Need help with possible receiver repair - Page 2

Keith Lockwood · 11th March 2010, 08:19 PM

srinath,

I don't have the cover off of the unit I have her e at the moment but you may not have to take the knob off of the switch to get some cleaner in there. It may be the case that you need a new switch as has been suggested previously but I would be worth a try to give some DeoxIt a try first.

Keith

Keith Lockwood · 13th March 2010, 06:04 PM

RJM1,

The 1/2 ohm 2 Watt resistors you are referring to are on the schematic as R233, R234,R235, and R236?

being an idiot electronically speaking and with a chronic brain infection to boot, what would be the color band coding to I.D. these little gems?

I have been testing resistors with my VOM. I just need to locate these bad boys and check them out. All the parts are mounted to the top of the beard if I remember right as I have had the bottom cover off within the last few weeks but my memory is not for S***.

Keith Lockwood · 13th March 2010, 06:26 PM

I think I have I.D.'d the .5 ohm resistors in question as largish green units. They all seem to have continuity.
Time to look elsewhere.

By the way, you don't need to remove the front knob to clean the power switch as it has an extension on it and the switch is mounted further back on the circuit board out in the open where you could easily spray some contact cleaner on it and work it a bit. It could as previously suggested just be plain worn out contacts, but you don't have to take the knob off.

Thanks everyone,
Keith Lockwood

RJM1 · 13th March 2010, 08:01 PM

Well If you try using just headphones on the receiver and it sounds ok then you probably have an open output transistor if those resistors are ok, Check the resistance readings on your meter on diode check between both channels on the transistors to find which one has opened. If anything had shorted you would have a large amount of DC at the output.
hth

Bob

Keith Lockwood · 14th March 2010, 12:19 AM

Bob,

Thanks I don't have a pair of phones around. I will get a hold of a pair to try that with.

DC at the output is the kiss of death for speakers isn't it?

Isn't that why they called the old big Crown amp the "DC" 300A? Seems it took down more drivers that even Bob Carver's "Flame"linear 400.

Maxgain

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11th March 2010, 08:19 PM	#11
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	srinath, I don't have the cover off of the unit I have her e at the moment but you may not have to take the knob off of the switch to get some cleaner in there. It may be the case that you need a new switch as has been suggested previously but I would be worth a try to give some DeoxIt a try first. Keith

13th March 2010, 06:04 PM	#12
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	RJM1, The 1/2 ohm 2 Watt resistors you are referring to are on the schematic as R233, R234,R235, and R236? being an idiot electronically speaking and with a chronic brain infection to boot, what would be the color band coding to I.D. these little gems? I have been testing resistors with my VOM. I just need to locate these bad boys and check them out. All the parts are mounted to the top of the beard if I remember right as I have had the bottom cover off within the last few weeks but my memory is not for S***.

13th March 2010, 06:26 PM	#13
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	I think I have I.D.'d the .5 ohm resistors in question as largish green units. They all seem to have continuity. Time to look elsewhere. By the way, you don't need to remove the front knob to clean the power switch as it has an extension on it and the switch is mounted further back on the circuit board out in the open where you could easily spray some contact cleaner on it and work it a bit. It could as previously suggested just be plain worn out contacts, but you don't have to take the knob off. Thanks everyone, Keith Lockwood

13th March 2010, 08:01 PM	#14
RJM1 diyAudio Member Join Date: Jan 2010 Location: Titusville, Fl.	Well If you try using just headphones on the receiver and it sounds ok then you probably have an open output transistor if those resistors are ok, Check the resistance readings on your meter on diode check between both channels on the transistors to find which one has opened. If anything had shorted you would have a large amount of DC at the output. hth Bob

14th March 2010, 12:19 AM	#15
Keith Lockwood diyAudio Member Join Date: Jun 2004 Location: Michigan	Bob, Thanks I don't have a pair of phones around. I will get a hold of a pair to try that with. DC at the output is the kiss of death for speakers isn't it? Isn't that why they called the old big Crown amp the "DC" 300A? Seems it took down more drivers that even Bob Carver's "Flame"linear 400. Maxgain

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