Mesa Fathom (M6 Carbine):Blown Lateral MOSFETs in the output stage. All of the gate resistors and source ballast resistors were blown, either turned into ash or just open circuit internally. I ordered new matched MOSFETs from the UK.These things were known for overheating until Mesa started providing a free upgrade with a new vented cover, larger heatsink, and extra cooling fan. This one had those mods done in 2011, based on what is written inside.Found a schematic for a Mesa WalkAbout. Looks like it basically has the same output stage. Same dude's initials are on the PCB.I put new 2.2 kohm gate resistors on the P Channel MOSFETs and 3.3 kohm on the N s, to compensate for the lower gate capacitance while maintaining the same cutoff frequency of ~100 kHz. All new 0.2 ohm source ballast resistors. 8 new Exicon MOSFETs at $6 each (I bought 20 to get a price break, will probably sell the remaining ones on ebay).Fired it up, no smoke, so I biased the MOSFETs to 130 mA and looked for oscillation at idle. Didn t see anything amiss. Applied signal from the function generator and cranked it up to just before clipping into the 4 ohm dummy load. Ran it until the heat sink got hot enough that I couldn t touch it. No problems. Played it through the speaker stack for a bit, then cleaned the pots. Sounds good, but maybe a bit too modern for my taste. It's not going to replace my GK 800RB.

Nate Dort wrote:Mesa Fathom (M6 Carbine):Blown Lateral MOSFETs in the output stage. All of the gate resistors and source ballast resistors were blown, either turned into ash or just open circuit internally. I ordered new matched MOSFETs from the UK.Found a schematic for a Mesa WalkAbout. Looks like it basically has the same output stage. Same dude's initials are on the PCB.Is it Dan Van Riezen? DVR? I like that guy's work; more so than Randall Smith. Nate Dort wrote:Sounds good, but maybe a bit too modern for my taste. It's not going to replace my GK 800RB.We have an M9 Carbine at my work that I modeled. I absolutely love it. If I was a bassist in a noiserock band again, I'd probably try and mooch the M9 and matching 6-10 from work. In fact, I use the M9 model in Helix for most of my bass recording now.

benadrian wrote:Nate Dort wrote:Mesa Fathom (M6 Carbine):Blown Lateral MOSFETs in the output stage. All of the gate resistors and source ballast resistors were blown, either turned into ash or just open circuit internally. I ordered new matched MOSFETs from the UK.Found a schematic for a Mesa WalkAbout. Looks like it basically has the same output stage. Same dude's initials are on the PCB.Is it Dan Van Riezen? DVR? I like that guy's work; more so than Randall Smith. Nate Dort wrote:Sounds good, but maybe a bit too modern for my taste. It's not going to replace my GK 800RB.We have an M9 Carbine at my work that I modeled. I absolutely love it. If I was a bassist in a noiserock band again, I'd probably try and mooch the M9 and matching 6-10 from work. In fact, I use the M9 model in Helix for most of my bass recording now.Yeah, DVR.It definitely has a sound to it, with a bump in the upper mids. There's no way to get a flat response on it though, the low-mids are always scooped. Confirmed this on the AudioPrecision.Maybe I should do some more A/B/C/D comparisons. It's certainly lighter than my SVT-II or YBA-1A. But then again, everything is.

I built up a parts jazz bass in August that I have been having a hard time getting along with. Initially I thought it was setup fine and sounded okay, took it to the practice space and it has been pretty meh. Overall kinda dead and muted sounding and the D string particularly just sounded *extra* muted. Finally brought it home yesterday and was messing with it, and noticed some buzzing that I wasnt hearing before on both the D and G strings, and I couldnt track it down or find out what was buzzing. Saddles were sitting right, springs werent buzzing, nothing.I had it strung up with La Bella Deep Talkin Stainless Flats, 45-105. This was my first time trying them but people here seem to dig the brand. I wasnt really impressed with them overall as, like i said, they were kinda dead sounding. I have some of the Steve Harris signature Rotosounds on another bass and I really liked them, though theyre a bit heavy. Did my Rotosound research, found out they were "monel" (whatever alloy that is), and found some other Rotosound flats made of the same material but the gauges I wanted.I went ahead and strung it up with the new strings before making any bridge adjustments or doing further investigation and holy cow...no more buzzing and no dead sound to the strings. I dont really comprehend how it is possible that one make of strings buzzes while the other doesnt, but its true.In conclusion, i love these:and these guys can fuck off:

I had the opposite happen, I had some Rotosound flats on a Hagstrom H II B N and while they sounded ok, they were on the meh/dead side. The E string would not intonate, period, no matter where the saddle was positioned. Maybe it wasn't jiving with the shorter scale, but I put on some other roundwound strings and poof, problem gone.Recently I put together a Tele bass and used some Fender 9050 flatwounds, these sound better than all the others I've tried. At least on that bass.

Got the Bassman fixed. New socket, new output tubes. Brought it up slow on the variac with the current meter on it, let it idle for a bit at 60 VAC before turning it up to 120 and setting the bias.JFC this thing sounds phenomenal. I was originally planning on flipping it, but now I want to keep it. I can see why some people consider this the best thing ever.

Fender Bassman '59 LTD:As mentioned in the other thread, grabbed a broken Fender Bassman '59 LTD that somebody had dropped a 5F6A circuit into. The eyelet board looks homemade, but the work was done well overall. Decent components were used (Sozo caps, one Mullard preamp tube). Took it apart yesterday and the fault appears to be arcing between pin 2 and 3 of one of the output tubes. You can see the smoke stain on the chassis and the charred spot on the socket. Maybe flyback from running it without a load? That tube is toast, and so is the socket. I've got a replacement socket to drop in after I do a tiny bit of drilling with the step-bit.

GK 700RB-II:Bought it assuming it had a broken volume pot. The listing said it only output "one volume", whatever that means. Got it and it seemed to work fine except for scratchy pots all over the place. Cleaned/lubed them all, reflowed all their joints just to be sure, tightened some loose screws, tested it for a few minutes, then listed it on reverb. Sold an hour later. Easy $230 profit. Took me longer to get photos and post the listing than it did to œfix it. I owned it for a total of 3 hours.

Peavey miniMEGA:Grabbed this on Reverb for $75 shipped, sold as œdoesn t power on. Class D, 1000W, weighs about 9 lbs. Apparently this is is a common issue on these. Couldn t find schematics for it. Emailed Peavey and they hooked me up with the quickness. I also asked them if they had any field service mod documents, and they sent two over to me, including one that describes the exact issue I m seeing. One PMIC (L6599 half-bridge LLC resononant controller) burned up due to an insufficient soft-start capacitance value, according to one of these docs. Cost me less than $5 in parts to bring this thing back to life.

GK 400RB:I had a guy contact me through Reverb looking to get his 400RB fixed. Apparently a shop had œfixed it, but it never worked and would blow fuses constantly and the shop shut down before he was able to get it back over there to have them do it over. This was like 10 years ago.I got it yesterday and the shop had replaced all of the driver and output transistors with NPNs. No PNPs to be found. I had the correct types on-hand, so I dropped those in there. Also did the following:Rebiased the output transistors, per original specs.Reworked the +/- 15 V power supply with new zener diodes and replaced a bad MPSA56 transistor. The -15 V rail was reading 200 mV when I got it.Replaced the power cord. The original was missing the ground pin.Cleaned and lubricated all the potentiometers.Drilled out and retapped the stripped screws on the bottom panel and replaced them with new ones.New rubber feet on the bottom and side.There s something immensely satisfying about turning around a repair in a few hours without having to order parts.