Normal for reverb to have hum on solidstate as you turn up?

[frank57]

This solidstate tends to have hum with nothing plugged in when I turn up the reverb past high noon.
It's always been this way.
Is it normal?I don't see shielded wires or anything like that on the reverb wires inside the amp.
You have a black and white on one rca and a red and black on the other rca.
Here's the schematic for that section:

[Zipslack]

I haven't played with that particular model, but a lot of SS Fenders have some reverb hum that I personally don't find acceptable.  Some amps don't do it.  Could be the use of actual shielded cable (like in the Blues Jr) helps, or it could be the layout on the PCB, or it could be noisy op-amps.  If it is excessive, try checking for other issues - how much ripple is on the rails? You could also try "bagging" the reverb pan to see if that makes any difference, but I doubt it will.  I guess the big question is - was it quieter in the past, or was it always that noisy?

[plexi50]

It's more than that. Reverb hum with no tank plugged in and increasing as the reverb pot is turned CW has to be a lead dress issue where there is coupling between wires and components. I have this same issue on my Princeton reverb. If i poke the wires and spread them out and away from each other in the reverb circuit and OT my hum becomes less and at one point gone all together. My build is a terminal strip build and not a fisheye board. I think terminal strip build are more prone to issues like this and all the wires in the amp must be angled and away from each other more so than on a turret board or fisheye board. Hit and miss

[frank57]

The tank is plugged in.
There's nothing plugged into the input.
There might be an error on the pcb board.I drew up the board before,
probably a mistake when I drew it up but it should be cut there I think where the reverb circuitry is.

Which wires go where?
Is Black always negative? Inside the amp the wires run right by the transformer.

[HotBluePlates]

This solidstate tends to have hum with nothing plugged in when I turn up the reverb past high noon.
It's always been this way.
...
HIWATT BULL30R

You seem to have to worst luck with modern Hiwatt amps.

... a lot of SS Fenders have some reverb hum that I personally don't find acceptable.  Some amps don't do it.  ... it could be the layout on the PCB, or it could be noisy op-amps.  ...

Given the mp has always had the hum, and given Frank's problems chasing buzz in another PCB Hiwatt, my gut instinct would be bad PCB layout.

I wish I could say it's worth diving in to fix, but hum chasing can be frustrating in a point to point wired amp where you have complete control over component and wire positioning. It may be more fruitful to sell the amp and get a different one that is issue-free, or at least will be easier for you to modify if you wish to dive in and get practice reairing/altering things.

[phsyconoodler]

Try reversing the reverb cables.Solid state opamp reverb will work with the cables reversed and will hum if they are the wrong way.And the reverb sounds bad that way too.
 Not saying that's the issue,but I've run across it with Fender SS amps before.

[frank57]

Yes fiddling with the wires does help.I reduced it a bit.
It's not a terrible hum to the point where you want to toss the amp out.
I can live with it.
Reversing the black and white for each connector seems to help.
One set of  wires going to the red rca plug has a stripe on it, what does that mean?

Does running those rca wires near the transformer wires in the amp add hum?

[Zipslack]

I would personally want to route them away from any transformers, opamps, or LEDs just to help reduce any noise from coupling-in, especially if they are cheaper un-shielded cables.  Does your cable have the RCA connectors on both ends (tank and PCB)?  If it's worth the expense and trouble, you could try getting some good shielded cable and some RCA plugs and make your own cable - ground the shields to a ground plane on the PCB.

[frank57]

I think I see part of the problem.
I forgot I did a slight mod to the reverb where r29 is 4.7k instead of 2.2k.
That's probably accounting for some of the hum.
It gives a sort of big hall surf reverb sound as you turn up the reverb to 7 or 8.
Whereas in the stock amp the reverb and the signal stay sort of 50/50.

It's not a big giant hum and when you play you don't notice it much at all.
It's not affected by the volume controls or gain so the hum level stays where it is as you go to 7 or 8 on the reverb.

The wires are rca on one end and then go to connectors that go in headers.
2 copper untinned wires in each plug but I don't know if one is a shield?
If I move the white wire to the + header on the white plug then the reverb does not work.

They are running right in front of the transformer.
I'll take a shot and post it.

[frank57]

Victory!
 Finally I defeated the Hiwatt gremlins on this one.
I would say 90% of the reverb hum is gone.
Just a small amount with the reverb on 8 and up.
I took out the connectors on the header connected to the red plug and put them back in the header.
Maybe there was a lousy connection there?

Then I flipped the RCA connectors as phsyconoodler  suggested and the hum was pretty much gone.
It works and that's what counts.
The small resistor mod gives a bigger Fender surf reverb sound when you turn it up.
I'll try to post a sample somewhere.

[Willabe]

Victory!
 Finally I defeated the Hiwatt gremlins on this one.

Well alright then! Good job.


                Brad