Bottlehead Forum
Bottlehead Kits => BeePre => Topic started by: davechen on March 12, 2014, 06:03:28 PM
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I finished assembling my BeePre yesterday. I checked all the resistances, and they seemed ok. So naturally I plugged it in and fired it up.
The two 6BQ5's glowed as did one of the 300B's, but the other one didn't. That was the one on the left when the tubes are up, i.e. the B socket. Also the front two LEDs (closer to the power switch & knobs) of the C4S board above the B socket didn't glow.
Here are my resistances with the tubes in
1: 3.4
2: 0L
3: 0
4: 5.3
5: 0
6: 143K
7: 455K
8: 0
9: 0
10: 0L
11: 144K
12: 457K
13: 0
14: 0
15: 0L
16: 3.9
17: 0L
18: 0
19: 5.0
20: 0
21: 0
22: 140K
23: 0
24: 0
25: 117K
26: 0
27: 0
28: 0
33: 0
34: 0
37: 0
38: 0
39: 0
40: 176K
41: 0
42: 0
43: 161K
44: 0
45: 0
46: 151K
47: 430K
49: 601
50: 0
51: 601
A1: 4
A2: 0-47K
A3: 0L
A4: 5.3
B1: 5.1
B2: 0-46.1K
B3: 0L
B4: 4.0
C2, D2: 214, 214
C3, D3: 0L, 0L
C4, D4: 72K, 70K Are these too low?
C5, D5: 78K, 72K
C7, D7: 144K, 144K
C8, D8: 144K, 144K
And my voltages:
1: 6.5
2: 130
4: 12.5
7: 186
10: 0L
11: 0L
15: 0L
16: 7.7
17: 0L
19: 12.9
22: 297
25: 297
29: 9.34
30: 9.34
31: 189
34: 194
35: 9.7
36: 9.7
37: .63
40: 301
44: 302
47: 302
A3: 138
B3: 262
C3, D3: 5.5, .15
C7, D7: 205, 268
C9, D9: 204, 266
I left off the 0 volt ones that corresponding with the manual.
Clearly my voltages are off. I didn't see anything obviously wrong in the wiring, although I'll go over everything again and re-heat the joints. That's what eventually fixed my first Bottlehead kit, a Foreplay 2 I built many moons ago.
I swore that my resistances were good before I plugged it in. But when I remeasured after plugging in, C4, D4, C5 and D5 seem to be low.
I guess I'm kind of bummed because my last kit, a S.E.X. worked without a hitch. Anyways, anything particular I should be looking at?
Thanks.
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Also, I'm a little worried about plugging it back in. The bottom of the 300B that didn't light up is a bit white, like it might have burned out. Do you think I nuked that tube?
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If the tube has a kind of milky white coating inside where you would normally see the shiny metallic getter flash, yeah, unfortunately the tube has a leaky envelope and has gotten some air inside. If the tube is forced into the socket the wrong way or twisted in the socket it can create a small crack in the envelope down inside the base where the wires come out for the pins. So you can't necessarily see where the leak is. Did you happen to notice that white part before you put it in the amp?
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Unfortunately I don't recall what the tube looked like before I put it in. I am sure I didn't force it in though. I've attached a picture of the tubes. I think the one on the left is toast.
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Yup, butter it now, it is toast.
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That's such a shame :'( If it were me i'd set it on my mantelpiece as an ornament.
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Yes, that tube is dead. Send it back to us so we can get a credit from the distributor and we will send you a brand new one.
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So I sent the bad 300B back, and USPS says I should get a new one today.
My concern is, if I messed up my wiring am I going to blow another 300B? Do you think it was more likely bad wiring or a bad tube?
I've double checked my wiring against the manual, and everything seems OK to me. Also I reheated the joints on that side of the pre-amp including all the ones related to the 300B and the power transformer.
Any other ideas? Or should I just plug in the new tube and pray?
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Your tube was physically damaged, which means physical trauma or a leak around one of the pins allowed air to enter the tube and ruin it.
An issue with how the circuit was built will not cause this kind of issue, so I don't believe you have anything to worry about.
-PB
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Yeah there was a hole in the glass inside the tube in a spot where I can't imagine an impact would have caused it. Looks more like it simply had a weak spot in the glass that gave out when the tube warmed up.
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Well, I've made a step forward, but not all the way there yet. Got the new tube, put it in, and powered the BeePree up. Joy! Glowing tubes!
So I put the pre-amp into my stereo. I get sound out of one channel, the B side, but not the other, A side. I tried swapping tubes and changing inputs and the sound stayed on that left side. When I swapped the outputs the sound did switch to the right speaker.
So now I've got to figure out what's wrong with the right side of the BeePre. I'll re-heat joints and measure voltages (when I get a new battery for my meter).
But for now, the one channel sounds very nice. :)
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Please do remeasure your voltages before you go too much further. Though it looked like a bad tube, let's make sure that the first tube died of natural causes and not something inflicted by the circuit.
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Will do. The bad tube was on the side that works now. But I will check the voltages tomorrow.
I've attached a pic of the tubes glowing.
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I just checked all the voltages and they came out good. :)
Maybe I'll check/reheat the joints that go to the output on the right side.
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So I'm back. Been trying to figure out why my BeePre isn't working properly. Right now the left channel sounds weak and hollow. The bass is pretty good, but voices sound distant. The left channel doesn't make any sound at all.
In checking the resistances, the following measurements were a bit funny:
25 & 40: 1M ohm and falling
43 & 46: rising to 120K ohm and continuing up
C3, D3, C4 and D4: slowly rising to 5K ohm and up
That last is lower than what the manual says. Is that a problem?
The measurements were made without any tubes in.
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Are your voltages still all good?
One possibility is that there is a miswire in the input selector that had right wired to a different step on the switch than left. Have you tried switching thru the input settings to see if the dead channel comes to life on another input setting? It's probably worth trying signal on every input just to see if you can spot an issue there.
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If the voltages measure in-spec, then the resistances would be OK.
It's best to try to narrow these issues down by swapping tubes, cables, etc. between channels.
-PB
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Yup, I just double checked and the voltages are good. I'll go over the input wiring and then try to hear all the inputs.
By the way, I'll be in Seattle for a few days next week. Could I bring my handiwork by Bottlehead HQ for some advice? I might be able to come by Monday or Tuesday.
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You are most welcome to come by, and we'll get her going.
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I'm in Seattle and plan on dropping by Tuesday.
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I'll make sure PB is around Tuesday to have a look. I can do it too, but if he handles it you and I can go up to the listening room and check out the system (including the new DAC) while he works on it.
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I'll be there!
Let me know if you have a specific time in mind.
-PB
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We're waiting for the 10:40 ferry from Seattle, so maybe 11:45?
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You're arrival estimate is a little off, but we're here and will see you soon.
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One possibility is that there is a miswire in the input selector
Just a note that Dave dropped by today with his BeePre, and this ended up being the issue.
-PB
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The guys tell me I get to keep the corner office for another day for guessing that one.
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I really enjoyed my visit to Bottlehead today. Thanks so much for taking the time to meet me and my family. I probably would have found my bug eventually, but this was much more fun. It was great talking to y'all and the demo system was amazing.
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Dave it was a pleasure for us to meet you and your family.