Hi
Thank you for your kind offer. I found an earlier thread where somebody requested and received a schematic for a similar amp (Marshall AVT 50) so I e-mailed the replier in that thread and received the schematic from them (thanks tmenzo!).
Could I ask an opinion on a possible mod to the AVT20? I find that the amp is very shrill at higher volumes, what would be the component(s) I could change in the tonestack to help the situation?
Thank you for your kind offer. I found an earlier thread where somebody requested and received a schematic for a similar amp (Marshall AVT 50) so I e-mailed the replier in that thread and received the schematic from them (thanks tmenzo!).
Could I ask an opinion on a possible mod to the AVT20? I find that the amp is very shrill at higher volumes, what would be the component(s) I could change in the tonestack to help the situation?
AVT 20 R53 burnt resistor
Please count me in too. I tried emailing to "doctor" but can't email yet as I am still in "moderation" mode.
I need a schematic for the AVT-20. I found a burnt resistor at location R53. The problem I was having is that the amp was motor-boating when turned on.
Anyone have any ideas on a) what caused the resistor to overheat, b) where I can find an R53 replacement resistor, and c) where I can find a replacement metal post for one of the speaker wires to connect to? One appears to have snapped off during as I was removing the amp board assembly.
Thanks in advance.
Regards,
Eric
Please count me in too. I tried emailing to "doctor" but can't email yet as I am still in "moderation" mode.
I need a schematic for the AVT-20. I found a burnt resistor at location R53. The problem I was having is that the amp was motor-boating when turned on.
Anyone have any ideas on a) what caused the resistor to overheat, b) where I can find an R53 replacement resistor, and c) where I can find a replacement metal post for one of the speaker wires to connect to? One appears to have snapped off during as I was removing the amp board assembly.
Thanks in advance.
Regards,
Eric
Is the R53 Resistor on AVT-20 same as AVT-50?
I found a schematic for the AVT-50 but not for the AVT-20 yet (still in moderation mode). The AVT-50 shows R53 as being a 22k ohm resistor (1/4 watt?). Does anyone have any root-cause experience for these blown resistors and/or know how similar the schematic circuitry is between the AVT-20 and 50? I guess I'll check for any other blown/shorted caps, diodes, ICs, etc in the immediate R53 circuitry area while I'm waiting for email approval..
Thanks,
Eric
I found a schematic for the AVT-50 but not for the AVT-20 yet (still in moderation mode). The AVT-50 shows R53 as being a 22k ohm resistor (1/4 watt?). Does anyone have any root-cause experience for these blown resistors and/or know how similar the schematic circuitry is between the AVT-20 and 50? I guess I'll check for any other blown/shorted caps, diodes, ICs, etc in the immediate R53 circuitry area while I'm waiting for email approval..
Thanks,
Eric
the avt-50 schematic is DIFFERENT from the avt-20 by miles...the avt-20 schematic has a 10ohm 1/2 watt resistor in r53...according to the tda 2050 data sheet it helps prevent oscillation/feedback? c71 is associated with it ...c71 is .22microfarad ...when r53 toasted it melted c71 as well...I know for a fact that letting the amp feedback alot will toast this resistor.
Hello Again
Would anyone care to make a suggestion as to how to make this little amp less shrill (see my post above). Would socketing the TL072 chips and trying different opamps there make any difference? How about the tonestack-is there any component changes that would help? Finally would changing out the 12AX7 for a 12AT7 or 12AU7 help matters any?
Thanks all for your time and efforts
earache60
Would anyone care to make a suggestion as to how to make this little amp less shrill (see my post above). Would socketing the TL072 chips and trying different opamps there make any difference? How about the tonestack-is there any component changes that would help? Finally would changing out the 12AX7 for a 12AT7 or 12AU7 help matters any?
Thanks all for your time and efforts
earache60
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