| 1540 | Beginning disassembly while observing DIB2 QET bias to ground resistances at ebox. QET B/C/D all ~300Ω. QETA starts at 60Ω. As IVC flange is loosened, resistance is unstable ~20 to 300Ω. Once IVC is open, it was found that DIB2 and DIB3 stripline edges were scraping on each other. Lightly jostling DIB2 stripline caused resistance to change as before. Sometimes it would settle at ~few hundred Ω, other times at ~70Ω. All other QET to chassis resistances unchanged. |
| 1600 | We discovered that we could make the DIB2pA QET short to chassis go away by slightly loosening the stripline connection to the SQUET for DIB2. There is still continuity between channels, but all QETs are isolated from chassis. Squeezing the connection tight again causes short to return. |
| 1615 | Removing the screws that attach the SQUET to the tower also causes the short to disappear. Presumably because now there is no possible path to chassis. |
| 1620 | With SQUET unplugged from tower but still plugged into stripline, tried measuring from DIB2pA QET to the chassis of the SQUET card itself. No short seen in this configuration. |
| 1625 | Upon unplugging the SQUET we saw that two pins at the end were somewhat bent. They were the two pins to the right as you face the tower. This is *not* the pA QET side as it turns out - that would be the leftmost pins. |
| 1630 | After straightening the pins, reattach SQUET to tower. The short returned only after attaching the SQUID card to the tower. |
| 1645 | Determined that contact between the flyover cable and the chassis of the stripline plug causes the short. The short disappears when a small piece of kapton is slipped between the flyover cable and the stripline plug. Apparently the flyover cable is not well insulated. It's also the case that if the rerouting board wasn't present, there would be no physical contact between the flyover cable and the stripline plug. |
| | The offending SQUET is ZC-70. The observed short fits well with the observations this run, except why was there no short initially? That's still a bit of a mystery. |
