This amp had not been used for many years. As a resuilt the pots were seized solid. Full revalve plus an annoying fault which took me WAY to long to fix!
A salutary lesson in where 'not' to store your temporarily unused amp. The four enemies and saboteurs of electronics: Dust, Damp, Vibration & Heat. 10 out of 10 for showing the reality of the wide range of problems that can occasionally flummox even the best techs.
Great video Stuart love how in-depth your videos are I hope you get a Laney gh50 or gh100 in I have both I’ve never had a problem with them other than re tubeing them love your show.
Stuart, you are correct. Leaving in the wild goose chases makes great content. Following your thought processes are what makes your videos so informative.
I have the same 2205/2210 model from 1985. Great head. Michael Schenker’s Marshall of choice. Definitely a different sound than the 2203/2204 single channel JCM800. Yep, that is the way Marshall mounted that reverb pan. A real pain to get at. I’ve worked on a half dozen besides mine and they are all the same on the pan.
@@stuartukguitarampguy5830 Hey Stuart, I noticed in one video you were experimenting with alcohol as a pot cleaner. How did that work out, are you still doing it? I would think a touch of sewing machine oil in the mix could be good in an aeresol spray bottle. Sure would save in Deoxit $$ :)
@@davidsimpson3380 Hi David. Okay here's the scoop, I've done a LOT more research into cleaners since I made this vid. Bottom line is there are two mechanisms for cleaning. Firstly 'flushing' - almost any maintenance spray (and alcohol) will do this - wash away dirt, dust etc. However, there is also oxidisation of the metal wiper. No amount of flushing will help this. DeOxit D5 (and their other sprays) are the only products I know which flush AND deoxidise the wiper. I was finding only 50% fix with alcohol before I realised I was only fixing the pots which needed flushing only. Anything with an oxidised wiper was not being fixed. So I have converted to using D5 for all my pots.
@@stuartukguitarampguy5830 Thank-you for the update Stuart. It seems DeOxit is still king of the hill but it's just a matter of time before the code is cracked and alternatives could be had as cheap as alcohol. I'll keep my eyes peeled :)!
My heart was in my mouth when you were trying to find the fault on that tube, with your screwdriver. I realise you may have edited the vid, but surely there is a fair bit of high voltage in there when you poke around. I wish you were nearer, to be able to have a look at my JCM900 2500, seems quite a bit simpler (less valves, less caps ), but still probably needs a service. Good to see an old, great amp be resurrected.
I bought a JCM800 2210 and someone removed the reverb from it, I wanted to have it put back in, but I thought I could do it myself. Wrong. Great Video 📹 👍 👏 ❤️✌️
Great Job sir thanks for the great work you do and the reality of what techs face with various issues including the tech himself… it’s easy to second guess something and not recheck your work it will lead you down a rabbit hole lolol been there done that and no doubt will do it again 😂
if i had a choice of any amp guy in the online world to fix my babys id want stuart to do it..his approach is classic he does not presume which the best do..and his got so much knowledge. your a treasure mate but your not in my country which i think you would like more then cold england ha ha
@@stuartukguitarampguy5830 actually speaking of heat and cold , whats your take on germanium components. is there a way to stop heat affecting them. ive hand made fuzz this wizard made for me but on the germanium chip his put a little piece of sticky velcro which i found weird to say the least . anyways interesting. i meant it Stuart you and Brad the guitaroligist are great people to learn from.im a player but ive done one build ...love your work cheers
Hi Pat I'm not sure why you are worried about heat affecting fermanium? It's bot an issue I am aware of. I have no idea why they stuck that to the velcro like that. Weird! Germanium diode is used in fuzz because it only needs 0.2V to clip, compared with 0.7V for silicon.
thanks for the advice i know nothing about the heat germanium thing .thanx stu, i think he covered it so i didnt know or other builders what he used and its glued on there weird..id like to get it off but his used a glue and im scared of damage..thats really handy info the .02 as to the .07 with silicone.been loving the channel watched the esoteric mixing desk series . crazy job@@stuartukguitarampguy5830
oh to be clear it is a fuzz pedal copied with old parts that jimi had in his pedal.roger mayer gave me 2 fuzz pedals in the 90s .sadly i dont have them now.great design and really different to all the rest. i dont know how he can make such a simple build better but he is roger mayer@@stuartukguitarampguy5830
And if it’s no joke, it’s hard to kill tube devices, especially old ones that are assembled by a canopy. Tube amps are a very good device, it’s a pity that every year fewer and fewer people are engaged in them.
