DGBass

EVO III and EVO IV heads have a speaker fuse on a small auxilliary circuit board beneath the back board for the send/return / footswitch sockets. I've seen this a few times on EVO III in particular where the output fuse works loose or the fuse clip looses tension causing no output. Or it might have blown but you'd need to be going some for that to happen. Earlier models had a T12A fuse ( 575 watt versions ) later models seem to have a smaller T10A fuse, 20mm type. From the pic the amp looks about six years old so I wouldn't expect fuses to be working loose at that age. If you hear absolutely nothing from the speakers with a bass plugged in and power on, and I mean absolutely nothing then good chance its something on the output. As the red pen says, the heatsinks are live so don't get fingers anywhere near them even when switched off! You can also check the pre-amp by making sure the meter registers if you cranck the input and if you have another combo or amp, run a cable from the line/tuner out to the other amp and make sure signal is going through the pre-amp section. Pic below shows roughly where the speaker fuse is located on most models, on EVO IV its usually on the back board assembly which tricky getting access to as it usually means loosning the transformer and the rear back board nuts and screws. Worth making sure there are no loose wires either.

That sort of rules out the tube input and a potentially worn tube as that part sits in front of the green channel. Series 6 GP12 pre-amps are pretty solid and most things i've come across with them are usually age/wear issues with stuff like input jack contacts/ dry solder joints on the front board or occasionally some components failures after a long time. These amps are getting on for thirty years old so a few issues are to be expected. The graphic/pre-shape circuit is solid state switching, a couple of transistors and IC chips. Later SMX heads went back to physical relays instead of ICs. Each have good points and bad points for reliability. It could be just worn buttons or a dodgy transistor in the switching circuit but to be honest without getting the amp up on a bench to test, its just guess work. A VA400 is definitely an amp worth repairing so unless its been in and out of a tech shop costing you tons of money to keep it going, I'd keep it and see if you can find a local tech to check it over for you. Some folks on this forum have mentioned Ashdown might look at a Trace Elliot repair and if your in Essex, Heybridge might not be too far to travel and get your VA400 checked out by them. Worth a phone call I would say. 🙂 For the record, I haven't come across buzzing from the pre-shape/graphic on a Series 6 GP12 other than the actual press in switches being worn out. That usually just causes issues actually switching on/off not random hum noises.

Is the short hum present when using both the valve pre-amp input ( RED ) and the standard pre-amp input ( GREEN ) or does the symptom change when using either input with the shape/graphic buttons? Also are you using the front buttons or a footswitch to activate the shape/graphic?

not wanting to stoke anyones GAS, I did something similar, although the Polar White lefty Player P-Bass doesn't come as standard with a maple neck so was a retrofit with a genuine Fender replacement. Stock pickguard changed from white to black as well. The one thing I found was unlike fenders of old which seemed to have neck pockets cut in varying degrees of accuracy, the modern player bodies and necks seem to be a very snug fit. It needed a gentle amount of persuasion to install and once the screws were gently tightened up, its one of the best Fender neck/body fits i've ever experienced. The neck was perfectly true and even with the stock bridge, the string and neck alignment is excellent. The satin finish on the back of the maple neck is super smooth as well and a joy to play. It's also much slimmer than my USA standard bass.

Ashdown do say that its not a class-D design.The big cooling fan on the rear panel is a giveaway as it looks overkill for an ICE module. Would be nice if the fan is thermostaically controlled in keeping with its Studio badge. The blurb also goes on at some length to state that the studio mini is repairable down to component level so fingers crossed no SMD's and no SMPS. A bit of quality and forethought in a design always pays off at the end of the day. Nice one Ashdown. Quite pricey though but i'm sure street prices will kick in eventually.

100 guage Fender stainless flats on my Fender Americal Standard. I find them very smooth to play and apart from a spell using Ernie Ball Cobalt flats ( same guage ), the only rounds that have been on my Jazz since new were the factory set it came with back in 2012. Always been flats since. A major pro for me is flats seem much easier on the frets and are also easier on the fingers. They last a long time and seem to get better sounding the older they get. The Fender flats also don't tarnish like the Slinky Cobalts do.

'Very quiet Trace Elliot' is not something i've come across before in my experience with this brand of amplifier. It's usually a good sign that something is not quite right! It's been mentioned that plugging direct into the return jack (on the rear panel should bypass the pre-amp) and let you test the power amp. If its still quiet and your bass and lead are good then something is wrong in the power amp section. I've never come across a quiet power amp in a Trace, usually they either work or don't. If its loud testing from the return jack then its likely to be a pre-amp issue. The SMX front end is usually pretty robust. The pre-amp will still work fine with the valve blend fully anticlockwise even if the valve was dead. SM and SMX pre-amps do have a few common issues though, again in my experience. The standy button can develop intermittent issues and most of the knobs on the front panels will wear and go crackly or cause drop outs after many years of service. It's a full stereo pre-amp and most of the pots are dual gang types and can cause bizarre intermittent issues when they are worn. The master volume control is particularly prone to this as its dual gang type. GP12 SMX pre-amps are about as complex as old TE front ends come so if you aren't confident popping one open for a look its probably a good time to seek tech help. Regarding the speaker, if the amp was working ok before the new one was fitted, its worth checking the wiring is ok and polarity is correct. Even better, using a test meter to measure the speaker resistance ( while unplugged ) will tell you if its good.

