| Author | Message | ||
| edward solberg |
Steve, Terry or Mike, Though I am no stranger to high voltage termination and all of the gear and proceedures associated with same (having spent 23 very productive years as a "master electrician: 4160vdc qualified."), however, when it comes to electronics, I am but a lowly apprentice. Ohm's Law is always Ohm's Law regardless of trade, but the usages from one to the other vary significantly. I find myself facing several dilemmas while in the course of recapping my "baby twin." in the filter stage, C42 and C43 (I am working off of schematic 2275-65), the 100 uF, 450 vdc caps I removed were comparatively large, "coors silver bullets." it is the relatively large size of these monsters that has me concerned. The replacement caps I received from The Tube Store, though of the same nominal electrical values, were possibly one third the size of the original units. I know that miniaturization has come a long way in thirty years, but: "damn man, am I missing something here?" the complete dissimilarity of the two parts makes me ask that question. Are those "silver bullets" not just general purpose 100 uF, 450 vdc caps OR some another genus of capacitor of which--in my ignorance of the nuances of electronics--I know nothing. would one of you gentleman please enlighten me? and, while I have your attention, might I tap your knowlege-wells a little deeper. My question concerns the subject of "forming" my new caps. In my trade we use large capacitors on heavy duty three phase motors and other electrical machinery. and, i am wondering if the forming proceedure is the same here. since my caps are "fresh" (2005 code on the cap bodies), can't I just use a current limiting resistor and power up? Must I use a variac on new capacitors? (I have read that this practice, while it does bring caps up slowly and safely, is just hell on one's tubes--or so I have been informed.) the method I have been told about involves soldering a 100K 2-5 watt resistor in series with line off the rectifier and into the first filter stage cap. Any thoughts on the subject? Precautions? dire warnings not to use the described method? I wish to thank you for your consideration of these matters in advance. Steve, I also want to thank you personally for spending the time and energy top make this site happen. it is truly an oasis in a desert of information on music man amps. Though I rarely post--I usually have nothing constructive to add--I have been following this web site for quite some time. I, personally have never regretted switching from my '65 twin to my little "baby twin" as my main amplifier for small venue gigs in 1975. I still have and maintain my twin but, as my playing over the years has evolved from blues to jazz I have come to appreciate my "clean," mean machine even more. may I propose} a toast to our little dynamo amps: "I wish Leo could have built more of them; God willing, let the ones we DO have last forever." edward solberg | ||
| michael kaus |
The new caps are just smaller. I guess wit new manufacturing techniques, they have better control. The new caps are much smaller , just make sure that the voltage rating is as high or higher. As far as forming, I think it's mostly guru talk as I have been installing caps for 30 yrs and never FORMED one yet. Can yo imagine Leo (or any other manufacturer for that matter) taking the time to do that. I think not. Like I said, sometimes it's just pudding for the goose- it adds to the mystery! Mike | ||
| edward solberg |
Mike, thank you for the input. You know, I should be mad at myself for falling for that line of hobbyist/tone-nazi-guru wishful thinking (busy work). In the electrical trade my bullshit meter was unerring (especially when talking with electrical engineer-types). as they say: "oh well." if this is the last time I fall for something I'd be truly surprised. the amp sounds great. I mean GREAAAAT! it has never sounded this good and I think I may have biased my new Ruby (read Chinese) EL34's a bit too hot. After about an hour playing time on the high switch at around six master/six reverb channel I get a distortion (sounds sorta like it comes from the preamp, maybe? it's an ugly distortion.) on the ends of notes played and/or sustained. I set my bias using the point "Y" method (still haven't been able to get the precision resistors I need for reading each tube's particulars) and used the old benchmark of .47 vdc. from what I've seen in some of the posts here, our amps love to dine on chinese power tubes. can you suggest another bias number range that might extend my tube life a little and get rid of the distortion? thanks for your earlier advice. (I guess I shouldn't have become impatient to get the amp back together...I wasted a full day in useless "forming" of my caps--don't laugh, it's true!) thanks for your and everyone else's help on this site...it makes maintaining our amps more than possible. especial thanks to jamie danter's post at the top giving the "blow by blow" procedural description of the job--it really helped, Jamie. edward solberg | ||
