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peacefuel 11th April 2009 06:36 PM

Does Anyone Know What This Is?
 
I've isolated a problem on my Peavey Mace Tube Amp circuit board. Can anyone tell me what the gray cylindrical object with the burn marks under would be referred to and if you know where I can get one. I tried googling the numbers I could read on it but nothing came up. Thanks for your help.

http://i378.photobucket.com/albums/o...s/amp005-1.jpg

Shenda 11th April 2009 06:47 PM

Some 10W resistor... I can't read value in ohms...
...probably :confused:

Netlist 11th April 2009 06:57 PM

You will need an ohm meter to measure the resistor, preferably out of circuit but I predict he's still okay.
The burned marks underneath could have been prevented by placing the component higher above the PCB.
Most important are the solder joints on the other side of the PCB.
I bet they need to be redone.

/Hugo

Hearinspace 11th April 2009 06:57 PM

It's a 10 watt power resistor. The other numbers will tell you what the resistance value is supposed to be - within 10% as marked. If you want to either post all the text that is printed on the resistor (or post a pic that shows it all) anybody here can tell you what the figures mean.
Replacing the resistor will be relatively easy, but it would also be a good idea to find out why it happened so it doesn't happen again, possibly taking out other components with it. Going for a higher power rating is also not a bad thing ie, if you find a 12 W or 15W you can use it.

llwhtt 12th April 2009 02:51 AM

According to the schematic it's a 400 Ohm, 10 Watt resistor. Supplies high voltage to the output tube screens (490VDC) and phase inverter transistors (300VDC).

Craig

DHT112A 13th April 2009 03:33 AM

Got a pic of the other side of the board?

nhuwar 14th April 2009 01:43 AM

The question I have is why did it fail. I could be wrong but I though failed resistor are usually a symptom and not a cause.



:2c:

Ty_Bower 14th April 2009 02:02 AM

Quote:

Originally posted by nhuwar
The question I have is why did it fail?
An earlier post said it "supplies high voltage to the output tube screens". The name Peavey in the first post implies guitar amp. I'm thinking about sustained drive in excess of clipping, and just plain way too much screen current. I'm not sure what's involved with the "phase inverter transistors", but I'm sure they draw current too.

400 ohms at 10 watts should be good for 160 mA. Exceed that for too long, and poof. It looks like the resistor was mounted a little close to the board for a 10 watt part anyway.

llwhtt 14th April 2009 02:32 AM

You are correct as long as the resistor was sized correctly in the first place. Peavey is usually fairly conservative when it comes to part selection. Either two filter capacitors (they are in series) on the PS board are shorted or you have a bad tube. Though R1(400 Ohm/10 Watt) does supply the phase inverter the two smaller series resistors(22K/1W) would have given up long before R1. I say you have a bad tube that may or may not show up on a tester. Is the resistor in fact bad or when you saw the melt down you assumed it was bad? Another possibility is prolooooooooooonged usage in the "overdrive" mode, maybe with a incorrect load. There are 100 Ohm 5 Watt resistor s for each output screen (pin 4), check those for open. Caps or tubes thats all there is.

Craig

llwhtt 14th April 2009 02:37 AM

Ty,

You beat me to the sustained overdrive reply!

Slow typerer,
Craig


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