Prism DS with a Weak Dewar Vacuum ( Can it be saved :O ) - Page 1
Forum section: electronics / general

author: MrSheep
author_rank: Frequent Contributor
timestamp: July 20, 2024, 01:45:05 pm
content: I currently have a Prism DS that I would like to attempt to save. Given that it is a for parts camera already, I would like to take the opportunity to experiment on it.It has a gold tube that houses the PtSi Detector (320x244) what a weird and interesting array. Normally I would expect an InSb FPA for MWIR (3-5um) but I guess it is what they decided to go with back in 1995.The issue with this camera is that when trying to cool down the cooler runs, however it never reaches the set point also when touching the dewar window/tube it is cold (Not enough to frost over though). Also I don't see any frosting inside when it runs. Was told there was a weak vacuum or no vacuum.I wonder if the weak vacuum has to do with the Janky soldering of the tube itself. Newer designs of the Prism DS no longer use the gold tube but a solid metal tube more commonly seen today.This camera uses the same Linear Cryocooler found in the Amber Radiance 1/Radiance HS Cameras. The Hughes 7060H-26SP.S. I will probably post the control/power boards I have at a later time. They are in pretty good shape still!

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 20, 2024, 01:52:47 pm
content: This definitely looks like either a prototype or first run to me. That soldering is absolutely hand-done, and I would dare guess that it might actually even be regular solder.If it's soft enough to slice off a couple chunks with a scalpel, stick it on a soldering iron and crank up the temp slowly to see where it melts

author: MrSheep
author_rank: Frequent Contributor
timestamp: July 20, 2024, 01:56:20 pm
content: Yes my thoughts exactly! This must have been a prototype model! The newer version of the Prism DS looks way more professional. I think it is RF or laser welded.And haha good idea! Doesn't really look like the high silver content solder you normally see.Also do you know what the nylon ring is on the dewar near the pinch off tube. I see this on many IDCCA's my guess is that it is to stabilize the Dewar PCB?

author: Spirit532
author_rank: Frequent Contributor
timestamp: July 20, 2024, 02:10:37 pm
content: Yes, it's just mechanical. Can be taken off with no problem.

author: IR_Geek
author_rank: Regular Contributor
timestamp: July 20, 2024, 03:19:49 pm
content: as long as the compressor doesn't sound like it's banging, then it probably is a weak vacuum.as for PtSi vs. InSb. InSb was harder to process, more sensitive, and more costly. With that being a hand held camera they were going for cheaper. Of course cheaper in this case is relative. 100K+ vs. 30K-50K

author: MrSheep
author_rank: Frequent Contributor
timestamp: July 20, 2024, 03:26:21 pm
content: Yeah I am leaning towards weak vacuum.And that is nice to know and very interesting indeed.

author: MrSheep
author_rank: Frequent Contributor
timestamp: July 26, 2024, 04:56:07 pm
content: Interesting picture they have on this page. Is that an inductive heater I see? I am guessing they working on a test dewar.https://ricor.com/innovations/ricors-rotary-cryocoolers-development-and-optimization-for-hot-ir-detectors/

author: MrSheep
author_rank: Frequent Contributor
timestamp: July 26, 2024, 05:19:53 pm
content: Also found this cool teardown of a dewar assembly:https://xdevs.com/article/sti/Also I finally found what a NEG (Non-Evaporable Getter) looks like inside the vacuum dewar. Probably a similar getter in my dewar (grey resistor looking thing)

author: MrSheep
author_rank: Frequent Contributor
timestamp: August 13, 2024, 09:21:57 pm
content: Found this nice little snippet about PtSi vs InSb in the Amber Radiance HS brochure