212Mavguy Posted July 29, 2015 Share Posted July 29, 2015 So I have had this amazing sounding amp head for a few years that I lent out to a friend who loves to play bass through it for a series of recordings...right after I had it out of the cab and had it biased and balanced to a tenth of a meter's millivolt. During this lengthy, 30 minute minimum time needed in particular for the Bendix 6384 pair's warmup and current drift to operating equilibrium, I restrung a guitar or two while the chassis was out of the headshell...sitting on the coffee table in the living room, I often restring guitars nearby and put the cutoff strings as well as the old ones on the same table nearby. I called him up later and asked him how it sounded and he said it was very weak, something was wrong. When I picked it up I noticed that the impedance selector was for 8 ohms...going into a 4 ohm cab. So I figured that something had let go in the power section from the impedance mismatch plus the added current demand in the preamp and power section of playing bass through the amp and that maybe there was other stuff he wasn't telling. This is one very well built, one of a kind Hiwatt DR504 style amp from a guy that used to maintain nuclear ICBM's in the USAF. The amp was built with the same tech and stoutness used in the nukes. I kept my mouth shut and took the amp home, I just couldn't believe it. I was also scared to trouble shoot it. This amp is from the brand "Toad Suck Tones" This ain't no horny toad. It's a highly refined mutant. The preamp dutifully follows the 4-holer British style inputs, Dave Reeves' and Harry Joyce's Mullard circuit heritage within the preamp, but the power supply is much more robust than even a Hiwatt for a 50 watt amp. It's a requirement for running the Bendix 6384 tube, built at a cost of 350 bucks of taxpayer money per pop to stick in globally extinct-ing nukes aimed at the Kruschev klan. The tubes operate the servos that guide the missile's trajectory toward our global doomsday. So the guy to who formerly teched on our world's most deadly weapons grafted a cold war military style nuclear missile build quality power amp onto one of the most beautiful clean to more than medium gain guitar preamp topologies ever conceived. When this amp was healthy it was tight, fast at attack and the Partridge clones had the tones of a Steinway Piano. Now it was barely audible. All the tone controls worked. I took the chassis out and stared at the guts and sniffed for the stink and colors of burned parts. All looked perfect and no detectable smells. And now the builder lives a long way away on the East Coast. That's around a c-note-fitty to ship it both ways plus cost of work. Waaaaaah. There was a schematic, but I was intimidated. On the back of the amp's faceplate is written in all caps..."THIS AMP WAS BUILT TO KICK ASS AND TAKE NAMES BUT BE WARNED IT CONTAINS LETHAL VOLTAGES THAT WILL RUIN YOUR DAY IF YOU CARELESSLY POKE AROUND IN IT" Double spaced below: "IN MEMORY OF DAVE REEVES AND HARRY JOYCE, BUILDERS OF SOME OF THE FINEST TONE MACHINES EVER CONCEIVED" So it sat for a year and a half. A week and a half ago my new multimeter arrived from eBay. I was ready to dive into the guts of the toad. I took the chassis out and flipped it guts up, again, nothing visual. But some of the parts in the area I suspected were under the power supply and power section turret board. That meant unbolting it from the standoffs and not breaking any of the many wires or resistor leads while working under it. This build was just perfect looking with great parts and great lead dress. I measured the bias, exactly where it was before. Both fuses still not blown. Then I got out the new Klein and started probing the tube sockets in the preamp. I found 16 volts on all the preamp tubes' plates, there should have been 310-330-ish. That would account for the low volume. So I went to the schematic. I'm deducing that a power supply dropping resistor had let go. The schematic took a good half hour to decipher to what was sitting in front of me, the writing was tiny and needed the reading glasses, I don't pretend to design amps. To add to the difficulty, there was a double section can cap sitting in the amp's power section at the problem area completely unaccounted for in the schematic...I stared at the top of the amp with glazed, red eyes, and by a glint of light and flicker of eye focus, my