212Mavguy Posted August 24, 2012 Share Posted August 24, 2012 Before starting this one, I went back to a previous purchase carefully researched but impulsively purchased and read my previous words.... "Came home from playing out at a late night film production party and pulled the trigger on this at 4:20 in the morning" I laughed twice as hard as I did very earlier this morning. Got home last night from being entertained in a 5 star hotel at 8,200 feet altitude on the mountain I have worked as an instructor the last 31 years. Some winter clients were in and they had invited me up for beers and apps. they had their kids with them, I went out to my car and retrieved my acoustic 12 string and played for the kids in the hotel lobby for a few minutes before saying goodnight. It was a wonderful evening. I stopped by a buddy's house on the way home and was treated to a nice late evening safety meeting. Went home and opened up my watch list, this had been there for quite a while. A previous experience with a rescue amp project of similar make and earlier vintage model with 6v6's freshly digested had turned out to be quite wonderful. I was unknowingly perfectly plucked and prepped to be tossed into the broiler by Chef Impulsivity, ready for another helping of self inflicting buyer's abuse... This was already sitting at a screaming deal BIN for what I thought it was and was capable of after a set of Franken-Mav bench sessions. http://www.ebay.com/....m1439.l2649#sf But because of the condition my condition was in (Yeah, Yeah, OOOOOO Yeah, what my condition was in)... I tossed in a Brently offer of 420 bucks and it was instantly accepted. 420 mood, 420 bucks, a model 420 amp and for the numerology frrrrrrrrreaks the purchase time of 12:28 digits add up to 13. Schweeeeeeeeeeet! Link to comment Share on other sites More sharing options...
DetroitBlues Posted August 24, 2012 Share Posted August 24, 2012 congrats on your usual old school amp! Using it for bass or guitar? Link to comment Share on other sites More sharing options...
212Mavguy Posted August 24, 2012 Author Share Posted August 24, 2012 It will be for guitar and baritone...should end up as a monster blues amp. Link to comment Share on other sites More sharing options...
FredZepp Posted August 24, 2012 Share Posted August 24, 2012 Link to comment Share on other sites More sharing options...
FredZepp Posted August 24, 2012 Share Posted August 24, 2012 It reminds me of an old Supro Thunderbolt amp that I used to have..... it was an incredible amp and I wish that I still had it. Good luck on your tone quest.... that amp looks capable of getting you there. Link to comment Share on other sites More sharing options...
212Mavguy Posted August 24, 2012 Author Share Posted August 24, 2012 Thanks for properly posting the pics! It's exactly that amp but with bass and treble knobs instead of a single tone knob. Link to comment Share on other sites More sharing options...
DetroitBlues Posted August 24, 2012 Share Posted August 24, 2012 The rectifier tube looks like its about finished... Link to comment Share on other sites More sharing options...
bolero Posted August 24, 2012 Share Posted August 24, 2012 wow that's cool I've never heard of the model 420 ( does it smell smokey? ) but have heard of the thunderbolt, nice score!! give us a report when you get it!! I don't think it has a tube recumfrier, those are just different brand 6L6's ? ps make sure he pulls the tubes & packs them up safely inside before shipping, or you'll end up with broken glass & no tubes Link to comment Share on other sites More sharing options...
212Mavguy Posted August 25, 2012 Author Share Posted August 25, 2012 I asked for the tubes not under shields to be removed wrapped and protected for shipment, hopefully they got it right, but I'm planning on replacing those mismatched power tubes anyway, SS rec allows much more potential filtering capacity for bass guitar use or dimed and boosted guitar leadwork.. This amp should be tight sounding, but still have some nice compression. When I get done it will sing like a diva coloratura opera soloist. Link to comment Share on other sites More sharing options...
