simpleman3441 Posted February 10, 2010 Share Posted February 10, 2010 Borrowed it from a friend. Thought it'd be nice to give him some info on it when I give it back. He's a novice player and had this amp given to him. From the research I did I think it was discontinued in '91? I'm really bad at findin the good info on gear. You guys know anything or have any resources to suggest? It also cuts out and then sorta fades back in every thirty seconds or so if I push it half way. I know this probably a question for myles, but I don't wanna bother him with something like that if you guys know what's up. Just a tube issue? We cannot accelerate the growth of a tree by pulling on its branches. - Ricardo Iznaola Link to comment Share on other sites More sharing options...
Larryz Posted February 10, 2010 Share Posted February 10, 2010 Won't hurt to check the tubes... Take care, Larryz Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted February 10, 2010 Share Posted February 10, 2010 "Everybody was kung-fu fiiiiigh-tiing..." Marshall Artist, what a great pun... Is this the one with a solid-state preamp mated to a tube driver/phase-inverter and output-section? Some kind of effects-loop insert or footswitch jack in the middle of the front control panel? A push-pull knob in the "lead"/"boost" controls that's for the clean-channel EQ or something? (This latter appeared on the first, original model, and was gone from the second version model.) If so, the earlier ones are supposed to be better (as is often reputed to be the case with everything, huh! ), but both tend to sound kinda thin with a wishy-washy, muddy low-end. I've known a couple of people who had these, and I didn't envy 'em those amps. Quick and dirty guess is that it needs a fresh set of filter-capacitors, slowly brought up to full voltage with a variac to "bed them in", and all new tubes- a matched duet of outputs, AND a "matched"/"balanced" phase-inverter. I believe that there's a total of three in these, no preamp tubes. A little tuner-cleaner in each pot probably wouldn't hurt, either. Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
simpleman3441 Posted February 10, 2010 Author Share Posted February 10, 2010 All that sounds about right. I can see the two power tubes. There's a metal casing next to them about the size of a preamp tube, but I've never seen anything with one preamp tube so I wasn't sure. Do you know what that casing would be for? Definitely sounds thin next to the Blues Jr. We cannot accelerate the growth of a tree by pulling on its branches. - Ricardo Iznaola Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted February 10, 2010 Share Posted February 10, 2010 It's almost certainly the phase-inverter (driver) tube, that drives the output-tubes, inside a thin metal shield/retainer. The metal shield should come off with a careful little twist and tug, probably locks at the base. Some amps do have capacitors inside vertical metal housings that vaguely resemble metal tubes; these are usually ganged capacitors, multiple caps within the same housing. But in your case, it's most likely the PI tube. Metal encased tubes- as opposed to the more familiar glass ones- have been made, but in guitar amps are pretty much only seen in vintage specimens, being largely an archaic, antiquated item, prone to noisy microphonic sensitivity. Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
simpleman3441 Posted February 15, 2010 Author Share Posted February 15, 2010 It's almost certainly the phase-inverter (driver) tube, that drives the output-tubes, inside a thin metal shield/retainer. The metal shield should come off with a careful little twist and tug, probably locks at the base. That's it! Quick and dirty guess is that it needs a fresh set of filter-capacitors, slowly brought up to full voltage with a variac to "bed them in" I've never done work on an amp before. Is this something I could reasonably try? I'm fairly confident in my abilities, but wary about workin on someone else's gear. I was thinking I'd replace the tubes and then try this if that didn't take care of it. Does that sound like a good plan? We cannot accelerate the growth of a tree by pulling on its branches. - Ricardo Iznaola Link to comment Share on other sites More sharing options...
