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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 1:42 am
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BasementBob wrote:
Just pulled my amp apart to see what was done a few years back to satisfy my curiosity regarding the colder bias.

R10 (pin8) was upped to 980-ohm, and R26 (pin 4) was upped to 1000-ohm,
which gives 22 v /1000 ohm = 0.022 Amp = 22 mA

I don't have a multi-meter...so I am not checking the actual values...those are the resistor code values...so take it for what it is.

I don't play the amp much...but it sounds fine to me...and has been for going on 4-years. :D


No multimeter !! Where the 22 volts come from ?


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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 2:07 am
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stratele52 wrote:
No multimeter !!


+1

WTF?

You can get an adequate DVM at any big-box hardware store for about the same price as two or three sets of guitar strings.

There's is absolutely NO EXCUSE for not having one!

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: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 2:22 am
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Retroverbial wrote:
stratele52 wrote:
No multimeter !!


+1

WTF?

You can get an adequate DVM at any big-box hardware store for about the same price as two or three sets of guitar strings.

There's is absolutely NO EXCUSE for not having one!

Arjay


+1

I guess it is "my " 22 volts :lol:
But "my" resistor was 470 ohms not 1000


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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 4:23 am
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The Resistors were changed out and are now 1000 ohm. That's all I said. The 470 ohm was modified...it was soldered onto the 510ohm in series to give 980+/- ohm. Volts are as per the schematic...

Now that I have been shamed for not actually owning the necessary multi-meter...I guess I must immediatley report to Homecheapo and purchase said meter... Go online to refresh my Grade 11 Electricity shop skills from 1982...and prepare to actually measure the voltage and the current....and report back to the Forum.

+1

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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 4:32 am
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DC volt are not the same with a 1000 ohms resistor. It could be twice = 44 volts
44 v / 1000 ohms = 44 ma this is a very hot bias like you have before
22v / 470 ohms = 46.8 ma

Shematic voltage is not very accurate to a bias adjustment.
You must know your wall outlet voltage and how work ( milliamp ) the Output Power tube need.
That is why some voltages reading in the amp are a must.

You must also read plate voltage; be careful this is a lethal voltage and can kill you

Resistor value and his voltage give the current
Plate voltage X current = tubes power dissipation


Voltages reading are a must. because when you change ( cathode) resistor, many voltage change and you must know them to calculate the bias.

Use that;
http://www.tedweber.com/webervst/tubes1/calcbias.htm


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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 5:03 am
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Stratele, I kinda doubt the idle current will increase with the increased resistance (1000 ohms versus 470 ohms) from cathode to ground. But, the calculation for the new voltage would not be linear. But, a function of that specific 6V6GT. So yes... dynamic measurement is the answer.


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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Wed Apr 12, 2017 5:07 am
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BMW2002Ti wrote:
Stratele, I kinda doubt the idle current will increase with the increased resistance (1000 ohms versus 470 ohms) from cathode to ground. But, the calculation for the new voltage would not be linear. But, a function of that specific 6V6GT. So yes... dynamic measurement is the answer.



Current is not increase with a 1000 ohms .

My calculation are a average and are a result with some tests with a power supply with 2 X 1000 ohms first and second ; one 1000 and one 470 ohms .


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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Sun Apr 23, 2017 4:34 pm
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BasementBob wrote:
Just pulled my amp apart to see what was done a few years back to satisfy my curiosity regarding the colder bias.

R10 (pin8) was upped to 980-ohm, and R26 (pin 4) was upped to 1000-ohm,
which gives 22 v /1000 ohm = 0.022 Amp = 22 mA

I don't have a multi-meter...so I am not checking the actual values...those are the resistor code values...so take it for what it is.

I don't play the amp much...but it sounds fine to me...and has been for going on 4-years. :D



My bad on the resistor values.
R10 was only upped to 570 ohm by adding a 100 ohm in series. (brown black brown)
Actually on my handy newly acquired multi-meter :D they read 565ohm. Which is only a minor change.

The voltage is 23.6volts across R10, again on said newly acquired multi- meter.

So...I guess that gives 23.6v / 565 ohm = 41.7 mA


44 volts? Nope. I don't think that would be possible, there is no new voltage supply, or reduced resistance somewhere else in the circuit decreasing a voltage drop somewhere.

So in the end not helpful in the least. No major change in "tone" that I can ascertain.

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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Sun Apr 23, 2017 6:17 pm
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It's not a total loss, Bob.

You got a pretty good meter out of the deal.

:wink:

Arjay

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Post subject: Re: Champion 600 upgrade tone is bad
Posted: Sun Apr 23, 2017 9:36 pm
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Bob,

That speaker you upgraded to, isn't 4 or 8 ohm? Just wondering.

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