Great work Stuart considering the customer brief you had. I'm sad to say I don't agree with the customer. This amp was meant to be used to make music. I just don't get 'collectors' and greed driven decisions to leave an amp out of original specifications because it might devalue it .. Crazy in my opinion. I've never been to a gig with my amp when someone has asked me to remove the chassis to check it contained 'all' the original components 😅. I only buy amps to use for their intended purpose and if I stop playing I'll sell them all in full working condition, not with 60 year old dodgy components waiting to fail inside for the next owner. .
Hi Pete good to hear from you. To be fair he IS going to use it, just not very often. Also I did manage to get the tremelo working, which is what he wanted. But yes, the vintage collectors market is an odd one in many walks of life. You should check out classic cars! If the upholstery is even slightly the wrong shade, or the wiper blades have been replaced, you can kiss goodbye to thousands in value. Same with Rolex watches etc. New hands? Knock £5k off the value!
@@stuartukguitarampguy5830 .. Ha-ha.. I used to do classic cars and got out of that just before it went to the stage that the potential buyer was expecting to see a 'brand new' example that had been carefully mothballed since the 1960's. I used to restore classic Mk 1 & Mk 2 Mini Coopers and even managed to break even on the sale of one of them 😅. I should have put my cash into collecting 1950's & 60's guitar amps ! 😂.. Flying weather today in the South West.. Hope you can find time to go aloft while there's a fair wind and good visuals..
Stuart, I'm always excited to see a new video from you. Once again, I always enjoy when you pull out the schematic and talk through it. The placement of thubes on this amp was curious and made for great entertainment. I'm actually surprised at the amount of resistors out of tolerance. As you know, I have a early 1960 Fender Concert and when I che ked the resistors on its there were about 15 which I replaced. This also helped the vibrato come back to life. I am impressed with your faithfulness to the customer's wishes and while some might argue otherwise, your arguments are correct. Thanks for showing us another amazing amp and sharing your expertise.
Wow, what a nice Vox and the owner should be very pleased having such an amp. Nice video Stuart, I appreciate you sharing your knowledge and experience.
Stuart I LOVE your sraightforward approach in your video's I love the honesty and the mistakes..it's brilliant. Thoroughly enjoyed watching this one. I have a late 1964 JMI AC30/6 with intergral Top Boost. Just subcribed and starting to watch your other videos.
The customer is not always right, but they have their reasons, and that's all that matters. It is their property, and it is their choice. Some amps are kept for collectible or sentimental reasons, and you can't treat them all like they are meant to be work-horses playing gigs every weekend. Thanks for showing us the inner workings of a very rare, original amplifier. Sometimes documenting originality is as important as showing us a repair.
Great video Stuart..Educational as always for us newbies. Lovely old amp as well. Like you say, you could spend hours on it but at what cost eh...! Top job as usual...Love the teddy by the way..🤣🤣 Ed UK.
Hi Stuart. Great as usual. As a 77yr old tec I am always aware that if I am the last tec to work on an amp no matter what vintage I will always get the blame if it goes wrong! For this reason if I recommend replacing ancient critical knackered components which will affect reliability but the customer wants to keep it original and ignore my advice they either sign a disclaimer to say they will NOT be using it or I leave it as is and give it back with no charge. Keith
Never seen one of those before. Rare as Hen's teeth and with some military grade pre-amp valves. I have found the odd EL84 with the CV number. Great video Stuart.
Hi Stuart. A great video for a venerable old amp. I understand your dilemma re. replacing parts but think it’s a bit daft that people want to keep everything original. Amps need maintenance and parts do age. I think I would have strongly recommend to the customer that the grid coupling caps to the power valves ( and possibly the cathode bypass cap too) were changed, as failure or leakage in those could lead to damage of the output transformer.
The old problem. Do you want to keep a completely original (poss non working, or not working very well!) Antique. Or do you want an amp playing at its best!!? Mmmmmm!! Always a dilemma! Nice one as always Young Stuart!
The "tv" front hasn't changed... it's used right up to the present day.... Mini watt tubes are Philips and come from Australia..! The Blue speaker is made by Celestion and are worth a fortune these days
Hi. Not totally sure you're right about that (happy to be proved wrong). Someone else said it was to remove vibrato thump, which seems more likely. Not sure.
