Sometimes I think about redoing this video but better now that I know more about recording (and have significantly more practice with the instrument under my belt), and rest assured, if I ever do get around to that, it will be this comment that guarantees I include Claypool Content.

@@nurrwick I would love to see that!

Esqueci de comentar que o volume não "zera" totalmente tbm.!

We are going to rely on Google Translate speaking better português than I do. I hope this ends up being helpful: Intermittent distortion and buzz should be most likely to be caused by bad electrical connections as a result of bad solder joints, a bad input jack, or a bad connection elsewhere on the circuit board. If you are interested in trying to fix this yourself, start by inspecting the soldering on the potentiometers and input jack on the front of the board, and then on the power and speaker output connections. There is a possibility you could have a failed resistor or transistor somewhere else in the amplifier, that is the next most likely point of failure. At that point, you would want to start with a physical inspection, looking for evidence of physical damage to components. If the physical inspection doesn't reveal anything, you have two choices, depending on how much you value your time and how much testing equipment you already have access to. Your next step would be to work with a schematic to test voltages and component values as you work through the amplifier's signal path. If you don't already have a voltmeter, though, it's probably easier to go find another 15G to replace this one. That said, this seems to be a pretty common problem with these amplifiers, so you might just end up back in the same situation. Most of the time, if you take an amplifier like this to a repair shop, they are going to tell you it isn't worth the money to fix, so keep that in mind for the amount of effort you feel like putting into it. Not everyone feels like their own repair bench time is completely worthless like me! :) I am pretty sure you have bad solder joints, though, possibly also with a bad input jack and volume pot. Not being able to turn the volume all the way down suggests you may have some signal leakage somewhere, too, but definitely start with reflowing the solder and see where you end up after that. Boa sorte!

First thing to be aware of: the control does not do a whole lot to the sound of the amplifier unless you're really driving the power amp hard. Most of what you'll see is a change to the feel of it. Somewhat more compression and 'lazy' attack on notes when the plate voltage is turned down. The easiest way to tell if the knob is doing anything is to play a note into the amp, then turn the knob more than half a turn over the course of a second or so. You should hear a low hum, 60hz I believe, but it will depend on your power frequency. The note you're playing will cut out completely while this happens, then fade back in as the hum fades out. If the knob makes no change to sound, the good news is that there is a very small number of components in the 12AU7 part of the circuit. If you hear sound out of the amp at all, you know your 12AU7 is at least holding vacuum and passing signal. The things I would suspect most in the rest of the circuit would be the solder joints on the pot on the preamp board (most likely), or I suppose the connection between the preamp and power boards. You can reseat the connector between boards easily enough, and it's much easier to pull the preamp board than the power board. If it isn't something easy, the next most likely cuplrit is the Q1 TIP-50. There's a test point on the schematic at the emitter, pin 3, of that package. You ought to see .7VAC + 120VDC. The schematic does not specify where the control should be to see that value, but based on what I would expect a 12 series dual triode tube to do with voltages, that is probably with the control turned all the way down. I hope this helps; there are a lot of threads on TalkBass that talk a lot about specific troubleshooting steps you can take with the tube gain/plate voltage circuit if you need more resources for figuring out that part of the amplifier.

@@nurrwick The regulator on my amplifier turned out to be working!!!!)))) The mistake was that I tested it at low power. I unscrewed the master and gein to the maximum and turned the tube gein from the maximum to the minimum with the string sounding. The sound, as you said, first subsided and then reappeared. Thank you so much for your help!!!!!! You've lifted my spirits!!!!! I already wanted to give it to the master))

@@СветланаКарамнова-ч2ъ Awesome, glad to hear it! I really like mine... I know they are heavy and not as loud as some of the modern class D amplifiers can be, but for what I play, it's just right. Enjoy!

@@nurrwick With the new lamps, its tone is simply amazing. I plan to buy an Ampeg Classic SVT-410HLF cabinet for him. Which cabinet do you use?

