My DMM GROWLS at me - Page 1
Forum section: electronics / repair

author: watchmaker
author_rank: Unknown
timestamp: December 09, 2023, 05:45:42 pm
content: I just bought a Philips PM2525 (cheap) for the helluvit. Works fine but it growls when switching settings.OK, there is a motor driven selector. What in the world were they thinking? (Makes it an interesting artifact).It sounds OK, like an old style selector in a vending machine. But should it be noisy or quiet?Secondly, there is, never was, an earth ground pin on the line cord receptacle. While I am only working under 30V right now, and I all my other bench equipment is earthed, I have less confidence in this.So my second question is: Should that be earthed?Regards,Dewey

author: edpalmer42
author_rank: Super Contributor
timestamp: December 09, 2023, 06:26:59 pm
content: There's a youtube video of a PM2525 that also growls. So it's either a common fault or normal operation.I have a PM2534 which is totally different. No motor.Now I'm sad.I want a bench meter with a motor.

author: watchmaker
author_rank: Unknown
timestamp: December 09, 2023, 07:35:14 pm
content: Thanks! and LOL!I will see if I can quiet the drive (disconnect it???).Anyway, any thoughts on why they went that way? Did they have an overrun of servo motors?And what about the missing (never installed) earth pin in the line cord socket? Should that be a concern?Regards,Dewey

author: coppercone2
author_rank: Super Contributor
timestamp: December 09, 2023, 07:40:03 pm
content: they wanted good contacts without putting a whole shit load of relays into the thing. with a motor you can get good contact force instead of the dinky push button gang switches that break and are also impossible to serviceprobobly just needs lubricantif you look at the cost of alot of good relays, the motor is suddenly appealing. also with a good layout, there is less wiring/traces for the drivers ETChaha if you put a fast settling and low drift on a high digits meter a steam valve and water tank would be acceptable. their often quite shit

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 09, 2023, 08:19:45 pm
content: Grumpy sounding stuff of that nature is usually indicative of dried up grease/oil gumming things up, probably time for a clean and relube. Careful application of WD40 (doesn't take much, don't wash stuff out with it, just wet the moving parts and work it in) can be used to diagnose.If it was built with a 2 pin power inlet, it was built and approved to run without a ground.

author: edpalmer42
author_rank: Super Contributor
timestamp: December 09, 2023, 09:02:25 pm
content: Quote from: watchmaker on December 09, 2023, 07:35:14 pmA DMMMUSTbe isolated from ground. You never know when the ground pin in the circuit you're repairing isn't ground. It looks like the PM2525 just makes the entire unit floating so that it can't be accidently grounded. Adding a random ground could make things very exciting in a very bad way.I did a quick look around and didn't find a version of the service manual that included a schematic so I can't be sure exactly what's going on. My PM2534 does have a 3-wire socket, but the ground pin doesn't come anywhere near the front panel. It stays on an isolated part of the circuit, specifically the outguard supply which powers the digital parts of the circuit. Even that can be disabled via a jumper. In that case, the only function of the ground pin is to provide shielding between the primary and secondaries of the transformer.Bottom line: Don't mess with it.Ed

author: watchmaker
author_rank: Unknown
timestamp: December 10, 2023, 01:03:38 am
content: Quote from: edpalmer42 on December 09, 2023, 09:02:25 pmA very big THANK YOU!!. I looked at the SM and has a warning attached as JPG. But as an experienced watchmaker, I know far too many people who think they know better than the manufacturer. So I had no intention of changing it.I looked at others and they do have the earth connector. SO I wonder if this was put up special?Can I use it at voltages under 120 w/o jeopardizing something?I took it apart to find the source of the vibration (found it, see next post) and took a pic of the socket. Happily I have time on my calibration battery, reads 3.1VDC.Regards,Dewey

author: coppercone2
author_rank: Super Contributor
timestamp: February 20, 2024, 05:06:36 am
content: why do watches not recommend lubricant though?I think it must be because the pressure on the surfaces of the gears and stuff is low enough and they are hard enough that their cycle life is long enough without.What metals are they made from etc?Also I suspect that if there is any lubricant at all in a watch after a while it will all be internally coated by at least a very thin layer of grease. maybe this is enough (atomic thickness)for ultra clean applications I read that basically 1 hour in the normal air leads to a film of grease forming on an object, after something like ultra cleaning with plasma

author: Smokey
author_rank: Super Contributor
timestamp: February 20, 2024, 06:55:09 am
content: Quote from: coppercone2 on February 20, 2024, 05:06:36 amI know everything I know about watch repair from watching wristwatch revival on youtube....https://www.youtube.com/@WristwatchRevivalHe does lubricate everything, but it's with different weight oil for different stuff and a minimal amount.

author: watchmaker
author_rank: Unknown
timestamp: February 20, 2024, 10:10:23 am
content: Well if it is on the internet it MUST be true.What I know is from being trained in Switzerland for a year and some other trips in programs funded by Rolex, Patek,Audemars, and Swatch (Omega and Tissot). And my site is used by many of the formal schools worldwide (in fact it is what got me invited to Switzerland in the first place).Look up WOSTEP.

author: coppercone2
author_rank: Super Contributor
timestamp: February 20, 2024, 10:22:05 am
content: I notice this effect with the salad spin dryer, it has a little bump that the bowl rests on. I noticed if there is a significant amount of water there it just slows the salad spinner down drastically. It rotates best mostly dry.it kind of gyrates around the center, I assume its hitting like a water pool when its slightly tilted and it makes it break hard.I think mechanisms that rest on jewels have a similar preturbance, there is no real shaft for themI still will assume there is some nanoscopic amount of oil there because you would need special provisions to keep that oil free AFAIK.those jewel bearings seem more like 'top (spin toy) holds' then shaft bushings/bearings