Always enjoy watching your fixes. I have the same schematic of the AC15 which differs at the phase splitter, that is, the middle line that is duplicated is not there on my version. Looks like it may be a misprint.
Quite a bit of time spent on the AC-15, Stuart. I admire what you accomplished without replacing the myriad of off-tolerance resistors. I know you had to work under the confines of the owner's request, so it was successful in keeping the components as original as possible.
One thing I always struggle with is when customers want to keep original failing components at the detriment of the amps correct and intended operation. It’s one thing to have a vintage amp but it’s much better if it works as intended as well. Customer is always right though and it’s their money.
Yes agreed. The other thing I think though is that 99% of the amps I work on are not gig-critical, so it doesn't really matter if it fails again, they can bring it back.
Hi. The direct answer to your question is the only way to tell would be to put a meter on them. The indirect answer is that, in my view, this is all nonesense and you should use a decent modern resistor. Carbon composite was fine in its day. That day has long passed!
Well done, as always, Stuart. Please ignore those screaming for replacing every out-of-spec component (and being a bit snide about it to boot). You can run your shop as you see fit, and you clearly articulated your rationale for what you did and didn't do. Sometimes it's a case of "the perfect is the enemy of the good (or good enough)."
I know what you mean Stuart when it comes to refurbishing compared to repairing. It;s a difficult call and always tricky to decide when to let it go. Plus it is also a matter of how many billable hours are fair when you put so much time into doing this sort of work. Great job as usual!!! Thanks Stuart, you are my favorite antique repairman on YT! It's a lost art to be sure!!!
I would have probably recommended to the customer that the coupling caps to the EL84 control grids were changed. Any leakage in those, the EL84s can get hot & bothered and if too bad, may result in damage to that precious output transformer. Their risk entirely, though of course. Tolex? Rexine on a British amp surely? 😉
The quandry with working on old stuff is that it may sound good BECAUSE components are out of spec and replacing stuff may make it sound worse, or different to what the customer wants. But another nice and interesting video. Never seen one of these before. I think CV was a mil spec valve.
Yes I had a guy in last week who swore by his amp because the power valves were TOTALLY mis-matched. Said it was the best sounding amp he'd ever had. The mismatch would cause distortion of course, and it's this that he liked (without knowing why). Makes a nonesense of selected phase-splitter valves where both halves are carefully martched! I always thought that was a waste of time.
The pentode input tube is an EF86, not an EF84. It's a classic Vox sound from that preamp tube and circuit, but replacement EF86 tubes that aren't microphonic can be difficult to come by nowadays, and expensive.
Thanks for clearing that one up because I didn't know what an EF84 was. I still have going strong a non- NOS Mullard EF86 from the 60s in myAC15 preamp add-on to my AC30 which I put down to being a Mullard. To my ears, it's a completely different tone to the Ecc83s in the preamp stage of my AC30.
STUART UK, Can you show in a video how to measure the output transformers in various guitar amplifiers to see on the oscilloscope the output transformers midrange bump? I don't know how to see the amplifiers output transformers midrange bump using an oscilloscope, how can you do this please?
@@stuartukguitarampguy5830 All output transformers have a midrange bump when you saturate them but I don't see it on the oscilloscope. There must be a way to see it on the oscilloscope the midrange bump of the output transformer. What would be the test setup?
@@stuartukguitarampguy5830 thanks for checking. When biasing up amplifiers its a common problem that the power tube dissipation is either below 70% or above 70% when adjusting the cathode bias resistor value or grid bias trim pot to make a clean No Crossover distortion. When getting a clean no crossover distortion but the tube dissipation is either way below 70% or way above 70%, what can you do to the amplifier to correct this problem? The plate voltage is already maxed out to the power tube data sheets so I can't increase or decrease the plate voltage either to fix this problem, what do you recommend doing?
@@waynegram8907 Hi Wayne. This is not something i ever check on a guitar amp. I'm wondering if you are talking Hi Fi here? I literally never check the crossover distortion on an amp as we don't care. The more distortion on a guitar amp the better the player likes it, in general! I don't have enough in depth technical knowledge about class AB amps to help with you question, sorry.
