RH-50 {#rh_50}
These are the longer resistors on the Ion Arm{.wikilink} of the Proton Pack{.wikilink}. They are made by Dale. These resistors are easy to find at surplus stores as they were made in large quantities in the 70's and 80's.
http://www.gbfans.com/images/store/231_9806069382.jpg
There are slight cosmetic variations of the RH-50 (for example, the Dale logo on the side) depending on when and where it was manufactured. Any version is technically accurate as they are all found on the different packs used.
The resistor is mounted on the right of the Ion Arm and has 1/4" diameter blue hose attached to both leads. The top hose goes to the Clippard{.wikilink} elbow on top of the Ion Arm, and the bottom hose goes to the PPD{.wikilink}.
On some publicity stills for GB1 they seem to have been replaced by a Sage Resistor{.wikilink}, but evidence seems to support this is a modification that was made after filming.
For Ghostbusters 2, resin copies of the RH-50 were made and used on Ion Arms for packs created specifically for the film. The addition of Clippard #11752 Hose Barbs in place of the original metal leads are a tell for spotting the resin copies.
PH-25 {#ph_25}
These are the round resistors on the Ion Arm{.wikilink} on the Proton Pack{.wikilink}. They were made by Dale and from what we have unearthed, they are no longer made. These resistors are easy to find at surplus stores however as they were manufactured in huge quantities in the 70's and 80's. However, the readily available model has a ring on the fins that was not present on the screen-used resistors; the PH-25 without the ring can be a little hard to find. The version with the ring was used on the Afterlife packs.
They are mounted by drilling a hole, and simply epoxying them into the ion arm. Some packs have the epoxy oozing out around it, and others have it mounted cleanly. You can remove the brass nut, and use that to hold it from the inside of the ion arm if you are able to. The brass nut was mounted externally on the Afterlife packs.
http://www.gbfans.com/images/store/231_2535216538.jpg