I have that same problem on a preamp valve on my Marshall JCM800 4010 combo as well. I can't for some reason get the pins to retention on mine, I'm just to the point of replacing the sockets already lol
Hi Stuart, I am doing the same on my JCM 800 4212 amp. After 10 year in the cellar the pots are seized solid. With WD40 I got them going except one where the shaft is broken (now it has a D-shape, guess I have to replace this one). However on my one, the knobs seem to worn out, I can turn them without turning the pots although they are turning. Any recommendation which knobs I should used to replace? There are ones with screws and others just to press on. P.S Merry christmas + happy new year
I have a JCM 800 that has what looks to be a capacitor soldered between pin 8 of the CA3046 transistor array chip and the end of a resistor (labelled R5). Do you have any idea what that might be about? It's driving me potty.
Not unless they are obviously bulging. It's quite an expensive business replacing all the electrolytics. Plus, if they fail, it's a 'soft fail' - i.e. it doesn't do any further damage to the amp. I also take a view on who owns the amp and what they are doing with it. If it's a hard-gigging professional, then I might suggest changing them. If it's someone strumming in their bedroom, I definitely would not change them. Hope that makes sense.
At 6:30, is that little half-round black thing an inductor or a bridge rectifier? If it's a rectifier, those types of little round bridge rectifiers are known to fail. I've replaced many of them in vintage solid-state hifi gear.
Nice job. I am surprised you saved all the pots. Not unusual when they stick like that it just eats a hole in the trace. I suspect that the output transformer is imbalanced causing the bias to be so off, but that is from a few thousand miles away. Finally, what if you spin that reverb tank around? would you get some hum or anything like that? Seems more practical to be able to use those plugs.
@@stuartukguitarampguy5830 if you spin that tank around it'll hum like a bastard. Marshall fitted them like that for a reason and that's the correct way 😉 Believe me, I've suffered the same inconvenience many times!
Hi Stuart! Maybe you could help me? I got an jcm 800 from a friend. It needs new pots (Normal Channel: Treble, Bass) and (Boost Channel: Volume) i cant find out the needed impedances for the pots. Also im not able to read all the schematics..:/ Can you tell me which impedances i need for the positions ? Thank you and a happy new year!
@@stuartukguitarampguy5830 it’s because the tone knobs are so fixed, I can’t turn Them a single millimetre. The volume pot seems to have struggle with something else. When I’m turning it, the amp does crazy fizzling tones and I really can’t get a good position where the amp is doing what it should. Sorry for my late answer. Thank you!
I managed to fix all the seized pots. Thanks to your video!! But one problem is still there… the volume pot of the boost Channel makes very loud „pops“ and „cracks” when I’m turning it while the amp is on. Thought I would change the pot. Or could it be something else?
Sorry to bother you . Is this one a 2210 dual channel. I had one in the 80' and that was one of the best Marshalls I have owned. I have had 3 full stacks and 2 410h half stacks.
@@stuartukguitarampguy5830 the treble on the clean side, the reverb, and the treble on the other side. Seized. And I broke one turning with a screwdriver.
I watched a lot of your videos about the repair of guitar amplifiers, I have a question, what do people do with these amplifiers, why do they look like they are from the garbage dump? Or just the owners of pig amps
Hi Mark. Ha ha! There are two main reasons an amp looks like a dog. 1. It's just been lying around in a garage for years without being used. 2. It's been heavily gigged and bashed about. Interestingly sometimes a user won;t let me clean up the amp. Some guitarists like that 'trashed' or 'well gigged' look!
@@stuartukguitarampguy5830 thanks for replying Stuart. I wasn't being sarcastic or anything, I wanted to ask because if it helped or needed to be done, my marshall jcm 900 slx has 2 big transformers and there's a little rust on the side of them. That was a good bit of advice about never leave your amp overnight where you would not sleep or be yourself. I've heard that before but with guitars not amps. Keep up tha great videos/amp repair.
@@Shiloh7377 Hi. No didn;t take it that way at all! I used to think rust was very bad and caused 'eddy currents' in the transformer which affected its performance. Apparently this is total tosh and rust does no harm. You might want to take it off for cosmetic purposes. It's bad to store amps in garages etc because it affects other parts like the valve bases and the pots. All the best Stuart
@@stuartukguitarampguy5830 very very true about it effecting other parts of the amp. I keep mine in the house on top of the 4 x 12 marahall cab, In an extra room. Do you have a Twitter or somewhere I could post a pic of it to ya?
