Hi Stuart. Thanks for the interesting video. Consider getting snap-on screw drivers. They fit very tight in the screws. Those are square tamper proof screws. They are used a lot in the USA. I don't know if you have Harbor Freight in UK but if so you can get a kit with all these strange screws. I work in th rf feild and have used that calculator very handy.
What a nightmare Stuart. If I'm not mistaken Rivera used RED Thread Locker on the board hold down screws. In the mechanics world RED Thread Locker is the strongest and requires heat to remove the fastener.
Hi Stuart, as a guitar tech myself with 30 plus years of work of everything from simple re stringing jobs to complete scratch built instruments, I thoroughly enjoy your videos. They're very much a case of... "This is what we have to deal with on a daily basis" Not some 5 minute heavily edited nonsense with all the difficult bits left out, this is highly skilled work with thousands of hours of accumilated knowledge. I tip my hat to guys like yourself taking the time to demonstate whats actually involved in a repair which some would think of as ... "Oh it's probably only a dry joint, It shouldnt take five minutes" Just to add also , I find the level of complexity in some of these PCB amps to be incredibly unnecessary to the point where many of my customers have opted to ditch their multi channel mass produced endlessly problematic tone stifled amps for a simple point to point from say Modulus , RD amplification , Ceriatone etc... and been absolutely blown away by the dynamic clarity. Keep it simple , it just works and thanks again. Greg at G.H.Guitars.
Hi Greg thanks for the feedback. Yes I like to kep it as real as possible, mistakes and all! It's 'real world' trouble shooting as you will well know. Agree about the PCB amps. I think becaise the components are cheap and small the temptation is just to load on more functionality on the hope it will lead to more sales. I like REALLY simple amps. All the best
I owned one of these about 15 years ago. I really enjoyed the amp back then - it's disappointing to see how difficult to service it proved to be. Glad you had success, Stuart!
@@stuartukguitarampguy5830 I've seen your videos on that one, and labelled it: "AVOID!!" 😬 Any further valve amp purchases I make will definitely benefit from videos like yours. A nice *simple* Cornell seems appealing, and then get the "versatility" (that was one of the commendations of the Rivera) from guitar(s) and pedals. And hands, one hopes. :)
Fender Rivera catch 22 amp built by Hulk Hogan. You got the Hulk Hogan signature model. It's up ad running though, that's the main thing. Another good video from the man with the patience of a saint!
Threadlock on the PCB screws and havens knows what those screws were holding in the output valve board. Rivera designed some great sounding amps, but it seems, as you observed, that servicing was not his top priority. You achieved a brilliant 'cheat' to overcome that particular adversity. More than one way to skin a cat eh ! Great video Stuart ..
The longer the screwdriver shaft, the less torque that is actually delivered to the screwhead. Some of the rotary force from your hands is being expended in the process of twisting your tools' shaft! 😁 Anyway, a round of heat and cold from a soldering iron and a blast of freeze spray will sometimes loosen the bond between the screw and the threaded fitting; there are also special pliers made specifically for grabbing the heads of small screws. Otherwise, you might need an impact driver and a hammer, which carries its own risks of bending the chassis or breaking a PCB. I wish you'd showed a closeup of the screwheads.... And here in the States anyway you can go to most auto-parts stores and buy a kit of bits to fit virtually every security screw known to man for less than 20 bucks.
Oh dear Stuart, I feel your frustration..You'd think the manufacturers would keep in mind that a tech somewhere might have to execute a repair to their product and free access to the components might be a plus..! Hey ho, great job; lots of tech info and love how to manage to get to the problem by any means.. Fab repair..Ed..uk..😀
Hey Stuart. Hee a smallish ballpeen hammer and strike the handle end .of the CORRECT size of screwdriver for the stuck fastener. You want to shock the thread of the fastener in what ever screw at bolt. Don't hit it hard just shock it.
Hi Jack. Yes that might have worked but the main issue was the head was some weird security screw and so the posi didn;t get a perfect match to it. Bizarre. No idea why they used those screws.
Your usual calm demeanor was bereft today, Stuart. This amp; as well as every other Rivera had only one designer: Paul Rivera. After designing for Fender, where his incorporation of push/pull pots was pioneered. It is true that many of his creations are very involved in circuitry composition. I'm trying to find a Rivera Knucklehead 55 for myself. I am happy you got the issue sorted. Please enjoy your weekend, Stuart. Stay safe, and well. Cheers!
These amplifiers were the result of the modification of the Fender and Marshall of the 70's. For example, they added a high gain and multiple different tones to the Fenders so they could fit any guitar and adapt to the most “rock” by turning up the gain, while the Marshalls, which are all overdrive, gave them clean channels and thus Rivera amplifiers were born. Sorry for my english. Good job. Greetings.
What a nightmare of an amplifier! On the one screw you were able to remove from the power tube sockets, was there any evidence of loctite on the threads? I have a nut driver with a round plastic head that fits in the palm or your hand and you can really get some torque on it. The other end accepts different size/style of tips.
Ho questo ampli da 35 anni e funziona ancora molto bene, è estremamente versatile dal funk al blues all'hard rock - la scheda normalmente si toglie con facilità
Stuart It looks like the screw has red loctite on it . ---------- Loctite Threadlocker Red 271 is a permanent solution for locking and sealing threaded fasteners and is only removable once cured by heating up parts to 500°F (260°C).
