Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
Normal or abnormal ?
Came in for an intermittant problem, fixed, and the following the owner lives with but is it normal or abnormal? With feed into a "normal" input and the "brilliant volume" at zero then there is no control of the bass on the tone control, you need to have a little advance on the brilliant volume. Trouble around V7 ECC83 ? DC voltages cathode,grid,anode "brilliant half" 0,1.4V, 182V "tone half" 182,183,290V all associated pots ,Rs and Cs check out agreeing with schematic as does the valve and same Vs with a different valve -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
On Wed, 14 Jan 2009 14:09:27 -0000, "N_Cook" wrote:
Normal or abnormal ? Came in for an intermittant problem, fixed, and the following the owner lives with but is it normal or abnormal? With feed into a "normal" input and the "brilliant volume" at zero then there is no control of the bass on the tone control, you need to have a little advance on the brilliant volume. Trouble around V7 ECC83 ? DC voltages cathode,grid,anode "brilliant half" 0,1.4V, 182V "tone half" 182,183,290V all associated pots ,Rs and Cs check out agreeing with schematic as does the valve and same Vs with a different valve Assuming I am looking at the correct circuit - the bass control is in the output of the brilliant circuit only. The "brilliant" and "normal" are mixed at the junction of the 220k resistors so the bass control will have no effect on the normal channel. The brilliant volume control effectively grounds the grid of V7a so I would expect 0v there and 1.5v ish on the cathode. -- Geo |
#3
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
Geo wrote in message
news On Wed, 14 Jan 2009 14:09:27 -0000, "N_Cook" wrote: Normal or abnormal ? Came in for an intermittant problem, fixed, and the following the owner lives with but is it normal or abnormal? With feed into a "normal" input and the "brilliant volume" at zero then there is no control of the bass on the tone control, you need to have a little advance on the brilliant volume. Trouble around V7 ECC83 ? DC voltages cathode,grid,anode "brilliant half" 0,1.4V, 182V "tone half" 182,183,290V all associated pots ,Rs and Cs check out agreeing with schematic as does the valve and same Vs with a different valve Assuming I am looking at the correct circuit - the bass control is in the output of the brilliant circuit only. The "brilliant" and "normal" are mixed at the junction of the 220k resistors so the bass control will have no effect on the normal channel. The brilliant volume control effectively grounds the grid of V7a so I would expect 0v there and 1.5v ish on the cathode. -- Geo So normal, in summary, for this amp? The "brilliant" half is upper in this section of schematic http://home.graffiti.net/diverse:graffiti.net/vox1.jpg There is treble control but not bass control with "normal" input and zero on brill vol. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#4
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
"N_Cook" wrote in message ... Normal or abnormal ? Came in for an intermittant problem, fixed, and the following the owner lives with but is it normal or abnormal? With feed into a "normal" input and the "brilliant volume" at zero then there is no control of the bass on the tone control, you need to have a little advance on the brilliant volume. Trouble around V7 ECC83 ? DC voltages cathode,grid,anode "brilliant half" 0,1.4V, 182V "tone half" 182,183,290V all associated pots ,Rs and Cs check out agreeing with schematic as does the valve and same Vs with a different valve -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ AC30's have always had weird tone circuits that don't do what you think they should. There may not be any fault at all. Gareth. |
#5
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
On Wed, 14 Jan 2009 16:22:39 -0000, "N_Cook" wrote:
So normal, in summary, for this amp? The "brilliant" half is upper in this section of schematic http://home.graffiti.net/diverse:graffiti.net/vox1.jpg Yes - that is the circuit I have. There is treble control but not bass control with "normal" input and zero on brill vol. Unless there is signal (e.g. from guitar) through the brilliant circuit then neither bass nor treble should really have any effect. The position of the brilliant volume control should not affect the normal path. Is it possible that C10 - the common cathode decoupling of the first valve is failing and letting some signal through from the normal to brilliant section? -- Geo |
#6
Posted to sci.electronics.repair
|
|||
|
|||
Vox AC30 6TB, 2002
N_Cook wrote: Normal or abnormal ? Came in for an intermittant problem, fixed, and the following the owner lives with but is it normal or abnormal? With feed into a "normal" input and the "brilliant volume" at zero then there is no control of the bass on the tone control, you need to have a little advance on the brilliant volume. Trouble around V7 ECC83 ? DC voltages cathode,grid,anode "brilliant half" 0,1.4V, 182V "tone half" 182,183,290V all associated pots ,Rs and Cs check out agreeing with schematic as does the valve and same Vs with a different valve The modern 'copies' are ****. I have a file full of AC30 schematics fronm the earliest to quite new. Will that help ? Often, guitarists compare 'their' AC30 with an well-maintained original and complain it sounds ****. They're right. It does but there's nothing wrong with theirs it other than cheapskating. Graham |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Vox AC30 , AC30CC2X, 2005 | Electronics Repair | |||
Vox AC30 / 6 TB ,all valve combo from 2002 | Electronics Repair | |||
VOX AC30/6 TB | Electronics Repair | |||
2005 Vox AC30 , AC30CC2X | Electronics Repair | |||
Best Screw of 2002 | UK diy |