Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: jwilliams79 on September 09, 2021, 07:07:53 AM
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Just finished crack build failed resistance check. b6 and 9 showing 0 ohms. Everything else passed. I thought it was because the wire moved while I was soldering b5 and insulation got in the terminal. Fixed that, it's still showing 0 ohms. Any ideas?
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Can you post some build photos?
If 9 is showing 0 ohms, I would suspect that the wire that's supposed to leave 10 and go to the headphone jack is connected to 9 instead.
On the off chance that you have powered up the amp (which hopefully you haven't!) and the 100uF cap at 9 and 10 is backwards, it could fail and also give you a 0 ohm reading there.
Still, looking over build photos would be super helpful.
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Thanks for the reply PB. I looked the amp over and moved some the sandblock resistor's wiring going in to 9L. I immediately got the proper resistances at 9 and b6. Then everything checked out but t22. I tightened down the transformer screws and got 0 ohms at t22. Voltage checks good ,leds light ,tubes light. Nothing but static out of the headphone jack. how due I check to see if the problem's the pot, vs headphone jack ,etc ?
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Can you post your voltages at terminals 1-10 and some build photos?
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Pics are coming PB. My voltages Terminal 1:88.3v
T2: 177v
T3 0v
T4 177v
T5 82v
T6 0v
T7 109v
T8 0v
T9 109v
T10 0v
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You really should clean up the green wires that go to the 9 pin socket. The one that goes to A9 is supposed to have only 1/4" of the jacket stripped off, but it looks like you have 3/4". If that wire touches the chassis plate, it will destroy the power transformer. The same goes for the other green wire going to A4/A5.
Did you have the same issue with the stock volume pot?
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I still have the stock one. This wires up the same according to members of the forum. I know you recommend the stock parts but I thought might as well just solder once. What are general ways to diagnose pot vs jack. Do the rcas look decent ? They seem loose when connecting a source. Using my phone as source.
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Yeah, I mean if things start pointing to the pot you'll end up having to remove it anyway to try the stock one, so swapping parts initially isn't always the best plan. Are those the RCA jacks we provided?
If you're using a 1/4" to 1/8" TRS adapter, those can cause problems.
Static and no audio in both channels with perfect voltages is what made me initially suspicious that possibly you got a balance pot by accident or something weird like that.
With the amp off and headphones plugged in, what resistances do you see at terminals 6 and 10?
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T6 and t 10 both .025k using 2k range adjustment. Not a auto dvm.
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An auto DVM might be a good idea. You're suggesting that the resistance reading there is 25 ohms, which seems somewhat improbable unless you're plugging in low impedance headphones. Which headphones did you plug in?
With just a 1/4" to 1/8" adapter plugged into the amp, you would expect to see 2.49K at 6 and 10.
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10$ sonys to test the amp out. Used massdrop 600s as well. I expected less static with 600s but it was basically the same.
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Can you send me a link to the pot you ordered or the part number?
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Pb its the stereo pot from audio note. I read on the forum where someone got the balance pot by mistake. So I made sure to get the stereo pot.
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Here's the part number : ANVPOT-81914
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I think you should put the stock pot in just to be sure.
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If you turn the pot all the way up, what is the DC resistance between the left RCA center pin and A2? What about right RCA center pin and A7? (do this with the amp off)
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Paul,
I did another resistance check, got over the limit and have a loose black wire. So Ill be soldering the loose wire. Should I reflow all black wires ?
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I would reflow all the joints other than the ones with the LEDs and the power switch.
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That's what I'll do. I just reflowed the one that was really loose and still over the limit.
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I got it working. I reflowed some ground connections, tightened up the loose rca, and used my usb dac as my source. Audionote pot is good and the amp is awesome. Makes 10$ headphones sound good.
Thanks for the help PB. What checks are necessary or precautionary steps to protect my headphones? Do a resistance check before turning on ?
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What checks are necessary or precautionary steps to protect my headphones? Do a resistance check before turning on ?
The resistance check won't change unless there's a flaky solder joint, and if you've reheated all of them I wouldn't worry about that.