Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
hum-loop-like problem
Laney VC30 valve amp, works fine in its own accord. But owner wants to set
it up with another amp , another make and solid state if relevant, for a pseudo stereo set up using the A and B outputs of a pedal effects unit. Produces mains hum on switching from standby to on. Making one of the feeds isolated and relying on the grounds from each amp makes no difference, still intrusive hum. Bridging stout wire from mains earth to the VC30 input socket makes no difference . Pulling V1 from the amp still induces hum in the other amp. Had to return the amp for owner to do a gig as normal mono set up. I did not try an isolation transformer and I did not get inside the works, just testing the valves. I'm assuming internal shared ground path for HT return current , anyone any thoughts for the next time if I'm faced with this. Only a year old so maybe PbF problem at the input perhaps |
#2
Posted to sci.electronics.repair
|
|||
|
|||
hum-loop-like problem
less than 0.1 ohm between input ground and mains ground in all 3 cases of
the VC30 , his other amp and my amp to confirm a VC30 problem |
#3
Posted to sci.electronics.repair
|
|||
|
|||
hum-loop-like problem
On Thu, 29 Sep 2011 10:03:30 +0100, "N_Cook" wrote:
less than 0.1 ohm between input ground and mains ground in all 3 cases of the VC30 , his other amp and my amp to confirm a VC30 problem Is one side of line bonded to ground where you are? If so there may be an incorrect bonding or lack thereof. ??-) |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
worcester filling loop key problem | UK diy | |||
Earth loop impedance problem | UK diy | |||
Tiger Loop? | UK diy | |||
Combi boiler filling loop problem | UK diy | |||
wiring problem wioth loop in wiring and two way switching | UK diy |