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Old 9th August 2011, 08:41 AM   #1
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Question PCB component codes..

Hi I am stripping and refitting my QED P300 as my first big project, just a quick question.. I relaise that the codes on the boards are the same as resistor parts names would this be true for the other parts ?
Example of my board / is there a universal code for the components? Does anyone have a website with them all on ? i.e R39 is a ...?

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Old 9th August 2011, 02:31 PM   #2
DF96 is online now DF96  England
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You need to find a circuit diagram. R39 is the component name for a particular resistor in that circuit. The circuit diagram will give the resistor value, which is also given by the coloured bands on the component.
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Old 9th August 2011, 11:07 PM   #3
Minion is offline Minion  Canada
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The resistors them selves use a color band code , those stripes indicate the Resistance value and tolerance , going through all of the codes can be time consuming and tedius , use a digital multimeter to measure the resistors resistance but you usually have to lift one of the resistors legs from the curcuit board and measure it to get a accurate reading ....

You wouldn"t generally replace resistors unless they are of inferrior quality or visably burned out or broken , they look like fair quality metal film resistors ......

On circuit boards they use letters and numbesr to show what type of component it is and its number in relation to the schematic .....

R -Resistor
C-Capacitor
Q-Transistor (sometimes T)
D-Diode
L-Inductor/Choke
T-Transformer (sometimes Transistor)

Then there are Varuous codes used for parts that don"t conform to the above codes and these codes don"t allways follow any particular convention .....

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Last edited by Minion; 9th August 2011 at 11:10 PM.
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Old 10th August 2011, 09:36 AM   #4
marce is offline marce  United Kingdom
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http://en.wikipedia.org/wiki/Electronic_symbol
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Old 10th August 2011, 10:03 AM   #5
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I agree with Minion - virtually all resistors and a lot of silicon can be kept as is. I recommend archiving as much component ID info as one finds for future reference. Unless memorizing things like the E48 resistor series is appealing to you. I also agree with DF96 - you'd do well to get a schematic. It's safe to assume "A" is test point A, but the more unconventional markings of Ta and Tb. for the middle TO92s are a mystery to me.
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Old 10th August 2011, 10:07 AM   #6
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http://itunes.apple.com/us/app/ohm-s...0510?ls=1&mt=8

Ohm Sense - The only app that lets you take a picture of a four band, beige resistor and have it tell you its resistance value with accuracy!
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Old 10th August 2011, 10:40 AM   #7
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I think I will use one of the free schematic programs to document the parts and create the layout, if what you say is correct, then one “R38” for example should be the same as all the others on the board. After reading several post it may be pointless replacing all the components in one go , but better to start by swapping a few and then test them for improvements in quality. I’m quite lucky as the QED has an inspection plate on the bottom of the case, so I don’t have to strip it to the board every time I want to replace a part.
My first part of the project will be to find out why it makes my TDL RTL2’s buzz continuously , once I have sorted that out I can then get recommendations for replacing components.
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Old 10th August 2011, 10:46 AM   #8
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As said before, there is almost no reason to replace those resistors unless they are brown from overheating.

Some transistors may have to be matched in sets...

Buzzing tends to be related to grounding problems.
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Old 10th August 2011, 10:48 AM   #9
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Quote:
if what you say is correct, then one “R38” for example should be the same as all the others on the board.
Not sure what this refers to, but there should be only one "R38" on the board. It may have a twin in the circuitry for the other channel, but that's about it.
If the buzz is in both channels, it may be a power supply issue. If it is in one channel only, you can use measurements from the good channel to compare with the bad.
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Old 10th August 2011, 11:02 AM   #10
AndrewT is offline AndrewT  Scotland
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Don't strip your PCB in the hope of solving a Hum Buzz problem.

The Hum Buzz fault is almost certainly in the interconnecting wiring.
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