hellion102792 Posted June 7, 2012 Share Posted June 7, 2012 Awesome recent acquisition. I was over my neighbors house helping move furniture when I see this little Gibson amp, upside down and being used as a table to hold a paper shredder. Made her an offer to buy it from her and she said those amazing words... "Oh, you help us enough. Nobody here even uses that so you can just have it". For the sake of feeling totally indebted to this woman for trying to just hand me a vintage Gibson amp I tried again to offer some money a few more times before she practically pushed it into my hands. So here it is (it does have the back covers, removed them to clean the ungodly amount of dust) All original, even comes with this little reference card! This thing has a unique tone and it is LOUD! It runs on a tube combo I haven't heard of before, 12AX7A pre -> 6BQ5A power -> 6X4 rectifier. I liken it to an Epi Valve Jr due to the simplicity in it's controls, with the only exception being it has a tone knob. It's a great little recording amp with a shimmering clean sound and a smooth-yet-ballsy breakup. A few small problems, the only physical one you can see in the first picture. The plywood bar that runs underneath the chassis and holds up the grill cloth has deteriorated in the middle and broken. Not a huge problem, the cloth still stays in place and I might just reinforce it with a metal strip just for aesthetic reasons. The other problem is it needs to be recapped. After it warms up it emits this low tone that isn't affected by the volume knob, and is loud enough to overpower the sound when the master is between 1 and 3. When cranked there is almost a tremelo/warble-like quality to the sound. I believe it's a '67 because of the design, anything I've found online shows the '67 Skylark with this "Medalist" design. There is also a version with tremelo, and this one has pop-out slots in the chassis and control panel for the tube circuit and knob, respectively. Gibson sent me a schematic so I'm considering building the trem circuit and having the local tech install it when I take it to get recapped. Anyone have experience with this amp? Link to comment Share on other sites More sharing options...
Searcy Posted June 7, 2012 Share Posted June 7, 2012 Very cool! I have been reworking a Kalamazoo of the same era. http://forum.gibson.com/index.php?/topic/87076-the-1966-kalamazoo-reverb-12-amp-project/ Changing out those caps will make a world of difference. What value is it? Link to comment Share on other sites More sharing options...
hellion102792 Posted June 7, 2012 Author Share Posted June 7, 2012 Very cool! I have been reworking a Kalamazoo of the same era. http://forum.gibson.com/index.php?/topic/87076-the-1966-kalamazoo-reverb-12-amp-project/ Changing out those caps will make a world of difference. What value is it? Just checked that link, freakin' cool amp you got there. I guess these little guys are left overshadowed by Fenders and Marshalls but they are interesting little beasts in their own right. What value is the amp? Or the caps? As far as the amp goes I've seen a few on eBay ranging from around $200 all the way up to $800. As for the caps, I gotta open it up again and go through the schematic to figure out what's what. Can't wait to get it into the shop and up to spec, these amps are great for recording. Link to comment Share on other sites More sharing options...
Searcy Posted June 7, 2012 Share Posted June 7, 2012 I mean the value of the caps. If you can use a soldering iron it's not to tricky to replace it yourself for about $5. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 7, 2012 Author Share Posted June 7, 2012 This is true, I do have electronics and soldering experience so it's a possibility. I just figured he would be able to spot anything needing replacement that I would otherwise miss and make sure the job is done right. I'll look into his rates and try to weigh the better option. Link to comment Share on other sites More sharing options...
Searcy Posted June 7, 2012 Share Posted June 7, 2012 I'd install a three prong cord too. But it's you're not comfortable with it then better to let the tech check it out. Can't wait to hear it! Link to comment Share on other sites More sharing options...
hellion102792 Posted June 7, 2012 Author Share Posted June 7, 2012 Definitely a priority, I've had some shocking issues with my '78 Peavey Classic with a removed ground prong. Not looking to die in the name of procrastinating safety But thanks and neither can I! Link to comment Share on other sites More sharing options...
Californiaman Posted June 7, 2012 Share Posted June 7, 2012 That's a nice score. Hope you ring every decible of tonal goodness out of it. Nice score. Link to comment Share on other sites More sharing options...
