johnnysomersett Posted December 2, 2015 Share Posted December 2, 2015 (edited) Hi all. I have an old Peavey Classic 400 head. Apart from the back-breaking weight of 6 stone to lift, I'm having issues and wondered if I could pick your brains? When it first arrived it blew an internal fuse (possibly down to condensation from storage/transport) which I replaced and had been using at home for a week or two at very moderate volumes. Come Monday night and the opportunity to open her up and it unceremoniously spat the dummy out and died Now, from what I can gather, before it goes into the amp engineer for an overhaul & re-tube (ouch), it's probably blown the same fuse again - a 2A slo-blo. It made noise for a few minutes before dying FWIW, although not nearly as loud as it should have been. Two things concern me: 1) The cab i used monday had speakon connectors and I used a speakon-jack cable. How should the speakon be wired for a standard bass cab? is it just +1 & -1? (I'm new to speakon, bit oldskool)....and could a mis-wired speakon cause the amp to blow? 2) maybe the old valves are just past it - they are the originals, but the amp is NOS so hasn't seen mush use in its long life. Some definitely look a bit sh*tty and glow different brighnesses. Could the cranking of it have killed some off? It's mostly the speakon Q I am curious about but open to ideas/thoughts/etc Thanks in advance Johnny Edited December 2, 2015 by johnnysomersett Quote Link to comment Share on other sites More sharing options...
icastle Posted December 2, 2015 Share Posted December 2, 2015 It sometimes pays to go for the obvious things first. Are you absolutely sure you replaced the fuse with a slow blow one? It should be labelled T2A. Quote Link to comment Share on other sites More sharing options...
johnnysomersett Posted December 2, 2015 Author Share Posted December 2, 2015 [quote name='icastle' timestamp='1449088237' post='2920737'] It sometimes pays to go for the obvious things first. Are you absolutely sure you replaced the fuse with a slow blow one? It should be labelled T2A. [/quote] 100% ...went out & bought them specially (I had pretty much every other size in stock already). There's about 5 internal fuses in this thing! Quote Link to comment Share on other sites More sharing options...
3below Posted December 2, 2015 Share Posted December 2, 2015 [url="http://www.hartsafire.com/classic400/"]http://www.hartsafire.com/classic400/[/url] has schematics and some interesting info. The only 2A slow blow fuse (at a quick glance) is on the main PSU for the HT (B+). Looks like a great amp, I think I want one - I like older Peavey kit, it is repairable, the schematics are easy to find and support at Peavey is excellent. I asked some 'left field' questions about early valve amp transformers and got excellent technical answers very quickly. Quote Link to comment Share on other sites More sharing options...
johnnysomersett Posted December 2, 2015 Author Share Posted December 2, 2015 [quote name='3below' timestamp='1449090822' post='2920771'] [url="http://www.hartsafire.com/classic400/"]http://www.hartsafire.com/classic400/[/url] has schematics and some interesting info. The only 2A slow blow fuse (at a quick glance) is on the main PSU for the HT (B+). Looks like a great amp, I think I want one - I like older Peavey kit, it is repairable, the schematics are easy to find and support at Peavey is excellent. I asked some 'left field' questions about early valve amp transformers and got excellent technical answers very quickly. [/quote] Not that Im' any good at reading schematics, but, from what little I know about internals of amps, the B+ is the voltage across the tubes right? So likely an issue connected with said old sh*tty Peavey-branded tubes? Quote Link to comment Share on other sites More sharing options...
3below Posted December 2, 2015 Share Posted December 2, 2015 (edited) [quote name='johnnysomersett' timestamp='1449091688' post='2920781'] Not that Im' any good at reading schematics, but, from what little I know about internals of amps, the B+ is the voltage across the tubes right? So likely an issue connected with said old sh*tty Peavey-branded tubes? [/quote] You are correct with B+ (or HT in British money). It could be tube issues - tubes, tube sockets, assorted resistors to achieve HT voltages, could be capacitors or diodes in power supply, could be failed solder connection or insulation somewhere. There, that narrowed it down (not). Open it up, have a look for anything obvious - burned / charred (or even destroyed) components. It might be a simple (cheap diy) fix. Remember the smoothing capacitors may be charged and can give serious electric shock. Yours was NOS, is there another one? Edited December 2, 2015 by 3below Quote Link to comment Share on other sites More sharing options...
johnnysomersett Posted December 2, 2015 Author Share Posted December 2, 2015 (edited) Sounds simple enough. To be honest? I want a tech to re-bias the new tubes anyway (some are literally disintegrating!) so it might as well have a full check-over anyway just for peace of mind. I like peace of mind. And I'll never get over my fear of capacitors... Just a shame it takes 8 goddamn power tubes! And I have no idea if there was more. There was a big Peavey deadstock auction here in the UK last year and I think it came from that. Warehouse clearance type thing. Edited December 2, 2015 by johnnysomersett Quote Link to comment Share on other sites More sharing options...
3below Posted December 2, 2015 Share Posted December 2, 2015 If you are getting new tubes fitted etc seems good to get tech to check & sort it all out. I know of the auction you refer to, you did well. Quote Link to comment Share on other sites More sharing options...
johnnysomersett Posted December 3, 2015 Author Share Posted December 3, 2015 [quote name='3below' timestamp='1449095422' post='2920815'] If you are getting new tubes fitted etc seems good to get tech to check & sort it all out. I know of the auction you refer to, you did well. [/quote] Yeah, makes sense to me. Hopefully, because of its crazy power, I'll not often have chance to use it in anger and push it hard so, theoretically, I should get some decent lifespan out of it between services. Quote Link to comment Share on other sites More sharing options...
johnnysomersett Posted December 4, 2015 Author Share Posted December 4, 2015 Just dropped it off at the tech, he seems positive about it Quote Link to comment Share on other sites More sharing options...
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