212Mavguy Posted September 1, 2012 Author Share Posted September 1, 2012 The amp arrived yesterday and all was not well, of course, it's a vintage amp from a pawn shop, if you're whining go figure! First unusual occurence as ai was atttempting to lift the amp out of its sarcophagus of packing hard foam was one of the power tubes falling out from 3 feet up and landing ont he deck. RCA 6l6gc blackplate for those that have any waaaah sympathy. The other was a GE grayplate. Typical vintage amp bastard pair of power tubes. Fired up, no sound, saw blue glow from the vintage TS 5881's now in it. Then I tapped the preamp tubes' shields and got a crackle out of the PI. so I removed both shields, a sheet of asbestos wrap fell out of the V1 shield. The pre's were both NOS looking RCA 12ax7a shortplates, but I had some stuff sittingout of my correction, so I stuck in a shortplate, 5751 style grayplate RCA in V1 and a vintage late 50's RCAongplate cleartop 12ax7 in the PI, I like longplate 12ax7's in PI spots as a rule. by the time I subbed out the tubes and wiggled a couple of time the sockets connected much better. Now I had sound, but all mid and treble tinny for a bass amp with a 15 in it, Then when I turned the bass pot up the output volume dropped to zero, no matter what the main volume pot was set to. Took off the panel covering the guts, and found a loose 4-40 nut from a power tranny mount lodged in the side of the bass pot shorting ne of the lugs to the body. Removed it, problem immediately solved. Has a bit of noise at hiighest voume, the two redundant from the factory death caps had been snipped one one leg and left to hang;. I like the basic amp sound and the fact that the power switch also pivots both ways for a ground polarity switch built in, so I just might get a couple more and reconnect those caps with new ones. Maybe go triple redundancy.at reduced values..or I might just stick in a 3 prong cord. This is a very smooth, honest, versatile amp that can cover quite a few guitar tones by itself, I played my Veillette baritone through it and it was wonderful for that spaghetti westen sound. With 6l6gc, guessing around 35 watts with true 5881;s around 22-25. But when I put an old DOD EQ pedal in front of it and hit that clean boost the amp starting to toss out some amazing flamethrower leads and world class crunch rocker monster sustain power chords at medium venue volumes. (had the volume down to two) and that was the secret to not being too loud and still getting the great tones, just hittng that first preamp tube very hard with the main volume turned way down, I settled on an old but still strong pair of Raytheon 6l6gb blackplates for the power tubes some of the nicest sounding 6l6 types ever made perild. Plate voltage is around 380, screens 370, OK for the older 6l6's here in this amp. OH YEEEEEEAH! The preamp is among the most simple in parts count of any guitar amp of this type, and there were only 4 tone caps that I am gong to carefuly remove and replace with russian military paper in oil units, ordered them today. The can cap and other electrolytic both seem fine and the circuit behaves as if all is still well there. I have put on a good 12 hours in the last few days on it since the retube no problems. Since the amp is not worth much on the vintage market despite it's being nearly identical and more versatile than it's Supro Thunderbolt sibling.(worth nearly three times as much,) there is no crime in subbing out old parts for better quality NOS ones. NO prob making a brudda T-bolt killah. The last amp made by the same folks that made this one saw huge improvement after the similar cap upgrade. There is a spare NOS JBL MI-15 in the basement that needs breaking in, and it will kil that Jensen, nice and sweet sounding as it is, I know what that JBL will do, particularly at higher volumes. It has a paper dust cap and is light weight and very efficient. Will allow a lower bass knob setting and that will open up the abundant harmonics even more. It's spectacular with what that amp can now do driven by a clean boost. Wants to sing and sustain for days. Put together a well enough matched pair of adapted 6bg6ga Sylvania for max power 6l6/7581a type Baritone/Bass use, it delivers a bass friendly tone with snap out of the strings easy to get, smooth but not muddy. This amp delivers for my hollowbodies, semi solids, semi hollows, and solid body guitars, single coils our HB's with equal aplomb. Kinda amazing what it can do, despite it's incredible simplicity not a one trick pony, it's waiting for your pedals. Pricewise, was a freaking steal, pure ptp/ terminal strips nicely lead dressed boutique build with Dr Z / Alessandro type of elegant simplicity in the circuit design. That paper wound OT is not all that large, so there is some compression and smoothness coming directly from that, however, it;s also very sweet sounding.. Link to comment Share on other sites More sharing options...
H Posted September 1, 2012 Share Posted September 1, 2012 Sounds like you got what you were looking for! BTW, I loved all the detailed tube and component references you made; I'm sensing a real electronics junkie at work here! Link to comment Share on other sites More sharing options...
brentrocks Posted September 1, 2012 Share Posted September 1, 2012 I tossed in a Brently offer of 420 bucks and it was instantly accepted. you have learned well young grashopper Link to comment Share on other sites More sharing options...