WD40 isn't really a lubricant, it's a water displacement formula, and it dries up leaving a semi-solid residue. You'd be better off using Liquid Wrench or Pb Blaster or some other purpose-designed penetrating oil. Heating up the pot shaft with a hairdryer, heat gun or soldering gun before applying the penetrant will drive the air out of the shaft bushing and a small vacuum will occur as the shaft cools, drawing the oil in. (I've used this heat/cool technique to free a frozen audio input selector switch on a Dynaco preamp and other electronic devices ---- but obviously you can't use heat on pots with plastic shafts). Your life is being made much easier here by the pot shafts having screwdriver slots, which is common for vintage trimpots (for bias adjust etc) but *most unusual* for ordinary volume and tone pots with medium length shafts, especially those that are modern PCB mount. If you didn't have those screwdriver slots, you would either have to cut them with a Dremel tool and cutting wheel ( the heat and vibration would also help loosen the shaft) or you would have to use vise-grips, what you call "mole grips", on every single potentiometer, which has the tendency to chew up the shafts and make life difficult when you put the knobs back on. I do hope you tightened all the shaft nuts that secure the pots to the chassis before attempting to turn the pots with the screwdriver, otherwise the high-torque rotary force applied to the potentiometers would tend to break the solder joints and perhaps even the copper foil traces on the circuit board. PS, I would generally avoid using the knobs as a fingergrip for leverage when working the stiff, sticky pots back and forth because the plastic knobs might have gotten brittle with age and you could break the knobs. I am currently in the process of fixing a rare and valuable vintage Hickok 539B tube tester on which every single potentiometer and rotary switch shaft was frozen solid. I managed to free them all up ---- except for the filament voltage selector switch, I'm still working on that one ---- with alternating applications of heat, penetrant and torque. Despite having a star washer behind it, and no matter how tightly I secure it, the filament switch wants to spin on the faceplate when I apply torque, and I don't want to break the switch wafers or any of the dozens of wires going to it. I may have to grind off the brass rivets that hold the switch wafers to the rotary mechanism (leaving the wafers attached to the wiring harnesses), disassemble the switch, and soak the shaft/bushing plate in oil. Thankfully, all the pot and switch shafts on the Hickok are steel ---- resistant to getting chewed up ---- and have a flat spot where the setscrew sits, making it easy to grab onto them with vise ("mole") grips. Also, as I've mentioned before, using a syringe or small eyedropper to apply the penetrating oil will lessen the chance of infusing the carbon tracks with a foreign liquid that might have deleterious effects on it's electronic operation. I have been extremely careful to use minimal lubricant with the Hickok mentioned above because soaking the switchwafers with any kind of oil or lubricant could make them conductive ---- the Hickok measures the "valve's" inter-element leakage on the main meter, up into the *meg-ohm* range ---- and risks ruining the tube tester. (Never clean the switches and controls of a tube tester by simply spraying them with electronic cleaner, you could ruin it permanently).
Aha! I actually cut out a section in the video where I said "Now someone is going to contact me and say 'WD40 isn't a lubricant it's a water disperant' etc etc!
@@stuartukguitarampguy5830 , well, it isn't a lubricant. People use it for that but it's really not that effective, and there are better products to use. Any hardware or auto parts store will carry a range of more suitable lubes and penetrants. Frankly many chemical companies just don't give a crap, and will sell anything to anyone just to make a buck. I have seen electronic contact cleaners that on one part of the can will say "cleans and lubricates!" but elsewhere on the can will say "leaves no residue!". Obviously both of these cannot be true, but the sales and marketing department doesn't care and they will say absolutely anything to make a sale. By the way, at work we have a device that looks like a cross between a large metal syringe and a small bicycle air pump, designed to screw onto the threaded shaft of a potentiometer and allow you to pump control cleaner or lubricant in, around and past the shaft of the control. Unfortunately, the threads only fit onto older US-made, SAE- thread controls and pots ( the type that were used on devices that are typically fairly easy to disassemble for cleaning the pots) ; and it doesn't fit the more modern, circuit-board-mounted, metric-thread pots that are often very hard to reach for cleaning. I always meant to make some adapters so that the pump would would be usable on metric pots, but haven't gotten around to it.
@@stuartukguitarampguy5830 , Google Hickok 539B or 539C tube tester, I'm sure you'll find some good photos, probably the terrifying interior circuitry as well as the airplane-cockpit-lookung exterior. I own a working 539C, it is a very desirable and collectible tester, and a very complicated beastie, somewhat time consuming to set up and use; I actually use my Hickok 752A the most because its faster, simpler, easier to set up and use, and tests virtually every audio or radio tube ever made. The 539B will eventually be for resale. Hopefully I can get it working again but even if not it still has significant parts value.
A little rust on transformers or chokes does no harm. I would recommend using a wire brush with the transformer upside down so any metal dust doesn't fall into the laminations , and please do this far far away from any speakers, as metal dust or rust can definitely find its way into the voice coil gaps, and that DOES LOTS OF HARM!!! Also never spray varnish Your beautiful cleaned transformer laminations, as the accellerating drying chemicals can make the varnish between laminations conductive enough to allow massive eddy currents to ruin the xformer. So much for good intentions. Had a tranny that worked fine for many years with rust, and then decided to clean it, and varnish it: BIG HUGE MISTAKE ! ! !
If the amp is used at home or just has been standing for many years, then it’s not clear. But if it is played in a barn, then it’s clear why they look like that.
