Hi Wolfgang,
I don't have an HP 5315A, but in my HP 5328A the power switch is wired this way because they want to keep the oscillator running always that the counter is plugged into the mains.
This is good for oscillator stability and if your unit is equipped with an OCXO, it insures that you will have zero warm up time. I would keep the power switch wired as it is now unless you use an external reference, or the calibration will suffer.
The hum is certainly caused by the transformer laminations "singing" and it can be corrected tightening the screws, if any, or even with some varnish.
Regards,
Ignacio, EB4APL
El 27/03/2019 a las 9:43, Wolfgang Mahringer escribi¨®:
Hi folks,
I recently acquired a HP 5315A Universal Counter in mint condition. It works perfectly too, but for two issues that annoy me.
First, it hums noticably loud. Its definitely a 100 Hz mains hum. The unit works nicely, the casing is not getting warm after an hour of usage.
I have the service manual for it, but before taking it apart I'd like to hear if other 5315A owners have the same problem.
Second: my 5315A does not have the battery option fitted, but still the unit hums as soon as the power plug is in, even if the unit is turned off. I'm thinking of making the power switch a "real" power switch, since I do not use the counter very often. Has anyone done a mod like this on a 5315?
Cheers,
Wolfgang
---
El software de antivirus Avast ha analizado este correo electr¨®nico en busca de virus.
