Resistance check issues [resolved]

[Kakuz]

Hi everyone,

So, this is my first project with anything related to electronics, so I expected something to fail along the way. I made sure to triple check the instructions, and everything looks solidly soldered, but I'm getting weird and unreliable resistance measures. This also happens to be my first time using a multimeter, but I followed the instructions on every manual (using the tip of terminal 12 as ground). Anyways, here is the mess:

1     *       * (increasing values in the M range)
2     *       * (same)
3     0       13.4M (first read) / 4.6M (second read)
4     *       * (same as above)
5     *       * (idem)
6     2.4k   2.49k
7     2.9K   13.3M (first read) / 4.6M (second read)
8     0        13.3M (first read) / 4.6M (second read)
9     2.9k    13.3M (first read) / 4.6M (second read)
10   2.4k    2.4k
12   0        0.L (whatever that means). Sometimes 0  
13   *        During first read it climbed steadily, second read it dropped from 8M (didn't wait to 270K)
14   0        0
20   0        0
22   0        5.5M

B3   2.9K   5.6M
B6   2.9K   5.7M

RCA
Ground  0  0
Center   Red = 106K; Black = 4.6M

As you can see, the measurements are way out of place. It seems like the 3K ohm resistors are messed up. I would appreciate any help.

Thanks.

[fullheadofnothing]

With this many incorrect readings, the most common culprit is an un-/mis-wired ground connection. Can you post pictures of your build?

[Paul Birkeland]

3     0       13.4M (first read) / 4.6M (second read)

This indicates that the buss of black wires through the amp is not properly connected and/or soldered.  Follow it from the unbanded ends of the UF4007 diodes as it crosses the power transformer, up to the headphone jack, then to T3.  I bet the solder joint on your headphone jack where the black wires meed is not all the way soldered, and one wire is loose or has popped out.

RCA
Center   Red = 106K; Black = 4.6M

This would tend to indicate that the jumper between the grounds on the volume pot isn't present.

Josh is correct, some photos would help a lot.

[Kakuz]

Sorry, I had to retake the pics once I found the camera's tripod. I tried to get as many angles as I thought were useful, but let me know if you want another take. I followed the paths of black wire and they were all solidly joined (cold maybe?).

Some notes: T15 was tough. As I finished soldering the whole thing moved, so I had to reapply. Also, I accidentally applied too much solder on the black RCA and it dripped. I tried to get as much out with solder wick as I could, but that thing never worked properly. I can assure that the solder is not "joining" anything it shouldn't here. Finally, I accidentally burned some cables with the iron. No exposed wire though.

Finally, I am curious about 2 parts that were not called by the manual: some kind of glass tube with 2 aluminum ends. One side has F1.5AL250V engraved on it. The other is a star lock washer. I know I double and triple checked everything, it's just that they were never called during assembly.

Thanks for your help!

[Deluk]

The imgur link takes me to Steam Community. Nothing relevant there. Your "glass tube" is of course your mains fuse.

[Kakuz]

The imgur link takes me to Steam Community. Nothing relevant there. Your "glass tube" is of course your mains fuse.

That's odd, it works for me. Well, I realized that if I add 3 pictures at a time the site doesn't crash, so I added them to my second post.

And sorry for being so ignorant, but in this context how would I use that fuse? Is it there just in case I short something?

[Tom-s]

Page 38 of my manual (2013) states after the resistance checks you insert the tubes and the fuse into its holder.
So it isn't left out.
And yes it has a purpose if a short occurs.
I'd recommend using it.

[Kakuz]

Page 38 of my manual (2013) states after the resistance checks you insert the tubes and the fuse into its holder.
So it isn't left out.
And yes it has a purpose if a short occurs.
I'd recommend using it.

I see, thanks. I only skimmed through the pages after resistance checks, so it makes sense that I didn't see it.

[Paul Birkeland]

This indicates that the buss of black wires through the amp is not properly connected and/or soldered.  Follow it from the unbanded ends of the UF4007 diodes as it crosses the power transformer, up to the headphone jack, then to T3.  I bet the solder joint on your headphone jack where the black wires meed is not all the way soldered, and one wire is loose or has popped out.
This would tend to indicate that the jumper between the grounds on the volume pot isn't present.

Please do check into these issues, they still seem likely after examining your photos.

[Kakuz]

Please do check into these issues, they still seem likely after examining your photos.

You are great, that did it. I had probed each black wire connection earlier, but I just applied some heat and solder to the jack and T12 and now everything is fine! some measurements are off by a bit (2.48k instead of 2.4k, or 2.98k instead of 2.9k) but that seems like the expected variation.

Thanks a lot, now onto voltage!