@@СветланаКарамнова-ч2ъ I've been playing with two Bag End S15X-D cabinets for years. I love the way they sound and they're very loud, but they do weigh about 24 kilos each so it's a bit of a challenge to get them moved around. I'd love to run it through a pair of 410s sometime to see how it feels, though!

The long and short of it was: the amp would bias correctly without any trace of crossover distortion at lower volumes. I was chasing a problem - random stretches of distorted sound or even complete dropout - caused by a different component - my unit had a failing output safety relay - when I decided to do this work and take all the bias measurements that told me I had a set of poorly matched output transistors, but it did fix the low volume crossover issue I would hear with some bias settings. I also ended up drawing less power at idle off the wall, which is a happy side benefit. I did not measure output power because I don't have a load I can feed that much power into, but I can tell you it seemed a little louder afterward. That *probably* means no change in output level, but significant change in my own personal opinion of the box.

If it's humming when it's not plugged into anything, there's definitely something wrong with it that needs to be addressed. Standard "check the cleanliness of connectors, filter caps for visible leaking, solder connections especially to ground, and solidity of any plug-in connectors to and from the internal power supply" are where I'd start here, but you might want to have him take it to an amp tech for evaluation, as there may be something helpful in knowing that using the XLR input makes the problem worse. Good luck!

I don't for sure, sorry. If you can get a parts seller to measure the inside dimensions of the covers, or if Fender customer service can tell you what they are, at least that would give you something to compare the bare bobbins against. Fender's customer service has been pretty helpful in the past when I've had questions for them, so that might be worth a shot!

This one is one of the ones without the battery, so I don't know what you should expect for one with. The manual for the Mini Charge says it's a lead acid battery and lists care tips for long life; they say it should last up to five years if you do what they suggest. Check into that to see if you need to make any changes to how you work with your unit, I'd say. For the microphone, this amp's user just rolls with an SM58. I've tested one with an SM57 and it's fine. You won't be able to use anything that requires phantom power directly off the amp, though.

Howdy! The good news is - if you have no other symptoms and the amp plays as loud as you need it to, your value range should be fine! The only reason you might need to worry about component value drift or poorly matched transistors is if you saw something like 28mV on the high side and 0 on the low. Even then, you should really only worry about that if you are experiencing audible issues or excessive idle current draw. If the values drift further, then you'd want to consider either a power board replacement or perhaps ordering a new set of IRFP240/IRFP9240 units, but you really shouldn't need to mess with that unless you have some kind of direct symptom.

@@nurrwick Thank U for the response! Now it is clear for me. Best wishes form Pioter ;)

crack under pin 4 of i/c indeed...but now tp7 goes from 104v to 298v, ? I'd assumed the 120v was max.arghhh

If nobody has done this part replacement, I would jump DIRECTLY to the output protection relay if you are inclined to perform this severity of repair yourself. The stock protection relay is not sealed and mine exhibited quite a bit of arc-related corrosion and/or contact ablation from the 25 years of use. The exact original part is no longer being manufactured, though there are some Ampeg parts dealers that still list it in their catalogs. I used the TE Connectivity T9GV5L14-24 relay (available from DigiKey as of 12/2021, search that part number and there's only one result) because it is electrically comparable to the original part and is sealed, though you can also use the electrically identical T9GS5L14-24 if you can't get hold of the sealed unit. I have every intent to put together a video of the diagnostic and replacement process for this part and will come back here and comment on it with a link if I do get it posted, but you can test this yourself if you are willing to tap the relay with a nonconductive implement of some sort. Chopsticks work great. The relay is the little black box located right next to the outputs, and if you tap it while the sound is out, it should come back. If you aren't comfortable doing the work, take the amp to a tech and ask them to check or replace the output relay. Chances are good you'll pay an hour or maybe two of labor and $10-15 in parts, but that should fix it if you are experiencing intermittent dropouts in sound, especially with weak, noisy, or distorted output just before and after dropouts, and doubly so if smacking the amp on the side causes either a full cutout or a return of ouptut. IF NONE OF THAT APPLIES TO YOU: standard advice is cleaning output jacks, cleaning pots, and checking solder joints on the jacks at the input and output. One of the real common suggestions people offer for weird sound issues with these is to put an instrument cable between preamp out and power amp in. Try it and see if it helps, it's certainly a lot less time and effort than documenting where all the 20 connections from the transformer to the power board go. Other potential sources of difficulty with early versions of this amp at this point are possible failed capacitors, possible failing output transistors (though this would not typically present cutouts in sound, more running hot and poor quality of sound), or failing tubes (again, non-conductive rod and tapping on the tubes may tell you a lot here). I can tell you I re-tubed mine and didn't find peace, I replaced the output transistors and noticed it pulled harder but still had the intermittent outputs, and the noise I was getting from my pots was cured by replacing them, but was not directly related to the other noise from the failing relay. I'm also just gonna go ahead and admit that this amplifier has been my personal project and really nobody should put as much effort into this stuff as I have unless they actually get personal enjoyment out of the process like I do. I think Full Compass will sell you a replacement power board for a few hundred bucks less time, effort, and materials than I've put into mine... but I do get to say that mine works now because I busted out the elbow grease. That said, if it acts up in a new and exciting way, even mine will be getting a new power board if the problem isn't immediately obvious. Your mileage may vary. And of course, good luck!

