Based on a very classic and well known 18W, with a tube booster …
A nice Fender Twin Reverb from 1976. Master volume, export version.
The voltage selector is dead :
Hope this helps …
A nice Boss CE1 to fix (in fact, the switch ON/OFF is malfunctioning … need to be clean up)
Anyway, here are some pictures of this nice effect pedal, hope this will help if you want to fix or build one.
A nice Blackstar HT Studio 20. My customer asked for new tubes.
I do not have the schematic, but what I see is that this amp has a mix cathode / fixed bias system … so bias must be adjusted.
Edit feb 2017 : another Studio HT 20 to deal with. This time, I got the Blackstar HT-Studio 20 schematic !
First of all, connect a speaker cab, then plug in a jack in the input : input jack is used as a standby : no jack = standby on (no high voltage), jack inserted => standby off (high voltage applied to the tubes).
Bias and bal pots …
 Look at R221 and connect a multimeter, then adjust the bias pot. You must read 11.5V
 You can check the « bal » adjustment to have the same voltage for grid1 (pin5) for both EL34. On my customer amp, I can read :
Hope this helps !
In case you can’t set a cookie from PHP when testing locally (localhost) with MAMP, you have to check « output_buffering » in your php.ini file.
Go to the right MAMP folder that contains the php.ini file. Be careful, there is probably several directories related to php.
On my Mac (MAMP 2.0.5), the path is :
Default php.ini file :
Here is a nice Tweed Deluxe 5E3 made by IT-11 Audio (see http://www.it11audio.com/deluxe).
This amp is great for blues and rock well known for its early breakup. What is the first stage involved in this saturate tone ?
Here is the schematic : deluxe_5e3_schem
Here are the voltage (DC and signal AC 1kHz) for the IT-11 Audio Deluxe :
Yellow trace : « input » : 12AX7 pin 7
Blue trace : « non inverting output » : 12AX7 pin8
« Clean » mode
Higher signal injected :
PI Spiced !
On this SPice model, PI enters saturation with a 40Vpeak signal (28VRMS). On my 5E3, it breaks up when input signal is 22VRMS … Real tube Vs simulation !
Here is the schematic simulated :
By the way : when you use your voltmeter to read the voltage at pin 7 of the 12AX7 PI, you read 17V or something like that : here is what happens (voltmeter impedance) :
An active AB Box covered with tweed (Input A : harp, input B : lap steel, active output to amp), made for Cotton Belly’s singer (see Greatness video)
A nice JTM45 / KT66 from Ceriatone, with IT-11 Audio 2×12 speaker cab and Gibson SG circa 66
Perfect combo ?