| michael kaus |
Actually, your bias voltage should be ok unless of course one of your tubes is hotter than the other. One thing you didn't mention though is whether or not you replaced ALL the elctrolytic caps. In you amp, you have some on the main circuit board as well as the driver board and (wait for it) THE BIAS SUPPLY. THe bias supply cap is VERY inportant. Seems to me it's like a 50@150 or something like that. They are very critical to controling control grid voltage, especially since you say that after an hour, it starts to grain up. I am very suspect of Ruby tubes for MM's since they just don't seem to like the HV. I'd try the JJ's but I'm a little biased since I use them in mine and they last really well. If you keep the ruby's, try going down to 42mv which would be around 21mA of current each. I still say that you should, however, measure each tube by itself as a precaution. Either with a bias adapter or the 1 ohmer's. It would be interesting to check the control grid voltage after an hour of cooking and see if it's drifted.Mike. | ||
| edward solberg |
Mike, again, thanks for your help. for the record, my 210-sixty five, with the 12AX7 phase inverter recieved a full cap job from me....I did the (4) filter caps and the (5)150uF, 50vdc caps on the chassis inside itself (as well as several burned-looking resistors). I'll back the bias off to 42mV and also read bias after a long session with the amp tonight (I'll dismount the chassis when I get home this afternoon, and play her that way) to check for drift. for the record, up until a month ago or so I was playing through my original, vintage '75 6ca7 sylvania tubes and had never bothered to learn the ins and outs of modern tube lore. knowing what I know now I wouldn't have bought the Rubys, more like the Tesla/JJ version of the EL34 recommended by you, steve and terry. oh well, the sooner I burn up the Ruby's the sooner I'll be able to change to a tougher tube (or conversely, I'll pull the Ruby's and keep them for backups while I install some JJ's from Eurotubes). I've since been reading materials about tubes at this site and gone out and began educating myself about tubes. I even went so far as to buy the tone-nazi-bible by mr pitman:} he pissed me off with his denigration of MMs as "wanna be fender hybrids"(paraphrasing, of course). On this site, steve, terry and yourself have made very informative posts concerning the efficacy of the different tubes....if only I had discoverted this site before I re-tubed my "baby twin".... thanks again, I'll let you know the results of my investigation tonight. ` e | ||
| michael kaus |
Sounds like a plan. The bias supply cap on the right side is just SSSSOOOOOOOOOO important since it's your "throttle" (or spigot as I like to compare it to) for your tube to prevent runaway. People don't think of it unless their expensive NOS tubes go poof and then they say, "gee, I wonder if I lost bias voltage?" DUH! | ||
| edward solberg |
yes. I had noticed that a strong and consistent theme of your posts in re., "cap jobs" is the importance of those two 150uF, 50v bias capacitors. I know I revised my intention of replacing only the filter caps to doing the full job after reading the emphasis on replacing all caps by the knowlegable folk at the site. I road tested the 210-sixty five this weekend. below is the report card on the amp that I attempted to post early this a.m. 1975 210-Sixty Five....REPORT CARD. after several false starts and intervening duties, I finally got around to doing my full cap job on the 210-65 (12AX7 phase inverter) last week. the new caps and tubes have resurrected my old road warrior (that amp and I have seen a lot of miles and gigs since 1975). It sounds better than I remembered and saturday and sunday nights I was able to give the amp some "field testing" while sitting in with two different groups, playing two different styles of music: urban blues and jazz. the old Music Man exceeded my expectations--over the years as the sound of my amp deteriorated ever so slightly, I had forgotten the original sound and tone of my amp. well, I remember it all now: super clean with virtually infinite headroom. let other jazz players keep their sterile little solid state beasties, the 210-sixty five has something they can't match with their line sixes and roland "boxes": TONE as well as "clean." the 210, while a cleaner amp you couldn't ask for, has a roundness and buttery warmth that wonderfully compliments an archtop hollow body's own rich tone...the combination is just incredible to hear. saturday night's two sets with a jazz quintet playing coltraine standards and 1950's bebop was a stone gas with my 210.... being the only guitarist on the stage I had nothing to compare it with...sunday night's venue fixed that lack. sunday nite it was two sets with a buddy's five piece blues combo (sixties butterfield, harvey musslewhite, bluesbreakers...your standard ass- kicker tunes). I left the archtop at home--it had no business