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I am trying to teach myself how to repair ham radio equipment. I have a blown power supply I am trying to repair.

I need to know the capacitance of this part:

enter image description here

It is from an Icom IC-PS15 power supply. Two of the four capacitors have blown. I want to replace all four and the rectifier.

JRE
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Andy Varney
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    Google for "103z capacitor", or see [Ceramic capacitors: how to read 3-digit plus 1-letter markings?](https://electronics.stackexchange.com/questions/16636/ceramic-capacitors-how-to-read-3-digit-plus-1-letter-markings) – Andrew Morton Sep 21 '21 at 10:53
  • Oh wow this is quite confusing to me. I am only a novice and trying to self teach myself more about electronics. I dont understand schematics propperly yet either. Thank you for your input i really appreciate it . – Andy Varney Sep 21 '21 at 11:20
  • Just a note that such high voltage capacitors inside power supply may have a special safey rating, so depending on what the capacitor does in the power supply. If a safety capacitor is needed, it is dangerous to both humans and other devices if a safety cap is replaced with an unsafe capacitor. – Justme Sep 21 '21 at 12:11

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As RedGrittyBrick says, that is a 10000 picofarad capacitor. That's from the "103Z" marking. "10" picofarads with "3" zeroes = 10pF*1000= 10000pF= 10 nanofarads. "Z" is the tolerance. It means "+80% to -20%." The tolerance is rather wide. A more typical value would be "J" for "+-5%."

See here for a complete description of all ceramic disk capacitor markings.

You also need to pay attention to the line below the value. It says "1kV." That means you need a part that is rated to withstand 1000 volts.

You need a replacement part that meets the value, the tolerance, and the voltage specifications of the original.

I've had a look at the schematic for the Icom IC-PS15 power supply.

enter image description here

Those four 10nF capacitors around the bridge rectifier should never be exposed to enough voltage to destroy them. Something really bad happened to that power supply. You should be prepared to replace nearly all components in it. Whatever killed the rectifier and those capacitors could have killed numerous other parts as well.

JRE
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  • This answer is useful, im touching buttons by mistake here on my phone. I do appologise. Oh dear it sounds like i might have a big expensive task on my hands then to be honest. Probbably a project to take on a bit later maybe ? I enjoy a challenge though so i wont bin it, i might need a bit more knowledge and experience before i do tackle this 1. I still really appreciate every bodys input on this .. so many thanks to you all. 1 day i hope to get it repaired . – Andy Varney Sep 21 '21 at 12:21
  • @AndyVarney another idea: see if the output transistors are good, and if so, remove the board and build your own regulator in the case. You get a nice big transformer (probably fine), a bridge rectifier (*might* be fine), led, output and input connectors and maybe even high-power transistors for free. C5 (main smoothing cap) is almost certainly blown too, though – 2e0byo Sep 21 '21 at 12:32
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103 suggests 10,000 pF.

Maybe there's an undamaged one with same markings that you can disconnect and measure.

RedGrittyBrick
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  • Hi. Im very new to the game of electronics. This one pictured is undamaged, there a 2 that are burnt out and unreadable . How do i measure this please ? Many thanks – Andy Varney Sep 21 '21 at 11:23
  • @AndyVarney: Many multimeters will measure capacitance. You can also make a capacitance meter from a [kit](https://proto-pic.co.uk/product/sparkfun-kit-09485-capacitance-meter-diy-kit/) or you can maybe use it in a breadboard circuit and measure the charge time (tricky with low values). – RedGrittyBrick Sep 21 '21 at 11:29
  • I do have a multimetre, thank you i will see if i can read it properly. I may have a go at a kit at a later date. Thanks – Andy Varney Sep 21 '21 at 12:10
  • I wouldn’t worry too much about measuring those caps. Just replace them if there is any doubt. They are cheap and besides, C3,4,20,21 aren’t needed for the operation of the power supply - they are there to stop some noise. Nevertheless, replace them. The power supply is a good place to start learning- it is a simple circuit with cheap components. – Kartman Sep 21 '21 at 12:26
  • hi. yes i will just replace all 4 caps and the rectifier ,even though i am not sure if that has been damaged or not . – Andy Varney Sep 22 '21 at 13:02
  • are these caps polarised or non polarised , i have not found this out yet, i have noticed that 1 of the caps is fitted in reverse to the other 3 – Andy Varney Sep 22 '21 at 13:04
  • @AndyVarney: These are non-polarised. – RedGrittyBrick Sep 22 '21 at 15:24
  • @RedGrittyBrick .. thank you that clarifies that one :) – Andy Varney Sep 27 '21 at 18:51