Correct me if I'm wrong (got old eyes, and a small phone screen), but at 19:50, if my eyes don't deceive me...... [EDIT ---- I watched the video again and realized that you were prying the push-on knobs off with the screwdriver and not releasing a set screw; but I will let the comments below stand because they might still prove usefull to others]....... those pots look to have knurled shafts like gear teeth, and yet the knobs it came with have set-screws? This is both unusual, and generally a bad idea. The set screws will tend to chew up the knurling on the (presumably) aluminum shafts, and depending where the set-screws sit, if you tighten the screw a little too hard you can collapse the gap between the two halves of the shaft (and attempting to spread the two halves of the split shaft apart with a screwdriver often breaks off one side, ---- been there, done that, on vintage hifi equipment, uggh). Anyway, regardless of how little or how much you tighten the set-screw, the knob will tend to wobble as you turn it. I hate pots with knurled shafts, especially knurled aluminum shafts (though not as much as I hate plastic shafts). Knurled pots might be OK for vintage hifi, but on an amp that gets gigged with invariably the knobs get hit and the shafts bend and so the knob wobbles as you rotate it, and only rarely can you straighten the shaft without breaking half of it off. Also the alignment between the knurling of the pot shaft and the internal knurling of the knob is rarely spot-on, and it's unusual to be able to get all the push-on knobs to rotate from 0 to 10 with the exact same alignment. Smooth potentiometer shafts, and knobs with set screws, work much better for this sort of thing; and anyway, vintage amplifiers rarely suffered badly bent pot shafts because typically the shafts were made of steel or plated brass, not aluminum ---- steel or brass shafts are far more difficult to bend than aluminum ones, especially when the aluminum has a slot in the middle of it and has less mass and less strength because of the loss of metal from the knurling and the central slot. Removing push-on knurled knobs is best done with *two" screwdrivers as levers, rather than just one; it's gentler on both potentiometer and knob. Also note that applying torque to a frozen aluminum potentiometer shaft is quite likely to break it, so proceed with caution. A sacrificial press-on knob from the scrounged-parts box, selected for having knurling that matches the pot shaft, can be modified with a hole drilled down through the middle of it, and slipped onto the frozen pot-shaft to keep the haves of the slotted shaft in alignment and prevent them from spreading apart and perhaps breaking while you slip a flat-blade screwdriver down through the hole in the modified knob to reach the slot in the shaft.
@@stuartukguitarampguy5830 2 teaspoons is much better to remove the pots, a bit of gaffa on the back will protect the face plate, and the leverage from both sides is nice and gentle, you can even make tea with them.
@@grimmmstudios2367 Nice idea, I may try that. But I am VERY gentle with the screwdrived and have never marked a front panel yet. Youll notice I lever with the screwdriver whilst simultaneously lifting up opposite side of the knob with my fingers. Seems to work!
It's super common. Young man joins a band and plays for a while. Gets married, has kids, 30 years later comes to me with an amp which has been on the garage all that time, and they want to start playing again.
A salutary lesson in where 'not' to store your temporarily unused amp. The four enemies and saboteurs of electronics: Dust, Damp, Vibration & Heat. 10 out of 10 for showing the reality of the wide range of problems that can occasionally flummox even the best techs.
Thanks Pete. There's an old adage "If you wouldn't sleep there, don't store your amp there!"
Great video Stuart love how in-depth your videos are I hope you get a Laney gh50 or gh100 in I have both I’ve never had a problem with them other than re tubeing them love your show.
Thanks Ricky!
Stuart, you are correct. Leaving in the wild goose chases makes great content. Following your thought processes are what makes your videos so informative.
Thanks Eddie.
Stored in a shed outside perhaps judging by the dirt and rust. Love your show.
Yep, probably!
Nice work saving all of those pots... lots of work for sure.
I have the same 2205/2210 model from 1985. Great head. Michael Schenker’s Marshall of choice. Definitely a different sound than the 2203/2204 single channel JCM800. Yep, that is the way Marshall mounted that reverb pan. A real pain to get at. I’ve worked on a half dozen besides mine and they are all the same on the pan.
Ok thanks for the info!
Thankyou Stuart! I really enjoy your videos and I’m glad you leave all the troubleshooting in, it’s like going on a safari :)!
Thanks David I like to keep it as 'real world' as possible.
@@stuartukguitarampguy5830 Hey Stuart, I noticed in one video you were experimenting with alcohol as a pot cleaner. How did that work out, are you still doing it? I would think a touch of sewing machine oil in the mix could be good in an aeresol spray bottle. Sure would save in Deoxit $$ :)
@@davidsimpson3380 Hi David. Okay here's the scoop, I've done a LOT more research into cleaners since I made this vid. Bottom line is there are two mechanisms for cleaning. Firstly 'flushing' - almost any maintenance spray (and alcohol) will do this - wash away dirt, dust etc. However, there is also oxidisation of the metal wiper. No amount of flushing will help this. DeOxit D5 (and their other sprays) are the only products I know which flush AND deoxidise the wiper. I was finding only 50% fix with alcohol before I realised I was only fixing the pots which needed flushing only. Anything with an oxidised wiper was not being fixed. So I have converted to using D5 for all my pots.