Right now, Jaime is not taking orders until the beginning of September according to their site: www.creamery-pickups.co.uk/ I know there are a few national-level folks in the US that make VI pickups, notably Joe Barden (again, order book is currently full) and Curtis Novak, but if you're looking for something local, you should be able to reach out to any experienced pickup winder and ask for them to wind a particularly hot set of VI pickups. They're mechanically the same as Jaguar pickups, so anyone that makes a Jag set can make three total, with the center pickup being reverse-wound/reverse-polarity to allow for noise canceling when used with the bridge or neck. You'll want to shoot for 8-11k resistance to get this output, but again, if you have a conversation with someone that makes pickups and tell them what you're trying to match, they should be able to figure that out, too.

Thank you @@nurrwick.

I have experience with the Model P+J and the SPB-1/SJB-1 combination; the SPB/JB is a notably more vintage (read: restrained highs) sound than the MP+J combination, and the SPB-1 soloed is missing a lot of the pick attack I expect out of a P pickup. It might be worth looking into the other SD options if you don't already know you want the quarter pounders specifically. I never liked the sound of whatever GHS flats I had on the short jag, but that was also before I changed pickups out. I did fit a set of the Ernie Ball slinky flatwounds onto my Mustang PJ and enjoyed that a lot, though. I can tell you the stock 2016 Fender Mexico P pairs really well with the SJB-1 in the bridge, especially with the tone rolled down some.

@@nurrwick I have actually considered the SPB-1s. A local shop here has a P and a J set. How are the SDs about hum in the J pickup?

@@kijekuyo9494 You'll hear single coil hum in bridge unless you back the tone off, and some of it with both pickups on though I never found it distracting unless I had a tweeter in my speaker cabinet and I played with the treble up. Properly shielding the pickup cavity will help a lot with that, and I am pretty sure the bass shipped with a ground wire going into there anyway, which makes it easier to ground the shield. If you play often in noisy places, though, you would probably be better served by getting some kind of bridge humbucker. I played both the Mustang PJ and the short jag with their stock pickup in the neck and a Fender Mexican Noiseless in the bridge for a while... it was fine, though the output level was lower than the SJB-1, and not even near the output of the Model J. If you want to look into that, look for Fender part number 006-8486-000

@@nurrwick Thank you for the Fender info. I went with the DiMarzios. Unfortunately, they are on back order at Sweetwater, so I can't report any results at this point.