with that rowdy group of musicians. no, it was time to play my 335 LOUD with that band--and, the 210 had no trouble at all keeping up with the other guitarist (silverface twin reverb) and the keyboard player. I used the amp on low power, master at ten and the channel volume at levels four thru six. that amp is still a screamer. though virtually distortion free, its response to a heavy pick attack allows for very dynamic soloing. it took all my humbuckers could give and never flinched. the other guitarist --with whom I've played for years-- did a double-take the first time I opened up the 210 to solo a couple of chorus'... at the break we did "amp talk" and he seemed amazed at the change that had come over my 210. suffice to say, after playing the second and third sets, I left the club with ringing ears and a huge smile on my face. my "baby twin" is BACK .... If it hadn't have been for this site's kindling a desire to get into the guts of my amps I never would have known just how great my thirty year old amp could sound. my 210-sixty five passed her road tests with flying colors and I can't wait to take her back out in public again. Mike, for the record, I dialed the bias down to .42vdc on friday and played it at that setting for a couple of hours, but I had already been spoiled by the warm, full tone I was getting at .47v. I found the colder bias a little too "brittle" for my tastes and so will accept a little shorter tube life in exchange for tone that won't quit.... besides, they're just chinese tubes--I am chomping at the bit to try a set of JJ/Tesla E34L's in my 210. that funny distortion I mentioned earlier on the ends of some notes has vanished. it played hot and clean both nights. however one problem that baffles me did crop up, I can't use my bright switch. if I turn the switch on it sounds almost as if I had blown a speaker; very disturbing to say the least. if you have any ideas on what this might be or where in the tone stack I should begin my investigation, I'd sure appreciate your input. e | ||
| mike kaus |
Not really sure unless the cap shorted. My gawd, if I turned the bright switch on my amp, it would probably hurt somebody! Mine's way tto bright as it is and always planned on re-voicing it a little but I've pretty much gone back to my Twin for a while with this band. I really got NO bass response out of my 2-10 65 without carrying a 15" cab to sup it so I went back to the twin for a while. Besides, the front end is so hot on my MM that the guitar I'm playing now(heritage 535 with Gibby classic 57's) feeds back pretty bad. I'm already carrying around my amp, a complete bass rig, and my keyboard(ok, I'm a glutten!) so that I can switch around with the other people in the band. Hell, I ran out of room!. Back to your bright switch, I would try changing the cap first and if not, you'll just have to trace down starting and ending signal. Let me know if I can help. Mike. | ||
| edward solberg |
Mike, by the way, I f-ing LOVE Heritage axes, I've wanted a 575 for a very long time. and the Gibson classic '57s, I have them too on my archtop Guild T-100 D (bought in in 1966)... I changed out the pair of alnico single coil PUs for the Gibbys a year ago or so. I absolutely love the tone I get off that neck pickup! anyway, enough guitars.... I've changed the bright cap and still no love. I think I'm just gonna proceed on to my next project and come back to it later. I'm hearing occasional "noises" (occasional crackling, etc.) that I am tentatively attributing to the need for me to refurbish my tube sockets. I'm planning on replacing all of the resistors and caps near/on the sockets. While about it, I think I'll try real hard to find those precision 1 ohm resistors for measuring the individual tube's bias numbers. I have a question regarding the installation of these resistors. I understand where they go for reading the output, my real question is are they then left there permanently to read at need or must they be removed when I put the amp back together for playing? another thing would be I'd like your recommendations for substitute parts (like where am I gonna find carbon composition resistors? do I then substitute carbon film? something else?) needed for the refurbishment job. Where can I find substitutes for those Mallory capacitors on each tube socket? and, exactly "what" is the substitute for same? I noticed that Mouser has some of those concrete block resistors now in stock, I've got a real hankering to try them if they'll fit my needs in that high-temp section of the chassis. lots more to do on the inside of my amp before I tackle the minor cleanup involved in my restoring the amp (really, it is in nearly mint condition ... excepting a deep layer of tobacco tar in the grill cloth and on the tolex) from years and years of club gigs. speaking of the near factory condition of my amp, I have to relate a stupidity on my part that happened. sometime this last week, I began hearing a great deal of hum coming from the amp, it always disappeared after I switched