Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: flyfisher55 on February 14, 2019, 07:09:31 AM
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Crack was working fine and then I finally got around to installing the Speedball upgrade.
Everything was good right up to the very end. I was checking voltage on OA and I let the probe slip in. I'm pretty sure I touched one of the TIP-50 legs. I heard a small 'zap' and the two Led's on the left went out.
What next?
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I need to clarify a couple of things... When I said two LED's on left went out I was referring to the two LED's directly behind the transistor and next to G terminal. The B side?
Prior to this all appeared to be working correctly. Resistance passed and stage one of the upgrade passed all test within parameters. I am a total newly to this and have bad eyesight to boot. Hope I can get some help from those of you in the know. Thanks in advance
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What voltages do you get on the big board and small board?
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small board
OA-51.5
1A-90.1
B-A/B-0V
1B-90
OB-53.7
Large Board
OA-99
OB-50.6
G-0
B+-90
Two LED's directly below 1B on small board are also out
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Your tip50 transistors are likely not properly mounted. Do not run your amp until this is remedied, as you're likely to burn up the 270 ohm resistors in the power supply.
One way to check on this is to pull the 6080 and run the amp without it. If the IA/IB voltages on the small PC board pop back up closer to 200V, that tends to confirm that the TIP50 transistors aren't mounted properly. Also use this test to check the OA/OB voltages on the small board to be sure they are appropriate (seeing 50V at OA or OB would make me suggest checking whether one or more of the PN2907 transistors is in backwards).
You can also post photos of your build if you aren't sure one way or the other.
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The fact that all LED's were lit prior to my slip where I allowed the red probe to short out against the TIP50 and heard the zap which at that very moment resulted in the LED's going out has no relevance?
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Nope. The manual is also pretty specific about this on page 31.
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I removed 6050 and these are my results on small board
IA-227
IB-227
OA-68
OB-81
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Could I see a close shot of each TIP50?
Your numbers are consistent with a shoulder washer not properly placed on at least one of the TIP50 transistors.
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Hope these help
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This shows LED's out. Note all were lit prior to my accident
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Are both LEDs on the 9 pin socket illuminating?
The small PC board should still work fine regardless of what you've done to the large board, so it's unusual that it doesn't appear to be (and even more unusual that the OB voltage is within range).
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Both LED's on 9 pin socket are lit. One on large board and two on small board.
I read the instructions and specifically what is said about LED's on page 31. As I said previously all were lit until I slipped with the positive probe and touched the Tip 50 and heard the zap. Immediately after that the LED's went out. Prior to that the small board passed ALL test.
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The next step would be to just remove the large PC board, then run the amp again with just the 12AU7 and the small board.
With the big board out, you can set your meter to DC resistance and measure between each pair of legs on each TIP50 and each 2N2222 transistor. You will likely find that some pairs of legs are shorted together, indicating that a transistor needs to be replaced.
Since the TIP50 transistors were properly mounted and working at some point, it's totally possible that both the TIP50 and 2N2222 where you had your slip are now shorted (thus providing a ground reference on the collector of the TIP50).
With the big board out, we can focus on restoring proper operation to the small PCB.
-PB
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I removed the large board and what to make sure I do this correctly. I am measuring DC resistance by Ohm setting on my multi meter?
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Is it safe to turn the amp on without the ceramic 10W resistors?
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Turned amp on with 12AU7 after removing large board. Two LED's under 1B are still out. I'm going to need a bit of guidance doing the resistance test on the large board. As I said previously, "total newby" Sorry! :-[
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Yes, you can run the amp with no 6080 and no 3K resistors. Yes to DC resistance, set it to the lowest range if your meter isn't auto ranging.
You'll want to do the same test for shorts on the transistors on the small board as well. It is highly unusual to have that kind of failure from a slip at one of the outputs on the big board.
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DC VOLTS OA 68.2
IA 233.6
B A/B 0
IB 233.6
OB 82.4
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can you give me a little more detail as to how I should check the transistors? The meter does have auto range
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Set the meter to ohms, touch each pair of terminals with the meter probes. If a pair of terminals reads a really low impedance (a couple of ohms), then the transistor is shorted.
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I'm a little confused as I see three pins on each transistor. When you say "pair" you're referring to the two outer pins on each individual transistor?