@@stuartukguitarampguy5830 Thank-you for the update Stuart. It seems DeOxit is still king of the hill but it's just a matter of time before the code is cracked and alternatives could be had as cheap as alcohol. I'll keep my eyes peeled :)!
My heart was in my mouth when you were trying to find the fault on that tube, with your screwdriver.
I realise you may have edited the vid, but surely there is a fair bit of high voltage in there when you poke around. I wish you were nearer, to be able to have a look at my JCM900 2500, seems quite a bit simpler (less valves, less caps ), but still probably needs a service.
Good to see an old, great amp be resurrected.
Hi Andy Yes I'm always very aware of and careful around high voltages. I'm sure there will be a tech near you somewhere who can look at your amp.
The fossilised spider definitely adds to the tone
You can buy them in packs of three apparently...
I bought a JCM800 2210 and someone removed the reverb from it, I wanted to have it put back in, but I thought I could do it myself. Wrong. Great Video 📹 👍 👏 ❤️✌️
Thanks Randy. Did you get the reverb working in the end?
Me too Stuart. Light handed with a very large hammer.You might try to tap it lightly with a 5 pound hammer. That will free them up. Fun video.
Great video, the Hum King rules again!
Thanks!
Great Job sir thanks for the great work you do and the reality of what techs face with various issues including the tech himself… it’s easy to second guess something and not recheck your work it will lead you down a rabbit hole lolol been there done that and no doubt will do it again 😂
Thanks Tim.
if i had a choice of any amp guy in the online world to fix my babys id want stuart to do it..his approach is classic he does not presume which the best do..and his got so much knowledge. your a treasure mate but your not in my country which i think you would like more then cold england ha ha
Ha ha! Thanks for the positive comments Pat.
@@stuartukguitarampguy5830 actually speaking of heat and cold , whats your take on germanium components. is there a way to stop heat affecting them. ive hand made fuzz this wizard made for me but on the germanium chip his put a little piece of sticky velcro which i found weird to say the least . anyways interesting. i meant it Stuart you and Brad the guitaroligist are great people to learn from.im a player but ive done one build ...love your work cheers
Hi Pat I'm not sure why you are worried about heat affecting fermanium? It's bot an issue I am aware of. I have no idea why they stuck that to the velcro like that. Weird! Germanium diode is used in fuzz because it only needs 0.2V to clip, compared with 0.7V for silicon.
thanks for the advice i know nothing about the heat germanium thing .thanx stu, i think he covered it so i didnt know or other builders what he used and its glued on there weird..id like to get it off but his used a glue and im scared of damage..thats really handy info the .02 as to the .07 with silicone.been loving the channel watched the esoteric mixing desk series . crazy job@@stuartukguitarampguy5830
oh to be clear it is a fuzz pedal copied with old parts that jimi had in his pedal.roger mayer gave me 2 fuzz pedals in the 90s .sadly i dont have them now.great design and really different to all the rest. i dont know how he can make such a simple build better but he is roger mayer@@stuartukguitarampguy5830
And if it’s no joke, it’s hard to kill tube devices, especially old ones that are assembled by a canopy. Tube amps are a very good device, it’s a pity that every year fewer and fewer people are engaged in them.
I have that same problem on a preamp valve on my Marshall JCM800 4010 combo as well. I can't for some reason get the pins to retention on mine, I'm just to the point of replacing the sockets already lol
Oh dear, yes sometimes that's the only remedy.
Hi Stuart, I am doing the same on my JCM 800 4212 amp. After 10 year in the cellar the pots are seized solid. With WD40 I got them going except one where the shaft is broken (now it has a D-shape, guess I have to replace this one). However on my one, the knobs seem to worn out, I can turn them without turning the pots although they are turning. Any recommendation which knobs I should used to replace? There are ones with screws and others just to press on.
P.S Merry christmas + happy new year
If your shafts are 'D' shaped I'd just get the push-on ones.
I have a JCM 800 that has what looks to be a capacitor soldered between pin 8 of the CA3046 transistor array chip and the end of a resistor (labelled R5). Do you have any idea what that might be about? It's driving me potty.
No need to replace any of the caps in such an old amp? Great video Stuart thank you.