Engineers!!!!!! Ha!! Bang their heads together ❤️ 👏 Good to see that this frustration cuts across different vocations. Yea, I got a good laugh at that one. They must think someone might steal the inside of the amp so they use security screws. Bahaaaa!!! Go figure! Thanks again for an entertaining time.
loctite on screw, perhaps tapping on top of the driver . You van also put a shifter on the handle to gaing better leverage whist forcing bit into screw head
I feel sorry for you when I see these PCB interior shots and they look like the surface of the Death Star Have you ever been inside a 70s Burman amp, UK made cascading gain monsters… not a pcb in sight. I’ve had mine since new… some piece of kit
Great, so the best way to service this sort of "amplifier", is don't service them!!! How much time we have to spend, how much is the customer conscius for this, they have not technical idea of what is going on, how to describe this to them? I'm very disappointed with this way to produce amplifier, but.... Where we go? Thanks Stuart for the patience Cheers Robi
Loving your videos Stuart, really informative. Can you put to bed the argument that valves will make a difference to the tone of an amp. I'm of the opinion is that all they'll do is control the flow of the current and amplify the signal coming from the guitar. All the claims that certain valves will add mid-range, more bass or treble surely are spurious aren't they?
My own personal view is that its all smoke and mirrors and there is no discernible difference between valve brands. Ditto capacitors. Ditto pcb -v- hand wired. Unfortunately it would be impossible to actually prove this. You'd need a specially modified amp where, at the flick of a switch, you could swap out one valve brand for another. That could be done but then you'd need say 500 guitarists to come in, play, and do an A/B switch, double blinded, and collate their comments. All comments would be subjective too like "I felt V1 was a bit warmer sound than V2" or "V2 sounded a bit cleaner than V1" and so on. You might perhaps ask if V1 sounded any different to V2 and try it that way. Having done all that, you've only checked say JJ against Tung Sol. There are many other combinations. If such an experiment was ever done (it won;t be) my view was that the results would be down in the noise, i.e. no discernible difference.
@@stuartukguitarampguy5830 Thanks for the informed response. I truly respect the opinion of people who work with these amps every day, have a working knowledge of what each component does and more importantly, knows what really influences the sound of an amp. I think there's far less emphasis is placed on the speaker(s) an amp in connected to in terms of tone by certain individuals which for me really is where the tone lies.
@@bandsbikesandboozereviews You are absolutely correct. A speaker will make 50x the difference to the tone compared wih a valve, capacitor, pcb etc etc. If someone ever brings an amp to me and says they don't like the tone I always advise them to try another speaker. If that doesn;t work I advise them to change the amp for another brand. You'll never get the tone you are seeking by changing valves or other components.
This amp should be kicked down the stairs and salvaged for parts! What a mess! Not only profound chaos in circuitry, also flux residue everywhere. I've been thinking the designer of this double regulator circuit was really incompetent, then I realized the same power supply probably also takes care of some opamp(s) inside, so that's not so bad. I can't reconcile the notion that this was handmade and designed in such a manner: clearly the design guys really hated the ones in manufacturing. Regarding the screws, some time ago I ran into this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-4WsTfJ-YwbM.html So the square bit would probably be your best bet to succeed in removing those sockets. Or (what I usually do with stripped or really hard screws) dremel-cutting a slot in the heads for a slot driver.
Your English is better than my Italian! Why is it disappointing? The amp was fixed, will last many years and the customer received a low bill. That's a result!
I'm splitting hairs here, Stuart, and busting your chops.....but your drawing of the 3 series-string preamp tubes would actually require 36 volts ---- not 18 volts ---- the way you drew it! The pair of heaters inside each preamp tube are actually being wired in *parallel*, not series, so that each tube runs off of 6.3 volts. Your drawing has the individual tubes wired for 12.6 volt operation, with each pair of heaters in series....which is the kind of mistake I'd expect from a Mesa schematic! 😁
@@stuartukguitarampguy5830 Whatever..You fixed the problem, and that's the main thing..Top job...Too many nit pickers on here, without any proof of electronic knowledge or content.🤣🤣
@@stuartukguitarampguy5830 , I understand now what's going on here: it's 36 V, not really plus or minus, just 36 V end to end, because there's no centertap connection for the heater-string of the 3 preamp tubes (and they're not using the centertaps of the individual tube heaters either). It's a stupid way to derive a DC supply for those three tubes, but this is Mesa "Engineering" after all. It occurs to me that the cold heater resistance of those 3 tubes, even in series, would be fairly low at turn on and probably stresses the regulated +/- supply, for the IC's and lord knows what else (relay switching? hopefully not used for negative bias!) until the tubes warm up. Having 3 pairs of heaters in series also means that if you have any oxidation or dust in one of those sockets or on the tube pins it could interrupt the heater circuit supply to all 3 preamp tubes, which is not really something you'd want in an amplifier that you're going to tour and gig with, and therefore subject to vibration and being bounced around in a van or plane. Not to mention that if a 12AX7 shorted (which fortunately doesn't occur often, but I've seen it happen) it would put high voltage into that regulated supply and likely do a shit load of damage to the IC's as well as the supply. I've actually seen some classic Fisher and Scott tube Hifi from the fifties where the negative bias voltage, obtained from a selenium rectifier, is also used to heat anywhere from 3 or 4 12AX7's. Again, not a great idea, but at least hifi equipment just sits on a shelf and isn't transported from gig to gig, so not subject to transport shock and vibration. If a 12AX7 heater failed and went "open" on this Mesa, it would knock all three tubes out of commission and disable the amp until the dead tube was replaced. Best to remember to bring spares along!
@@goodun2974 Yes all those points you make are valid plus if you lose one heater you lose all 3 which makes diagnosis more difficult. Btw I only said +/- 18V because the 36V is derived from a positive 18V regulator (7818) and a negative 18V regulator (7918).
Wow this amp got the best of you, there are 2x quick connect that after removing them, you only need to desolder the 2 wires for the grid, one for the neg feedback and unscrew the ground, the board would’ve come out easily. I admire your videos but honestly you could’ve done better
