Building an amp from a kit

Ben Jones · Post by **Ben Jones** » 12 Jun 2009 5:41 am

hey thanks Jim! The wire came from mojo yesterday and I was able to get some more done. First heres the cab, not the best photo sorry

speaker is jensen c12Q

the board fully wired, i was definetly making my leads way too long, but better safe than sorry thought I

back of the board, no shortz please!

and the heater wiring (those green twisted wires)
this was a bit of a pain and took some time. fun tho.

almost there!

Jim Newberry · Post by **Jim Newberry** » 12 Jun 2009 1:23 pm

Lookin good Ben!

Ben Jones · Post by **Ben Jones** » 13 Jun 2009 8:41 am

jack wiring. I see others connecting all their jacks grounds together with wire. I dont understand why...arent they grounded already by touching the chassis?

view with pots. all that remians to be done is to figure out how to ditch this deathcap and ground switch. thats it. I wll be firing her up today i suspect if I can get that last connection figured out. I dont understand the fuse lugs as shown on the layout vs. the physical reality of the fuse holders lugs. One is in the middle of the fuse holder, one is on the tip. maybe it doesnt matter wether ac chord or PT black wire gets connected to which lug of the fuse holder as long as it is in the loop?

this has been alot of fun. man, i hope this thing works!!

Ben Jones · Post by **Ben Jones** » 13 Jun 2009 9:03 am

remaining power Tramnsformer and ac chord wiring. switch above PT on left side is unused ground switch.
So i am thinking white ac wire to power switch. black PT wire to other pole of power switch. black ac chord to fuse holder, remaining and final black PT wire to fuse holder...??? but which lug of the fuse holder? if thats even correct...lol..this should really be the simplest part of the whole thing, but since i am not following the diagram , Im lost. i dindt quite get the level of understanding I was aspiring for...oh well, first amp, maybe I'll learn, as long as I dont kill myself trying.

fuse holder

Ben Jones · Post by **Ben Jones** » 13 Jun 2009 7:12 pm

all done and its nice and quiet and sounds just awesome. I am so happy.

Dave Harmonson · Post by **Dave Harmonson** » 13 Jun 2009 7:22 pm

Super job there Ben. I've got to check it out in person one of these days.
Dave

Ben Jones · Post by **Ben Jones** » 14 Jun 2009 7:52 am

You bet Dave. Next gig, or next time you have a chance to give me a lesson

After reading some and playing the amp some more. i realize now its not quite working as it should. I get some low pitched booming feedback or runaway oscillation when i use both volume knobs. I can use one channel and be fine, and it sounds awesome cranked, but if I start ramping up the volume on that unused channel I get that feeedback and it sounds like the speaker is being overloaded.

My hunch is there is a wiring issue somewhere.
The two possible areas I have in mind are :
1. i soldered the black ground wire from the OT to the ground lug of the speaker jack. maybe i should have just soldered this wire to the OT casing outside the chassis like ive seen others do?
2. I didnt ground my input jacks figuring they were grounded by contact with the chassis. i didnt see any need to ground the "swtiches" for these shorting jacks either, but since ive seen others do this, maybe its necessary? there is no hum , buzz or other things I (perhpas mistakenly?) associate with ground issues. its really quiet otherwise.

Ive asked elsewhere for help, but maybe our local experts have an idea?

I could die happy with just the one channel functionality of this amp, its that great osunding to me, as is. but obvioulsy I'd prefer to have it functioning as it should and have the full range of tones its capable of.

i guess i will now be learning how to troubleshoot and work safely on a live amp.

Jim Newberry · Post by **Jim Newberry** » 14 Jun 2009 12:52 pm

Great job Ben!

I've had a similar problem with some runaway oscillation when turning up the "unused" volume channel, but my clue was that I had just plugged something in to that channel and then unplugged it. So, it was an issue with the shorting of the input jack. You can pretty easily torque those things out of shape when tightening the jacks to the chassis. So, the jacks on the unused channel are what I'd look at first.