What happened to my amp?

[marthur]

I've got a Matchless Spitfire clone. I'm playing it today and there is a crackling noise every once in a blue moon. Later on, I come back to play and the amp isn't sounding very loud and its pretty crackly and hideous sounding (think dying cat) if i really lay into the strings. I've got the master all the way up, but once i turn it to about noon, the volume INCREASES....??? Just glancing at the tubes, they all look fine, but I'm thinking this must be a power tube issue given the loss of volume. Before I do a clean sweep and get all new tubes, I figured I'd see if anyone knew what was up.

 

[Mor Paul]

Who put your amp together? I don't think it's (just) tubes, but I'm no expert.

 

[jimh]

I'd say you've probably got bad / miswired caps in the power supply.
Has the amp ever worked properly?

 

[marthur]

A local guy put together my amp, worst comes to worst I just ask him to take care of it. The amp has worked before  :laughing11: I've been using it for over a year now and its sounded fine until this very afternoon.

 

[Mor Paul]

I'd say you've probably got bad / miswired caps in the power supply.
Has the amp ever worked properly?

And I'd say it's mighty early for you to be up!

 

[-CB-]

I've got a Matchless Spitfire clone. I'm playing it today and there is a crackling noise every once in a blue moon. Later on, I come back to play and the amp isn't sounding very loud and its pretty crackly and hideous sounding (think dying cat) if i really lay into the strings. I've got the master all the way up, but once i turn it to about noon, the volume INCREASES....??? Just glancing at the tubes, they all look fine, but I'm thinking this must be a power tube issue given the loss of volume. Before I do a clean sweep and get all new tubes, I figured I'd see if anyone knew what was up.

Crackling in the amp.  Wont say never the caps, but hardly likely.  When power supply caps fail, you get a constant hum.  Ditto when the bias supply cap(s) fail.  Coupling caps fail, and they will give you terrible constant distortion, because they pass DC which throws the next stage's (cathode) bias off.

Lets round up the usual suspects.  Tube.  Do the flick test, and "ker-ploing!" each tube and see what you get.  Then, try the tube sockets, but for this you need to ABSOLUTELY make sure the amp is drained.  If ya dont, you're gonna get zapped, not might get, but WILL get ZAPPED bad... REAL BAD.  I'm hoping your clone building had the good sense to put a pull down resistor as a drain, someplace down the B+ rail toward the preamp end of things.  If that happened, you're in good shape, but you can only be sure with a meter reading.  Anyway, loose pins will do that scratch thing.  Then, its component/wire time.  You can do a chopstick test on each component and see if one is loose and causing a problem.  Ditto, chopstick the wire connections, looking for a loose one.  Then, jacks can be oxidized - this seems to happen more in winter for me... dunno why.  Then, controls can be culprit.  Lastly... those pesky screen grid resistors can be goin' bad.  Happens.  Heat gets 'em.  I like the sand cast ones, but... to each his own.  The ceramics are also excellent.

There's yer homework assignment.  Report back!

 

[marthur]

I'm back to report that, thankfully, it was just a power tube! Thanks for the help though!

 

[-CB-]

Didn't I say tube?

 

[NLD09]

here's a tip if you ever suspect an electrical problem. with the amp running use your drummers drumstick to poke around in there. if something farts out when you touch it... chances are you found where your problem is.

good that your amp is working now though.

 

[Wana_make_a_guitar]

here's a tip if you ever suspect an electrical problem. with the amp running use your drummers drumstick to poke around in there. if something farts out when you touch it... chances are you found where your problem is.

good that your amp is working now though.

Make sure he doesn't use those fancy weighted metal ones though, you could be in trouble then...  :icon_jokercolor:

 

[NLD09]

here's a tip if you ever suspect an electrical problem. with the amp running use your drummers drumstick to poke around in there. if something farts out when you touch it... chances are you found where your problem is.

good that your amp is working now though.

Make sure he doesn't use those fancy weighted metal ones though, you could be in trouble then...  :icon_jokercolor:

hey don't joke... that happened to my uncle once.

 

[-CB-]

here's a tip if you ever suspect an electrical problem. with the amp running use your drummers drumstick to poke around in there. if something farts out when you touch it... chances are you found where your problem is.

good that your amp is working now though.

Didn't I say chopstick test?

 

[NLD09]

Oh, that's what you meant... I thought that was some fancy electrical term that I didn't understand.  :sad:

 

[Superlizard]

Didn't I say tube?

Didn't I say chopstick test?

You certainly did... and I hear ya loud 'n' clear.

(Ah, the life of the online troubleshooter: never get credit, rarely get a "thanks" and everyone
tries to steal your thunder so they can sound like the... "expert".  :doh:  )

 

[-CB-]

at least there's a great dental plan!