Bottlehead Forum

Bottlehead Kits => S.E.X. Kit => Topic started by: skyej on January 17, 2013, 09:06:43 PM

Title: Having Issues with Resistance Check
Post by: skyej on January 17, 2013, 09:06:43 PM
I am putting together a SEX kit for a friend, and have run into some issues. I know it isn't a whole lot of information to go on, but I have included my resistance values below. Hopefully you guys can provide some intuition about my problem! When the volume is at zero, I have resistance issues with 15,25, and A3. However, when I go to full volume, everything checks out except for the input pins. Let me know what you guys think, or if you need any more info. Thanks!

   Pin      From Manual      Pot Full CCW      Pot Full CW   
   right center pin      100k      90k      0.9k   
   left center pin      100k      90k      0.9k   
   1      *      4.8m      40m   
   2      0      2.7      2.7   
   3      0      2.7      2.7   
   4      *      6.36m      4.9m   
   5      *      30m      6.2m   
   6      *      12m      3.9m   
   7      0      2.7      2.7   
   8      0      2.7      2.7   
   9      249k      249k      249k   
   10      *      5.5m      40m   
   11      *      4.7m      28m   
   12      0      2.7      2.7   
   13      0      2.7      2.7   
   14      ??      4.1      900   
   15      890      384      900   
   16      *      33m      8.9m   
   17      0      2.7      2.7   
   18      0      2.5      2.6   
   19      249k      249k      249k   
   20      *      12m      5.7m   
   21      *      10m      4.9m   
   22      0      2.7      2.8   
   23      0      2.7      2.7   
   24      ??      4.2      904   
   25      890      386      900   
   A1      249k      249k      249k   
   A2      *      5m      7.7m   
   A3      680      172      690   
   A4      ??      172      690   
   A5      *      450k      5m   
   A6      1.27k      1.2k      1.2k   
   A7      *      753      752   
   A8      *      750      756   
   B1      249k      249k      249k   
   B2      *      36m      36m   
   B3      680      690      684   
   B4      ??      228      685   
   B5      *      450k      7.3m   
   B6      1.27k      1.2k      1.2k   
   B7      *      753      752   
   B8      *      754      754   
   C1      *      753      754   
   C2      *      753      752   
   C4      *      753      753   
   C5      *      753      753   
Title: Re: Having Issues with Resistance Check
Post by: Paul Birkeland on January 18, 2013, 03:38:25 AM
The 900 ohm reading from the center pin to ground when the pot is turned all the way clockwise isn't too concerning, seeing that it's 90K when all the way open, there's probably just a bit of error with the meter.

The other variations are terminals that have capacitors "in the way" of getting the most accurate readings, so seeing readings that aren't zero is reassuring.

I'd move onto voltages.
Title: Re: Having Issues with Resistance Check
Post by: Paul Joppa on January 18, 2013, 11:48:26 AM
You should have the rev 1.1 manual, June 15, 2012 - right?

The first two lines suggest that the RCA jack center pin is not wired to the "hot" end of the pot, but rather to the center lug. In that case, make sure the other lugs are properly wired as well.

I suspect that A3 and A4 have the same reading because they are accidentally connected to each other. B3 and B4 appear to have the same problem, intermittently. Because of the way the lugs are twisted, it is sometimes easy to mis-read which lug goes with which tube pin. (Not like I ever made that mistake ...  :^)

A4 and B4 are the driver grid, and should be 220 ohms with the volume all the way down, 100K with it all the way up.
Title: Re: Having Issues with Resistance Check
Post by: skyej on January 18, 2013, 03:02:29 PM
Awesome. Thanks for the responses! I am going to take a look tonight, and see if I can figure if I crossed A3 and A4. I will also check that my lugs on the pot are correct. I will let you know the outcome.
Title: Re: Having Issues with Resistance Check
Post by: skyej on January 19, 2013, 08:19:54 AM
Turns out ALL of the resistance issues were resolved when I fixed the crossed connection between A3 and A4. There was an ugly solder tower that was contacting the side of the resistor between A3,B3 and pin 12,22. I put in the rc circuit tight, and in both the A and B sides, the jacket of the resistor was just barely contacting the the tube pin of A4, or B4. I bent the top of the pin over to the side, and voila, correct resistances across the board. This resolved the input center pin issue, pin 15 issue, pin 25 issue, and obviously A3,B3 and A4,B4 issue. Picture below.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi48.tinypic.com%2F2ihpm5g.jpg&hash=d0d40c7a35e2f3eb6b93da9ad3a63a6f6454abfe)

I know how ugly it looks, but I have resoldered about every pin connected to A3,4 at least 3 times trying to figure out what was going on.

Thanks for your help!!! I am going to check my voltages now.
Title: Re: Having Issues with Resistance Check
Post by: skyej on January 19, 2013, 09:29:39 AM
It works!!!!! Thanks all for you help. I am going to enjoy this amp now. It's been a long build.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi48.tinypic.com%2F2e3odnk.jpg&hash=0efe125830156a56ea568fee2385031a149ad66d)
Title: Re: Having Issues with Resistance Check
Post by: saildoctor on January 19, 2013, 11:56:26 AM
I like the matte/glossy black look!