Bottlehead Forum
Bottlehead Kits => Mainline => Topic started by: SmashBruh on May 06, 2020, 08:11:28 AM
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Hey guys! I had a strange issue this morning. My amp has been running fine for the last year or so, however when I turned it on this morning after leaving it for the usual warmup time (around 30 mins) I noticed there was a faint white noise coming from the right channel and no other audio would come through. I checked my RCA connectors and tubes and found that they seemed fine (unplugging my RCAs made no difference) then turned off the amp and turned it back on. This time the noise appeared for a few moments and then vanished. After that audio would come through just fine and the amp seemed to be functioning normally. I'm going to check the resistances as soon as the power drains, however I wanted to ask if this is something I should be concerned about? I figured it's probably just a tube on it's way out (I use my amp pretty much all day while I work, and sometimes it can be on for a couple of days on end) however I wanted to ask- if this IS a tube on it's way out is there any chance that it could kill my amp and/or headphones when it ultimately dies? I use some TOTL headphones with my Mainline; and am pretty attached to the amp itself so obviously this is something that worries me a lot. Would really appreciate any thoughts or input on the matter! :)
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This could absolutely be a solder joint issue. If you notice that it comes back while you're listening when you flip switches or adjust the attenuators, I would be focusing on reflowing solder joints.
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Just tested my voltages and resistances- everything seems to be normal except for the +275 VDC on the power supply board and the IA on both CS4 boards. Those voltages come back at around 250 VDC instead of 275. I'm guessing that's probably an issue...
I've attached a picture of that board for you guys to give me your impressions (it would be really great if I didn't have to disassemble the whole thing :'( )
EDIT: The T4 and T5 joints look suspect to me... Gonna start with those...
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What country are you in? What is your AC line voltage?
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What country are you in? What is your AC line voltage?
I’m in the US, so I’d guess 120V?
The weird thing is I know I’ve done these measurements in the past and had them come up right, so something must be amiss... right?
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Measure your AC line voltage. If it's a little low, then having a slightly lower voltage coming out of the power supply isn't abnormal. There is still plenty of voltage there for the high voltage regulator to be able to properly do its job.
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Measure your AC line voltage. If it's a little low, then having a slightly lower voltage coming out of the power supply isn't abnormal. There is still plenty of voltage there for the high voltage regulator to be able to properly do its job.
I just measured the socket the amp is usually plugged into and you're right, it is indeed undervolted (it reads between 111-112 VAC.) I re-soldered those joints anyways just to make sure that wasn't a problem, but alas, it still reads between 245-250 VDC. Oddly though, now the Bregs read between 220-222 (I hope that's fine?)... Given what you just said though I guess I'll just buy some new tubes and hope for the best! :)
Thanks for all your help Paul!
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Yes, your line voltage is low. Provided the power supply board puts out more than 225V, the amp should still work fine.
I would recommend checking the line voltage elsewhere where you are using the amp. 111V is very low these days, and there may be something else at work.
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Yes, your line voltage is low. Provided the power supply board puts out more than 225V, the amp should still work fine.
I would recommend checking the line voltage elsewhere where you are using the amp. 111V is very low these days, and there may be something else at work.
The highest voltage I seem to have in the house is 115VAC, and when tested there the +275vDC terminal reads 255 and the Bregs sit between 220-221 on the left and 221-222 on the right like in the other outlet. All other values are just like the manual. I live in an apartment unfortunately, so all I can really do about the low line voltage is complain to the manager. Hopefully there's nothing else at play and it's just the crappy line voltage.