This video was infinitely helpful when servicing my 3-PRO from the 90’s. Originally was just going to change the input jack but then went down the rabbit hole of checking everything else, haha. Thanks!
The more I watch of yours and Lyle's channels, the longer the list of equipment not to buy grows! I'm not in a place just yet to set-up a commercial studio, but when I do it's looking like it's going to have to have a lot of hand built boutique gear in there. It doesn't seem to matter if it's guitar amps, mixing boards, mic preamps, outboard processors - it's majority junk. When even the expensive more boutique end manufacturers are also cutting corners it's bad news. There's no wonder the music industry is plagued by such bad sound.
The boutique stuff can be the worst of the bunch in my experience. Slap a big pricetag on it and pose as a big player. Get to know your local tech and they can chime in as to what's nice and what's not. EVERYTHING will need maintenance, and sometimes random component failures are a factor, and that shouldn't reflect on the manufacturer, as they have to use what's available.
@@BradsGuitarGarage I hear you on that! Luckily I know just enough about electronics and circuit design to know where I would be looking for the boutique gear. It would be guys like you or Lyle building me guitar amps for a start. As for the rest of the equipment there are some small builders who make great stuff for a price it's just knowing where to look I suppose and keeping your wits about you. That's why I watch and learn from guys like you and Lyle. I'm a musician first and foremost, but I've made it my business to learn about what makes a good piece of equipment. I cannot thank you enough for all you share!
Thanks Brad. My Stv 3 has the same issues. Lots of crackle when the tube gain. EQ board is as loose as Brittany Spears. And speakers are farting like a brewery draught horse. Help!!!
Great video Brad, love the walk thru, tips and tech info as you go..Quite flimsy some of the initial factory installation of components. Thanks for sharing your knowledge..Ed..uk..😀
At 42:10, you can stabilize the cracked plastic on that switch by bridging the crack with a staple or similar piece of bent wire heated with the soldering iron and pushed into the plastic. I have seen commercial products designed to do exactly; that they're often used by automotive repairers for stabilizing cracks in plastic trim for car dashboards, headlights, cowlings and so on.
Fullcompass have the genuine part in stock for anybody following along. www.fullcompass.com/prod/195997-ampeg-88-108-01-5-pos-switch-for-svt-3-pro-and-svt-4-pro
I had one of these. When I first got it there was hideous crossover distortion so I set about biasing it. The bias trim pot was stupidly twitchy so I replaced it with a multi-turn trimmer. Biasing was still a compromise because the power MOSFETs were so poorly matched. Also the Tube Gain control has nothing to do with gain, it actually sets B+ for the valve part of the circuit and hence the headroom. I no longer have the amp.
Yes, it is certainly a questionable setup. It put out about max 150w with the tube gain turned down. Normally "tube gain" is a form of preamp soft clipping distortion effect, but this implementation is pretty dumb.
@@BradsGuitarGarage It simulates the full tube poweramp if you turn in to the left, turned to the right it has more snap, like a mosfet poweramp. This is how I understand it. I use on 3'o clock usually. It really does feel like a full tube amp if tube gain is rolled off, slow and mellow :D
Thanks mate. Lyle wipes the floor with me as a tech though. I need to cut my fingernails to play finger style bass properly, but I'm also growing them to learn finger-picking. Dilemmas, dilemmas.
There's always a low buzzing in the background almost like a radio station just wants to come busting out, however, its not that. Just a weird distorted noise in the background when I'm playing or stop. almost like its a bad cable but it's not. I've tried multiple brand new cables. I had it fixed once because of a low distortion in the background while I play. It went along my playing like a I had a distortion track in the ground. It comes back every time the head hits a bump when being moved. Great head, just finicky as all hell.
Hopefully the module glued to the bottom of the circuit board wasn't installed with any type of glue that might become conductive or corrosive. Still, it makes it difficult to change or even merely reflow the joints to the jacks in front of it, and impossible to examine and resolder anything underneath that module. The header pins near that module also look to be poorly soldered. And wouldn't the bare-metal input jack create a potential ground loop to the front chassis? I assumed the original input jack was plastic and didn't ground to the front panel, just like the plastic jacks on the rear for the effects loop.....
The SVT3Pro wasn’t a bad design…but it was dreadful execution. The MOSFETs need to be matched and every unit that left the factory were neither matched or even biased correctly. I always offer to replace with matched output devices as well as replace the source resistors with 1% tolerance 6.5W. It makes a world of difference along with correct bias adjustment.
Have you checked out stock levels on IRFP240's and IRFP9240's recently though? I got some equivalents from Exicon for a Mesa Walkabout recently, but they are costly and so is postage from the UK.
I had a scour for the IRFP's which could be substituted for the Mesa's original BUZxx MOSFETs but nobody has sufficient stock of the complementary types. Lead times pushing into 2023 for the next batch, unfortunately which is why I was forced to go with the Exicon ECX10N20 & ECX10P20. Good times!
Any resemblance between this device and a proper SVT is purely coincidental and implied only by the presence of sand resistors. It does seem to sound good, however. I'm surprised you didn't have to replace any microphonic preamp tubes.
@@BradsGuitarGarage , gotta be careful, however, to not leave any wood fibers inside the socket contacts. As for the guitar string technique, chuck it into a miniature Dremel tool or similar die grinder, and clean each contact in three seconds flat! A phosphor bronze .033 to 038 string works particularly well but any wound string will do .
