Siemens V72

This article is about servicing one of the famous German vintage tube preamplifiers, which had some usual and some less usual defects, with perfect examples of the "devil being in the details". Along the way, I pretty much dissected the whole unit, including some of the transformers (well, to some extent). Lastly, while checking all four of my V72 modules, I've come up with some measurements documenting the drift of gain and bandwidth, tips for realignment, and comments regarding possible modifications.




Gain and Filters - Realignment and Modification

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Working on electronic devices such as described on this site can involve LETHAL VOLTAGES - especially in tube amplifiers, you're dealing with up to 500 Volts. If you're not absolutely sure about what you're doing, better have a qualified tech do it for you - otherwise, there's a chance you might hurt or even kill yourself. Really.
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