Dime d100 hum

[guitarboomer88]

Hello all, this is my first post so please go kindly on my amateur knowledge.  I have a dime d100 head that I hooked to my di box with no speakers attached.  I was using the clean channel and it was sounding rather distorted.  Next thing I knew all I heard was a bassy hum with no output from the guitar.  I took it to my electrician friend's house, took it out of the casing, started it up, and it now has guitar sound coming through that sounds fine but the low hum is still there in the background.  Any ideas and comments are very much appreciated.   Maybe I'm just really nitpicking a hum that was always there.  Maybe a noise gate in the effects loop would fix it but something crazy definitely happened when the speakers were unhooked. 

[guitarboomer88]

Also, is it safe to use a resistor to accept the load for silent recording?  I know it's fine with tubes but I've heard different responses about solid states.

[Roly]

Try and find a circuit/schematic and post it here.

Basic truth - you can't fix an amp that isn't playing up.  We can perhaps follow the hum, but the fact that it is again working okay makes it impossible to fault find why it stopped.  If it has Pre Out/Main In or Fx Send/Return sockets you can try giving them a bath in metho or Deoxit contact cleaner and working a plug in an out of each a few dozen times.

If the input socket mounts directly on the Printed Circuit Board you can give that area a close look for any loose/fractured solder joints or cracked tracks.  Similarly around the connections for the electrolytic caps in the power supply section (the largest ones).

Valve amps must never be operated without a suitable load connected (speaker or power resistor of the same value), i.e. run with the output open circuit.  Solid state amps are fine open circuit, but must never be shorted.

HTH

[guitarboomer88]

Thanks for the quick response...is it safe to use a resistor to soak the power from a solid state though?

[J M Fahey]

Safe?  Yes.
Needed?
Not at all.
Only useful to heat the amp ... and in a thermal way, not sound

As of the amp, it looks 120% like a 2014 reincarnation of a Randall RG100, with a couple little tweaks.
FWIW it must sound good.

Try to get a schematic to chase that hum better and post a couple pictures of its innards.
Write them, tell them about the problem you have, that you want to be sure it was 100% repaired, but that the Tech can't go further without it.

It might be similar to an old Randall or be a new, SMT full version, don't  know.

It must be Chinese made, of course (or Korean or Vietnamese), doubt it's made in Florida.

Thanks.

[guitarboomer88]

Thanks again for all the info.  Took the head to a shop for them to check it out.  Plugged into a cab...no hum.  Bought a new speaker cord thinking maybe that's where my problem was...hooked it up to my cab with new cord...still a little hum.  This may be something I have to live with but I have a new cab coming in already that I have ordered a few days ago so maybe that will fix it. The old cab works well with my other amps though...weird but maybe cured.  Even though it seems weird I definitely will not be running this head without the load attached again just to be safe.   Thanks again

[guitarboomer88]

By the way J M Fahey...the amp does sound great...I don't really use the traditional dimebag tone, but the amp does a lot of different sounds awesomely.

[J M Fahey]

Rather than a new cab, buy the shop and move there  :lmao:
I bet location/grounding is the main suspect there.

[guitarboomer88]

I thought of that too, but would it not effect my other amps also?  And I had already ordered the cab before the problem began so no extra money is being spent really.

I've had that issue before but not at my house...in my friends shed we were building a couple matching les Pauls and wired them up.  Then he brought an amp out to the shed to test the wiring but had an overwhelming roar.   Rewired fifty times to no avail...as soon as we took them in the house they were perfect.

The weird thing in this situation is that I never noticed the hum before I tried to record with no load...but I'm so crazy in the head over this thing now I am nitpicking every sound.

[g1]

I never noticed the hum before I tried to record with no load...

That was probably the first time you ever had it running without speakers, so you had never heard it dead quiet before.
Now you will never be able to "un-hear" the quiet, no speaker sound 

[guitarboomer88]

It was actually during that time period when the speakers were unhooked and I was monitoring the recording through headphones that I noticed the hum and distortion in the clean channel like I mentioned in my first post.

[guitarboomer88]

Took it to another shop and it hummed there...I believe the guy that hooked it up without hum hooked it up through the line out or in the effects send or something because it has now hummed at 3 locations and stayed quiet at one.  The amp tech wasn't at the shop today, but everyone agrees the hum is not usual or just noise the amps make. 

I've tried to find a schematic with no luck.

Maybe time to let the pros handle it