Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: ericoto on January 07, 2016, 02:17:12 PM
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Hi all, built Crack over weekend, tested all looked great, hooked up and worked fine. Tonight assembled and placed speedball, now however unit no working, getting very low unstable voltages and no leds lighting, recheck solder joints and assembly of boards, all look OK. Even small leds around 12AU7 not lighting any more, received small shock after I turned unit off and flipped over. Have disconnected and looking at speedball more closely, Any thoughts or tips?
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Just another thing, with unit off and plugged, looked at terminal 7, noted small arc. measured voltage between 7 and 12 to be 70 V, between 12 an 9 to be 145 V. ??? Unit off and unplugged.
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Check the mounting of your TIP50 transistors, especially the hardware used to mount them. (By check, I mean read every step in the manual regarding this and double check each step against what you have built)
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Thanks, tried that TIP installed correctly, screw, fiber washer, mica plate, transistor, heat sink, flat washer, lock nut and screw. did note heat sinks not soldered in well, resolder tighter. Still no leds, Voltage reading with power off unplugged now 190V between 7 and 12. Re did connection between boards and wires. Did note brief moment where LED's did light however quickly out and MJE350 transistor was HOT on one board, not the other. was small board closest to headphone jack. Thanks
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Please remeasure and repost your voltages.
-PB
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Thanks, took votages. all high did note that if I touched 11 12, half the LEDS lit. I measured following voltages,
1 140
2 240
3 240
4 240
5 120
6 0
7 230
8 0
9 240
10 0
11 230
12
13 240
14 240
15 240
16 240
17 123
18 90
19 90
20 0
21 240
22 120
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Are your tubes still glowing? Do the LED's on the 9 pin socket light up?
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yes tubes glow, although 12 AU7 hard to see. LEDS around nine pin do not light up
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If the tubes are glowing and the LED's on the 9 pin socket aren't lighting, your voltages on 1 and 5 should roughly be what they are on 2 and 3, or 0V. In any case, I would start by focusing on getting the smaller boards functional. Dark socket LED's mean that no current is flowing out of those boards. The most common case for this is that you need to reheat the center leg of each MJE350. This transistor can take a ton of heat, so feel free to really cook that solder joint to ensure that the solder flows properly.
-PB
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Well, I have resoldered center pin MJE350, resoldered connections on the small board , retraced all the wires, confirmed connections, Still no LEDs, voltages are the same, still will get a shock even when turned off. It worked well when it was just the crack.
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received small shock after I turned unit off and flipped over.
Was the power cord still plugged in? Did you touch any terminals in the amplifier when you flipped it over?
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No, unit was unplugged, I don't know what terminals I touched, but one was the metal cover.
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Well, I have resoldered center pin MJE350, resoldered connections on the small board , retraced all the wires, confirmed connections, Still no LEDs, voltages are the same, still will get a shock even when turned off. It worked well when it was just the crack.
You have a loose ground wire in the amplifier. The one that's most common is the junction of the black wires on the headphone jack.
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OK, found ground problem, L3 ground had broken off, fixed. Took apart Speedball, examined all solder joints, and reconnected. Now voltages lower, but 12AU7 not clearly lighting, although feels warm. one led on large circuit board lights intermittently, others nothing even on 9 pin socket. Voltages
1 0
2 1.5
3 0
4 1.6
5 0
6 0
7 90
8 0
9 1.7
10 0
11 0
12 0
13 1.5
14 0
15 220
16 0
17 0
18 93
19 90
20 240
21 1.5
22 0
Thanks
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Terminal 13 and terminal 15 are connected by a 270 Ohm 5W resistor. Yours is either not properly soldered, or there are some issues with your measurements.
For example, having 1.5V at terminal 13 and 90V at terminal 7 at the same time would be impossible (it's only possible if you measured terminal 7, then the fuse blew, then you measured terminal 13).
I would suggest rechecking your measurements.
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Alright, replaced batteries in multimeter, seems to be working better, now have LED's one side of large board, nothing else. Voltages readings now
1 0
2 210
3 0
4 201
5 0
6 0
7 98
8
9 70
10 0
11 0
12 0
13 210
14 0
15 218
16 0
17
18 92
19 90
20 0
21 228
22 0
Thanks, sorry about crappy measurements
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7 and 9 will not get anywhere near 70-100V if terminals 1 and 5 are actually 0V. Do the LED's on the 9 pin socket light up? They will also not light up if terminals 1 and 2 are 0V.
T2 and T3 will also not differ by 9V, as they are connected by a piece of wire.
I would start by focusing on terminals 1-5. Their proper functionality will allow the bigger speedball PCB to work properly.
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The voltages at t2 and t4 are the same, that was typo 210V each, sorry. I still get nothing out of T1 and T5, and when I check the voltages on the octal base 1 and 4 I get the same. I have rechecked all connections on terminal 1-5 with no issues. The leds the 9 pin do not light. One side of the large boards seems to be working with LEds on, the other side gets B voltage, but still no leds heat sink cold.
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Ok, 0V on T1 and T5 and no LED's tends to indicate that you need to resolder the center leg of each MJE350.
-PB