| Products > Test Equipment |
| Fool for the 8656A Sig Gen |
| << < (37/37) |
| VK5RC:
I used a pair of metric o-rings to replace the original hp grommets, I used ID 3mm, 2mm thick o-rings but sanded them down to about 1.2mm using the same technique as jrharley - stuck the o-ring to aluminium tape and used a disk sander. Lost a couple in the shed! See photo 1 in above post old grommet on LHS new o-ring type on RHS. Reassembly was a bit tricky - my actuator cover - when it's screws are loosened - doesn't lift up much but by prying it gently up with a screw driver and angling the fork in - see photo 3 below - and with a little encouragement from a long fine flat blade screw driver advancing the grommet part of the fork into the actuator mechanism. You can confirm that it is lodged by pulling and pushing the fork and you get a reassuring clunk of the actuator solenoid. Final reassembly was pre-dated by cleaning in IPA and a bit of de-oxit D5 on the contact surfaces. Testing so far looks good 👍 I have a few spare forks and are happy to forward to fellow HP 8656A restorers. Again thanks to jrharley for his PMs and this post Rob VK5RC |
| jrharley:
Great work Robert! Thanks for adding to the information on this notoriously problematic component of the 8656A. The information on the tolerances is good to know. I think I've come to the conclusion that, even though the attenuator approach seems pretty whacky within the context of more modern equipment, those actuator forks and the solenoid assembly, seem to be pretty tolerant of small dimensional variations mechanically. Nice to see someone go the distance on molding replacement parts as proof of concept. Well done! :-+ jrh |
| Tony_G:
That's outstanding guys - Well done. When you created the mold, did you 3D print the piece originally? I'm just wondering if you might be able to get away with just printing using something like PLA-CF? TonyG |
| VK5RC:
@TonyG - I used the original glued (epoxied) back together fork for the original in the moulding process. I don't think the resolution of a 3D print - unless an exceptional printer - would be accurate enough - and the strength would also be a bit questionable - the 'neck' of the fork - just before the base that holds the grommet is only 2-3mm thick - my repair deliberately made it a bit thicker there - maybe 3-4mm and that is where the kevlar is in the epoxy. Getting that shape into your fav 3D program would be a right PITA as well. Talking to my dental mate - some dental practices have 3D laser scanners attached to CNC mills that can scan then make your next large filling or section of tooth from ceramic blanks. They have to be super careful as the forces that go through a tooth when you bite down are huge. Dentists are a fantastic resource about making small things and their materials / bonding knowledge is amazing 👍 |
| Navigation |
| Message Index |
| Previous page |