Gitfiddler Posted September 1, 2012 Share Posted September 1, 2012 Hey 212Mav~ Um...if you ever decide to unload that JBL drop me a pm. Link to comment Share on other sites More sharing options...
yoslate Posted September 1, 2012 Share Posted September 1, 2012 Great score; great report, as always 212'! I'd gig that puppy in a new York Minute! Link to comment Share on other sites More sharing options...
212Mavguy Posted September 2, 2012 Author Share Posted September 2, 2012 Hey 212Mav~ Um...if you ever decide to unload that JBL drop me a pm. Here ya go. Similar to g135-8 in tones but a little smoother, slightly more compressed, great with low power tube amps as well as 50 watters. This guy is pro all the way to deal with. http://www.ebay.com/itm/270719583493?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#sf ...did sub in that model speaker for the Jensen. The Jensen sounds great but there is a bit of indistinct stuff in the transients, the louder the more apparent. Also, it's mid scooped, that little voice coil can't do everything, noticed that the spider was sagging back a little, this speaker had been heavily worked and probably would sound best with a recone. The JBL was expressive to pick attack in a natural manner. The midrange opened way up and I was able to hear things that the amp had been doing there but suppressed by the Jensen. Remember, this amp is "vintage cheese," not a high end priced amp, but the sum of the parts again and agan in amps I've experienced by this particular builder of several economy lablels made some very, very good tones, and with parts upgrades can truly excel, competing with the modern boutique amps designed to sound like these ah, vintage cheese circuits for a fraction of the modern boutique build retail bite in the back pocket. Link to comment Share on other sites More sharing options...
212Mavguy Posted September 8, 2012 Author Share Posted September 8, 2012 4am...done! Went to bed, napped, and fired it up 8:30 for morning coffee. It's the same amp, but there's a lot more going on every where now. All the indistinct mush in the transients is gone, harmonic content is off the charts, sustain has improved to the "unusually good clean sustain" typical of this builder's circuits. It's a good bit louder, as loud now with a pair of 19 watt coke bottle 6l6G's as it was originally with a pair of 30 watt 6l6 GC's. Some volume increase comes from that JBL, which is a major unknown wow all by itself, and some from the full recap. Supro Thunderbold killer she now most certainly is, and she does sing like a diva coloratura opera singer for sure. WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOEEEEEEEEEEEEEEEEEEEEE!! I enjoyed firing 'er up after each part was subbed in and so I got to hear the differences happening step by step in true mad science fashion. My room mate calls me "Igor" when I start pulling an amp related all nighter.. Had one interesting surprise after another on this one. This amp, although typical for its day, did not have enough power supply filtering capacity, being a true vintage cheese amp with true vintage cheese caps in it, and I think that contributed some to the original speaker's indistinct pick attack at high volumes, Also, for a bass/guitar multi purpose circuit the low amount of power supply filtering was just plain wrong. Bass amps need more capacity than guitar amps, lots of instant oomph available on call needed. There was a three section can cap, 20/10/10, and a 20mfd axial type cap also wired inline elsewhere, a big fat Mallory. 60 total for starters. This is a solid state rectified amp and those can take much more than a tube rec'ed circuit. My old tube rectified silverface Fender Champ had more than that! I know some are going to take me to task for not having equipment to test caps with, but In this case I went drastic and did the conventionally unforgiveable, removing that cap can, leaving an open hole and "ruining the vintage look" of that old amp. Every original tone cap went bye bye over the course of the night. But-but-but-but-but-but those are the original VIIIIIINTAGE parts! You CAAARIIIIIIIMMMIIIIINAL!!! Waaaah! pffffffffffffffffft. So what. It cost 420 bucks plus shipping and ain't a valuable collector. Worshiping rather than replacing out of tolerance old parts for collectibility is functional incompetence at its finest. Vintage correct is when parts within a given circuit operate at their designed values! Respect the circuit, not the half dead or worse old cheesy parts. especially in vintage cheese amps. get rid of the old cheese, all of it, and stick in some meaty military muscle. Went down to the old school electronics store and found a bunch of 22/450 radial lead electrolytics, joined up as two pairs, a drop of zap-a-gap super glue to tack them together, followed by a generous helping of clear silicone glue for backup. While they were drying I drew a pic of the wires around the cap can and labeled them by color and position. I needed two of the caps to be parallelled and the other two to each go to their own