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Messages - dmeek

#1
The 100K resistor along with the resistor from the input jack sets the input impedance.
If anything I might make it larger like 220K or 330K. It does not change the gain.
Gain of the first stage is set by the feedback resistor divided by the resistor from
the - input to common.
In this case common is the +12V. The gain of the first stage is 1+47K/2.2K = 22.4
You could change the 100K to 1M but you would want a FET op-amp  like TL071 for the first stage
#2
Here is what I get with my pencil-and-paper style

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#3
The 5534 often needs a small compensation capacitor between pins 5 and 8, usually 22pF.
Without that it might be oscillating thus drawing more current.
#4
I can't see all of it very well but here's a rough schematic

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#5
Amplifier Discussion / Re: fender amp schematic
February 13, 2023, 07:56:00 PM
It is in post #3
#6
Amplifier Discussion / Re: Jordan Two/01 Repair
December 20, 2022, 06:31:07 PM
Here is the Tremolo-Reverb board
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#7
Amplifier Discussion / Re: Jordan Two/01 Repair
December 19, 2022, 06:09:54 PM
Here is the input schematic. Please post another photo of the tremolo-reverb board.
I can't see the circled area very well.
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#8
Amplifier Discussion / Re: Jordan Two/01 Repair
December 19, 2022, 10:16:45 AM
Here is the schematic of the power amp board. I believe it is correct but there could be mistakes.
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#9
Amplifier Discussion / Re: Jordan Two/01 Repair
December 16, 2022, 05:16:17 PM
Are there any numbers on those 4 transistors? The blue 1000uf cap seems to be reversed.You cannot view this attachment.
#10
It's in this schematic: 130 ohms/1W

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#11
SVR1 is to set FET bias for the compressor. Don't touch it. I don't know how to set it.

I guess Q4 is not the problem. I'm running out of ideas. Are you sure there is something wrong with this amp? It's normal for the overdrive channel to be louder.
#12
If the overdrive channel sounds like it should with a guitar you don't need the check it with the oscilloscope.
Leave the amp switched to the clean channel and remove Q4. See if there is a difference with or without Q4
#13
Try the amplifier with Q4 removed. The clean channel will be always on even when switched to overdrive but you can see if there is a difference in gain.
You can measure the resistors after desoldering one end.
#14
If the overdrive channel is OK, the problem in the clean channel must be R44 100K, or Q4 2SK30A, or R41 10k
All ICs in your amp are dual op-amps like this

#15
You need a stable tone of some kind. There are many oscillator apps for phones and computers or you could use a keyboard organ sound, just tape one key down.
Plug the tone generator into the input and check its level with the scope. Set the vertical gain for about 1 division amplitude on the scope, then move the probe to
IC6 pin 1. the amplitude should be about 5 divisions. Turn the Clean Gain full up, move the probe to the center terminal of the gain pot. The level should be the same 5 div.
Move the probe to IC6 pin 7, should be more than 5 divisions amplitude.