pre-geezer vision saw what looked like a hair thin piece of wire. HMMMM...damn, there it was, lodged under the end of two cap cans from the top down into the guts. and one end was charred black and brittle. It was almost impossible to see from its hair-thinness and matching color to the stainless steel chassis. A piece of .010 string trimmed from the headstock during a string change had unknowingly dropped in, lodged in place, and shorted out a power supply dropping resistor through the wire directly to the chassis, there was some charring in the side of the chassis cutout for the cap can. I felt real guilt at what I had thought about my friend. Of course the location of the suspected fault was hidden under the power supply and output section's turret board, it was big, had a lot of wires leading from it, and it had to come up to work on what might be wrong underneath, a major PITA to get to. I could carefully pry it up enough to look under it. With the aid of a bright LED headlamp, EUREKA! There it was, a well fried crispy critter. Got the clamp and can cap out, a bit of a struggle, the resistor was soldered between the two sides and had to clean the soot off the sides with a dampened green kitchen scrubby to read the codes, even then had to consult with the schematic, it was so fried. Had a hard time telling whether a purplish band was a fourth code band or not. It turned out to be cracks from heat. Made sure to draw a picture of the top of the can cap, labeled the color and number of wires going to each side, and bundle those groups together for when I came back to reassemble, was tough to get them off, not much room to work, the military wire penetration and wrap on the terminals was hard to get off without damaging the wires. The parts ordered arrived today, a new resistor and a new 100/100/500v can cap, not needed because when I thought the old one was bad I wasn't using the new multimeter properly. So now I'm going into the guts of the most mighty sounding Toad I know of, when I button it up I hope to hear it's melodious roar shaking the floors, windows, and walls and getting my Sun and Green Cheeked Conures to dance and shriek their little birdy fill licks. The Green Cheek AKA Mr. Happy keeps time and bobs his head like an orchestra conductor, while his head feathers flare out a bit in back so he looks like he has a flat top hat on. Birds and Toads and Guitars, oh my! Boutique amps for boutique guitars! Boutique guitars for boutique amps! Link to comment Share on other sites More sharing options...
schundog Posted July 30, 2015 Share Posted July 30, 2015 Wow! Thank God for guys like you. I'd have done like I do with my car if something goes wrong; open the hood, look concerned, knob knowingly, and call a professional..... Good call on leaving the birds in their cage this time!! Link to comment Share on other sites More sharing options...
DetroitBlues Posted July 30, 2015 Share Posted July 30, 2015 Wow, good deal. Well done too I might add.... Link to comment Share on other sites More sharing options...
212Mavguy Posted July 30, 2015 Author Share Posted July 30, 2015 Well, it took an hour just to reattach the two screws that held the can cap bracket to the chassis. There's a reason why I'm not a pro amp tech. But man, when I finished bolting the turret board back down and stuck all the tubes back in... put it guts down on the table top, hooked up the Altec 417 stuffed Seismic "Luke" 2/12cab, stuck the TC Nova system into the front end, well, screw the multimeter, time to see smoke or not. Fired that toad up, stuck a Gibby The Paul in front, and got my chest smacked and my face ripped from a major dose of Hiwatt roar. I forgot how loud Hiwatts are watt for watt, well, let's just say that as far as clean headroom there is way more than enough..even for playing bass through it. Power and elegance at the same time in the sounds. DG would like, I'm sure. It has been left on two hours straight, and it just keeps sounding better and better, "Wow" doesn't cut it for describing how good it sounds, even at small room volumes, no prob. Link to comment Share on other sites More sharing options...
kidsmoke Posted July 30, 2015 Share Posted July 30, 2015 the most riveting amp diagnosis thread ever. Thanks for the entertaining read. You own a camera to go with all that hifalutin' gear? geesh.... Link to comment Share on other sites More sharing options...