Not unless they are obviously bulging. It's quite an expensive business replacing all the electrolytics. Plus, if they fail, it's a 'soft fail' - i.e. it doesn't do any further damage to the amp. I also take a view on who owns the amp and what they are doing with it. If it's a hard-gigging professional, then I might suggest changing them. If it's someone strumming in their bedroom, I definitely would not change them. Hope that makes sense.
those first few opening notes had a distinct Page vibe
Try using a oil called ballistol. Works amazing
Thanks for the tip
I have found that a penetrating oil called Kroil by Kano industries is much better than wd40 for loosening stuck screws. Might be worth a try.
Hi John Oddly enough I've recently started using this myself!
At 6:30, is that little half-round black thing an inductor or a bridge rectifier? If it's a rectifier, those types of little round bridge rectifiers are known to fail. I've replaced many of them in vintage solid-state hifi gear.
Thanks. Yes I think I've done a few as well.
Nice job. I am surprised you saved all the pots. Not unusual when they stick like that it just eats a hole in the trace. I suspect that the output transformer is imbalanced causing the bias to be so off, but that is from a few thousand miles away. Finally, what if you spin that reverb tank around? would you get some hum or anything like that? Seems more practical to be able to use those plugs.
@@stuartukguitarampguy5830 if you spin that tank around it'll hum like a bastard.
Marshall fitted them like that for a reason and that's the correct way 😉
Believe me, I've suffered the same inconvenience many times!
@@DrWatts-bi1jv I wondered about that. They can be finicky.
@@DrWatts-bi1jv Right. I'm staggered that it even works there, it's about 5mm above the mains transformer.
what do you do if the knob has a solid tip and not a gap to use a screwdriver?.
Put some WD40 down the shaft and leave for an hor. Then use some pliers
is dioxite same as wd specialist contact spray?
Hi. Almost certainly not. I have no idea which is better though. I always use DeOxit D5.
Would you suggest that your customers give their amplifiers before repair for sandblasting))))))))
Hi Stuart! Maybe you could help me?
I got an jcm 800 from a friend. It needs new pots (Normal Channel: Treble, Bass) and (Boost Channel: Volume) i cant find out the needed impedances for the pots. Also im not able to read all the schematics..:/
Can you tell me which impedances i need for the positions ?
Thank you and a happy new year!
Hi Niand I can probably dig out that info but before I do can you tell me why you think it needs all these pots replacing? That's very unusual.
Stuart
@@stuartukguitarampguy5830 it’s because the tone knobs are so fixed, I can’t turn Them a single millimetre. The volume pot seems to have struggle with something else. When I’m turning it, the amp does crazy fizzling tones and I really can’t get a good position where the amp is doing what it should.
Sorry for my late answer.
Thank you!
I managed to fix all the seized pots. Thanks to your video!!
But one problem is still there… the volume pot of the boost Channel makes very loud „pops“ and „cracks” when I’m turning it while the amp is on. Thought I would change the pot. Or could it be something else?
@@Niandmolar Hi Just give it a squirt of DeOxit or similar and see if that sorts it.
@@stuartukguitarampguy5830 I did! But it doesn’t help. Maybe it’s something else :/
Sorry to bother you . Is this one a 2210 dual channel. I had one in the 80' and that was one of the best Marshalls I have owned. I have had 3 full stacks and 2 410h half stacks.
I can't recall tbh.
yes it is 2210 i have the same amp but in immaculate condition
whats causing the pots to go stiff?
I'm not really sure tbh. Probably just a build up of gunk.
Reverb tank installed backwards?
Can't remember it was 3 years ago.
I need to replace 3 pots on mine. What are the values?
They're all different. Which ones?? Also, are you sure you need to replace? What's wrong with them?
@@stuartukguitarampguy5830 the treble on the clean side, the reverb, and the treble on the other side. Seized. And I broke one turning with a screwdriver.
Ugh. WD40 is good for that.
I watched a lot of your videos about the repair of guitar amplifiers, I have a question, what do people do with these amplifiers, why do they look like they are from the garbage dump? Or just the owners of pig amps
Hi Mark. Ha ha! There are two main reasons an amp looks like a dog. 1. It's just been lying around in a garage for years without being used. 2. It's been heavily gigged and bashed about. Interestingly sometimes a user won;t let me clean up the amp. Some guitarists like that 'trashed' or 'well gigged' look!
Does getting rust off the side of the transformers really help? I have some on marshall.
Hi. I've recently discovered that it doesn't help at all, apparently!
@@stuartukguitarampguy5830 thanks for replying Stuart. I wasn't being sarcastic or anything, I wanted to ask because if it helped or needed to be done, my marshall jcm 900 slx has 2 big transformers and there's a little rust on the side of them. That was a good bit of advice about never leave your amp overnight where you would not sleep or be yourself. I've heard that before but with guitars not amps. Keep up tha great videos/amp repair.
