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Messages - dmeek

#1
I can't see all of it very well but here's a rough schematic

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#2
Amplifier Discussion / Re: fender amp schematic
February 13, 2023, 07:56:00 PM
It is in post #3
#3
Amplifier Discussion / Re: Jordan Two/01 Repair
December 20, 2022, 06:31:07 PM
Here is the Tremolo-Reverb board
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#4
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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#5
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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#6
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.
#7
It's in this schematic: 130 ohms/1W

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#8
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.
#9
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
#10
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.
#11
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

#12
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.
#13
I posted this photo at mef a few years ago: https://music-electronics-forum.com/forum/amplification/guitar-amps/maintenance-troubleshooting-repair/44114-possible-to-repair-a-loose-potentiometer-leg/page2

I ground out these pliers to use for AC cord strain relief installing/removing. They work very well for that, so when I was looking for a crimper the tool was at hand. I have to be careful not to squeeze to hard. It can easily break the wafer.

#14
Sometimes the terminals get loose. Check them after they're removed from the board. If the terminals can be moved side-to-side at all, crimp them or just replace the pot.
I had a Vox amp a while ago where almost all the pots needed to be crimped
#15
C6 and C7 are part of the compressor in the overdrive channel.