Marshall JCM900 4100 Head With Low Output
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- čas přidán 26. 07. 2024
- Webpage: www.bradsguitargarage.com.au
Facebook: bradsguitargarage
Instagram: / bradsguitargarage
Equipment:
Soldering:
Pace MBT station w/SX100 & PS-90 handpieces
Hakko 474 w/815 handpiece
Hakko 936 w/907 handpiece
Hakko FX-888D w/FX-8801 handpiece
Quick 861DW hot air station
BOFA fume extraction unit
Loctite Multicore solder (C511 / 362)
Test Equipment:
Fluke 11, 175, 177 & 179 handheld DMM's
Tektronix 2236 analog oscilloscope
Rigol DS-1054z digital oscilloscope
BK Precision 4017A sweep / function generator
BWD 160a function generator
HP 6236B triple output DC power supply
Kyoritsu 3132A insulation / continuity tester
Video equipment:
Overhead cam: Panasonic HC-V785 w/Audio Technica AT9946CM mic
Handheld cam: Panasonic DC-G85 w/Olympus M.Zuiko Pro 12-40mm f/2.8
On location cam: Panasonic DC-GH5s w/Panasonic-Leica 9mm f/1.7 & 12-60mm f/2.8
Capture card(s): Magewell HDMI USB, ATEN UC3020-AT, ATEN UC3021
Headset Mic: Audio Technica BP892xcW-TH
Lapel Mic: Rode Go
Editing: Adobe Premiere Elements
Hand Tools:
Wiha, Felo, Stanley screwdrivers
CK & Engineer cutters / pliers
RS Pro wire strippers
Sidchrome & Gear Wrench spanners, sockets & shifters
Veritas planes & chisels
Materials / Consumables:
JJ's / TAD electron valves
Elixir / Ernie Ball / D'Addario / Rotosound strings
Electrolube & DeoxIT cleaners, lubricants & chemicals. - Věda a technologie
Thanks for the tips on this one. I dig this amp, not my favorite but it’s a fun one to crank up through a 4x12. As seems to be the case with a lot of amps, it isn’t hard to make it sound pretty good. Sure it isn’t a 2203 but it doesn’t deserve a quarter of the hate that the internet doles out to it.
Kinda nice to see one of these Marshalls come in that hasn't been abused and modded to death. A "legitimate" service with actual issues that were not the owners fault. I had heard of tin whiskers before, but I've never seen them. Crazy that you spotted those tiny things.
I think it sounds excellent! Thanks
Great work as always Brad. Thank God no Vaseline residue this time!
Very interesting phenomenon. Thanks for pointing this out. I get the feeling there will be a heap of people on internet forums checking for 'tin whiskers' in the amps in the not too distant future.
We had a whisker problem while moving one of our datacenters back in the day, what a pain in the ass.
Another excellent vid! Love the newish format and grats on 5k subs!
wow i'm seeing my first 900 in for a service in a few days, thanks for the heads up!
Congrats on 5K subs!! 🍻
Great info on the Tin Whiskers. Thanks again
I just bought the same head and the only way to get a really nice crunch out of it, is by using my Behringer V-Amp II FX Processor plugged into channel A and the dials tweaked.
UPDATE: Getting a Revv G3 Dist pedal soon...should be killer in the clean channel !!!
Brad, I bet that was fun. Playing a 100-watt marshall through a good cab is just a blast. Nice lesson on the whiskers.
Man, the video really doesn't show how loud it was. Painfully loud!
I do all of these tests outside of office hours for that reason!
Tin effing whiskers! Who knew! Great video, Brad.
Cool! I see you hit the 5K subscriber mark 🙂
Thank you Brad, for teaching me something new today. I had never hear of "Tin Whiskers" before. It's a very pertinent subject for me to know about, with the RC Warship radios that I mod.
The deterioration process that tin undergoes is sometimes referred to as "tin pest" and was noticed hundreds of years ago in the solder joints of church-organ pipes in cold northern Europe. Cold temperatures seem to exacerbate the deterioration and so I can hazard a guess that it would be a particular problem in electronics used in outer space (and what better place to create a plasma arc than in a vacuum!).
Mixing lead with tin tends to stabilize the tin. Antarctic expeditions have apparently been derailed because of poor choices of solder. People who enjoy reading about historical adventures may be aware that one such expedition suffered food poisoning from lead being used to seal their canned food rations; but another expedition failed because a cache of fuel canisters all mysteriously leaked and everybody froze to death. I'll hazard a guess that the fuel cans may have been soldered with pure tin and the seals failed in the cold.
The tone wheel mechanisms of Hammond organs also are known for growing tin whiskers, which can be cleared with a spritz from a 9 V battery.
@@goodun2974 I've heard of "Zink Pest" ... the bane of vintage model railroad locomotives. Now I know about "Tin Pest" 🙂
sounds great
Aloha Brad! Looking at all the components. Makes me what a simple amp. At least the tube sockets are mounted to the chassis.
