Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: marco08 on February 08, 2015, 06:07:55 AM
-
I had started getting an intemittant low freq buzz in the right channel, which would go off as soon as a gave a light thump on the top plate or played with the balance button. after a week or so, the channel went on a continuous very loud buzz, from startup and every time. My beepre's been a charmer for almost two years, so I'm miffed. after the obvious cable and tube swapping, socket tightnening, i went and reflowed everything in sight on the troubled channel. Resistance check is ok, voltage a bit low:
10&15 are 178v vs of the given 186
22&25&40&43&46 are 205 vs of 213
31&34 are 12.8 vs 13.6
35&36 are 6.3 vs 6.8
but the low voltages are consistant on both channels, and only one is contaminated.
any ideas, because after two afternoon of resoldering I'm p.. off and thinking of sending the darn thing all the way around the globe for some TLC, and live withour music for long weeks.
thanks guys and gals.
-
Your thump on the chassis indicates a loose connection or loose hardware. I would move on to the chopstick test, where you run the preamp flipped over and feeding an inexpensive loudspeaker at low volume. With a wooden chopstick, you can poke around carefully at various parts of the amp, and when you find the suspect area, you'll be able to hear the buzz go away.
-
thanks, my friend, tried that to no avail.. I'll try again next week for the last time.
Anyone worried by those low voltage readings on both channels ?
-
If OA, OB, and POS OUT are correct, and IA is above 160V, you should be just fine.
-
I let it go for a while after re-reflowing the solder joints, and finally took it off my system for almost a year. horrible failure sensation !!
I've read a few posts by fellows in europe (netherland in particular) that have had the same kind of buzz, and it does seem AC voltage related. In france, we used to be 220v as standard, and it was bumped up to 230 average a few years ago. However, it frequently is between 220 and 230 and it seems that this creates problems on the filament voltage for the beepre.
As the Beepre seems "calibrated" for 240, is there any changes that can be made on components to adapt it to this situation. Using a rheostat or some kind of UPS to try and up voltage the wall AC seems an iffy proposition to me -, no ?
thanks guys, I can't really stand to let my beautiful Beepre not sing.
-
You can use an isolation transformer to bump up the voltage. Look for a 1:1.1 isolation transformer and that will put your voltage at 240V.
-
Thanks,
I'll try to get one. google hasn't been any help yet, I only see 1:1 or 110/230 options. But I'll keep looking. Today, the wall gives me 236v and the beepre sings with no buzz.
cross my fingers
-
The other option is to get a 1:1 transformer with a very high rating (750VA may do it). The BeePre will draw such little power that the voltage available on the secondary will creep up.