into standby and took the "high voltage legs" off the tubes. (This is when I conceived of my plan to refurbish the sockets.) I looked all over that sucker for a source of the noise. about two days of trying everything I could think of, I'm playing with the knobs to see if my tone or volume pots are making the hum. there is one knob that I replaced on the amp some many years ago... I couldn't find a musicman knob; and this was long before amp restoration brought those specialty supply companies into existence. so I got a generic black skirted knob with a brushed aluminium center... fine, right? there are no numbers on the knob I used as my "speed" control, only a white, diamond-pointer. somewhere in all the moving the chassis in and out, messing with the knobs, etc. the vibrato speed knob got set on ten but the pointer seemed to indicate that it was zeroed and I never checked... I found the source of the greatest humming only by accidently turning the speed knob when I meant to adjust the master! damn, did I ever feel stupid.... turned off the "speed" and the amp got much quieter, in a hurry. anyway (all BS-ing aside), I'd appreciate your input on my next amp project. thanx again, e I think I read somewhere on this site that a cure for noisy amps is the rehab of the sockets, so I think I'll tackle that job next. | ||
| mkaus |
I usually use either cement for the plate resistors or metal oxide(which I prefer) due to the heat. After that, I think it's mostly personal choice on resistors. I really can't say I hear any change from one to anoher although there is great debate over small cap choices in the preamp stages. Some people say this mallory is better than that mallory and all that but I really don't hear THAT much dif. That's why we have tone controls! I personally only notice the change in power tubes and preamp tubes. On the MM's, obviously you don't have a big tonal change with preamp tubes since it's only used as a phase inverter. The power tube, on the other hand, change tone drastically. The Sovtek type tubes are harsh and brittle sounding(to me), Real Svets(winged C) sound great as do the JJ's. I prefer JJ's since I seem to get better life out of them and they sound greatand are pretty damned cheap considering what you get. By the way, I've been noticing a lot of hum lately being generated in power tubes so I think I'd look there first and then start looking at grounds and things. The sockets do need to be cleaned and retensioned as they will get nasty and will cause(somethimes) eratic volume and a general thin sound. If you have extra tubes, try subbing them one at a time to see if the hum goes away. You might be surprised. Clean sockets and let us know. | ||
| edward solberg |
Mike, you know, though I will do some "house cleaning" in the power section (sockets, etc.) this weekend, but I think I'll go ahead with the rebuild anyway. my thinking is this: I use a lot of hollow-body and semi-hollow guitars and we both know that even with humbuckers they are just noisy as all hell. I put my old Guild S100 Polara Starfire (the Guild SG) through the amp last night to gauge its actual quietness. the S100 is the quietest instrument I own--had shielded control cavity and star grounding when I bought it back in 1970! it is my test for amp quietness because the hollows are just so damned noisy anyway. though the amp was very quiet using the s100, I want it quieter for my hollows so I think I'll go ahead with the rebuild as soon as I can assemble all of the needed parts. I'll let you know the results of the cleaning activities this weekend and the later rebuild... who knows, maybe cleaning alone will improve the sound enough for my hollows? thanks always, e | ||
| Steve Kennedy (admin) |
I'm glad you two have simply gone at it without my intervention! I am gratified to see that Edward got his baby restored. These amps are amazing when they are running right and I think God smiles in heaven for every MM amp brought back from the brink! Myself, I have been working long hours and just haven't had much time to spend on the Message Board. I would like to thank Mike for his presence here! This web site would look pretty dead if it were only up to me! Steve | ||
| edward solberg |
Steve: amen to that. Mike is one hell of a resource to this site. Sorry I haven't gotten back with the results on my "house-cleaning" in the output section. the press of affairs made it impossible to get back to my mm and I had to use my real twin for the little gigging I did during the time. though I'd still like to rebuild the power section of my 210-sixty five, the cleaning, retensioning and replacement of a burned resistor made a huge difference in quieting the amp down. I can only surmise that the resistor was a recent casualty after the cap job as it played great the night I took it out "clubbing." be that as it may, that noise problem is resolved. mike, steve, all, thanks for a great site. it has become a real resource for this music man owner. edward solberg | ||
| mike kaus |