I learnt so much from this. I've got one of these amp's (sounds fantastic with a JMP 1 pre-amp' into the effects return) and I'm in the process of replacing the main filter cap's and tubes. I'll now upgrade the bias coupling capacitor while I'm at it. I've also got a Marshall 30th anniversary that's been in pieces for years with a popped bias coupling capacitor and was wondering how to improve this part of the circuit. Thanks very much for all the info'! (South Aus')
I didnt know that happened with the X caps, but it makes sense they should only be used upstream closer to the mains input. Also dash 213 o-rings work well on these retainers, and only add about 3mm to the tube height, great job Brad!
Nice video, subscribed
Me whiskers!! Me bloody tin whiskers!!!
One good thing about plastic pot cases I guess.
Learned something new. We need whisker free metallurgists to help us here. Seems they may even grow via some weird electrolysis to me like AC or DC where it ain't supposed to be maybe? Kudos on your background and audio improvements not to mention camera and zoom upgrades. Lookin' good there down under. I use high temp silicone washers on top with my tube spring retainers. Surely fixed the "low" output. Get you an SPL meter....and some good ear protection lol.
"If you can fake a moon landing"... 🤣
Brad will have the flat earthers subbed next!
The pipes of church organs in cold northern Europe were exhibiting failure symptoms hundreds of years ago because the pipes were soldered with tin. The tone wheels of Hammond Organs also grow tin whiskers and I've seen video of people clearing them out by arc flashing them with a 9 V battery! The deterioration of tin seems to be exacerbated by cold temperatures and therefore I can see why NASA in particular would experience failures of solder connections in cold outer space. As for short circuits that form a plasma arc, I can't think of a better place to do that then an outer space vacuum!
The US government is reported to keep a stash of tin at Fort Knox and periodically they melt the ingots down and recast them to head off the deterioration process.
The time-honored way to make tin more stable is to alloy it with lead which is why we like traditional tin-lead solder and not the new crappy lead-free stuff. People who enjoy reading about historical exploration may be aware that lead solder poisoned an Antarctic expedition when it was used to seal their food cans, but there was another case where an expedition was derailed and the explorers all froze to death because their stash of fuel cans all mysteriously leaked. I will hazard a guess that the cans were sealed with tin and not lead or a tin-lead alloy.
if you need to get into tight places, and want to be thorough, you can get one of those between the teeth toothbrushes from the pharmacy. they're good for cleaning inside of sockets and they bend too.
Sounds like a Marshall. 😎
TIN WHISKERS... Sounds like a great band name.....
I ran into this a few years ago on an Orange Bass Terror, tube preamp and solid state output. The complaint was the treble control had no effect. I thought "bollocks". But it was true. I got new pots from Digikey and replaced them and all was well. The tone stack was exactly the same as a Fender tone stack right down to the same component values. Leo was a genius.
Try giving them a blast with compressed air, next time mate!
@@BradsGuitarGarage I would do that today but at the time tin whiskers were not the thing they are today.
Because lead free is the place (not) to be. FYI: 5201 chips can be bought from Ali Express for $1.45 each. They are no name Chinese made linear op amp chips of dubious quality. Tin whiskers are really neat in microgravity. We had that NASA article on a poster at Micro Chimp. (Micro Chip) They would encapsulate (pot) stuff that was going into orbit.
When you could if you have time would you explain why the 900 does not sound as good as the 800
Capricorn One
A movie about making a movie, conspiracy theories alive with flared leisure suits,not a bad movie either
known problem on some old germanium transistors , 0C170 for instance
I watched a video of a guy clearing the tin whiskers from inside the metal encapsulated transistors by use of a flashlight battery or DC power supply.
@@goodun2974 yeh i've seen it too!👍🏻
This is off topic a little bit but….High purity Silver will grow long whiskers when it’s cooled too fast from its molten form. It happens in seconds and is really cool to watch. But they aren’t microscopic like with tin whiskers, they are much thicker.
A drop of mercury in a silver nitrate solution will also generate long needle like silver crystals, andvyou may end up with something that resembles the Sagrada Familia cathedral in Barcelona.
I can't understand why you don't have a half million subs at least. Bizarre 🤔
The grid stopper is to stop oscillation thus every tube need the stopper. Hi fi is not the reason for this bad practice. Lead is what stop tin whiskering best.
Hey Brad, how did Ozzies get on with the Rugby against Wales cobber?
No idea, mate. LOL!
When you hear it worked fine last time I used it. Beware.
So the only amp without WD40 and grease, and slime everywhere, is the only amp to have tin whiskers problem. I sense a pattern haha
My 900 just lost its loudness
sounds like it is at 1 when cranked to 10 on both channels, any idea what it could be.
Taking it in for service soon
Bad PI valve, bad plate load resistors, bad speaker jack, bad OT, broken pot, tin whiskers in pot, cracked solder joints, bad FX loop jack, dirty FX loop jack, failed choke, failed dropping resistor, you name it, mate. Could be so many things. A decent tech will narrow it down quickly.
Someone just gave me a pt and ot out of a 1992 100-watt jcm900. I think I'll be building a 1959 type thing with them. No op amps. No sir😊
8 min 38 seconds : 600v is not enough you need a x class capacitors in this position (kemet 440vac caps rated are what you need). You are seeing ac voltage on this capacitor.
Later in the video, Brad shows that he installed a 1.25kv coupling cap instead of a 630v cap.
@scottwilcox6313 and it was only 2.5 minutes later lol. I see this all the time on repair oriented content.