Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: galyons on August 06, 2022, 03:06:54 PM
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My BeePre has performed marvelously for years now, But today it just did not sound right. So I did a voltage check. Everything was within spec, except for one C4S board. All the LED's are glowing on the C4S board. There are no visibly burned resistors. But I am getting off voltages on the board:
T16 3.2VDC v. 5VDC
T17 116.6VDC v. 90-110VDC
T19 10.16VDC v. 9.86VDC
So it looks like I have lost the magic smoke somewhere. The Smash is filling in, but...
Thoughts to resolve?
Cheers,
Geary
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The 3.2V is an oddball, what is POS OUT on that side of the preamp? I suspect that is your 10.16V, and that in combination with the low 3.2V is the root of the problem. Does this set of voltages happen to follow a tube? The high voltage at T19 tends to suggest that the 300B on that side is not drawing a lot in the way of current, and this is confirmed by the low bias voltage at T16. If these voltages are not dependent on a particular 300B, there's likely a loose solder joint at work preventing the filament from drawing appropriate current.
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:-[ The good news is it is NOT a bad solder joint! The bad news is that it is, in fact, the 300B. I should have thought to swap sides! I was just shocked, as the BeePre has been pretty faultless! Known pair of 300B's in and making beautiful music!!
Thanks PB for the rapid and correct diagnosis!!
Cheers,
Geary