18Watt.com

my 2nd 18w build ( first for a friend ) has 2 basic problems I cant seem to cure - and Ive tried to find the causes without success.

First - the normal channel squeals like a pig when cranked right up
Second - the amp seems to have unacceptable hum levels even though Ive taken care with ground bus bar and power supply earths. I'd like to know whats considered "normal" hum level when cranked right up.

The trem channel doesnt squeal at high volume like the normal channel.

The Mains hum seems much louder than on the first amp I built though I dont ahev the amp handy for reference - and I cant think of any difference in my layout/wiring - it must be a missed earthing somewhere I guess.

Any thoughts on ground points to check, and also any experience of the squealing ( only at max knob positions in last quarter of the dial really )

Itr driving me insane trying to find causes after getting back from work at night!!
Any thought Oh experiemced ones ?

Aside from that the amp is bloody great tone-wise.
Rgdfs
Pedro

Pedro...

Is there any way you can shot a couple of chassis pics and attach them to the a post to this thread?
Pictures are a great vehicle to troubleshooting. A lot of people got great help posting pics of their troubled amp... Including me...

There are keen eyes on this group.

gab

Gab , thanks , will do -
working away most of this week so wont be near the amp after tonight but will get some pics done by the weekend for the keen eyed and more experienced to scrutinise.

All help really welcome ...

( If all else fails maybe I could switch the amps while my mates not looking

TIA
Pedro

just noticed that I havent grounded one side of the OT as per Marks schematic which Ive used to build both amps - would this make a difference.
Not sure I grounded one side of the OT on the last amp I made.

errrr......unsure here....

Sometimes grounding the OT secondary helps get rid of squeal...