places. So I made a little brick out of the pairs of caps and twisted the 4 wires together for a common ground, and soldered it hanging free into place, suspended by the several wires it is soldered to, man, does it look ugly, but it can't start rattling around and functinally it works muuuuuch better than stock, even with the improvised lead dress imposed by the mod. YAAAAAY! Values are now adding up to 44/22/22 with a 47/450 replacing the 20 inline cap, for a total of around 135 mfd now, double stock, it worked to perfection. I was expecting a lot of bass response now, was worried about having to tweak the preamp, but no, the sound was the same but no mush at attack anymore and more clarity/note separation in loud power chords, particularly at the attack, nice and crisp now but yet not too punchy, typical of the smaller than usual but high quality iron used in these designs. This gave the amp a much more articulate character in responding to picking nuances, particularly in the lower notes and the texture of those lower notes when pushed into OD improved greatly. Out of the farty and into the cello camp now on the baritone guitar, and that got better and better with each new part transplant throughout the night. . . With the power supply finshed, now on to the preamp. I looked at what I was going to use the amp for,and decided that 35mfd/50v was too much capacitance for the first gain stage, that would not allow as much harmonics to come through because it was tuning the pre for bass frequencies, not needed anymore. So i dropped the value to 22mfd, stuck in a Black Gate semi unobtanium out of production NOS unit. Fired it up, and wow, the increase in clarity was shocking, like taking off a layer of blanket over the speaker. Gain seemed to be about the same as before in where I was turning th volume knob. The old cap was a Mallory, black and fat, yellow in the end plugs. It was a real tone sucker, that one part. I plugged in the baritone and dimed the amp, started playing output was even high to lowerst, so sigh of relief, no prob for the lower notes and a more opend up sound overall...nice! On to the tone caps, these were tough to get to and took quite a bit of time to remove and replace lying paralell to terminal strips and covered over the top by various carbon comp resistors...with the leads originally wrapped around each connection under each blob of solder..I went through a small roll of solder wick on this amp alone! All values were left stock, and the new caps were Russian military k40y-9 paper in oil with aluminum foil and silver in their build, equivalent to the spendier US cold war milspec Spague Vitamin Q's. After every sub, the amp was fired up to test. Could hear imrovement with each new part. I pinched each of the old ones, the sides collapsed inward a little bit and I heard some sticky tacky sounds inside, so these had long ago ceased to be what they were originally. Not all tone caps are like this, but I was suspicious of the build type and was proven right. Then, one more cathode bypass cap needed to be transplanted, this time it was for the phase inverter, so the stock 35mfd/50v value could not be dropped this time. This was a white molded Sprague unit. I subbed in a Black Gate 33/50 unit. Upon fireup the difference was shocking, that white Sprague was more of a tone sucker than the black one in V1! I was too spent to appreciate my surgically enhanced Frankensteeena's little hard round knobs, though... By now it was 4 am, I was done, totally done. Even though each fireup revealed no problems to diagnose and fix, a lot of time had passed in the sesh, I was gratefully wiped. This was a loooong 420 work session on a 420 dollar model 420 amp.. Went to bed for a nap and got to sleep before the rain birds started chattering outside the window. Fired up the morning coffee, and played for a bit. I started drooling onto the fretboard. She's simply, amazingly... Frankensteeena Gnarly! Link to comment Share on other sites More sharing options...
bolero Posted September 9, 2012 Share Posted September 9, 2012 wow...thx for posting that, very interesting read!! especially the bits where you replaced old vintage ( and commonly revered ) parts; caps dry out over time but most ppl only focus on the power supply caps...so you selectively swapped out signal & tone caps, found a difference in how the amp behaved? makes sense if they were old & dried up/drifting!! I have a bunch of old salvaged amp chassis ( and old amps ) that would be perfect for upgrades like this those old transformers were decent, as good as the boutique ones today ( or maybe even better? I remember reading about how the recycled metal we use in a lot of electronics now, is not as high quality as what they used in the tube heydays ) I wish I knew how to mess with stuff like this Link to comment Share on other sites More sharing options...
Gitfiddler Posted September 9, 2012 Share Posted September 9, 2012 Mav212's NAD adventures are of true epic proportions!! Igor indeed! Link to comment Share on other sites More sharing options...