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There are 3 pins on each transistor, so there are 3 pairs of pins to measure:
1. The DC resistance between the two outer pins.
2. The DC resistance between the middle pin and one outer pin.
3. The DC resistance between the middle pin and the other outer pin.
-PB
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These are my readings
QIB Outer two pins 0
R+C 35m
L+C 30m
Q2B Outer two pins 0
R+C 11
L+C 11
Q2A Outer two pins 26.5
R+C 16
L+C 0
QIA Outer 2 pins 0
R+C 35
L+C 30
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Large Board
02A outer 2 pins 21.54
L+C 16.63
R+C 0
O2B outer 2 pins 21.43
L+C 16.59
R+C 0
Q1B outer 2 pins 52
L+C 52
R+C 1.1
Q1A outer 2 pins 0
L+C 21.62
R+C 21.23
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You have no units on the numbers you have. When you write 21.54, is that 21.54 ohms or 21.54 megaohms?
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Meter shows m and ohm sign
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That's millions of ohms. Your meter may also show "OL" which means "over limit", but is not 0.
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O.L not 0
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OK, so now that you know that, do any pairs of leads actually measure zero ohms?
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Everything that I in error labeled as "0" is in fact 0.L m ohms. My apologies.
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I would recheck Q1B on the big board.
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I need steady hands, someone to teach me ohms law and a drink!
ok don't ask me where I got those previous numbers but this is what I'm seeing now .08 L+R, L+C .09, R+C 0 all M ohms
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I need steady hands, someone to teach me ohms law and a drink!
ok don't ask me where I got those previous numbers but this is what I'm seeing now .08 L+R, L+C .09, R+C 0 all M ohms
Is R+C 0, or OL?
If it's 0, then that's a dead transistor.
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I'm seeing zero
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She's toast! (I'd replace them both on that side)
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what about the others and my wacky readings? These parts are cents ... Not better off just swapping all parts in question?
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also the issue with small board still not working after having removed the large. Do we need to replace parts there?
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You can do the same readings again on the small PC board to check for shorts.
Again, it's low impedance values between any pair of transistor legs that mean a problem. If there's an "M" in the reading or it says "OL", those are OK readings.
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Sorry it took me awhile...
these are the transistor readings from small board
Q1A- L+C 32.23 m ohms
L+R 0.L m ohms
C+R 37.78 m ohms
Q2A- L+C 0.L m ohms
L+R 28.10 m ohms
C+R 16.85 m ohms
Q1B- L+C 33.0 m ohms
L+R 0.L m ohms
C+R 38.25 m ohms
Q2B-L+C 11.36 m ohms
L+R 000.7 m ohms
C+R 11.52 m ohms
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Q2B looks to have a short.
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Should I order defective parts from an electronics part shop online or through Bottlehead?
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Whichever is easier. There are a decent number of local electronics shops that will carry the NTE line of semiconductors. The NTE123A and NTE198 are the equivalent transistors that go on the larger PC board while NTE159 and NTE39 go on the smaller board.
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Hello Paul, I'm back to trying to restore my crack. I ordered parts online and replaced the parts in question. Here are my results on large board OA- OL
OB- OL
G- 0
B+- OL
02B heatsink hot
LED nearest outside rim on B+ side lit
Both LED's on left side of small board lit
One LED at vaccuum tube base lit
All other LED'S are out.
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I'm presuming the problem has to be traced so I removed large board.
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Can you post voltages?
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Small Board
OA-O.L
1A- O.L
B-A/B- 0V
1B-0.L
0B-00.09V
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Small Board
OA-68.2 V
1A-226.9V
B-A/B-000.0V
1B-226.8V
OB-000.0V
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LED at A3 is the one out along with two on small board below 1B
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Can you post some photos of your build? It's very unusual to see 0V on one of the outputs of the small PC board.
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I'm enclosing a few hope these help.
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Can you unscrew the board and tilt it out of the way so we can see the socket wiring?
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I tool these last night.
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more pics
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The wire at A4 is not attached and not particularly well soldered.
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I resoldered both A3 and A4
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amp on one LED on
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Re checked voltage,
OA 68.2
1A 230.1
B-A/B 000.0
1B 229.5
OB -000.1
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Can I see a photo of the bottom of the small PC board?
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small board
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I would be looking for a broken wire. 1L is also not well soldered, but that won't cause the issue you're having.
-PB
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I appreciate your knowledge in troubleshooting my build but I keep thinking that this amp was fully operational for almost a year prior to my trying the speedball upgrade. It wasn't until my hand slipped and shorted that the LED's went out. Is it possible that the 250 V capacitors would be the culprit? That was where the zap and spark occurred when my probe slipped. What wires would I have to replace? Are we talking about rebuilding the entire amp?
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I appreciate your knowledge in troubleshooting my build but I keep thinking that this amp was fully operational for almost a year prior to my trying the speedball upgrade. It wasn't until my hand slipped and shorted that the LED's went out. Is it possible that the 250 V capacitors would be the culprit?
No, there's absolutely no possibility of this. A blown cap will short, and a shorted cap will blow its insides out all over the place immediately. This will also drag your high voltage rail way, way down, and yours is still just fine.
