Handbox R400 dropping volume

[MrTea]

My Handbox R400 has started dropping volume after being up and running for about 30 mins. I'm pretty sure it's the pre-amp as plugging into the FX loop return seems fine. 

 

Has anyone else experienced this? I'm hopeful it's just a tube on its way out but has anyone else experienced this? 

[BassmanPaul]

Link Send and Return with a short signal cable and see if that helps. Sometimes these jacks get corroded and the switch contacts fail to connect properly.

[wateroftyne]

^^^ Wot he sez

[MrTea]

Good thinking - will give that a go tomorrow. 

[MrTea]

Tried this today by bridging the FX loop with a patch cable but no luck - the volume still dropped. Unplugging the 'send' on the FX loop gives a ground buzz again at the appropriate volume so I'm still convinced it's somewhere in the pre amp stage. Looks like replacing valves is the next step ...

Edited December 11 by MrTea

[Dan Dare]

47 minutes ago, MrTea said:

Tried this today by bridging the FX loop with a patch cable but no luck - the volume still dropped. Unplugging the 'send' on the FX loop gives a ground buzz again at the appropriate volume so I'm still convinced it's somewhere in the pre amp stage. Looks like replacing valves is the next step ...

 

Before loading and firing the parts cannon, take it to a tech' for diagnosis. It's easy to spend a lot of money - more than you'd spend on a tech' - on replacing parts by guesswork.

[shug]

I used one of these on a gig in Poland a couple of weeks ago and had a similar experience in that a half hour or so into the set it lost volume and tone and then went into protect mode. I didn't think I was hitting the pre-amp that hard - just a standard JB and no effects - though I did have the gain and master a fair way up to get the output required. I was using a Mark 410, 4ohms, which seems a pretty efficient cab. 

 

I was 100% pleased to be using this amp - the promotor provided it - as they're on my list and up to that point it sounded great. Once I'd turned it off and on again it worked and sounded fine, though as it was a one-night-only scenario I couldn't say whether it'd be a regular occurrence or not. 

 

I'd be interested to know how yours turns out. They seem to be real nice amps - I've used a LOT of heads and this stood out sound and apparent build quality-wise - so it'd be a shame if they were prone to issues like this.

 

Shug

[wateroftyne]

I’ve used these amps constantly, week-in-week-out for about 7 years, never had problems like this. OP - I can send you a schematic if you need one.

[shug]

1 hour ago, wateroftyne said:

I’ve used these amps constantly, week-in-week-out for about 7 years, never had problems like this. OP - I can send you a schematic if you need one.

That's good. I've read your stuff over the years and thought of you when I got to the venue and found the Handbox laid on. And later that same evening, too, come to that...😉

 

Incidentally, WoT, have HB changed the pre-amp design? The one I was using didn't have a mid control as such but the ones on their current website do. Or have I got that wrong? 

 

I loved the amp up to but not including the moment it gave out on me. I'm still planning on contacting HB to see if they'd cut me a deal of some kind.

 

[Beedster]

9/10 when a tube amp that’s been working fine develops a fault it’s a tube, so it’s always worth having a few spare tubes around to test before getting techs involved.
 

I do think I’m missing a trick not owning one of these heads 🤔

[ped]

1 hour ago, shug said:

That's good. I've read your stuff over the years and thought of you when I got to the venue and found the Handbox laid on. And later that same evening, too, come to that...😉

 

 

😉Dude 😂

[wateroftyne]

1 hour ago, shug said:

That's good. I've read your stuff over the years and thought of you when I got to the venue and found the Handbox laid on. And later that same evening, too, come to that...😉

 

Incidentally, WoT, have HB changed the pre-amp design? The one I was using didn't have a mid control as such but the ones on their current website do. Or have I got that wrong? 

 

I loved the amp up to but not including the moment it gave out on me. I'm still planning on contacting HB to see if they'd cut me a deal of some kind.

 

The newer ones have a mid control. I prefer the original pre.

[MrTea]

@wateroftyne I appreciate the offer of the schematic and will shout if I need it.
 

Have ordered some new valves as I didn’t think it’s a bad idea to have some spares. I also gave all the jack sockets and switches (mute, bright, overdrive) a spray with some deoxit inside the head and on initial tests this may have solved it. Will try running it again for longer tomorrow but maybe it was a dodgy contact somewhere. 

Edited December 14 by MrTea