Resistor identification from schematic

Thread Starter

Nigel Surtees

Joined Oct 2, 2020
5
Hi
I have a 1970's cassette deck that i am using to learn about electronics. I have identified a burnt out resistor that i cannot read the specs of as its burnt so badly. I do have a schematic and it reads R1 1/2w 4.7. Is this a 0.5 watt 4.7 ohm resistor? Thanks for help in advance.
resistor.png
 

MrChips

Joined Oct 2, 2009
22,096
Welcome to AAC!

You are spot on.
½W 4.7Ω resistor.

If the resistor is burnt then something else made it happen, possibly the transistor TR1 is bad, short across collector and emitter of the transistor.
Show us more of the circuit schematic.
 

Thread Starter

Nigel Surtees

Joined Oct 2, 2020
5
Welcome to AAC!

You are spot on.
½W 4.7Ω resistor.
Hi
Thanks for the quick reply. I caused the resistor to burn out. A npn transistor was bolted to a metal heat sink. when i fixed it back into place i didn't realise that here was an insulator between it and the heatsink. i missed this out and voila burnt out resistor.
 

MrChips

Joined Oct 2, 2009
22,096
Hi
Thanks for the quick reply. I caused the resistor to burn out. A npn transistor was bolted to a metal heat sink. when i fixed it back into place i didn't realise that here was an insulator between it and the heatsink. i missed this out and voila burnt out resistor.
Live and learn.
Yes, the collector is bonded to the metal case. You can buy variants of the same transistor with insulated case. This saves the hassle of having to insulate the transistor from the heatsink.
 

Thread Starter

Nigel Surtees

Joined Oct 2, 2020
5
Live and learn.
Yes, the collector is bonded to the metal case. You can buy variants of the same transistor with insulated case. This saves the hassle of having to insulate the transistor from the heatsink.
Yes I have replaced the transistor. Are there any suppliers that stock electronic components On the high street or is it online only?
 

Alec_t

Joined Sep 17, 2013
11,744
If you use RS, check the small print of their pricing and packaging. Many of their items are sold in multiples only.
 
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