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Post subject: Bassman plate resistor values
Posted: Tue May 02, 2017 1:40 am
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Hobbyist
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Joined: Tue May 02, 2017 1:27 am
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Hi everyone!

My Bassman AA864 developed cracking sounds at all times, no matter the volume or other settings. I did my homework and found out that the first thing to look into, aside of tubes which I checked already, is about the plate resistors. I can change them, no problem, but question is about the wattage: schematics do not show any value for those except for resistance 100k. Is it safe to assume that wattage does not matter here and even 1/4 W will do? If not, what would be the recommended wattage value?

Thanks!


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Post subject: Re: Bassman plate resistor values
Posted: Tue May 02, 2017 9:00 am
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Joined: Tue Nov 27, 2012 6:56 am
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Location: Coastal Bend, Tx.
All resistors 1/2w 10% tolerance if not specified otherwise.
The correct schematic should have a "notice" w/ three notes.
1.voltage +/-20% red to ground
2.resistance as stated above
3.capacitance 400VDC minimum if not specified otherwise


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Post subject: Re: Bassman plate resistor values
Posted: Tue May 02, 2017 10:38 am
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Roadie
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Joined: Sat Dec 13, 2014 7:34 am
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You could check the screen and grid stoppers (resistors) on the back of the 6L6's and make sure your tube sockets are clean. The 470k's can be replaced with 2 - 3 watt metal oxide, the 1.5k's can be 1/2 watt. I always run the 470's on the outside of the socket.

I'm assuming you know how to drain the DC voltage before working on this amp.

UN


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Post subject: Re: Bassman plate resistor values
Posted: Tue May 02, 2017 1:33 pm
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Location: Tombstone Territory
upnorth2 wrote:
I always run the 470's on the outside of the socket.


+1

That alone can double their expected service life.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Bassman plate resistor values
Posted: Wed May 03, 2017 1:36 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
Trafo wrote:
Hi everyone!

My Bassman AA864 developed cracking sounds at all times, no matter the volume or other settings. I did my homework and found out that the first thing to look into, aside of tubes which I checked already, is about the plate resistors. I can change them, no problem, but question is about the wattage: schematics do not show any value for those except for resistance 100k. Is it safe to assume that wattage does not matter here and even 1/4 W will do? If not, what would be the recommended wattage value?

Thanks!


There is no 1/4 watts resistors in this amp, use only 1/2 watts or more.
I alway put 1/2 watts or 1 watts for plate resistors


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Post subject: Re: Bassman plate resistor values
Posted: Wed May 03, 2017 7:01 am
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1/2-watt metal oxide resistors work fine on anode plates, screen resistors, PSU resistors, etc. I like carbon comp on grid stoppers.


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