Jasco Posted February 15, 2010 Share Posted February 15, 2010 I had one of these amps years ago and sold it. Kind of wish I wouldn't have. Cool lead tones, but crappy clean tones. And from what I remember, 2 power tubes and 1 pre tube. "Imagination is more important than knowledge." - Albert Einstein http://www.thesymbols.net http://www.jascoguitar.com Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted February 15, 2010 Share Posted February 15, 2010 Best bet is to have the amp re-biased for a new, matched duet of output-tubes, and a fresh "matched"/"balanced" phase-inverter tube to go with them. You will almost certainly hear and feel a noticeable difference once that's done. (I can highly recommend Doug's Tubes for purchasing them; tell him exactly what you want to get out of what make and model of amp, he'll steer you right; great guy, great service.) Go directly to the "Feel free to ask Myles"-thread and feel free to ask him about biasing with a proper meter, output-tube recommendations for that amp, and what bias range to stay within when setting the bias. You may need to acquire a type of bias-meter or plug-in adapter that will allow you easy bias readings- which would be a good thing for you to have in the long run. - I've done this before with a Digital Multi-Meter and tight-tolerance (1%) 1-ohm 2-watt wire-wound resistors wired in-between the cathode and ground for each output-tube; part of Ohm's Law states that voltage divided by resistance equals current- so, when you read across those resistors for voltage (in DC mv) with a DMM, the measured result will give you the same number-value as the current being drawn; X divided by 1 = the same number as X. Cool, huh? (Requires savvy safety practices for working with live high-voltage circuits- potentially hazardous or even lethal. VERY important.) Also impoertant- this will NOT work for a "cathode-biased" amp, aaka "auto-biased", etc. - There are devices on the market that plug into the tube-sockets, and then the tubes plug into them, with test-points for a DMM's probes, that do this same thing. And I believe that there are also meter devices available that have permanently attached socket-adapters like that, as well. Several options. Safety is still important, if a little less potentially hazardous. I'd leave buying the new filter-capacitors and having them professionally and/or properly installed (or not) up to the amp's owner. You'll have done PLENTY for him and then some already if you pop for the tubes and biasing. Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
simpleman3441 Posted February 15, 2010 Author Share Posted February 15, 2010 What happens if I don't bias and just put in new tubes. I know this wears the tubes out quicker and the tone isn't ideal, but I don't think it'd hurt the amp, would it? This guy doesn't have an ear. He barely plays. Long as it's functioning, he'll be happy. We cannot accelerate the growth of a tree by pulling on its branches. - Ricardo Iznaola Link to comment Share on other sites More sharing options...
Bluesape Posted February 15, 2010 Share Posted February 15, 2010 I really think you should touch base with Myles before touching that amp, just in case there may be safety issues associated with it that only a tech would know.... Never a DUH! moment! Well, almost never. OK, OK! Sometimes never! Link to comment Share on other sites More sharing options...
Larryz Posted February 16, 2010 Share Posted February 16, 2010 What happens if I don't bias and just put in new tubes. I know this wears the tubes out quicker and the tone isn't ideal, but I don't think it'd hurt the amp, would it? This guy doesn't have an ear. He barely plays. Long as it's functioning, he'll be happy. You should have the bias checked any time you change your power tubes (the other tubes can usually be changed without a bias check)...otherwise you run the risk of having a melt down...it's not just an [ear] question...you can check the power tubes and if they are good and you put them back in the same slots, you don't need to worry about setting the bias...however, if the amp is having problems someone may have changed the power tubes without checking the bias (and/or without a matched set), so it my be good to take it in and have the tubes and bias setting checked out...IMHO. Take care, Larryz Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted February 16, 2010 Share Posted February 16, 2010 Yeah, biasing is something that you really should have done, and done right- it's just part of the whole tube thing. Especially on an amp that hasn't had it done in a long time. There are amps that either don't need to be biased like that (most of the time, under expected/normal conditions), or have external built-in test-points for a DMM and bias-control to make it simpler; but as far as I know, this is not one of those amps. Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
simpleman3441 Posted February 17, 2010 Author Share Posted February 17, 2010 It looks like they were stock tubes. I replaced em and it took care of the issue. The amp actually sounds really good. The owner doesn't want to pay for it to be biased and I don't have the time to do it. Thanks for the help though, guys. We cannot accelerate the growth of a tree by pulling on its branches. - Ricardo Iznaola Link to comment Share on other sites More sharing options...
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