@@Shiloh7377 Hi. No didn;t take it that way at all! I used to think rust was very bad and caused 'eddy currents' in the transformer which affected its performance. Apparently this is total tosh and rust does no harm. You might want to take it off for cosmetic purposes. It's bad to store amps in garages etc because it affects other parts like the valve bases and the pots. All the best Stuart
@@stuartukguitarampguy5830 very very true about it effecting other parts of the amp. I keep mine in the house on top of the 4 x 12 marahall cab, In an extra room. Do you have a Twitter or somewhere I could post a pic of it to ya?
@@Shiloh7377 Nah, I try to avoid social media!
WD40 isn't really a lubricant, it's a water displacement formula, and it dries up leaving a semi-solid residue. You'd be better off using Liquid Wrench or Pb Blaster or some other purpose-designed penetrating oil. Heating up the pot shaft with a hairdryer, heat gun or soldering gun before applying the penetrant will drive the air out of the shaft bushing and a small vacuum will occur as the shaft cools, drawing the oil in. (I've used this heat/cool technique to free a frozen audio input selector switch on a Dynaco preamp and other electronic devices ---- but obviously you can't use heat on pots with plastic shafts).
Your life is being made much easier here by the pot shafts having screwdriver slots, which is common for vintage trimpots (for bias adjust etc) but *most unusual* for ordinary volume and tone pots with medium length shafts, especially those that are modern PCB mount. If you didn't have those screwdriver slots, you would either have to cut them with a Dremel tool and cutting wheel ( the heat and vibration would also help loosen the shaft) or you would have to use vise-grips, what you call "mole grips", on every single potentiometer, which has the tendency to chew up the shafts and make life difficult when you put the knobs back on. I do hope you tightened all the shaft nuts that secure the pots to the chassis before attempting to turn the pots with the screwdriver, otherwise the high-torque rotary force applied to the potentiometers would tend to break the solder joints and perhaps even the copper foil traces on the circuit board. PS, I would generally avoid using the knobs as a fingergrip for leverage when working the stiff, sticky pots back and forth because the plastic knobs might have gotten brittle with age and you could break the knobs.
I am currently in the process of fixing a rare and valuable vintage Hickok 539B tube tester on which every single potentiometer and rotary switch shaft was frozen solid. I managed to free them all up ---- except for the filament voltage selector switch, I'm still working on that one ---- with alternating applications of heat, penetrant and torque. Despite having a star washer behind it, and no matter how tightly I secure it, the filament switch wants to spin on the faceplate when I apply torque, and I don't want to break the switch wafers or any of the dozens of wires going to it. I may have to grind off the brass rivets that hold the switch wafers to the rotary mechanism (leaving the wafers attached to the wiring harnesses), disassemble the switch, and soak the shaft/bushing plate in oil. Thankfully, all the pot and switch shafts on the Hickok are steel ---- resistant to getting chewed up ---- and have a flat spot where the setscrew sits, making it easy to grab onto them with vise ("mole") grips.
Also, as I've mentioned before, using a syringe or small eyedropper to apply the penetrating oil will lessen the chance of infusing the carbon tracks with a foreign liquid that might have deleterious effects on it's electronic operation. I have been extremely careful to use minimal lubricant with the Hickok mentioned above because soaking the switchwafers with any kind of oil or lubricant could make them conductive ---- the Hickok measures the "valve's" inter-element leakage on the main meter, up into the *meg-ohm* range ---- and risks ruining the tube tester. (Never clean the switches and controls of a tube tester by simply spraying them with electronic cleaner, you could ruin it permanently).
Aha! I actually cut out a section in the video where I said "Now someone is going to contact me and say 'WD40 isn't a lubricant it's a water disperant' etc etc!
@@stuartukguitarampguy5830 , well, it isn't a lubricant. People use it for that but it's really not that effective, and there are better products to use. Any hardware or auto parts store will carry a range of more suitable lubes and penetrants.
Frankly many chemical companies just don't give a crap, and will sell anything to anyone just to make a buck. I have seen electronic contact cleaners that on one part of the can will say "cleans and lubricates!" but elsewhere on the can will say "leaves no residue!". Obviously both of these cannot be true, but the sales and marketing department doesn't care and they will say absolutely anything to make a sale.
By the way, at work we have a device that looks like a cross between a large metal syringe and a small bicycle air pump, designed to screw onto the threaded shaft of a potentiometer and allow you to pump control cleaner or lubricant in, around and past the shaft of the control. Unfortunately, the threads only fit onto older US-made, SAE- thread controls and pots ( the type that were used on devices that are typically fairly easy to disassemble for cleaning the pots) ; and it doesn't fit the more modern, circuit-board-mounted, metric-thread pots that are often very hard to reach for cleaning. I always meant to make some adapters so that the pump would would be usable on metric pots, but haven't gotten around to it.