@Stuart ukguitarampguy Ah, that's interesting, I try to get an idea of these things but there's so many valves!. I have an old W.E.M from '64, from what I can gather it's a Mersey Super 15, it's basically a Dominator with a single 10 inch Elac, they where made for Hesseys Music in Liverpool but never went into full production, only 7 where ever made, apparently that's the shop where John and George picked up there Vox AC15/30's?. Thanks mate, always enjoy your content.
@Stuart ukguitarampguy Hiya, I've no idea what it's worth but it sounds fantastic. At the moment it's making the "frying eggs" sound so it'll have to go get sorted out, I'm not at all precious about old amps, if it needs fixed then that's what it needs, I wouldn't drive a car with faulty brakes!. I've had a look inside but that's all, I'm in no way qualified to determine what is wrong but I did notice that it seems completely untouched and has a full set of mullards which look original, thanks.
Owning a vintage AC 50 that I refurbished 10 years ago, I am in the opinion that if a component is out of tolerance then it needs replacing regardless of age or rarity. It's only collectors that want internals to look the part event if they contain a load of knackered resistors. Get out the crap and get in the new for gods sake! 🙂
Regarding the filter caps at some point they are going to have to come out. I would not my self become to sentimental over it and leaving them in could cause damage and destroy the EZ81 and may be the mains transformer reducing the value of the amp.
Agreed they will need changing at some point but I am restricted by what the customer wants me to do. It's not my amp. Also, I've never come across a case of a faulty filter cap destroying either a rectifier tube or a transformer in mnay thousands of amps and many years of doing this. But 90% of the time I'll swap out old filter caps. In this case I was specifically instructed not to do so.
Hiya Stuart, I've got a 1964 Vox AC-10 twin that I can't get to overdrive. It's just clean pretty much up to painful volume levels, it has all its original valves and is in remarkable condition. Am I missing something because all the examples I've seen/heard online sound incredible. Thanks.
Hi, I have a 1964 AC10 Twin also, purchased 1970 for £20, great amp and still working well, I've used it live since I bought it, has to be nearly on full to over drive but many years ago I went to see Rory Gallagher at the Bridge House in Canning Town London, he used a Vox AC30 of course but had a great sound, while packing up his gear we were asking him about his sound and how he got it, he said he used a RangeMaster treble boost (it was sitting on top of his amp) he said any treble booster would work, you just need to hit the front of the amp a bit harder than what Fender pickups were capable of, Great advice from Rory, he was so helpful but humble with it. I couldn't find a Rangemaster at the time but Electrharmonix sold a Screaming Bird treble booster around this time, so I tried one and sure enough It gave me the best sound I'd had ever, The perfect Jimi Red House tone with a Strat. Since then Many people have been reported to be using Rangemaster/treble boosters with Vox amps. Brian May, Eric Clapton, Mark Bolan and many others. I think Brian May markets a version of his treble booster, I've seen a few for sale on ebay. So your Vox AC10 twin sounds perfecttly normal to me. Try a treble boost or EP boost to kick the front end.
@guitartech-uk Hiya, It's funny you mentioned Rory, my amp is currently being sorted out by the guy who worked with Rorys' actual Hawk boost and Dallas rangemaster, Stevie Flynn. Donal gave him access to all the gear, he even got to play Rorys' Strat!. My AC10 had several changed resistors/caps that where the incorrect values, I've to deliver a set of N.O.S Mullards (cost a fortune!) on Monday to Stevie and I should have it back by the end of the week, I can't wait!. Stevie is an incredible amp builder. Thanks for your help.
@@keiranbradley3238 Sounds great, I nearly purchased a hawk boost from ebay a year or two ago ,(having heard Rory had used them) they seem very few of them about, your amp should be great when you get it back, mine hasn't even had a valve changed in all these years, it definitely needs re capping a d probably a valve or 3, I bought various spares for it years ago when valves were cheap and easier to come by but never wanted to fit any until I really needed to. I haven't fired it up for a while, but when I do I suspect it will have a problem or two, I must treat it to a service, also they seem to have become quite valuable, I don't think I'd ever sell it but I'm getting on a bit now, if I snuff it my wife will probably just flog everything not knowing they're worth. Enjoy your Vox when you get it back.
