Amiga 1200 Cap Replacement - Testing Outcome

ilgello

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Hello Guys, just replaced caps on my newly acquired A1200, in addition to using it normally is there anyway to verify that everything is working as intended ?

I have a multimeter but have no clues where to check readings.

Thanks!
 

Bryce

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It's a bit late now, but one test you can do is to put your multimeter on AC and measure the value across the 5V and 12V rail. This is a crude way of measuring the noise portion of the rail. The lower the value, the lower the noise. You could have done a "Before & After" to confirm the repair, but you can always just measure it now to see how low a value you get.

Bryce.
 

ilgello

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It's a bit late now, but one test you can do is to put your multimeter on AC and measure the value across the 5V and 12V rail. This is a crude way of measuring the noise portion of the rail. The lower the value, the lower the noise. You could have done a "Before & After" to confirm the repair, but you can always just measure it now to see how low a value you get.

Bryce.

Thank you Bryce, how am I going to do it ? Just need to read how much I have on 5v and 12v ?
 
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Bryce

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If you measure between GND and 5V on the DC range of your meter you should probably read about 4.8V - 5.1V (lower than 4.75 would a problem). On the AC range the meter is only reading the varying portion of the signal (ie: noise), so you should get a reading less than 200mV. Any higher than that could cause problems. Same on the 12V rail, although the noise tolerance is much higher there.

Bryce.
 

ilgello

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checked voltages from the rgb port, it seems I have 4.5v :(( should I worry ?

Unfortunately my multimeter has only 200v and 500v setting on the AC so I don't think it's sensitive enough ?

- - - Updated - - -

C408 could be the culprit ? PSU is a modded atx unit
 

Bryce

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The RGB port isn't a good place to measure from. Measure directly across one of the electrolytic capacitors if possible. Also. Are you sure that the meter is reading correctly? 200V and 500V sounds like you have one of those €6 meters, maybe you should consider splashing out on something that can measure a bit lower: http://www.ebay.de/itm/Multimeter-V...4x7-2x4-5CM-/351142831799?hash=item51c1be66b7

Bryce.
 

ilgello

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It is a cheap meter indeed :) Seems measuring other stuff quite ok tho.

I will try measuring the capacitor, I'd assume directly below the motherboard?
 

Bryce

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Yes, if you can measure one of the thru-hole capacitors directly below the board this should give you an idea of what steady voltage the Amiga is getting.

Bryce.
 

bebek

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You measure DC voltage so set meter to DC not AC. Also measuring anything with incorrect meter range will give you false, not accurate readings. That is how meters work and you will do nothing about it. Tolerance changes with range of meter.
 

Bryce

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You measure DC voltage so set meter to DC not AC. Also measuring anything with incorrect meter range will give you false, not accurate readings. That is how meters work and you will do nothing about it. Tolerance changes with range of meter.

??? If you want to measure the DC portion of the supply rail then you use the DC setting on the meter and it should be about 5V, but if you want to measure the noise on the supply voltage you need to set the meter to AC, where it will accurately read the AC portion and it should read less than 200mVAC. Of course this is only reading the noise up to the frequency that your meter can read, but most decent meters should be able to read up to a few Khz AC.

Bryce.
 
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keitha

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Can't comment on the technical issues! But re-cap means: Crystal clear graphics, beautiful sounds, and an enjoyable experience; like it was 1993 :D (without the crappy crashes, read/write and guru errors either).

If you still seek the technical stuff? I'd recommend you spend a few hours; going over the umpteen/numerous posts at the EAB website.
 

bebek

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You measure DC voltage so set meter to DC not AC. Also measuring anything with incorrect meter range will give you false, not accurate readings. That is how meters work and you will do nothing about it. Tolerance changes with range of meter.

??? If you want to measure the DC portion of the supply rail then you use the DC setting on the meter and it should be about 5V, but if you want to measure the noise on the supply voltage you need to set the meter to AC, where it will accurately read the AC portion and it should read less than 200mVAC. Of course this is only reading the noise up to the frequency that your meter can read, but most decent meters should be able to read up to a few Khz AC.

Bryce.

Oh, and were in my post you have seen advice on noise measurment? But thank you for a lecture, I would not know otherwise ...
 

Bryce

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Nowhere, but here's a quick recap (no pun intended) of the thread: The original poster asked for advice on how to test whether his cap replacement had been successful. A successful cap replacement can be tested by checking how much ripple and noise is on the rail. I suggested that he measure the AC content on the rails, whereby you told him that measuring DC on an AC setting would be incorrect and give inaccurate readings. My last post was just clarifying why he should use the AC setting. I didn't mean it to sound like a lecture, I just wanted to explain why the AC setting should be used.

I didn't expect that you would learn anything from my post, you seem to know your stuff as far as hardware is concerned, but I was hoping that others might.

Bryce.
 
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