: September 15, 2008, 07:23:37 AM »
Standard polarised ones are fine.  If you want to know more, read the detail in this thread.

I'd suggest using Panasonic capacitors, or any similar well known brand.  Be wary of buying components from Ebay, there are some parts coming from the Asian market which are of very doubtful quality.  Digi-Key is a good place to source low quantities of these kinds of parts.