I had one of these in 1965-ish which was used to gig in relatively small venues and so it had to be used pretty well at full volume to overcome the drummer. Even with a treble boost, I still couldn't get a proper overdriven sound with it.
I hope that I am not teaching my grandmother to suck eggs but Philips owned Mullard from 1927 onwards and so perhaps it matters little whether the valves are Philips or Mullard. I have an NOS Mullard Ef86 from pre decimalisation in the primary section of my AC15 add-on to my AC30 and also an EF86 spare NOS which although labelled Mullard is identical in construction as far as I can tell to the two Philips input valves in your customer's AC 15. So I agree that it is likely that both the Mullard and Philips valves are likely originals. I have never heard of EF84s in AC15s but maybe it's because this is an early version. Nearly all the AC15s had Mullard EF86s at preamp stage which is what were responsible for that wonderful and much sought after 1960 guitar lead tone of the Shadows. Fragile but much better tone than the ECC83 replacements. I always thought that the EF86 was supposed to be at V1 being the primary tone shaper. The white jacks on my 1997 AC30 are the Vib-Trem channel.
ef86 valves are not fragile..only get trouble when put in a combo due to vibration from speakers..put in a head and no problems...and hanks sound was more than a ef86 valve on its own,,his echo.. guitar... amp ...fingers all in combination
@@richardcray2919 I have to concede the fragility bit apart from the fact that Vox are supposed to have switched to the Ecc83 because of that. However, I got part of my post wrong. The Ef86 in my add-on preamp is not NOS and since I have the packaging from pre decimalisation, it must have been used before me and it's still going strong. I agree about HBM's sound but I am factoring in that he was playing in exactly the same way after the change to Ecc83s and the general consensus at that time was they could not emulate the original tone of the EF86s in his AC15s and the AC30/4.
The old paradox. I want it working and reliable, but I don't want anything changed and I want to pay nothing. That's a hard no from me. You don't need those kinds of customers. You're an amp tech, not an amp taxidermist.
Cheapskates! The rectifier heater is fed from the same mains transformer winding as all the other valves. If there is any heater to cathode leakage in the EZ81, it will hummmmmmm.
Next time you get somebody who wants you to work on a 60 year old amplifier but wants you to keep it "original", and isn't willing to spend any money on it, nor change the parts that need to be changed in order to make it safe and reliable., tell him or her *NO*. This is not an amp that has been "played for 60 years" as you claim; from the looks of it it's an amplifier that has been sitting in somebody's closet for decades unused, otherwise it would never be in that kind of super-clean cosmetic condition. The chances of it surviving a couple of heavy jam sessions or gigs are almost nil; and when it blows up in spectacular fashion and takes out a transformer or two, it definitely won't be original after a tranny or two are replaced. And, since you were the last person to work on it, you'll be the one who takes the blame because in the customer's eyes you gave it a clean bill of health. And as a side effect, all technicians look suspect afterwards. Either the customer knows best, or the experienced technician knows best; which is it to be? Would you suggest that somebody bypass their doctor's advice in this fashion? As for the factory bias setting being ultra-hot, that was semi acceptable 50 or 60 years ago when line voltages weren't as high as they are now and when you could go virtually anywhere and get a replacement pair of new Mullard or Brimar or other ultra high quality EL84's, but nowadays rellacement tubes are limited to JJ's and various Russian or Chinese tubes, none of if which would last an hour at that dissipation setting. Not to mention that although the 2 used output tubes in the amplifier are drawing the same current, one is a GE which, if it is an American made 6BQ5, likely it isn't a true EL84; the 6BQ5 is a beam power tube, not a Pentode, and therefore doesn't have a suppressor grid. That output tube pair is sufficiently mismatched that they're going to be severely stressed when pushed hard. If you were an auto mechanic and somebody brought in a "classic" and collectible old automobile that hadn't had any proper service in decades and maybe had been sitting around undriven for years, would you simply jump start it and tighten a few connections, maybe replace one belt, and declare it ready to go ? Of course not. You'd be draining and flushing the crankcase and the transmission and replacing all the fluids, changing all the worn out belts and rubber, replacing corroded electrical connectors and cables and spark plugs, replacing the tires and the battery, etc, giving it a thorough check before it left the shop; even if the car's owner only wanted to drive it to the occasional car-collectors convention. Please stop doing this type of non-repair work, Stewart. There's next to nothing that anyone can learn from it, and any take away lessons are likely to be the wrong ones. Either service something sufficiently to be reasonably reliable and unlikely to self destruct in spectacular fashion come or turn away the job and let somebody else be responsible for a classic amplifier that blows up and becomes a paper weight. PS, Vox made it easy to repair; virtualy all the components are easily reachable right there on a tagboard, nothing is really hidden or hard to get, and only a couple components are directly hardwired to the tube sockets. Access wise, this amplifier is just about as easy as it gets for something of this vintage. And yet, apparently we are supposed to deal with an amplifier that was built in such a way as to be repairable ---- by not even attempting to repair it.