I had been using MY Twin for a couple of months and last night we worked in a small place that is a pain in the ass to get a full sized Twin, IN a flight case, loaded with JBL's in. Needless to say, the damned thing is heavy. Anyway, took my 2-10-65 in and used a single 15" cab with a D-130 underneath for some bottom. Really sounded good after I found out why it was honking funny. That was the first time I had used it since going to my Heritage 535 from a Steinberger(which I played also!). I actually had to turn the mids DOWN for a change. I wasn't used to getting that much middle out of the Steiny! Anyway, if you've never used a 15 with the little 2-10's, try it sometime. It's interesting. The 10's in my MM are a little tight-they are Weber Cal 10's so they are pretty stiff but I figure I'm using pedal born drive so what the hell do I need speaker distortion for? Anyway, we're actually pretty damned loud at times(not by my choice> but that seems to be what they want to hear when your in a crowded noisy bar. Anyway, I'm rambling but the point is, the MM sounded great again and reinforced my opinion that these things will go on forever. Now if I could just get down to my shop and fix my 130 that I blew up( a subject for another long ramble!) Mike. | ||
| edward solberg |
No, Mike, I?ve never used my 210 with a fifteen-inch satellite. Bet it sounds cool. When I was playing electric blues at much higher volumes in the 80s I had an old Bassman cab with JBL D120s in it (I always loved the sight of those aluminum cones shining through the grill cloth, it?s just cool-looking!) for increased speaker surface area (+volume) and to handle some of the low lines I love playing. (I think that cab is in my garage somewhere, though I imagine its value as vintage collectible went out the window the moment I put the JBLs into it, I?m keeping it for a ?just in case? situation.) I imagine a D130 would absorb A LOT of guitar lows. I?ve been thinking about trying the Weber ?California? 10-inch speakers. Are you using the ceramic magnets or the alnico? When you say that your speakers are a ?little tight? I?m guessing that you put the ceramics into your 210. I think I?d like the alnico speakers better but (there?s always a ?but,? isn?t there) that $150-price tag per speaker is a little bit daunting? Frankly I?d been puzzling about your repeated statements on this site about the exceptionally bright character of you amp?s voice. I?ve always played hollow or semi-hollow guitars through my amps (I own only 2 solid bodies) and have always found the mids and lows of the amp to be more than adequate? I was puzzled, as I say, but you just explained it all when you mentioned playing a Steinberger through your amp: you could slice steel with the tone from one of those EMG-voiced guitars! Do you run the ZW- (?active?) pickups? Every example I?ve heard had brilliant treble (IMHO, too much?but then for my own style I like much more mellow-voiced instruments). I imagine you noticed a huge difference when you put your Heritage 535 thorough the amp (for my money?s worth, the tone on the Heritage is far and away superior to that of a Steinberger? but that?s just me I ?spose). Through your mentioning the saga of your 130 in many posts throughout the site, I believe I have the essence of the story. Apparently you witnessed one of those all-too-tragic ?tool-suicides? where those pliers jumped to their death on a live circuit board. Tragic, what else can I say? I hope you do resurrect your 130 soon one of these days. It must have been a traumatic event to have witnessed? have a really good holiday; ed. | ||
| Mike kaus |
Actually, the Steinberger has Gibson Classic 57's in it. It sounds great with this combination as the Gibby's ofset some of the small body lack of sustain with gain. My 2-10 does indeed have a LOT of treble but really sounded great when the 15 was added. It may get more use now as I figured out the mid's were giving me the trouble with feedback. The cal 10's are ceramic and I got them because I wanted the JBL clean sound but really, I forgot to factor in the fact that 10's don't give you much bass response. THe 15 took care of that though. I use the 2-10 for 2-3 years with the steinberger before switching to the Twin again for a while. You know, the wind blows, guitar players change! Anyway, great THanksgiving and holiday season to all on the MM board and I want to thank Steve for the opportunity to help and get help with our toys. Without great people like him volunteering thie sight, we'e be stuck wandering in he dark. The people here are nice, no hissy fits and sniping, and are trying to help keep the MM line alive. WELL DONE STEVE~. Mike Kaus. | ||
| Impersonal Trainer |
If new caps needed - Change 'em: amp is louder, fuller more assertive, good for another 10 years. Approx $150 by a pro. Don't change 'em: Sounds the same for a while, sound degrades, loss of bottom end, damage to amp. Cost: Whatever your next amp costs. |
Tue, 03/25/2014 - 09:27
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