Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Krishk on October 20, 2019, 03:13:01 PM
-
So, I finished the setup of the Crack, and once I plugged in the power source everything was normal. However, once I check terminal 3's voltage a small spark went off. Did the terminal spark because of my testing method or did I solder something incorrectly? I check all the soldering connections and they all seemed good with no incomplete joints. What should I do next?
-
Did you pas the resistance tests?
A spark usually means you touched 2 terminals with the meter probe.
I use a clip lead for the ground connection so I can concentrate on the measurement point.
-
Did you pas the resistance tests?
A spark usually means you touched 2 terminals with the meter probe.
I use a clip lead for the ground connection so I can concentrate on the measurement point.
Yes I passed all the resistance tests. I have a clip for the ground as well but my hands are so shaky with the other lead probe, so I am betting I did touch two terminals. Did I ruin my kit? I rechecked all the resistances and everything was in a normal range.
-
Did you pas the resistance tests?
A spark usually means you touched 2 terminals with the meter probe.
I use a clip lead for the ground connection so I can concentrate on the measurement point.
Would it be harmful if I assume I pass the voltage tests due to passing the resistance test and plug in a pair of headphones?
-
Yes that is risky. PB will probably step in, but meanwhile just re-do the voltage checks (being extra careful about touching the terminals). Better yet, use clipleads for both terminals, turning the preamp off when moving the clips. It takes longer, but has a much better chance of getting clean data without accidental shorts.
BTW, I sympathize with the shaky hands, I have that too.
-
Yes that is risky. PB will probably step in, but meanwhile just re-do the voltage checks (being extra careful about touching the terminals). Better yet, use clipleads for both terminals, turning the preamp off when moving the clips. It takes longer, but has a much better chance of getting clean data without accidental shorts.
BTW, I sympathize with the shaky hands, I have that too.
That's a really good idea I'll definitely try that. Do you think I damaged my amp in anyway with the previous sparking? I rechecked the resistances and they all came back normal again.
-
Maybe, maybe not. I'm not the Crack expert :^) But the only way to know for sure is to do the resistance checks (which you did) and then do the voltage checks.
-
Do you think I damaged my amp in anyway with the previous sparking? I rechecked the resistances and they all came back normal again.
As PJ said, you really can't tell until you do the voltages tests - that's real test for whether you have a working amplifier. There's more than a fair chance that the spark failed to cause any real damage - and if if something is damaged it will almost certainly be cheap to replace. The only pricey stuff in the amp is the transformer and the tubes, and i can't imagine a momentary spark doing them in.
Following up on PJ's recommendation, i suggest you get some alligator and mini-hook test leads. AmZon sells sets of test leads for under $15. I use mini-hooks almost exclusively. The hooks are small, so it would be very difficult to connect two difference points and cause a spark. And they grab onto the target terminal or wire really well. And in the occasional circumstance where they pop off the terminal you are measuring, an internal spring instantly retracts the hook: no accidental contacts.
cheers, Derek
-
Thanks a lot guys your help is greatly appreciated!
-
A spark at terminal 3 with your other probe at terminal 12 doesn't really say a lot about what the voltages might be. Having that happen and then plugging in headphones and using the amp is not a wise course of action.
-
Take a piece of tape and wrap the metal tip of your red probe so that only the very end of it is exposed. That will help to avoid touching terminals you don't want to touch when you probe around in the circuit. Then redo your voltages measurements. They will most likely be fine.
-
Ok, so I got some hook leads and I tried to do the voltage testing again but the tube leds weren't lighting up however they were lighting up before. I checked all the soldering connections and everything was fine. Is it possible that I blew the fuse? If so how would I get a replacement?
-
Ok, so I got some hook leads and I tried to do the voltage testing again but the tube leds weren't lighting up however they were lighting up before. I checked all the soldering connections and everything was fine. Is it possible that I blew the fuse? If so how would I get a replacement?
Also, when I check to see which tube is glowing, only the 6080 is glowing where the 12AU78 does not.
-
Could you post the DC voltages you get on terminals 1 through 10?
If the 6080 lights up and the 12AU7 does not, the green twisted wiring going from the 8 pin socket to the 12AU7 may be loose at either end. Do remember that the 12AU7 doesn't glow particularly brightly.
-PB
-
Could you post the DC voltages you get on terminals 1 through 10?
If the 6080 lights up and the 12AU7 does not, the green twisted wiring going from the 8 pin socket to the 12AU7 may be loose at either end. Do remember that the 12AU7 doesn't glow particularly brightly.