@@stuartukguitarampguy5830 , Google Hickok 539B or 539C tube tester, I'm sure you'll find some good photos, probably the terrifying interior circuitry as well as the airplane-cockpit-lookung exterior. I own a working 539C, it is a very desirable and collectible tester, and a very complicated beastie, somewhat time consuming to set up and use; I actually use my Hickok 752A the most because its faster, simpler, easier to set up and use, and tests virtually every audio or radio tube ever made.
The 539B will eventually be for resale. Hopefully I can get it working again but even if not it still has significant parts value.
@@goodun2974 Yes I've seen that type of valve tester. Above my pay grade tbh!
A little rust on transformers or chokes does no harm. I would recommend using a wire brush with the transformer upside down so any metal dust doesn't fall into the laminations , and please do this far far away from any speakers, as metal dust or rust can definitely find its way into the voice coil gaps, and that DOES LOTS OF HARM!!! Also never spray varnish Your beautiful cleaned transformer laminations, as the accellerating drying chemicals can make the varnish between laminations conductive enough to allow massive eddy currents to ruin the xformer. So much for good intentions. Had a tranny that worked fine for many years with rust, and then decided to clean it, and varnish it: BIG HUGE MISTAKE ! ! !
Yes I only recently learned that rust on laminations was not a bad thing as I had always believed!
If the amp is used at home or just has been standing for many years, then it’s not clear. But if it is played in a barn, then it’s clear why they look like that.
oh btw i bet someone put the reverb tank in reverse its not standard
Correct me if I'm wrong (got old eyes, and a small phone screen), but at 19:50, if my eyes don't deceive me...... [EDIT ---- I watched the video again and realized that you were prying the push-on knobs off with the screwdriver and not releasing a set screw; but I will let the comments below stand because they might still prove usefull to others]....... those pots look to have knurled shafts like gear teeth, and yet the knobs it came with have set-screws? This is both unusual, and generally a bad idea. The set screws will tend to chew up the knurling on the (presumably) aluminum shafts, and depending where the set-screws sit, if you tighten the screw a little too hard you can collapse the gap between the two halves of the shaft (and attempting to spread the two halves of the split shaft apart with a screwdriver often breaks off one side, ---- been there, done that, on vintage hifi equipment, uggh). Anyway, regardless of how little or how much you tighten the set-screw, the knob will tend to wobble as you turn it.
I hate pots with knurled shafts, especially knurled aluminum shafts (though not as much as I hate plastic shafts). Knurled pots might be OK for vintage hifi, but on an amp that gets gigged with invariably the knobs get hit and the shafts bend and so the knob wobbles as you rotate it, and only rarely can you straighten the shaft without breaking half of it off. Also the alignment between the knurling of the pot shaft and the internal knurling of the knob is rarely spot-on, and it's unusual to be able to get all the push-on knobs to rotate from 0 to 10 with the exact same alignment. Smooth potentiometer shafts, and knobs with set screws, work much better for this sort of thing; and anyway, vintage amplifiers rarely suffered badly bent pot shafts because typically the shafts were made of steel or plated brass, not aluminum ---- steel or brass shafts are far more difficult to bend than aluminum ones, especially when the aluminum has a slot in the middle of it and has less mass and less strength because of the loss of metal from the knurling and the central slot.
Removing push-on knurled knobs is best done with *two" screwdrivers as levers, rather than just one; it's gentler on both potentiometer and knob. Also note that applying torque to a frozen aluminum potentiometer shaft is quite likely to break it, so proceed with caution. A sacrificial press-on knob from the scrounged-parts box, selected for having knurling that matches the pot shaft, can be modified with a hole drilled down through the middle of it, and slipped onto the frozen pot-shaft to keep the haves of the slotted shaft in alignment and prevent them from spreading apart and perhaps breaking while you slip a flat-blade screwdriver down through the hole in the modified knob to reach the slot in the shaft.
Hi again. Yes you're right they did have gnurled shafts, but the knobs were the standard el-cheapo push-on knobs, not set screw.
@@stuartukguitarampguy5830 2 teaspoons is much better to remove the pots, a bit of gaffa on the back will protect the face plate, and the leverage from both sides is nice and gentle, you can even make tea with them.
@@grimmmstudios2367 Did you watch the video? The man specifically addresses this point and the comments(like yours) that were sure to come.
@@grimmmstudios2367 Nice idea, I may try that. But I am VERY gentle with the screwdrived and have never marked a front panel yet. Youll notice I lever with the screwdriver whilst simultaneously lifting up opposite side of the knob with my fingers. Seems to work!
On this model it came with toothed shafts and knobs, and no set screws. I'm guessing this amp lived in a very damp basement for too long.
Thats a shame letting that amp go like that .
It's super common. Young man joins a band and plays for a while. Gets married, has kids, 30 years later comes to me with an amp which has been on the garage all that time, and they want to start playing again.