Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: clamhost on March 20, 2014, 06:30:06 PM
-
As the title said. Other than that my multimeter sucks. I will be uploading the checks I did. I didn't finish the voltage checks since the cap was smoking. Resistance checks seemed fine but again my multimeter is awful.
-
Generally you'll smoke a cap when it's backwards.
There are other ways to make smoke from your amp, generally by having a short somewhere in the circuit that draws excessive current through the 270 Ohm resistors.
If you post pics, we might be able to spot what's awry.
-
http://m.imgur.com/CFoodo0,rcaA2Ra,GI0Rcpv,qyU8Ddt,ISyVBAF,578HCl9,j0tK83R,7V3VfLK,KT5q14X
I uploaded a bunch of pics. The meter even told me a 270k resistor was 1.
-
In looking at the 6th photo it appears (I can't see under the cap to be sure) the black jumper may be connected from T15 to T12 (should be T14 to T12 as shown on P.29 of the manual)
-
Its on T14.
-Thomas
-
OK, I also noticed the untrimmed lead on B3 appears to be close to, or possibly making contact with the bare wire connecting B5 to B2.
-
Its not from what I can see. Took a closer pic as well.
http://m.imgur.com/OVqrCY5
-
Help?
-
If your multimeter is bad get a better one. We need reliable measurements to be able to help. Typically caps don't smoke, resistors do. Are you sure the smoke is not from the white resistor under the cap? If that resistor is having to much current drawn though it from a short somewhere further on in the circuit it could overheat. Look for miswires and look for wires and leads shorted to the chassis or touching terminals that they should not be touching.
-
It would help to get more shots of the power supply as well.
If you want, you can disconnect the red wire leaving 13U, then turn the amp back on and test the power supply unloaded.
As others have pointed out, you have a lot of extra pieces of wire here and there that really should be removed, as eventually they may move and contact other parts.
It's also possible that the leads on the 270 Ohm resistor crossing over the power transformer are touching something other than the two terminals that they are soldered to, and that would also cause some potential issues.
-PB
-
Good news. Asked my grandfather if I could borrow his nice Craftsmen meter and I passed all the checks. Bad news is when I put my HD800 in I can't put it in all the way or I don't hear anything. I have to put the headphone jack in almost all the way to get stereo sound. I believe my TRS jack is bad on the crack.
Opinions or perhaps I'm wrong?
Thanks,
Tom
-
This is covered in the Crack FAQ.
When you have the plug 1/2 way in, you feed one channel to both ears (ring to both tip and ring). IIRC, this means there's an issue with the left channel.
To diagnose this, you'll want to download a 60Hz test tone and feed it into the Crack.
Measure the AC voltage from ground to the center pin of each RCA jack, then to each of the outer lugs of the pot, then (with the volume up all the way) out the center lug of each level of the pot.
After that, measure the AC voltage at terminals 6 and 10.
-PB
-
Alright I'll start working on it
-
To diagnose this, you'll want to download a 60Hz test tone and feed it into the Crack.
Measure the AC voltage from ground to the center pin of each RCA jack, then to each of the outer lugs of the pot, then (with the volume up all the way) out the center lug of each level of the pot.
After that, measure the AC voltage at terminals 6 and 10.
Craftsmen Multimeter set to VAC 200.
RCA White Jack had AC of 01.0
RCA Red had AC of 01.1
The pot had 01.1 on all red and white wires.
All ground (including ground on RCA jacks had 0.00 AC)
Terminal 6 had AC of 09.6
Terminal 10 had AC of 09.2
-
Ah, good!
This means that voltage is getting to the terminal strip. Triple check the red and white wires leaving 6 and 10. Also, if you did the grounding modification (forum sticky), try undoing it to see if that helps.
-PB
-
Just triple checked it, didn't do the grounding mod. The wires look good, but I can try resoldering them if it might help?
-
Looking at the white wire more closely, it looks like there's about 3x the amount of solder that you would actually need to make a connection. This excess of solder in and of itself could be part of the problem.
You can set your meter back to Ohms and measure the resistance between terminal 10 and the uppermost lug on the headphone jack where the white wire is connected. This should be near 0 Ohms.
-PB
-
2.45ohm when my meter was set to 20k. On the white wire in the headphone jack.
-
Just removed some excess solder. Will test now.
-
Left side still doesn't work lol.
-
Amp is MUCH louder though. That is good news.
-
Can you measure the AC voltage with that 60hz tone and the volume cranked between the chassis and the end of the white wire where it solders to the headphone jack?
-
09.3 AC with my meter on VAC 200.
-
If you have ~9V there, can you see if the tip of the headphone plug touches the metal on that connection with headphones plugged in?
Also, can you add a photo of the jack from the side with the terminals and resistors?
-
Here's the pic:
http://imgur.com/z0j5Pss,NmJCvyO
-
I also took a pic of my HD800 plugged in the crack.
http://imgur.com/oOjZNJP,736QZA0
-
Help?
-
I think the tip is touching the plastic internally.
-
That looks pretty cooked, we can send you a replacement, just email replacement parts.
When you solder, take a wrap with the wire, then add just enough solder so that the space between the wire and the terminal has solder between it. It is not necessary to fill the entire hole with solder, and putting solder up the wire does nothing but melt more plastic and make the construction process much tougher.
-PB
-
You have just traced the audio signal path to, and I think through, the volume pot where it disappears at terminals 6 & 10.
Note, this is a feat you couldn't perform before. It is a logical straight forward troubleshooting technique.
Congratulations on your new skill. It is amazing what folks learn here.
-
Good news. Asked my grandfather if I could borrow his nice Craftsmen meter and I passed all the checks. Bad news is when I put my HD800 in I can't put it in all the way or I don't hear anything. I have to put the headphone jack in almost all the way to get stereo sound. I believe my TRS jack is bad on the crack.
Opinions or perhaps I'm wrong?
Thanks,
Tom
Smoke... and your eager to stick those 800's in eh? Very brave... First line of business is to get yourself a cheapie set... and a 1/4" adapter if you need it.
-
Once I soldered the new headphone jack the amp works. It sounds good.
-Thomas
PS: When I remove my headphone jack from the amp the metal plate comes up and knocks down. Is there a way to secure the plate to the wood base?
-
You can use glue; I'd go with real silicone caulk as it is highly heat-resistent.
But you know the base is not that heavy. You would likely just pull it up along with the amp.
Easiest is to put down your "adult beverage of choice" (mine is usually gin in some form) and use your other hand to hold the chassis down.
Ultimate is to make a base out of lead or depleted uranium.
Yes I seem to have an April 1st hangover. I blame it on the gin. :^)
-
IMO silicone calking is the way to go. If you need/want to do some mods, you can still push the top plate off the base, rub off the calking and re-glue the top to re secure it. ( and if you're careful you probably won't ever break anything)