-PB
Hi so my voltage tests results are
Terminal 1: 170 Volts
Terminal 2: 190 volts
Terminal 3: 0 volts
Terminal 4: 190 volts
Terminal 5: 170 volts
Terminal 6: 0 volts
Terminal 7: 170 volts
Terminal 8: 0 volts
Terminal 9: 170 volts
Terminal 10: 0 volts
Just to reiterate, the leds and the 12au7 are no longer lighting up. However, yesterday before I sparked terminal 3 the leds and the 12au7 tuber were both lighting up.
Once again thanks for the help, I'm a bit of an amateur when it comes to electrical wiring so the help is greatly appreciated.
-
Hi Krishk - I'd follow PB's advice here and really scrutinize the green heater wiring that runs between the two tube sockets.
... the green twisted wiring going from the 8 pin socket to the 12AU7 may be loose at either end.
No 12AU7 glow suggests that there's no heater current, and the green wires carry that current directly from the transformer. And you know that the heater winding of the transformer is working b/c the 6080 glows. So all of this points to a possible faulty joint on the green wires between tube sockets. The problem might turn out to be somewhere else, but this is the first thing you need to rule in or out.
It might be helpful if you posted clear pics of each socket and of the solder connections of the green wires at each socket.
cheers, Derek
-
Hi Krishk - I'd follow PB's advice here and really scrutinize the green heater wiring that runs between the two tube sockets.
No 12AU7 glow suggests that there's no heater current, and the green wires carry that current directly from the transformer. And you know that the heater winding of the transformer is working b/c the 6080 glows. So all of this points to a possible faulty joint on the green wires between tube sockets. The problem might turn out to be somewhere else, but this is the first thing you need to rule in or out.
It might be helpful if you posted clear pics of each socket and of the solder connections of the green wires at each socket.
cheers, Derek
I've attached pics of the tube sockets. Please let me know if you need better pictures. I checked all the solder joints and they all seem stable however, please let me know what you think.
-
This wire needs to be soldered for both tubes to glow.
You have some wires on the 9 pin socket with way too much jacketing stripped off, and that may cause shorts down the road.
-PB
-
Thanks for the advice I'll re solder that wire and I'll trim down any extra leads to prevent shorting, I'll let you know what happens.
-
It turns out that was the faulty solder joint, after I applied more solder the lights for both the led and tube turned on. thanks for the advice!
-
Hi Paul,
After getting the tubes relit again I redid the voltage tests and I found these terminals to be a bit out of the suggested range given in the manual. Should I be alarmed by these rather high voltages? The terminals not listed all came back within the range.
Thanks!
Terminal 2: 208 volts
Terminal 4: 208 volts
Terminal 7: 123.8
Terminal 9: 123.8 volts
-
Just a shot in the dark here: you might want to (a) double check your mains voltage coming out of your wall outlets, and (b) make sure you wired the transformer for the corresponding voltage. It looks like your measured voltages are about 20% high. I imagine a mains voltage of 120V or more with a transformer wired for less than 115V would result in higher voltages.
cheers, Derek
-
I see, I used a different power strip to wire my transformer than the outlet I used to test the amp. Will that explain the difference I am getting? Thanks!
-
I doubt it, but I can't say for sure. To take the strip out of the equation, try measuring the voltage coming out of the power strip.
[Edit: apologies - I misread your post. If you're not powering the amp through the power strip, and instead directly from a wall outlet, I'd measure the voaltge coming out of the wall outlet - that said, measuring both would tell you whether your power strip is putting out less voltage - in which case I'd say there's something wrong with it).
cheers, Derek
-
I'm sorry, I didn't correctly identify that I used a surge protector, not a power strip, to figure out the voltage to wire my amp. Would a surge protector change the result?
-
Dunno :) Just measure it!
-
I see what you mean, the voltages are the same and when I redid the powerline voltage test, the voltage came back as 123 volts. So I must have misread the multimeter. Anyways fixing the wiring should solve my high voltage issue then right? Thanks!
-
Anyways fixing the wiring should solve my high voltage issue then right? Thanks!
My guess is "yes", but at the very least you'll be a lot closer :)
cheers, Derek
-
If you have 123V coming out of the wall and you wired for 120V AC, then I'm not worried about those voltages that you have which are a bit on the high side.
-
Just to update, I reconfigured the transformer setup and now passed all my voltage tests. I tried the amp with a pair of zmf headphones and the amp sounds incredible! I have a very slight buzz when I have nothing playing, this is probably result to a faulty solder join right? Thanks for all the help with my build guys!
-
A bit of a buzz could indicate that one of the 220uF caps isn't all the way soldered. You can wiggle each one and see if the leads move through the terminal strips.
A little bit of buzz with the volume control turned all the way up and nothing plugged into the inputs is also completely normal and not indicative of anything amiss.
-
What's weird is that I hear the buzz with my zmf headphones but not with other sennheiser ones, could this be a cable issue?
-
I would start by looking at those 220uF filter caps and being sure that you hear the noise with the volume pot turned all the way down.