Bottlehead Forum
General Category => Technical topics => Topic started by: soundsgood on April 04, 2015, 09:30:58 AM
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I bought a tube tester many years ago for $10 at a swap meet. I have always trusted its results. I would like to rebuild it. I have a schematic and calibration info. It is a sencore tc136 with 12au7a tube. It has a 20uf/70v electrolytic and .1uf/200v cap. It has just a hand full of resistors. Any advice on type or brand of parts to use would be greatly appreciated, thanks.
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Any thing in the power supply should be beefed up. In particular the capacitors. You don't need to increase the value but increasing the voltage one step will help. Remember, it was made with a line voltage of 110V, we have 120+V now.
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It may be fine, worth visibly checking the electrolytic for any signs of budging or venting, but its probably had very little use over the years. The .1uf is probably a mylar or some sort of film and should be fine, however check the schematic and see what it does incase it ties the case to the AC line, in which case replace it for safety. Only other thing worth checking is the resistors if they are carbons as they can drift a lot with age and heat. I have restored a few testers and vintage Heathkit equipment and been surprised how resilient old test equipment can be.
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Electrolytics are good for 10-20 years maximum. Even the ones in a "can" dry out. All electrolytics should be replaced since those haven't been made in over 20 years.
I should have put that in my first post.
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Thank you for the replies. Would 1% metal film resistors be a good choice?
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They should be fine. The stock resistors were either 5% (Gold band) or 10% (no band). Metal film are good in hot areas and this should be at least warm.