Popping and cracking without response to the percussive maintenance is a bit more complicated, but if it's showing up across at least two different input cables, I would start with inspecting the solder joints, cleaning the input jack, and reseating the speaker connections. It's always possible you have bad components - the TDA2050 or whatever output device this one is (sorry, away from the schematic PDF) is an IC, not a discrete transistor, so it's a little harder to diagnose it specifically - and if reflowing suspect solder joints doesn't help you, the next places I'd look are in the output stage. The schematic does have voltages available on it, and none of them are very high after the power transformer (30VDC or less by memory), so you should be able to watch for sags on the voltage rails pretty easily with any multimeter. If they all hold stable while you hear the bad noises, then you're going component spelunking. Thanks for the feedback on the video! Good luck with your repair!

@@nurrwick great info, appreciate your time very much!

I don't, but I've been able to find everything I needed at Mouser. There are (at least?) two physical sizes of the 5600uF/80VDC filters in the power supply, and you need the narrower ones. I believe you're after the 30x50, but you should be able to measure the ones that are in there unless it's a REALLY bad one (as in all the caps have exploded... in which case you've got a different problem). So you're looking for something like Nichicon LGU1K562MELB for the main filters. The rest of them I was able to order and replace based on values alone. The other snap-in electrolytics on the power board are 47uF/450VDC (and I think there's one on the preamp board, too), and then there are a bunch of much smaller caps distributed across the board. I only ever bothered replacing the 47s because I had some weird issues with voltage stability on the tubes, but if you've got something that's not powering on and you want the practice troubleshooting, cannon as many parts as you want in there. The boards are easy to work on, with the hardest part being documenting the places all the transformer leads plug in, and then making sure you seat them all the way down when reinstalling. Also, worst-case, you can order a whole replacement power board from Full Compass (and probably other places) if things go south. Good luck!

@@nurrwick Thanks. It's the 47uF/450VDC that's bad. Amp worked except for a squeal. I found kits at Fliptops and read good things about them.

@@midi510 Great! I will file that away for future reference, too. These amps are big and heavy relative to class D stuff, but they sound and feel good and seem to hold up to service well. Plus all the components are values that they still make, which is nice.

Not a name I expected to show up looking for information about a dumb bass guitar... Hope you've been well!

My guess would be failed solder joints somewhere, as the intermittent failure you're describing sounds an awful lot like the way my SVT-3 PRO acted because of its failing output protection relay. It's *possible* the output amplifier package is bad, but I would start troubleshooting by checking the solder joints on things like the input jack, volume pot, and output device (can't remember offhand if it's an IC, mosfet, etc... but it's the big guy screwed into a heat sink inside) for obvious cracks or the appearance of cold solder joints, and reflow whatever looks suspicious. Sometimes you can do an impact test - if you are willing and have a safe space to conduct open-chassis testing - by opening the amplifier, connecting everything, and then run a signal into it while you tap various components with a wooden dowel or something else non-conductive. Actually, having said that, you can attempt to rule out the output device as the source of your problems by connecting an aux input and seeing if its sound is affected. You'd mimic hard and soft strums by running the aux device at high and low volumes. Hopefully this is sort of helpful. If the easy stuff doesn't work out, you're probably at chasing voltages using the schematic. There is one available via thetubestore that you can find via search engine of your choice. Good luck!

It looks like they made versions of this amp without aux in, so disregard that if you don't have the ports on the front.

The peak light can be lit from five different places on the circuit. The easiest one to check would be the mute switch - does pressing it work correctly, does moving the switch around with your fingertip cause any signal dropout? - and then the remaining four are between V1 stages, between V1 and V2, between V2 stages, and completely after V3. I could be missing a trigger for it somewhere in the graphic EQ, too, but it doesn't look like that's the case. If the signal issues correspond to the peak light coming on, it would stand to reason that your issue is at or before V3 in the circuit. It could be tubes - those are certainly easy enough to buy replacements for and try out - or it could be a failing component or solder joint somewhere early in the circuit. The first time I had problems with this amp, the techs I took it to did a solder reflow before checking anything else because broken solder joints are apparently so common on these. If the signal issues do not correspond directly to the peak light, you could have two problems, but that seems really unlikely. Give the mute switch a press or two to make sure it's not that, then you can move on to circuit troubleshooting. Good luck!

