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Audio and Video Talk
The Vintage Audio Section
Quad 303 restoration
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<blockquote data-quote="mygoggie" data-source="post: 899900" data-attributes="member: 18916"><p>These values were measured by connecting the base to the collector and using the multimeter's internal voltage to switch the transistor. A simple test to check if the transistor is switching. I found a nice video showing this trick - https://www.youtube.com/watch?v=qnVGwfc8CB4</p><p></p><p>As you suggested I am going to check each component on the boards as something is not right. Part of the fun of restoration.</p><p></p><p>One thing I thought of last night is that all four TR1 and TR2's had a mica insulation tab with white heat transfer paste on both interfaces. Tr3 had no insulation tab and no heat transfer paste. IMHO this is not correct as mica is a thermal insulator (remember those old oven windows!) and secondly Tr3 should have been insulated.</p><p>I will get new thermal conductive insulators with the new power transistors as a first step.</p><p></p><p>[member=17429]HB[/member] maybe this is the case with your failed power transistor setup as well?</p></blockquote><p></p>
[QUOTE="mygoggie, post: 899900, member: 18916"] These values were measured by connecting the base to the collector and using the multimeter's internal voltage to switch the transistor. A simple test to check if the transistor is switching. I found a nice video showing this trick - https://www.youtube.com/watch?v=qnVGwfc8CB4 As you suggested I am going to check each component on the boards as something is not right. Part of the fun of restoration. One thing I thought of last night is that all four TR1 and TR2's had a mica insulation tab with white heat transfer paste on both interfaces. Tr3 had no insulation tab and no heat transfer paste. IMHO this is not correct as mica is a thermal insulator (remember those old oven windows!) and secondly Tr3 should have been insulated. I will get new thermal conductive insulators with the new power transistors as a first step. [member=17429]HB[/member] maybe this is the case with your failed power transistor setup as well? [/QUOTE]
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Audio and Video Talk
The Vintage Audio Section
Quad 303 restoration
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