@@cloudconnect , disseminating the erroneous idea that you can do next to nothing on a 60 year old amp and both make it function reliably and bring it back to sounding pretty much the way it did in 1961 does no one any good; not the owner, who will be playing through an unreliable amp, and not the inexperienced people watching this who have now been lead to believe that they too can buy an antique, vintage amp and spend next to nothing on it for repair and maintenance. This attitude disrespects the product ----- which, by the way, the designers never dreamed would be useful, usable or "collectible" 60 years later, and they certainly didn't build it for that kind of longevity --- and demeans the techs who work hard for years to accumulate the necessary skill set to fix these devices properly so that they can continue to be used to make music for a generation or two. If the customer only wants it to be a "shelf queen" on display, then stick it up on a shelf and don't plug it in and don't turn it on. If the owner wants to play music through it, however,, then it should be gone through and made reliable, at least to the point where it is unlikely to catch fire (as old Vox amps in particular are known to do). People should be discouraged from buying vintage amplifiers if they are not going to put the time, effort and money into them to make them stable and reliable; and service techs should *never* give people the impression that a 60 year old amplifier can just get a little bit of inexpensive magic-wand treatment and go on to work for another decade or two. It's inaccurate, and ultimately it's disrespectful to the customer. And PS, I don't give a hoot about being "nice". Long ago I gave up on the idea of "going along to get along" . Even a dead fish can go with the flow. I've got 50 years of electronics repair experience under my belt, and I know from personal experience that when you let the customer dictate the terms of how you work on their equipment, no good will come of it. If a customer's budget won't allow you to do the job properly, you need to be honest with the customer and advise them of this; and if they insist they know better than you do, you should turn away the work. You should also be honest enough to advise them that if somebody else does a bad repair on their amp, or the customer attempts to work on it themselves and botches the job, it will cost more to fix bad work or a badly blown up amplifier then if they had paid you to do the job right in the first place. Them's the breaks, and this is how things work in the real world. And frankly I don't give a rat's ass if people don't like receiving an accurate assessment of the state of their amp. The world is full of people who will lie to you in order to make a buck. The world is also full of well-meaning people who aren't sufficiently experienced, or haven't the strength of will, to tell people an inconvenient truth that they don't want to hear.
I'm actually happy to do what the customer wants. I have no vested interest at all in what is 'best' for an amp like this. I actually believe he made the correct call on this amp on this occasion. He's not going to gig it, just play it now and then, so he wanted it working, with minimal change. Reliabilty is not an issue as it's not gig critical. It now works fine and will probably work for many years, so I call that 'job done'.
@@stuartukguitarampguy5830 , The problem with your attitude here is that the next guy with a vintage amp *won't understand the difference* and may want the same low-budget treatment for an amplifier that is going to be well-used; and thousands of people watching this video online will expect the same low-budget accommodation from their own local techs. Haven't you ever had an amp that you "repaired" on the cheap subsequently fail and be returned to you by an upset customer? I can tell you from experience that the customers who want to spend the absolute least amount of money to get something operational without giving you the go-ahead to really do the job correctly are invariably the worst type of "squeaky wheel". There's an old saying that "quality goes on long after the price is forgotten". Conversely, I think it was Mark Twain that said " The difficulty in getting a man to understand a thing is directly related to the effect on his wallet that understanding it would have". All I can say in conclusion is that I hope you have a disclaimer on your invoicing, one that you make the customer sign, to the effect that you are not responsible for any damage caused by aged and known to fail parts which you were not given the budget or the go-ahead to change.