I did, both for that reason and because my factory nut had one of the strings WAY off alignment. You can use regular Fender preshaped/preslotted nuts for this as long as they're the right width, if that helps. Good luck!

Hello, apologies for not responding sooner but I lost my calipers for a while... Short answer: I have to get used to playing the VI with my fingertips if I don't do it for a while, but changing back and forth once I'm up to speed isn't very difficult. If you're already switching between instruments with different spacings, I don't think you'll have a tough time adding this instrument to your rotation, especially if you're already comfortable with guitar. Numbers to back up that assessment: I just measured the outside string width spacing (so E to e) on the VI at 2.175 inches or so (somewhere around 2 and 3/16" or 55.25mm). The distance *between* the E and A strings at the middle pickup is, for me, .317" or 8.05mm. This is with La Bella 767-6S strings, so a .095 E and a .075 A. For comparison, on my Squier Contemporary Stratocaster, the outside spacing is 2.065" (about 2 and 1/16" or 52.4mm) and about .341" or 8.66mm between the .046 E and .036 A halfway between the pickups. I believe the strat has a narrower string spacing than you'd find on most acoustic guitars, but I don't have a lot of personal experience with acoustics. For comparison to a bass - my Fender Mustang PJ's outside string width at the bridge is 2.315"/58.80mm, with .622"/15.80mm between the .105 E and .85 A strings.

@@nurrwick Perfect response!! Thanks a ton!! Literally everything I needed to know, it's settled!! My next instrument purchase will be this 😄

@@HerroVincey That's great! I think you will enjoy the experience and, even if it's not something you fall head over heels in love with, it should open up new ways of thinking about playing for you. Good luck and have fun!

@@HerroVincey Great question...I just ordered one for this very reason. I'm a fingerstyle guitar player that wants to dig in w some real bass lines!.

Fair enough; I play plenty of full-scale bass and it's not insurmountable, but there are definitely things other musicians have written for the way they play that I just can't reach with my hands being the way they are. It's an important consideration for some folks like me, but not a written-in-stone "you must play short-scale instruments." My February purchase this year was a Caprice bass that I couldn't be happier with, as a thing unto its own, but still gotta be cognizant of right-tool-right-job stuff. That said: I think regular six-string basses (low B high C) are forever out of my comfort zone, though. Even if someone made a shorter scale version, the width of the necks on every current mass-production instrument are more than my index finger can reach everywhere past the second fret. Sure, you can move the thumb and crane back to hit the thick string, but I find that motion uncomfortable on my wrist.

Hey Tracy, glad you found this helpful! This bass became a bit of a project for me as I did some experimentation with it. I have a Seymour Duncan SPB-1/SJB-1 installed right now, which are a very good match to one another but lack a little bit of the top end clarity I expect to hear from my playing. I will probably switch back to the model P/J configuration once I have the energy to order a spare control plate and some mini toggles instead of push/pull control pots. I hate the way they feel, and am not much of a fan of how far they have to stick out when in the out position. I think you'll like the DiMarzio combination, though, even if you only have them in series or parallel modes.

oh and to address it: yes, the stock bridge pickup was pretty awful, you definitely aren't alone in that assessment.

@@nurrwick Have you ever tried push/push pots? They don't stick out so much.

@@nurrwick Haha yeah. I have an Ibanez Talman short scale TMB30, which was sold at the same price point as these when they were new yet the stock PJ pickups on the Ibanez sound good. So go figure. Haha

@@tracyc7813 I had one instrument where I tried them... a Squier Duo-Sonic from the initial Classic Vibe run that I ended up adding some coil-tappable pickups to. I don't know what happened to them after I changed to micro toggles, but you're right - I should give them a try on the bass. I have a short-scale Stingray that has the push/push for the volume "boost" on it and, while I don't like the way turning the knob feels, it's not really much different from how the push/pulls I've used in the past have felt but is a whole lot easier to use without paying attention.

