Decipher Marshall scem

[Valvehead]

Looking at a Marshall scem for a 8100 model amp.

the resistor i need to replace , r118 , says this on the scem = 0 (ohm symbol) 33 .

color is orange/yellow/ gold , its a 5 watt

which comes up to 3.4 ohms ??

or .3 ohm ?

I dont understand why they just cant have a normal number on there !

[drewl]

Gold and silver are the multiplier in the color code like black is zero, gold moves the decimal point to the left once, silver twice.
So your value is 3.4 ohms.
If it was orange yellow silver it would be .34 ohms.

[Valvehead]

oops--- i meant or/yel/ silver . r118 is burnt , but r96 is the same value....so i can see it has silver as the 3rd band . thanks !

on Mouser's site this would be listed as 350 mOhms ? they dont show a .34

having trouble finding a .34 ohm at 5 watts

edit---- Newark had them

[Jazz P Bass]

Can you post the schematic?

[Valvehead]

http://www.drtube.com/schematics/marshall/pc0689p.pdf

[The Dude]

.34 isn't a standard value. Probably the closest you will get is .33.

[g1]

On the schematic the ohm symbol is used as the decimal place. So it is 0.33 ohm.
The modern standard is to use R rather than the ohm symbol (or K or M or u or n for caps).
R22 would be .22 ohm
1K8 would be 1800 ohm
2M2 would be 2.2 meg ohm
2u2 would be 2.2 microfarad
3n3 would be 3.3 nanofarad
I find the "new" way very simple and prefer it over most any other identifiers. Much preferred over the numerical codes (like 104 on a cap. or smt resistor).

[Enzo]

Yes, 0.33 ohms. Schematic says it clearly. It should be a 5 watt part, and those don;t usually even have color codes, indeed the value is usually just printed right on them, as you wanted. All you need is common cement block 5w resistors. 0.33 ohm is about as common a value as it gets for those. You don;t need to order anything special.

Mouser:
280-CR5-0.33-RC

[Jazz P Bass]

I would expect that you also found shorted output transistors, along with the open .33 ballast resistors.

[Valvehead]

thanks guys !!

[Jazz P Bass]

Mouser:
280-CR5-0.33-RC

Is that from Mouser in France?

[Enzo]

Gives the amp a more European tone...

[olddawg]

A .33 Ohm 5w ceramic block emitter resistor is about as common as it gets. You can probably find them at any local electronics supply place or any online supply house. Are those Darlington output transistors? If you opened an emitter resistor you probably have a bad output transistor as well and I would replace the pair and the other emitter resistor as well. And... Check the drivers, bias, etc.