Sunburst PB Posted June 7, 2012 Share Posted June 7, 2012 That amp is a real classic. You will love the sound when its fully restored. You are so lucky. Link to comment Share on other sites More sharing options...
badbluesplayer Posted June 9, 2012 Share Posted June 9, 2012 Nice score!! Keep us posted on your progress fixing it up. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 11, 2012 Author Share Posted June 11, 2012 Thanks guys! It's exciting, can't wait to get it up and running. I've been trying to get my confidence back with electronics work after not having done it in a while. I have a soldering gun I took from my old high school when they shut down the electronics program, but it's just too damn hot. My dad let me fix his Roland 303 and I almost melted the plastic around the spring, so I invested in a regular soldering iron/toolkit this weekend. Modded my old Multivox echo rack a couple days ago (vid demo coming soon) which kinda helped get me back and familiar with working with components and soldering. Gonna start scouring online and at local stores for the right components and work on this throughout the month. Yesterday I undid the stubborn bolts securing the chassis to the cabinet, removed it and got it all cleaned up. Used cut-up pencil pieces to brace and reinforce the broken wood holding the grill cloth on and Tite-Bonded them into place, gonna post a couple pics when I get out of work today. Link to comment Share on other sites More sharing options...
Searcy Posted June 11, 2012 Share Posted June 11, 2012 Very cool. I'm betting the new cap is all you'll need to get it running again. When you get the time take a picture of the marking on the cap and I'll help you find the one you need. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 11, 2012 Author Share Posted June 11, 2012 Very cool. I'm betting the new cap is all you'll need to get it running again. When you get the time take a picture of the marking on the cap and I'll help you find the one you need. Okay cool, thanks! Gibson did send me a schematic but it's kinda hard to read in some spots. Here's what I got so far without the schematic. First here's the repair to the wooden structure in the cab (appears to arch because of the picture's angle): Main filter cap is a multicap, with a 20uf 10uf 10uf arrangement inside. (cap states Red 20uf, Blu 10uf, Grn 10uf, Blk is common negative) It's been about 2 years since I last had an electronics class so there is one question I have about the schematic. I can see the negative leads of the caps will all be tied to the common neg black wire which is grounded to the chassis. Can I just buy the 3 separate electrolytic caps and wire them with the schematic? Or do I have to get a multicap? I'm assuming it doesn't matter, though Vibroworld.com sells one that matches what I need (but they're temporarily closed?). Here are some detail shots of the component side of the chassis: I'm going to swap the cord for a 3-prong grounded plug while I'm already inside this thing. I read that first I'm supposed to remove the "death cap" shown below. Fair enough, better safe than fried. Hope these are some help. Here's a link to a different copy of the schematic I found online: GA-5T 67 Skylark As said I might just build the trem circuit and work it into here seeing as it has the slots and room for it. From what I can gather I need: 1 9-pin socket for 12AX7A Resistors: 68K 510K 1.5M 500K (VR3) 4.7K 150K Caps: .02uf .02uf .033uh 10uf to pin 3 of power tube Link to comment Share on other sites More sharing options...
surfpup Posted June 12, 2012 Share Posted June 12, 2012 Very cool amp. My first great tube amp was a '66 Epiphone that I scored in a pawn shop. Recapped that myself (fortunately without electrocution) and it's been sounding amazing ever since. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 13, 2012 Author Share Posted June 13, 2012 Sounds cool, I was looking at some old Epi amps on eBay before I came into this one. I've heard a lot of good things about them. Link to comment Share on other sites More sharing options...
Searcy Posted June 14, 2012 Share Posted June 14, 2012 I would start by reworking the amp in stages. First I would get it working by replacing the big orange multistage cap three new caps. Your multistage is a 10-10-20. You can replace that with two 22uF caps and one 47uF. The grounds of the three caps would be soldered together to the black lead from the original multistage cap and then connect one of the 22uF caps to the green wire. Connect the other 22uF to the blue wire and finally connect the 47uF to the red wire. Once that is done and the amp is working I would move on to job #2. Replacing the cord and deleting the death cap from the circuit. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 14, 2012 Author Share Posted June 14, 2012 I would start by reworking the amp in stages. First I would get it working by replacing the big orange multistage cap three new caps. Your multistage is a 10-10-20. You can replace that with two 22uF caps and one 47uF. The grounds of the three caps would be soldered together to the black lead from the original multistage cap and then connect one of the 22uF caps to the green wire. Connect the other 22uF to the blue wire and finally connect the 47uF to the red wire. Once that is done and the amp is working I would move on to job #2. Replacing the cord and deleting the death cap from the circuit. Ahh okay, cool. Makes sense to break it down into stages. I'll look around locally or online and get a hold of those caps this week. Quick question, could I just chop the wires from the cap without discharging it? Like say I just bent them far enough away from each other, put on shoes and rubber gloves and cut the leads without my clippers touch the chassis, and then dropped the whole thing in a Ziploc bag where it couldn't be touched, would that be a dangerous rook move? Otherwise I can go pick up some alligator clips and do it proper. Link to comment Share on other sites More sharing options...
flem snopes Posted June 14, 2012 Share Posted June 14, 2012 Ahh okay, cool. Makes sense to break it down into stages. I'll look around locally or online and get a hold of those caps this week. Quick question, could I just chop the wires from the cap without discharging it? Like say I just bent them far enough away from each other, put on shoes and rubber gloves and cut the leads without my clippers touch the chassis, and then dropped the whole thing in a Ziploc bag where it couldn't be touched, would that be a dangerous rook move? Otherwise I can go pick up some alligator clips and do it proper. Discharge the Capacitors! Link to comment Share on other sites More sharing options...
