Garey Barrell <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- Dick -
"Disconnected ALL AC wires of the transformer"? And it still hums! Wow, that must be some transformer!! :-) Perhaps it just doesn't know the words............. (sorry)
All the AC-3 and 4 power supplies are specified for 120VAC @ 50 or 60 Hz. I'm not aware of a different transformer for Europe.
The "other" possibility that I didn't mention before because of the "increase" in hum you mentioned is a shorted turn in the (usually HV) secondary. This will of course cause the transformer to hum AND heat up with no load. If you have a Simpson 260, (or other ohmmeter with a "reversing" switch,) an easy way to check for a shorted winding is to hang the ohmmeter across each winding, let it settle, then reverse the polarity with the switch. A good winding will cause the meter needle to "kick" sharply, while a winding with a shorted turn will give only a small inductive "kick". Lacking a Simpson, an external DPDT switch cross-wired will give the same result.
73, Garey - K4OAH Atlanta
Drake C-Line Service Manual <http://hr99.home.mindspring.com/R-4C_Servicez/>
[EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] made an utterence to the drakelist gang ---------------------------------------------------------------------- Hi all,
I disconnected all AC wires of the transformer, result was the same hum. So I concentrated on the transformer and tightened all screws/nuts and it seems slightly better but it was still trembling a lot and getting rather warm too! This AC3/T4XC was imported from the US before I bought it, so the transformer is a 60 Hz type. In EU we have 50 Hz, so I think that this is the actual cause. I only wonder why I assumed the hum to be less before changing the caps... imagination I guess..
I now placed the AC3 outside the MS4 on the ground below the desk, so it can hum as much as it wants untill I traced a 50 Hz transformer hi!!
Many thanks to all who responded, this list is a great recource of practical knowledge!
Best 73, Dick PA2DW
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