Hfan Posted September 9, 2012 Share Posted September 9, 2012 I am digging Mavguy's amp posts. I will bookmark these for future reference. This stuff would make a great hobby when the kiddies go off to college if I make it that long. I'll be too broke to buy a new amp so an old beater needing TLC should work out. Mavguy, did you mention you don't have a cap tester? Link to comment Share on other sites More sharing options...
Hfan Posted September 9, 2012 Share Posted September 9, 2012 I saw this on a local CL today looks interesting... If I had the time to tinker I'd jump on it http://jerseyshore.craigslist.org/msg/3227568706.html Link to comment Share on other sites More sharing options...
212Mavguy Posted September 11, 2012 Author Share Posted September 11, 2012 wow...thx for posting that, very interesting read!! especially the bits where you replaced old vintage ( and commonly revered ) parts; caps dry out over time but most ppl only focus on the power supply caps...so you selectively swapped out signal & tone caps, found a difference in how the amp behaved? makes sense if they were old & dried up/drifting!! I have a bunch of old salvaged amp chassis ( and old amps ) that would be perfect for upgrades like this those old transformers were decent, as good as the boutique ones today ( or maybe even better? I remember reading about how the recycled metal we use in a lot of electronics now, is not as high quality as what they used in the tube heydays ) I wish I knew how to mess with stuff like this Gosh, I wish I knew what I was doing too! Gotta start somewhere. If you find an old tranny where the laminations are rusty, leave the rust on, it hwlps prevent eddy currents, the rusty one might end up sounding better than if you cleaned it up all spic and span and shiny. Old trannies were made out of both better iron and wire. Have read reports about the insulation/coating on the wire that the Chinese often use in their cheap guitar amp trannies is inferior to the old US wire and their build suffer a higher fail rate as a result.over long time. I'm very flattered at the compliments my posts recieve, but how excited do you think i'd be to read the story about one of you guys commenting on my OP locating a decent rebuild amp and starting out on a similar project? I might even be able to help. I can't afford three thousand dollars for purchase of a new, handmade boutique fancy one, but I just finished with two one of a kind customs for less than a grand by redoing the right vintage redo's. Old parts are only to be revered if they are still performing as designed after all this time! I thought there might be room for some mprovement in the transition from clean to OD in my '61 Harmony H-306-A and for more chop on the tremolo. The original .03 ceramic caps were on the grids in V1 still, I had not cdhanged those out with the other tone caps. The parts I had ordered from eBay aucions had arrived. So I stuck in some vintage Micamold PIO caps in place of the ceramic ones, and the sorta crackly edge transitioning into the dirt was pretty much eliminated. Once again, the amp became more musical sounding tha before. @ Hfan, the Sano line of amps were uncommonly high in quality of parts, workmanship, and sonics. That price of 350 is a third of what a nice one in great working conditon is worth. Playing through a "big" Sano is a Jazzer's heaven. Link to comment Share on other sites More sharing options...
Hfan Posted September 11, 2012 Share Posted September 11, 2012 @ Hfan, the Sano line of amps were uncommonly high in quality of parts, workmanship, and sonics. That price of 325 is a third of what a nice one in great working conditon is worth. Playing through a "big" Sano is a Jazzer's heaven. Mavguy, it is still listed. Two 8"s and one 15" sounds interesting. Looks cool too, wooden handle? The guy is asking $350, could probably get it for less.Bet it sounds good cranked (50W). Illustrates your point about unknown brand amps flying under the radar. Average guitarist just like me never heard of one. And this sounds like a motivated seller. http://jerseyshore.c...3227568706.html Link to comment Share on other sites More sharing options...
Hfan Posted September 11, 2012 Share Posted September 11, 2012 tried to add some pics the editer timed out. price is actually $325. Check out those old .050uF caps..even a mouse eaten vintage cover..tempting. Actually appears to be two different 8" speakers. Link to comment Share on other sites More sharing options...
212Mavguy Posted September 11, 2012 Author Share Posted September 11, 2012 The lead dress in that amp is impeccable. The iron is huge. Link to comment Share on other sites More sharing options...
Hfan Posted September 12, 2012 Share Posted September 12, 2012 The lead dress in that amp is impeccable. The iron is huge. I thought you would like those slightly rusty xformers. If I bring it home I may get hit with an iron about the noggin by the Mrs.. I can't justify another amp or project and at 50 W more than I need but man it is interesting... Link to comment Share on other sites More sharing options...
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