Searcy Posted June 15, 2012 Share Posted June 15, 2012 I advice discharging the caps. Better safe than stupid. Here is a common method for big caps but I just used a jumper lead with a 500K resister soldered to the end of it to short the caps to ground. The caps you'll need look something like this. Buy these two 22uf caps http://www.ebay.com/itm/2PC-Axial-Electrolytic-Capacitor-22uf-450V-Tube-Amp-DIY-/260761351219?pt=LH_DefaultDomain_0&hash=item3cb6967433 and this one 47uf cap http://www.ebay.com/itm/1PC-Electrolytic-Capacitor-47uF-450V-Axial-f16x34mm-/280762713274?pt=LH_DefaultDomain_0&hash=item415ec304ba Those three parts and a little time on the iron and you'll know if your amp will be an easy save or a bigger project. The reason I discourage trying to go ahead with the tremolo addition while doing the recap is so we don't get confused if things don't go right. If you recap the amp and replace the cord and build and install a trem system all at once and then you turn it on and there's some strange noise or something.... where do you start checking? Better to work in stages. Link to comment Share on other sites More sharing options...
hellion102792 Posted June 15, 2012 Author Share Posted June 15, 2012 Heh alright, don't worry that was more of a hypothetical question than something I'd actually try. Thanks a lot for those links, just bought them but unfortunately the 22's won't get here until early July. Good things come to those who wait I guess. I was going to do the caps before installing the trem circuit, I just thought I'd build it on a breadboard first. It's been a while since I've done any actual circuit building so I'm planning on making it separate and wiring it to a small amplifier kit I previously built with an external power supply just to test it. That way even if the amp requires more advanced work I can still get in some practice with building circuits from scratch again. Thanks again though, this forum is a goldmine of info for those who seek it Link to comment Share on other sites More sharing options...
hellion102792 Posted June 29, 2012 Author Share Posted June 29, 2012 The caps did the trick! Damn this thing sounds great. Hard to see but here's my jumper with a 100k resistor tied in: Gone! Quick and easy, got it empty fairly quick. Unless my meter was screwing up it actually recharged a bit after I discharged it, that normal? Tied in and soldered, made sure nothing was shorting: And ready to go! Very rich sound, I'm gonna mic it and post some sound clips within the week. Next up is adding the 3-prong plug, the ground noise is the only noticeable issue now. Tubes might also be due for replacement as they are the 1967 originals. This is definitely proving to be a worthwhile project, these amps are gems! Link to comment Share on other sites More sharing options...
JAC Posted July 1, 2012 Share Posted July 1, 2012 Nice score! Link to comment Share on other sites More sharing options...
retrosurfer1959 Posted July 1, 2012 Share Posted July 1, 2012 post another picture of the front now that it's cleaned up and you did your high tech pencil stretch. great little amp brings back allot of memories. Link to comment Share on other sites More sharing options...
Searcy Posted July 1, 2012 Share Posted July 1, 2012 Nice work! You might want to secure those caps so that can't short out against the chassis. I used those little stick on wire tie things to do that. At the very least you should bend the leads up to they are farther away from the chassis. Can't wait to see the new cord. Link to comment Share on other sites More sharing options...
hellion102792 Posted July 2, 2012 Author Share Posted July 2, 2012 Retrosurfer, I'll add a front pic when I get home today. It looks nice and almost new now just with having the grill cover propped up rather than still sagging in the middle. Thanks Searcy! I have some zip ties lying around so I'll set them in correctly. I might even go back in when I do the plug, clip the leads a little shorter and resolder the joints, just to clean it up a bit and make it harder to accidentally make contact with the leads when the back is open. Heading out to buy the plug this week and then all that's left is a cosmetic cleanup; there's a nasty amount of dust ingrained into the ridges of the knobs, the tolex, pretty much everywhere on the outside. Checked out your blog the other day and read more into your Kalamazoo, good stuff. Especially because I was thinking the other night about possible installing a standby switch if I end up doing the tremolo circuit, glad you put that bit about why some amps just don't really need them. Link to comment Share on other sites More sharing options...
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