cGil Posted November 18, 2008 Share Posted November 18, 2008 Just got my first VVR-equipped amp fired up and I'm stoked! Way better at bedroom volumes than any speaker attenuator I've tried. Here's the porn. No, that's not a VJr with a 6U8 and 6AQ5 in it. It's a Crate VC508 that needed rescue after a stock v2 VJr blew it out of my house rack. :D Gil... Link to comment Share on other sites More sharing options...
nighthawk Posted November 19, 2008 Share Posted November 19, 2008 Gil. are you using a heat sink under the mosfet? Link to comment Share on other sites More sharing options...
cGil Posted November 19, 2008 Author Share Posted November 19, 2008 Nope. No heat sink. The Crate's PT only produces 300vDC at B+, and I haven't noticed any heat boiling off the mosfet or the zener diode or power resistors! Besides, this amp's got a wire screen with the handle on it for the top, so I don't expect any heat problems. Ever. And it looks cool being able to see the point to point job inside anyway. The screen "top" used to be the original speaker grill. But I hated the speaker and sawed the cab in half! :D The cab is now rolled over on it's former face so that the amp controls face the front. Instant head cab with hanger chassis! The original chassis cover on the former backside was just cheep, unshielded clapboard, so I put that on the bottom to cover the half moon of the former speaker cutout. I'll post pics of that once it's finished up and all mounted nice and, uh, pretty ugly. Gil... Link to comment Share on other sites More sharing options...
nighthawk Posted November 19, 2008 Share Posted November 19, 2008 Ugly and cool at the same time! Looks like you had fun making something useful out of something that wasn't. Way to go=d> Link to comment Share on other sites More sharing options...
layboomo Posted November 19, 2008 Share Posted November 19, 2008 "It's a Crate VC508 that needed rescue after a stock v2 VJr blew it out of my house rack." Correction Gil....It "Was" a Crate VC508........it ain't now! Looks really cool in a down and dirty minimalist kinda way.......I mean that as a compliment.:D Link to comment Share on other sites More sharing options...
cGil Posted November 19, 2008 Author Share Posted November 19, 2008 Thanks! Needs more tweaking, though. By the time I'm done, it'll look a lot different. It needs more gain, so to get at those signal attenuating resistors, I've had to rip out a few of the Orange Drops that were in the way. Figured I should replace 'em with some Sozo's to make it a little more interesting while I was at it. And I gotta lift the heater's center tap from ground with a 100R resistor to kill some hum. The fun never stops! :) Gil... Link to comment Share on other sites More sharing options...
Eracer_Team Posted November 19, 2008 Share Posted November 19, 2008 I think you're going to regret not having a heat sink on that mosfet. Just bolt it to the chassis with the isolator that came with it and an isolation screw/washer. Link to comment Share on other sites More sharing options...
cGil Posted November 19, 2008 Author Share Posted November 19, 2008 I was considering mounting the mosfet to the chassis, but couldn't find a nut and bolt tiny enough to fit through the hole at 11pm. Hardware and auto parts stores should be open all night, IMHO! :) I will have to burn in the Sozo's for 100 hours, so that'll give it plenty of time idling on the bench to get an idea how hot the NTE2377 mosfet and NTE137A zener diode are gonna get under extreme conditions. As it is now, the leads on the mosfet were just barely long enough to connect it directly to the pot; but if necessary, I may be able to avoid a major rebuild with just a Rat Shack heatsink inside the chassis. Either way, the heat can easily vent through this amp's extra cheesy screen top. Gil... Link to comment Share on other sites More sharing options...
cGil Posted November 19, 2008 Author Share Posted November 19, 2008 Meanwhile, back at the Crate, I finally realized I had gotten off course. (Thank's Doug!) Just because I can think of an easier way, or a quicker way, or a manyana way, doesn't mean I should do things that way. After all, good tone is the end game and the cherry on top if you succeed, but it's really the journey that counts! So I dove back in and tackled the VVR heat sink issue just to see if I could. I dropped by RatShack and picked up some tiny little #2 screws and nuts that would fit the hole in the mosfet, but they didn't have any heat sinks! Arrrgh! So, I rummaged around in my junk boxes and scavenged a big old heatsink off of a computer CPU, and then proceeded hack it into quarters. Snapped the center cooling fin out and drilled a hole. Because the VVR was mounted, I had to figure out a way to keep a nut secured underneath it long enough to get a screw started. SuperGlue-gel helped with that. And now it's in there! I'll never know for sure if I actually needed to add the heat sink on this particular VVR, but more importantly, I now know that I can whip one up anytime I need it. I may still have to go back in and add some heat sink grease. Rat Shack didn't have any of that, either. Anyway, here's the obligatory porn. And the chassis is now mounted in the cab. Should've mounted it right after I got the sockets and iron mounted, but noooo, I gotta use my jello buckets. Easy ways. ~ Meh! ~ Gil... Link to comment Share on other sites More sharing options...
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