mikk Posted July 30, 2008 Share Posted July 30, 2008 Hi, guys. I bought an Epiphone Valve Standard , was told it was new and returned, it looked brand new, I played it for 3 months, OK, except occasional volume drop. Played only acoustic 3 months, didn't plug it in. Last week, plugged in, got NOTHING. No noise, just a red light on the Power switch. I'm an electronic tech, but never fixed a tube amp. I have a schematic, anyone hear of any common problems, or an Epiphone Valve Standard just dying, all of a sudden? Any help would be greatly appreciated. I really need someone to tell me how to take the chassis out. I'm well aware of high voltages, etc., been a tech for 25 years. Just cant find the screws! Link to comment Share on other sites More sharing options...
ricach Posted July 30, 2008 Share Posted July 30, 2008 There are four black plugs in the top of the cabinet. Pull these out and you'll see the screws. Can be one of two things. The tabs where the Power Transformer connects to the board is flimsy and will 'break' the circuit. Fix this by soldering a jumper from the tabs to the correct points in the diode rectifier circuit (obviously need a schematic). You won't need to remove the board to do this. The other cause, and just as likely because the PT is underpowered and does not supply enough current to properly heat the tubes -eventually burning out those particular windings in the PT. Expensive fix is replace the PT with something more robust - cheap fix (and what I did) was to buy a small 12V 3A transformer, mount in open space on chassis and supply heater current from this instead. Want exact particulars let me know. Link to comment Share on other sites More sharing options...
mikk Posted July 30, 2008 Author Share Posted July 30, 2008 :) :D/ Hi, ricah! I just wanted to say THANK YOU! With one paragraph, you've done more to help me than all the geeks at 18 watt.com, and other places. THANK YOU!, again. I'm going to try your suggestions right now, I'll let you know what happened. Mike Link to comment Share on other sites More sharing options...
cGil Posted July 30, 2008 Share Posted July 30, 2008 edit: global apology for reactive rudeness retracted. Totally sucks that your PT filament winding crapped out. I've got a VSpecial PT. Only used it for a couple of hours before I gutted the amp.I'll let you have for $10 bucks plus shipping. Unfortunately, shipping these days is killing us non-commercial folks; and what's worse, I'm afraid this PT will eventually die like the one you have. However, it might be a good candidate for the 18watt lite DIY pcb project. Losing a preamp tube for the 18watt lite board might've been enough of a reduction in filament load to have kept that winding working. Then again, this set of iron may simply be the almost worthless junk it appears to be. Just in case, here's some fancy iron for your amp... A Hammond would be fine for many rectifier tubes like the 5Y3 or 5AR4 that require a 5v supply, but not so great if you want to use a traditional EZ81 rectifier with a 6.3v filament. And you can't use the main filament supply for the rectifier tube due to noise and hum. Check out the 270EX http://www.hammondmfg.com/263.htm or the 370EX http://www.hammondmfg.com/300series.htm Here's some great 18watt iron that will support an EZ81 http://www.musicalpowersupplies.com/ http://www.turretboards.com/transformers.htm And this is considered by some to be the holy grail of vintage 18watt clone iron made by Heyboer. I've got a set with the non-vintage OT and even that has tone to die for. http://gdsamps.com/?page_id=7 Gil... Link to comment Share on other sites More sharing options...
ricach Posted July 31, 2008 Share Posted July 31, 2008 no problem mikk, glad i could help. the exact transformer i used was this: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=120-200 only $12. should have mentioned it was a 12VAC center tapped to get the 6.3V necessary for the heaters. there was one hole already in the chassis, and instead of drilling another one, i got creative and was able to secure the other side with what was existing. while you're in there, and don't mind losing the DSP and reverb, jumper over all that tone and gain sucking circuitry. Link to comment Share on other sites More sharing options...
layboomo Posted July 31, 2008 Share Posted July 31, 2008 Mike glad you got some good advice here......the guys at 18watt are still pissed off about their site getting swamped with valve jr discussions when that amp first came out. It really did pollute their site,but that's no excuse for the way they treated you. Best of luck with the amp. Link to comment Share on other sites More sharing options...
gjcamann Posted March 5, 2009 Share Posted March 5, 2009 Any suggestion on how to go about disabling the DSP section. I think what i want to do is jumper from after R17 to after R41 and disconnect the 12V power (that supplies the OPAMPS). Would this work or should I actually cut the traces after R17 and before R41 to completely disconnect the signal chain from the DSP section? Link to comment Share on other sites More sharing options...
MrMod Posted March 5, 2009 Share Posted March 5, 2009 Mike glad you got some good advice here......the guys at 18watt are still pissed off about their site getting swamped with valve jr discussions when that amp first came out. It really did pollute their site' date='but that's no excuse for the way they treated you. Best of luck with the amp.[/quote'] It is a pity that the 18Watt girls never got competition from the 18 Watt Valve Senior. Link to comment Share on other sites More sharing options...
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