If you have access to a current monitoring device like a kill-a-watt, definitely use it during power up. You should see an inrush spike but current draw at idle should be around .8 amps for a properly configured SVT-3 pro. If you don't have a current monitoring device, order or go buy one at home depot. If you can't swing that, be prepared to immediately throw the switch if you see any evidence of excessive heat, smell anything untoward, or have any signs of smoke at all. I have had that thing apart three times and each reassembly is still a bit like "welp is this gonna be the one that finally stops getting me to try to fix it?" and I'm never sure if I mean that I fixed it or that I broke it beyond repair. Good luck!

The amp stopped misbehaving after this job, yes. My experience was that you could hit the thing and that would make it pop out of buzz back into normal operation for a while, but I guess internal temperature changes caused whatever component was creating the bad ground to flex and move its joint. It works fine now except for picking up a lot of environmental hum from the terrible HVAC dungeon below my office.

@@nurrwick thanks for the reply. I tried banging the top of mine when it buzzes and it stops it temporarily too now.

@@AdamCheong Sounds almost certainly like it's bad solder joints then... that said, I only just noticed (sorry, bad reading comprehension) that you said it's under warranty... if you're not comfortable doing the soldering yourself, definitely feel free to take up the company on the warranty. Fender should be able to send you one that works right.

@@nurrwick I sent them an email about it, so hopefully...

Thanks Chris, hopefully it's easier on you next time you want to do work on it! I know that having been into this one three or four times before I recorded this video helped a lot... and of course, once you start working on guitars, there's a lot of similarity between them, so the experience adds up quickly.

Yeah it was a bit of a struggle but worth it for the knowledge gained. And I find the pickups sound a lot better with the 500k pots.

Awesome! I really like the satisfaction of poking around inside an instrument and then hearing the final product for the first time. It reminds me a little of the old feeling of getting a roll of film back from development. Take care and keep playing!

Uneven bias measurements between the transitors. I had some that were less than 5mV across their resistors while others were approaching 30mV. I don't know if it was the march of time, or if they had always been that poorly matched, but current manufacturing tolerances on the IRFP240 and IRFP9240 meant that the new set I put in were much more closely matched, I think down to within 2mV for the whole set at any given bias pot setting.

oh and the 'issue' I was chasing was crossover distortion. Probably highlighted by the low-quality bias pot shifting in value, and then the correction of it revealing the above problem that warranted evaluation and eventual replacement of the transistors.

I got my Ampeg-specific replacement parts for this amp via fullcompass. I can't find the photos I took of the backs of them installed, but the tube gain should be a 1M pot, and if you can contact FC and give them the part number off the back of it, that is an ampeg part number. I have one of the old EQ pots in front of me, and you'll need the part of the stamped number that goes XX-XXX-XX. This one also has a four digit date code and what I'm guessing is a revision number on the back as well, but those shouldn't be necessary for a service department to identify the right part to send you.

I have mine open again (chasing what i hope to be a bad solder joint in the tube gain circuit) and the part number on the plate voltage/tube gain knob is 70-105-22

they blow out 100% of the time if you park at less than like 10% to 1% taper or less! see my new vid

Thanks! 'Tales' was one of the first albums I bought after I started playing bass way back in 2000, so the music has a special place in my heart and mind.

Agreed; I REALLY like the cobalt flats personally, but they definitely don't quite make it all the way to the top end response of the fat-beams, and probably wouldn't even begin to approach a brighter stainless string. For my ear, though, the cut in finger noise and increased comfort of playing works well on this instrument. A note on why this comparison happened in the first place - I have been wrestling with a fretless stingray for a couple of years and finally got the fingerboard leveled correctly, the neck seated properly, and strung it back up with flats... the set I used was the slinky flat five-string, and I was blown away by how much zing I had access to and how I had finally found a set of strings where notes played on the E string had a similar character to notes played on the A, D, and G, and that the B was even remotely close was the icing on the cake. I actually like playing that instrument for the first time. I did just realize I haven't played these strings at all with the tone knob on this Jag turned down, so it'd be an interesting comparison to see if there's any detectable difference in thump... but considering that these strings should last an eternity, that video isn't coming any time soon.