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Thanks for your reply Enzo. I've heard another one of these Cambridge 15s with a 10" speaker and the result just might surprise you. Yes, it's an entry-level practice amp, but for years I have used it as a grab-and-go amp to get me through rehearsals where space and volume constraints were the rule of the day.
I do realize this place is full of engineers and techs and that is the very reason I'm attempting to assimilate into the community with a couple of small projects at first. Compared to all of you I am a mere hobbyist on the electronics work bench. As a complement to my daytime career, I am also a professional musician (30+ years) and in registering here I hope to advance what knowledge I do have and make some friends along the way.
In recent years I have serviced and tweaked my own amps examples of which are rewiring the Fender silverface bias balance to adjustable bias, power supply filter cap and dropping resistor replacements, locating and replacing leaky coupling caps, and adjusting capacitors in the tone stacks in an attempt to achieve specific results. Most of the time these efforts go well, sometimes not so well. I'm comfortable with most of the basics and have a full understanding of the safety procedures one should practice on the bench. I'd love to be able to pose my questions here and receive solid advice from those who have real-world experience with a particular amp.
In the Cambridge 15, I've upgraded the speaker to a 10" 30-watt alnico (Fender 0994810001) and the single preamp tube to a 1950's GE 7025 since my last post. Based solely on a cursory visual inspection, the only points of concern are a couple of 1 or 2 watt resistors (R66, R67) that are discolored to the point that I cannot determine their values. Thus far, I've been unable to locate a schematic, so I cannot possibly tell if these two resistors are within spec, or not. The amp was working fairly well before I opened it up, but the Sovtek 12AX7A preamp tube measured very weak on my Hickok tube tester and the 8" Celestion Bulldog speaker that was removed from the amp has a voice coil rub, which validates my initial assessment.
I'd like to make sure the circuit is within spec and then put it back together, so if anyone has a schematic for a Vox Cambridge 15 V9159 I would be most appreciative.
-Stan
I do realize this place is full of engineers and techs and that is the very reason I'm attempting to assimilate into the community with a couple of small projects at first. Compared to all of you I am a mere hobbyist on the electronics work bench. As a complement to my daytime career, I am also a professional musician (30+ years) and in registering here I hope to advance what knowledge I do have and make some friends along the way. In recent years I have serviced and tweaked my own amps examples of which are rewiring the Fender silverface bias balance to adjustable bias, power supply filter cap and dropping resistor replacements, locating and replacing leaky coupling caps, and adjusting capacitors in the tone stacks in an attempt to achieve specific results. Most of the time these efforts go well, sometimes not so well. I'm comfortable with most of the basics and have a full understanding of the safety procedures one should practice on the bench. I'd love to be able to pose my questions here and receive solid advice from those who have real-world experience with a particular amp.
In the Cambridge 15, I've upgraded the speaker to a 10" 30-watt alnico (Fender 0994810001) and the single preamp tube to a 1950's GE 7025 since my last post. Based solely on a cursory visual inspection, the only points of concern are a couple of 1 or 2 watt resistors (R66, R67) that are discolored to the point that I cannot determine their values. Thus far, I've been unable to locate a schematic, so I cannot possibly tell if these two resistors are within spec, or not. The amp was working fairly well before I opened it up, but the Sovtek 12AX7A preamp tube measured very weak on my Hickok tube tester and the 8" Celestion Bulldog speaker that was removed from the amp has a voice coil rub, which validates my initial assessment.
I'd like to make sure the circuit is within spec and then put it back together, so if anyone has a schematic for a Vox Cambridge 15 V9159 I would be most appreciative.
-Stan
) that may be your only alternative at the moment.
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