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Guitar News / Re: Nutube is the word of the day at NAMM - Vox and Korg Nutube pedals
« on: January 11, 2020, 11:05:55 AM »
Ibanez also uses a NuTube in the new Tube Screamer.
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Amplifier Discussion / Re: Crate CR112 tone stack
« on: January 05, 2020, 09:33:05 PM »
The 'Bright' capacitor C41 is 680 pf.
You could try a lower value, like 220pf.
You could try a lower value, like 220pf.
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: January 03, 2020, 01:30:01 AM »
I am stuck on the squirrely voltages on Q8.
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: January 01, 2020, 08:59:11 PM »
Q8 according to the schematic:
B:Not specified (47K from ground, it's an NPN transistor so I would expect minimal Vdc)
C: +38Vdc
E: -1Vdc
Q12 should have a negative voltage on the base: 0.6Vdc
(You do have the schematic don't you?
The expected static voltages are well marked.
B:Not specified (47K from ground, it's an NPN transistor so I would expect minimal Vdc)
C: +38Vdc
E: -1Vdc
Q12 should have a negative voltage on the base: 0.6Vdc
(You do have the schematic don't you?
The expected static voltages are well marked.
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: January 01, 2020, 04:47:26 PM »
Not too sure what you are seeing.
Reverb output ic looks good but Q8 base looks bad.
That makes no sense unless Q8 is toast.
Q10 should have +49 Vdc on it.
Q11 should have +1.2 Vdc on it.
Which leads me to believe Q10 is bad.
You have more problems here than I think you can solve on a forum.
Reverb output ic looks good but Q8 base looks bad.
That makes no sense unless Q8 is toast.
Q10 should have +49 Vdc on it.
Q11 should have +1.2 Vdc on it.
Which leads me to believe Q10 is bad.
You have more problems here than I think you can solve on a forum.
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: January 01, 2020, 03:02:15 PM »
What does the signal look like at the base of Q8?
Q10?
Q11?
Q12?
Take care that the specified 250mv AC signal into Q8 is NOT exceeded.
Q10?
Q11?
Q12?
Take care that the specified 250mv AC signal into Q8 is NOT exceeded.
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: December 31, 2019, 06:13:29 PM »
What does "Q8 is irregular pattern" this mean?
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Schematics and Layouts / Re: shcematics for true tone/ western auto amp mod# 5dc 9528e
« on: December 31, 2019, 06:08:02 PM »
First of all, you need to be aware that this amplifier configuration is called 'The Widow Maker'.
The ac mains voltage is directly coupled to the rectifier.
There is not a transformer to supply the secondary voltages.
To work on and operate these safely you must have an isolation transformer that would separate the mains voltage from the amp (110-110Vac)
The ac mains voltage is directly coupled to the rectifier.
There is not a transformer to supply the secondary voltages.
To work on and operate these safely you must have an isolation transformer that would separate the mains voltage from the amp (110-110Vac)
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: December 31, 2019, 02:35:06 PM »
Follow the signal into the power amp.
You do have a scope, correct?
What does the signal look like at the base of Q8?
Q10?
Q11?
Q12?
You do have a scope, correct?
What does the signal look like at the base of Q8?
Q10?
Q11?
Q12?
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: December 30, 2019, 05:24:49 PM »
So you feel the output is 'low'.
What is the maximum Vac out into an 8 ohm load before clipping?
What is the maximum Vac out into an 8 ohm load before clipping?
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: December 30, 2019, 12:25:26 PM »
Other than having the designators wrong on the outputs and the leg assignments wrong on the Negative outputs, I see nothing majorly wrong with the static voltages.
The schematic indicates a 225mv AC signal entering the amplifier.
What value do you read coming in there?
The schematic indicates a 225mv AC signal entering the amplifier.
What value do you read coming in there?
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Amplifier Discussion / Re: 1988 Randall RG100ES
« on: December 29, 2019, 09:42:57 PM »
Where is the schematic?
Can you please post it?
On the last three transistors, what are the designated 'Q' numbers?
Can you please post it?
On the last three transistors, what are the designated 'Q' numbers?
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Amplifier Discussion / Re: Gallien Kruger GT200
« on: December 25, 2019, 08:26:43 PM »
Not too sure what you are attempting to fix here.
Yes there is a small x over notch at higher settings.
I really doubt that you could here that.
What I see from the image is a gross mismatch in the top & bottom width of the waveform.
THAT will be noticeable.
Yes there is a small x over notch at higher settings.
I really doubt that you could here that.
What I see from the image is a gross mismatch in the top & bottom width of the waveform.
THAT will be noticeable.
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Amplifier Discussion / Re: Gallien Kruger GT200
« on: December 20, 2019, 01:06:31 AM »
Can you take a picture of the distortion as it appears on a scope?
If so, upload it.
If so, upload it.
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The Newcomer's Forum / Re: Fender Mustang II v.2
« on: December 08, 2019, 03:28:54 PM »
The issue needs be to better defined.
Shuts off as in the front indicator goes out?
Shuts off as in the front indicator goes out?