Dears, I have some fettling story to share. Somehow, I promised one guy to fix his two lamps. He is not a collector, just want to use them while travelling by his old Volkswagen camper. Optimus 930 was the first one. Quite good condition, nothing missing. It is not old enough lamp to be interesting for me but looking good. I decided to help that guy to make it work. So I disassembled it, cleaned, assembled, changed seals etc. and got a “fire ball mantle”… I replaced jet and needle for a new 250CP set and got a “fire ball mantle”… I replaced jet and needle for a new 150CP set and got a “fire ball mantle”… I replaced jet and needle for another new 150CP set and got a “fire ball mantle”… I was doing integrity tests after every change – whole pressurized lamp into the water, finger on the jet etc. etc. – no leakages. Maybe that infamous Optimus 930 J-tube was causing problems? I made some 2mm thick steel ring and put it on the J-tube to increase the air gap between the jet and J-tube and got a “fire ball mantle”… I cleaned the generator again and got a “fire ball mantle”… I noted every several seconds tiny spits of liquid fuel on the jet while using 150CP set. I presumed that 150CP was not big enough and can not keep the generator hot enough to vaporize the fuel. After pre-heating it was quite OK, but after a minute or so these tiny droplets were dancing on the jet and a “fire ball mantle”… Just to try something else I put a rolled piece of tiny brass mesh inside the generator to help vaporize fuel better (ar at least this was my idea), just like with alco fuelled lamps. And I got a “fire ball mantle”… Integrity tests all the time - no leakages. So, I added above the mixing chamber that small dish-shaped steel disc from old Petromax to keep more heat close to the generator. I also put more pressure to the tank – approx. 15-20 pumps instead of 5-10 from the beginning. Maybe more pressure=more fuel=more heat= better vaporisation? Victory!!! Lamps works great. But I needed that old Petromax part, so I made something similar from a bottle cap. Still works great!!! So I removed the distance ring and reduced the air gap. Still works great… So I removed the bottle cap dish. Stupid lamp still works great… I did not want to have anything more with that lamp so I did not removed the mesh from the generator not did not tried another bigger jet. It works great with 150cp in configuration that developed a “fire ball mantle” many times before… Lamp gets hot while working, but reportedly it is normal for Optimus 930. I would suspect that maybe inner casing/J-tube was askew, but design of that lamp does not allow for such mistakes – everything is pretty tight and well fitted all the time. And I dismantled/assembled that lamp like 20 times, so that would be hard to get the same problem every time. I just do not know what was wrong and why. That is why I like these lamps and personally prefer over stoves - plenty of potential factors that may impact lamp performance and some technical mysteries and theories to battle. Just to be mean to that lamp I listed stuff that I do not like about the Optimus 930: - Small cage makes harder to install generator properly, so the Preston loop does not touch the cage rods. - It gets really hot while running - One can not adjust the air gap between the jet and J-tube – c’mon other lamps could do it even 50 years earlier. - That small, all rubber pip/seal in the NRV cannot be repaired. It needs replacement when rubber is too hard. If someone has any idea what the problem cause might have been, then please let me know, share your opinions, feel free to speculate. All the best, Piotrek
Just a comment to the last two of your 'complaints'. The very first 930 did have an adjustable J-tube. As a way of cutting costs, the non-adjustable version was introduced. From my experience, they tend to be ok. Especially with a 250cp jet. The fettle box has a brass cup replacement for these Optimus NRVs. It wasn't only the 930 that used them, but all later production Optimus items.
Sometimes the mystery cause can be a random piece of carbon appearing at the wrong place. The lantern gods have a strange sense of humour sometimes..
I guess you'd never accept defeat on this particular Optimus no matter what it takes. Not for someone who's already experienced enough on pressure lamps. I guess I'd do a mantle-less burn first after fettling. Just to make sure it burns well before putting on a mantle.
Hi Guys, @Nils Stephenson – thank you for info, my experience is mostly limited to pre 1945 lamps. @Fireexit1 – I totally agree and actually I like that particular “mysterious” aspect of this hobby @MYN – I was really dedicated to restore that lamp, because I promised that to the owner. Experience helps, I learned a lot from you guys here. Unfortunately I am not a well-organized, meticulous German type, but “do it somehow” Polish bloke, so it takes more time and humility for me Mantle-less burn – I always do it, but this time there was an old mantle installed already when I received the lamp and I did not want to waste that mantle. Of course, I have never expected that it would take me so many trials to make the lamp running. all the best, Piotrek
I probably might have taken even longer to get the issue resolved. I guess we all have taken long, winding routes at some point in time or another. That journey would eventually lead to what would work in the end but more importantly, it reveals a whole lot more of those that wouldn't work for the particular problem. It seems to me, the more such 'winding paths' we take, the more experienced we become.
Well done. When the 930’s just run - they are great runners - if not, they can be a PITA like yours. Regarding the J-Tube - If you order an Optimus 1200 J-Tube, they’ll fit, and can be easily adjusted. In worst case you’ll have to shorten it a bit, but that is easily done. Same 1200 J-Tube might also come in handy when repairing and old PX 821/827 as the PX 250 J-Tubes are getting rarer to find.
