17-06-2020, 08:24 AM
Hi Andy
Many thanks. Yes, I do have a lamp limiter and a variac and several scopes (Telequipment etc although I do have say that I am not an expert in using these - always an opportunity to learn).
As you have indicated, I will have to go back to first principles to find out where the problem is. The best way of describing the 'hum' is that is like plugging in a guitar lead and putting a finger across the contacts, the noise does increase with volume.
One of the initial things I checked yesterday was to review the ESR level of the electrolytics (except the dual 50uF) and these are all showing good on the meter (home built ESR kit).
No work tomorrow or Friday so its a good opportunity to look at this amp in a level of detail.
Best Regards
Many thanks. Yes, I do have a lamp limiter and a variac and several scopes (Telequipment etc although I do have say that I am not an expert in using these - always an opportunity to learn).
As you have indicated, I will have to go back to first principles to find out where the problem is. The best way of describing the 'hum' is that is like plugging in a guitar lead and putting a finger across the contacts, the noise does increase with volume.
One of the initial things I checked yesterday was to review the ESR level of the electrolytics (except the dual 50uF) and these are all showing good on the meter (home built ESR kit).
No work tomorrow or Friday so its a good opportunity to look at this amp in a level of detail.
Best Regards
if all else fails...read the instructions!
