Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: jboehle on May 01, 2014, 08:05:17 AM

Title: Couple of resistance check issues (SOLVED)
Post by: jboehle on May 01, 2014, 08:05:17 AM

Hi, finished my Crack last night.  Did the resistance check and have two issues.  Before I get to those, I wired tab 4 on the transformer to terminal 14 in the Crack as is suggested in the manual.  I am using an HP 3478A meter in 2 wire resistance, auto-ranging mode.

Reading at terminal 13 - starts at 30M ohms, slowly drops until 2-3M ohms, then meter switches to K ohms range, then slowly grows from 150K to 270K ohms.  I've had the meter hooked up here for ~15 minutes and it's currently reading 262.K.  The manual does not mention the first part of that (starting at 30M ohms and dropping).

Reading at terminal 22 - 6.8 ohms.  The manual says this should be 0 ohms.

All of my other resistance checks matched the manual.

Title: Re: Couple of resistance check issues
Post by: jboehle on May 01, 2014, 08:15:10 AM

I solved the 2nd issue.  I checked readings at terminals 11, 16, & 17 and those were all 0 ohms, so I thought maybe the lock washer on the screw at terminal 22 did not fully penetrate the paint on my transformer bell.  I tightened the screw at terminal 22 down harder, and now terminal 22 reads 0 ohms as well.

For my other issue, I went back and read the manual and it does say that the * readings will vary from meter to meter, so I'm guessing my issue at terminal 13 is a non-issue, since it does eventually slowly grow to 270K ohms, and I'm probably ready to power up.

Title: Re: Couple of resistance check issues
Post by: Paul Joppa on May 01, 2014, 12:10:26 PM

That slow ramping of the reading is because the ohmmeter is charging a capacitor; apparently when your meter changes range is also changes the voltage it uses for the measurement, thus reversing some of the charge it put on in the first place.

Title: Re: Couple of resistance check issues
Post by: jboehle on May 01, 2014, 04:36:26 PM

Powered up without incident!  Listened to it a good part of the afternoon, it sounds amazing with my Senn HD 650.  Below are my voltage check numbers.  All are within the 10-15% variation range.  I think my AC line voltage was 122 at the time.

1. 79
2. 175
3. 0
4. 175
5. 78
6. 0
7. 108
8. 0
9. 105
10. 0
11. 0
12. 0
13. 175
14. 0
15. 197
20. 0
21. 219

A1. 78
A2. 0
A4. 0
A5. 0
A6. 79
A7. 0
A9. 0

B1. 79
B2. 175
B3. 108
B4. 78
B5. 175
B6. 105
B7. 0
B8. 0

I have the Speedball and Crackheadphone up next.  :)

Title: Re: Couple of resistance check issues
Post by: jboehle on May 01, 2014, 04:41:38 PM

Oh yeah, and mine is bone stock at the moment, other than painting the chassis plate and transformer bell.