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RE: GRAAF GM 200

Thanks Bernard. Appreciated. My GM200 is balanced. It actually came with a manual but a very terse one on how to tune up the amp. I was hoping that there would be a more thorough service manual with diagrams and further specifics on adjusting the amp.. At any rate, happy to take a look at the manual you have (my email is luisavcatao at gmail.com). The previous owner kindly indicated to me the recommended bias and am familiar with both DC offset and bias setting from a previous amp, so guess I can get by with those basics for now.

I am indeed planning to take the amp at some point for some tune up by Mr. Mariani but doubt I will have time for that until the Spring. At the moment what seems more pressing is the decision as to whether to get a tube tester which tests PL504s since I basically have no replacement power tubes, so should one or more blow up I can't operate the amp. Any reference to not-so-expensive tube testers that do a decent job at testing the PL504s are welcome -- I hear great things about the Amplitrex tester but that's beyond my price range at least for now. Also hear good things about the Hickok TV7 and the B&K Dynascan 667 but haven't been able to confirm whether they test the PL504s. Regards, Luis


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