What wires would I have to replace? Are we talking about rebuilding the entire amp?
What I would suggest is getting a wooden chopstick and poking around the 9 pin socket and the small Speedball board with the amp on. You may find a spot where you can tap with your chopstick and suddenly the LED on the socket that's out lights up, and this can be used to direct your efforts.
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I removed all the wires from small board and replaced them with fresh wires left over from the build. Voltages at small board remained exactly the same. One note, I used the tip of a number 2 pencil and shorted A3 to A4 with the lead and this caused the LED at A3 to be lit. This had no effect on the LED's on right side of small board.
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I replaced the existing 12AU7 equivalent tube with a new 12AX7. I had no other 12AU7 laying around. Only the one LED lit at the socket base and none at all on the small board. Upon restoring the provided tube the two Left LED's came back on but right two remain out.
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The Crack is not designed for a 12AX7. It's not a replacement for a 12AU7.
See the tube rolling thread for suitable alternatives.
Since your Crack is malfunctioning, i'd only use it with a good 12AU7/ECC82 for now.
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Thanks for the reply. As I was instructed to probe around with a chop stick on my last post from Paul I took a stab at trying a different tube. Unfortunately not having much success.
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I'd put the 12AU7 back in and poke around some more with the chopstick like PB said.
Good luck with the trouble shooting.
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You don't have a bad tube. A bad tube would leave very high voltage at OB if it had no emission and would blow up the LED if it was shorted.
Another likely course of action would be to put the 22.1K resistors back in and remove the small PC board, then continue debugging the circuit.
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Okay, so after making makeshift extension wires in order to reinstall the 3K resistors and the 22.1K resistors I got them back in and both LED's on the 9 pin socket are lit.
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I would grab the chopstick again and poke around to see if you can disturb any connection to make the socket LED go out.
I looked over your board work again and everything looks great, so it's difficult to imagine how you're getting no voltage out of OB.
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Just checked all voltage and these are my readings.
1. 74.4
2. 170.7
3. 0
4. 170.3
5. 78.1
6. 0
7. 102.9
8. 0
9. 104.2
10. 0
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Faulty board?
Options?
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Though the solder joints on the board look good, it's completely possible that there is one that isn't making good contact.
A faulty board is usually the result of a shorted transistor, and a shorted transistor will make IB and OB roughly the same voltage.
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Just a shot in the dark, but maybe resolder the legs of the transistor on the OB side. The circled leg looks a bit iffy in the photo (but could be perfectly fine). I'd try soldering it from the top, tinning and putting the tip on one side of the leg/trace-hole and applying solder to the other side. Might be worth a try
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Just a shot in the dark, but maybe resolder the legs of the transistor on the OB side. The circled leg looks a bit iffy in the photo (but could be perfectly fine). I'd try soldering it from the top, tinning and putting the tip on one side of the leg/trace-hole and applying solder to the other side. Might be worth a try
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Thanks Deke, I tried what you said. I've put three PN2907's into O1B. all three including original shorted one and two that I ordered read differently than O1A.
O1A L&R = O.L M Ohms
L&C =O.L M Ohms
R&C =40.19 M Ohms
O1B L&R = O.L M Ohms
L&C = O.L M Ohms
R&C =00.00 M Ohms
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here are latest photos of small board.
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The other option is to use the repair service. Many times the repair only requires resoldering all of the joints in the amp.
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After all this time and effort, sending it in for repair feels like throwing in the towel, Especially when we've confirmed that the unit was working prior to the upgrade and upon being restored to the original is once again operable. Is it an option to order another Speedball kit?
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I'm confused, Despite the fact that the unit is operational and reading within the correct parameters presently you still feel that the fault lies with bad solder points?
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I'm confused, Despite the fact that the unit is operational and reading within the correct parameters presently you still feel that the fault lies with bad solder points?
Potentially solder points on that small PC board.
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Do present resistance values have any relevance on parts being damaged? Are we we 100% sure the board it self is not the culprit? I'm willing to desolder every component and start from scratch. I'm very interested in finishing this project but I'd like to do it without returning it for someone else to fix.
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The problem with simply saying "the board itself" is that it could just be a flaky solder joint on that board that's causing all that trouble. We have never had a problem that turned out to be a production issue with a PC board, and dead transistors will cause a short that presents high voltage at the output. You have no voltage at the output. One cause for this would be a short to ground in the amp itself, which we have narrowed down to not being possible because the stock amplifier is working properly. The other possibility is that a connection is not adequately soldered on the board, causing a complete lack of voltage on the output (and none of the associated heat of having a short).
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That being the case, do my latest resistance readings reveal anything and should I replace any parts which may be causing the problem?
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You could request a replacement small Speedball board from the replacement parts e-mail.