dlloyd Posted September 14, 2007 Posted September 14, 2007 (edited) *edit* Edited January 12, 2009 by dlloyd Quote
The Funk Posted September 14, 2007 Posted September 14, 2007 Doesn't sound like a bring problem. Get the guy to take it to a respectable tech and get it checked out. Could just need a rebias and new fuse. Quote
Dodge Posted September 15, 2007 Posted September 15, 2007 Swap the 6L6's around - if the dimmer tube stays dim, replace it. If it's the socket that stays dim, take it to an amp tech. It's probably a failing resistor. Hum in an amp tends to mean the power supply is 'out of balance' - i.e. one of the tubes is mismatched some how. My guess is it's a failing tube. Cheers Quote
Hamster Posted September 17, 2007 Posted September 17, 2007 You might get the right fuse at B&Q, but are more likely to get it from an Audio/Visual or guitar shop. Your twin might have an adjustable bias and if vibration has caused the bias to slip, it may be putting too much current through one of the 6L6's. Has the dimmer valve got any red patches on any of the internal metal plates? What year and model is the Twin? Hamster Quote
The Funk Posted September 17, 2007 Posted September 17, 2007 (edited) I'd always take it to my tech. Very rarely costs me more than £30. Edited September 17, 2007 by The Funk Quote
Hamster Posted September 17, 2007 Posted September 17, 2007 There is a bias adjustment facility on those, but of course it might not be the bias! As The Funk advises, it will only be a few quid for an amp tech to stick his probes in it to diagnose what's gone wrong. Hamster Quote
Bill Fitzmaurice Posted September 17, 2007 Posted September 17, 2007 [quote name='dlloyd' post='61516' date='Sep 17 2007, 04:30 AM']The fuse that blew was a 12 amp glass bodied fuse.[/quote] That doesn't seem right. The US version runs no more than a 6 ampere fuse at 110v. so a UK transformer version shouldn't use more than 3 amps at 220v. Blowing a 12 amp fuse at 220v indicates a dead short inside there somewhere. Powering it up again with that large a fuse could compound the damage. Quote
Bill Fitzmaurice Posted September 20, 2007 Posted September 20, 2007 [quote name='dlloyd' post='62057' date='Sep 18 2007, 05:02 AM']The warning on the back of the amp specifies a 12 A 250V fuse. I've taken the amp to the local guitar shop, where there's a good tech, to be looked at. I think I'm going to start considering weight as a factor when I buy amps. Ouch.[/quote] I just double checked my schematics file to be sure, the fuse for the Twin 1968-1982 was 2.5 amp/110v. That would make a UK version 1.25 amp at 220v. Reissue versions woudn't be siginificantly larger. A 12 amp/220v fuse is large enough for arc welding, and your shop should know that. Since they don't, and they can't fix it either, that would serve as notice that they should be avoided in the future. BTW, the hum is probably from power supply caps that are in need of replacement. Quote
EBS_freak Posted September 20, 2007 Posted September 20, 2007 [quote name='Bill Fitzmaurice' post='63127' date='Sep 20 2007, 02:57 PM']I just double checked my schematics file to be sure, the fuse for the Twin 1968-1982 was 2.5 amp/110v. That would make a UK version 1.25 amp at 220v. Reissue versions woudn't be siginificantly larger. A 12 amp/220v fuse is large enough for arc welding, and your shop should know that. Since they don't, and they can't fix it either, that would serve as notice that they should be avoided in the future. BTW, the hum is probably from power supply caps that are in need of replacement.[/quote] I'm with Bill on this one. They don't know what they are doing. I have a Pro Tube Twin and that has a 2A fuse (main) and the internal fuse is a 5A fuse - off the top off my head. If it's the same Pro Tube Twin as I have got (the tremolo equipped two channel amp), the 5A internal fuse goes from time to time (I think it has gone twice in 3 years). If the internal fuse goes, you'll have to take the chassis out to replace it. It is in a fuse holder just off the main board. If this fuse goes, you'll see the tubes light, but you'll only get the heaters. A cap change may well be in order as Bill says. If it hasn't been used for a while, the caps may have gone bad. They don't make 'em like they used to. These amps are quite hard on components... expect at least a set of tubes a year - most due to the fact that they are hanging upside down, inches away from a pair of speakers... This amp shouldn't need sending back to Fender unless the boards are whacked. Any amp tech worth their salt should fix this in a jiffy. PS - don't even think about doing anything yourself unless you know what you are doing. Fairly big caps inside that beast and they will give you heart a little bit of a tickle... Quote
Bill Fitzmaurice Posted September 20, 2007 Posted September 20, 2007 [quote name='dlloyd' post='63253' date='Sep 20 2007, 01:48 PM']Is that what a healthy fuse looks like?[/quote] C'est morte. Quote
vegas_hooker Posted September 20, 2007 Posted September 20, 2007 Not exactly the same but kind of related, my bassman tube head is giving off a fair bit of hum. Im going to have it looked at and will post back what the score is. Quote
EBS_freak Posted September 21, 2007 Posted September 21, 2007 [quote name='dlloyd' post='63339' date='Sep 20 2007, 09:57 PM']Why would anyone return a burnt out fuse to an amp after trying new tubes in it?[/quote] a) because they are that tight they can't spare the fuse they haven't touched the amp c) they don't know what they are doing d) all of the above Quote
The Funk Posted September 21, 2007 Posted September 21, 2007 Yeah, sounds like it. We should probably know who they are so that we don't take our amps there. Quote
The Funk Posted September 21, 2007 Posted September 21, 2007 It's not really such a big guess: 1. You went in to get your amp repaired 2. When you got it back there was a burnt out fuse in it But obviously you don't have to tell us who it is if you don't want to. Quote
EBS_freak Posted October 10, 2007 Posted October 10, 2007 "a mismatch in the preamp tubes"? Erm. OK. Glad you getting it sorted anyway. Stick with it, if you are into your clean sounds, these amps are magical, it'll be worth it in the end! Quote
EBS_freak Posted December 11, 2007 Posted December 11, 2007 [quote name='dlloyd' post='102503' date='Dec 11 2007, 12:31 AM']Anybody want to recommend an amp tech who is worth his salt? The twin has had a lengthy holiday and is coming back unfixed. The problem indeed appears to be in the power supply, but for some reason the guy who has had it for a while has been unable to fix it.[/quote] 'fraid I can't help you up that neck of the woods? Anybody else want to give this chap a hand? Quote
Hamster Posted December 11, 2007 Posted December 11, 2007 Steve will fix it - [url="http://www.stevesamps.co.uk/"]http://www.stevesamps.co.uk/[/url] he's in Godalming Surrey though. Steve also recommends this guy - [url="http://www.chambonino.com/"]http://www.chambonino.com/[/url] in Nottingham Hamster Quote
lonestar Posted December 11, 2007 Posted December 11, 2007 (edited) I don't know if this is any help or of interest but I have a '94 twin which melted it's transformer. After replacing a blown fuse at a rehearsal. I noticed a burning smell and looked in the back to see all power amp valves glowing like fluorescent tubes and black molten stuff dripping from the power transformer. It was still under warranty so it went back to Fender (then arbiter in Cricklewood) via Coda music where I bought it who were extremely helpful in chasin Fender. They replaced the transformer and valves. Apparently the transformer fitted in the US was only rated 220v and they upgraded it to 240v. it's been fine ever since. I don't know whereabouts you are but you could try Panic Music near Cambridge. They aren't cheap so get an estimate. you can find them via google I should think. Edited December 11, 2007 by lonestar Quote
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