Hfan Posted July 30, 2015 Share Posted July 30, 2015 Congrats..I love that feeling..the a ha! moment when you fix a piece of equipment..especially something you love like a guitar amp. It is sweet. I checked out the web site..not much there..interesting stuff though. Pricey I assume? Where on the East coast is he? http://www.toadsucktones.com/ Link to comment Share on other sites More sharing options...
212Mavguy Posted July 31, 2015 Author Share Posted July 31, 2015 Not as pricey as you might think. I won't box him into a corner by saying any numbers, but I think that the amp in this article could be had for less than the equivalent model of vintage or newer production Hiwatt. Keep in mind that the Hiwatt and Harry Joyce amps are the Rolls Royces and Bentleys of Briish ampdom. Expensive nice parts and one off hand assembly won't go for cheap. Much stouter builds than Marshalls, except the earliest turret board ones. Still, you might be surprised at what he quotes, in a good way. He would be a great member of HOC. Somebody needs to introduce him to his first Heritage. He's a hobbyist, not a businessman. He builds amps on the side. He does up some nice stuff, one of his fave builds is getting a POS Solid State Marshall amp from where ever, rips the guts out and builds up a hybrid Fender/Marshall preamp, instead of a normal and bright channel like old school British, he does up one volume knob to a Fender preamp circuit, the other volume knob goes to a Marshall circuit. This allows the blending of the two voices to taste, and he often does a 30w cathode bias power section that uses typically the vintage mil stock Philips 6l6wgb or Tung Sol 5881, for some sweet, sustaining, warm tones. I have another bulletproof amp of his that I'm not using much, it's an 18 watt killer, just volume, TMB, and Master, it uses the Bendix 6094, a 15 watt tube that sorta looks like an el84 on steroids. It does the Jimi "Red House" tones all day, hugely fat bottom unlike el84 tubed amps as a rule. Lots of clean headroom for what it is, and nice sustain. The toroidal PT has enough juice to run a 100w Marshall. Ed builds really beefy power supplies in his amps that run the Bendix tubes. They apparently don't like saggy circuits. If it had a serial fx loop I'd use it a lot more. Link to comment Share on other sites More sharing options...
mtpatty Posted July 31, 2015 Share Posted July 31, 2015 wow- this is the type thread that I love reading and wish I could offer some comments on, but alas, I cannot. This is WAAAAYYY beyond my capacity. Great read though! Link to comment Share on other sites More sharing options...
212Mavguy Posted July 31, 2015 Author Share Posted July 31, 2015 ...just like I was 10 years ago. Pretty much self taught, I'm not Einstein, just stubbornly curious. Link to comment Share on other sites More sharing options...
Gitfiddler Posted July 31, 2015 Share Posted July 31, 2015 ...just like I was 10 years ago. Pretty much self taught, I'm not Einstein, just stubbornly curious. I think you're being modest. I have a tough time keeping up with your technical wizardry. Fun reading however. Link to comment Share on other sites More sharing options...
Hfan Posted August 1, 2015 Share Posted August 1, 2015 I'm diving into my Blues Jr. again tomorrow. After doing most of Bill Ms mods to it (one at a time pretty much) it's a good little amp. The tube board is trouble some I've reflowed the tube socket connections once but they are acting up again. Hofffman amps has a mod kit for Like 30$ That replaces the tube board with a new Board, sockets and straight wire for the heater connections. I'm also ripping out the ribbon cables and installing straight wire. I already did that for the pre amp tubes some time ago after the ribbon connections failed due to me having the chassis out too many times. Should be fun knock wood of course. I am on a roll just replaced the tailgate Window motor on my Sequoia with no disasters to speak of ha ha Off topic. I Hate typing on my little I phone with my fat fingers Link to comment Share on other sites More sharing options...
bolero Posted August 1, 2015 Share Posted August 1, 2015 wow that is a wild story!! I will be more careful about where I change/cut strings from now on glad it is working again...any chance of some amp pics, of those toads? ps I thought this thread was going to be about Ginger Baker Link to comment Share on other sites More sharing options...
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