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Wagner
02-22-2012, 12:04 PM
Working on an old pair of Monitor Audio boxes for a friend


Fried resistor for the tweeter


I have determined that it is a 3.3ohm resister but am not certain as to the wattage rating


The part is marked:


EGR
74ER
3R3 (which is the ohms value, 3.3)
5%


Guessing from the looks of it, I'd say around 3 watts, but I don't know and can't find the code on-line

Any help with this would be greatly appreciated!


Thank you


Thomas

Ruediger
02-22-2012, 12:15 PM
Buy a resistor which is physically larger (thicker), then You are on the safe side.

How could You manage to fry it?

Ruediger

Wagner
02-22-2012, 12:37 PM
Buy a resistor which is physically larger (thicker), then You are on the safe side.

How could You manage to fry it?

Ruediger


No idea, but I would suspect clipping, being over driven or an amp in poor health, all common in those wacky '70s!

The friend I am assisting received them this way. The resistor saved the tweeter.

While looking for the British code, I found another thread elsewhere, a guy with the same questions regarding the same speaker.

It may have been a common problem with this model.

I couldn't tell you.

Thomas

Jonis
02-22-2012, 05:29 PM
The resistor saved the tweeter.

if so, might think about not giving any headroom and let that resistor act as a fuse for protection.:dont-know: Something to consider.

Wagner
02-22-2012, 09:10 PM
Well, the scorched resistor replaced, still no signal to the tweeter although there is continuity on the circuit?

Once off the board and out of the circuit, the resistor still measured correct value, so the heating has taken out something else as well.......

............burned a nice black spot on a glass board

The tweeter is good.

Spent the afternoon researching obsolete British Standard COLOR coding for capacitors, think I know what I need there, but would like confirmation before I start lifting pieces

Research also indicates that these speakers had issues with overheating networks, but of course no details

Does anyone have, or know where I can find a network schematic with values for this old model

Monitor Audio MA5

Thank you,
Thomas