Resistance Check Help

[friedfish]

Hey, I'm having a bit of a problem with my Crack build and I can't quite diagnose the issue. After first finishing my build all resistances checked out correctly however the rectifier between 19 and 21 was installed in reverse causing a blown fuse. I corrected the issue and everything seemed to be working correctly. Tubes successfully lit, LED's were on etc... however, I failed on a voltage check (I've now forgotten which connections failed).

I attempted to touch up a couple of solder points however my resistances have all gone to hell now and I just can't figure out why or how. Here are my current measurements:

Terminal     Manual           Measured

1                  *                22.6k ohms
2                  *                .545k ohms
3                  0 ohms       27M ohms
4                  *                .545k ohms
5                  *                22.7k ohms
6                  2.4k ohms   0 ohms
7                  2.9k ohms   26.1M ohms
8                  0 ohms        26.2M ohms
9                  2.9k ohms   26.2M ohms
10                2.4k ohms   2.48k ohms
12                0 ohms        0 ohms
13                *                 .54k ohms
14                0 ohms        .2 ohms
20                0 ohms        4.1M ohms
22                0 ohms        0 ohms
B3                2.9k ohms   25.5M ohms
B6                2.9k ohms   25.5M ohms

I've re-checked my build again and can't find any problems/faulty solder points and would REALLY appreciate your help/feedback.

[Paul Birkeland]

If you don't have 0 ohms at terminal 3, your amplifier was never safe to turn on...

Which terminal are you using for ground?  Whatever terminal it is, it appears to not be grounded.

Also, there appears to be an "extra" wire around/under terminals 12 and 13.

-PB

[friedfish]

Hey PB - thanks for your reply!

The extra wire you're seeing under 12/13 is actually the power switch to power transformer 1 connection (page 17 in the manual).

I've been using terminal terminal 12 as ground as suggested in the manual (sorry I should have stated such in the beginning). I originally had to spec resistances including 0 ohms at terminal three before resoldering a couple of connections which is partly why I'm is so confused at the moment. For what it's worth the resistance reading at terminal 3 is not stable - it jumps erratically and in fact is now settling at 38 M ohms

Visual inspections don't reveal any incidentally overlapping connections or touch points on the chasis body itself nor does there appear to be any insulation missing from any wires.

While trouble shooting I also uncovered an additional layer of mystery - there are currently no connections to terminal 11, 16, or 17 yet I measure between 50 and 100 ohm resistance at each of those terminals (none at 22). This seems to suggest a connection between the mounting tab screws and the chasis itself in spite of the rubber brackets. Perhaps excess solder slipped into the power transformer area? Have you heard of anything like this before or have any suggestions about how to proceed?

Thank you again for your help.

[Paul Birkeland]

I've been using terminal terminal 12 as ground as suggested in the manual [...] For what it's worth the resistance reading at terminal 3 is not stable - it jumps erratically and in fact is now settling at 38 M ohms

These terminals connect through the ground buss of black wires.  Since you don't have 0 ohms between these terminals, there is a failed connection or a missing wire. The amplifier must not be turned on until this is corrected.  The most common issue here is the junction of the black wires on the headphone jack not being appropriately soldered.

The resistances  of 11, 16, and 17 are not all that important, and can be disregarded.