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Peavey Classic 30 Amp issue

 
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blues_mang



Joined: 25 Mar 2013
Posts: 45

PostPosted: Tue Sep 08, 2015 1:13 pm    Post subject: Peavey Classic 30 Amp issue Reply with quote

Ok, looking for a little help on this one. I had been gigging with my Classic 30 pretty regularly and then a month ago, I turned it on one day and it's not passing any signal. It has new preamp and power amps tubes. I checked the speaker connections and tried hooking it up to another speaker with no luck. I even tried the speaker out jack to a 1x12 that I have and still nothing. So, what/where would be the next logical place to start looking? I've built a couple of small tube amps, but have never had to troubleshoot one. Any help would be appreciated.
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Tue Sep 08, 2015 2:38 pm    Post subject: Reply with quote

two common failure points for these-- input jacks and tube socket solder points.

this is assuming you've tried a different guitar, a different cable, etc.

No signal at all would have me suspecting something near the very beginning of the amp, i.e. input jack, etc.
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blues_mang



Joined: 25 Mar 2013
Posts: 45

PostPosted: Tue Sep 08, 2015 2:57 pm    Post subject: Reply with quote

tangelolemon,
yes, I did try a different guitar and cable as well. I'll start with the input jack and see if that's the culprit. It would be nice if it was something as easy as that.
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blues_mang



Joined: 25 Mar 2013
Posts: 45

PostPosted: Sun Sep 20, 2015 8:55 pm    Post subject: Reply with quote

Update: Well, so far, it's not the input jack. I used a signal tester and the signal gets through the input jack and makes it to the first preamp tube. I'm now in the process of tracing the circuit so I can figure out where it heads next, of course being careful not to touch any lethal voltage. As I was testing the signal though, one of the power tubes went. So, maybe it's just time for a complete tube change. I realized that the tubes are not as new as I thought.
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WildIowa



Joined: 06 Mar 2004
Posts: 490
Location: Henderson IA

PostPosted: Mon Sep 21, 2015 8:40 am    Post subject: Reply with quote

You can start with the old chopstick probe routine and then go back and re-solder as many points as you can and hope you catch it, otherwise it is likely a component and may require a tech. Fire it up and poke around the chassis (a plastic or bamboo stick will hopefully prevent you from getting killed by lethal voltage) and tap/push every wire, resistor, connection etc. and see if you can uncover the area or component at fault. A cold solder joint could also be the problem or bad ground. Make sure you drain the caps etc. before you do that. I don't know if this amp has a PC board but sometimes they can flex or take a shot and there may be a break in one of the tracers. If you can't uncover the cause, that's when I have to take it in because I am not good at schematics or checking resistors, caps etc.....if there is not even a hum or other sound hopefully you can uncover a specific and easy to fix issue. Good luck.
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blues_mang



Joined: 25 Mar 2013
Posts: 45

PostPosted: Mon Sep 21, 2015 4:20 pm    Post subject: Reply with quote

The funny thing is, when the amp starts and gets warmed up, it has the usual hum coming from the speaker like it usually does. However, when I plug a guitar in, nothing comes out of the speaker. There is actually 3 PC boards in a "U" shape which makes it difficult to trace the audio path while the amp is on. I'm pretty good with schematics, so I'm going to try and trace the audio path and see if I can figure out where the sound is cutting out. If that doesn't work, then yes, I'll definitely be taking it to an amp tech.
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ajeffcote



Joined: 09 Nov 2009
Posts: 2184
Location: Baytown,Tx

PostPosted: Wed Sep 23, 2015 3:40 am    Post subject: Reply with quote

If you can't find the trouble, you could gut it and put an eyelet board in it. Make it into whatever you want. You have the chassis, transformers and cabinet and speaker. Those are the expensive parts.
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blues_mang



Joined: 25 Mar 2013
Posts: 45

PostPosted: Fri Sep 25, 2015 8:03 am    Post subject: Reply with quote

Well, it looks like I've got it narrowed down to the power section of the preamp tubes. The tubes aren't glowing, so it doesn't look like they are getting power and the signal does not get past the V1 tube when tracing the path and using the signal tester. So next is to figure out which is the faulty component.
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Fri Oct 02, 2015 1:46 pm    Post subject: Reply with quote

if it appears the tubes are not glowing, check filament voltage on them. Sometimes those things are sneaky, and the filaments are buried within the cathode and plate structures, and glow is not always obvious. However if you're not getting 6.3v at the heaters, then as they say, "there's yer problem."
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