Thought i'd just post a note to say what transpired with my porthole cab refurbishment. It's taken a while to get everything together and as always testing and making adjustments does involve time when its something non standard. Unfortunately the original 38 year old Fane Sovereign Pro 15-250 driver failed after three rehearshals after developing some voice call rub. Spending a decade in a damp garage and then a few weeks in a warm dry indoors environment seemed to have distorted the cone. However, I had a spare woofer boxed in the cupboard as all well prepared bass players have. It now has the spare 8 ohm Faital Pro driver I bought a few years ago. Some fine tuning with my internal volume calculations brought the tuning frequency as near as can be to about 50Hz which seems to be fairly standard for a mid nineteen eighties cab. Lined with 3/4 inch dacron the cab sounds well damped and the big 15 PR 400 doesn't seem to complain at all no matter what I throw at it. Everything sounds crisp and clear to me. Pick playing especially sounds good and thats not usually my bag. The original TE grille was re-mounted with new rubber pads, and a new speaker jack plate fitted with combi speakons. It's approx 19kg all in and lighter and smaller than my MM cab so its very likely to get a bit of use soon. It's not perfect but the cab was donated free and the spare driver was already paid for. Mostly it was just a little cosmetics cost required to get it to where it is. It's good enough to gig now and only needed a minimal amount of science to understand the cab design. For the most part it was finalized with some old fashioned listening time 🙂

Band not gigging at present due to band member health issues and rehearshals are also infrequent. The opportunity for some rehearshal studio shake down time was too good to pass up today. If I was gigging this weekend, I'd be using this lot of bass noise making stuff.

Bought a Boss synth pedal from Gaz and has been a perfect fuss-free purchase. Friendly comms, quick delivery and well packaged item. Many thanks Gaz, you are a top basschatter.

The first bass is reminiscent of KAY branded medium scale basses which were fairly common in the 1970s and even into the early 1980s. There used to be a pawn shop /music store I recall in the east end of Glasgow in the late 70s called Golumb's. That was when you could actually still come across a genuine pawn shop bargain. They sold all manner of new Kay design guitars and basses alongside pawned p-basses. jazz basses and even gibson RD basses and the like etc. The Kay stuff always seemd to have quite thin bodies and seemed flimsy to me but lots of people used them as they were inexpensive, cheerful, and actually quite playable. No idea what that second bass is.

Most folks of a certain age have probably played through a Peavey at some point in their gigging career. They were prolific from the late seventies, eighties and a part of the nineties and dependable gigging amps imho. My only 2 ohm load version was a MK VIII bass head. I ran that into a 4 ohm 115BW and a 4 ohm TVX 410. 600 watts it said on the rear panel at 2 ohms and it did feel alot when wound up. Never had a single bit of trouble with it. I did own a MK III 150 watt head until recently and that too was completely trouble free ownership although i'm sure that was a minimum 4 ohm load. Mostly the bigger wattage heads from around 250 watts up ( BH400 power module) seem to be labelled as being able to run at 2 ohms.

These might help. EV mention a specific response for a 3.2cu ft TL606 enclosure and that can't be far of the mark if i recall the size of my old Mesa/Boogie Diesel 1x15 cab. The power rating on that cab was 400watts @ 8 ohms for what that is worth. There may have been a 200 watt version as well.

There are always options. Just saying I can't find any commercially available rack case that weighs 2.5kg. Even with a 5kg rack case, you would in theory only be adding an extra 2.5kg over your ideal 2.5kg CF case. Thats about the combined weight of the front and back lids on a typical 3U or 4U case so if you were prepared to use the rack without the lids that would get you to within 0.5kg of your target weight. I've seen plenty players over the years use open rack cases with no front or back as its more about the convenience of having the kit in one box, in effect just like an amp sleeve. The kit still has some protection from the main part of the case and theres some weight saving by not having the front and rear lids on it. A comercially available nylon padded case might also get you down to about 4kg which would be 1.5kg over your target 2.5 kg weight. I've always found the best approach to having a lightweight rack system is to start with the rack of choice and then fill it with lightweight stuff.

I would think a 12kg SVT 3Pro would negate any real notion of saving substantial weight once installed in any rack case. A couple of kg won't feel a lot but I suspect the dent in your wallet for a full 3U carbon fibre case if there is such a thing that weighs only 2.5kg would be a lot more painful to carry! Actually, an SVT7 pro only weighs around 7kg, thats a 5kg lighter option if fitted in a decent polycarbonate or Aluminium case 🙂 I did have a look for CF cases ( ECS make them as well as composite versions), and also injection moulded types as alternatives but couldn't find off the shelf CF stuff and the injection molded cases were around twice the weight of conventional cases. ECS make a 4U composite case but it weighs 21kg. I am super interested to see if anyone on BC can find what you are looking for. I suspect though it doesnt exist (yet!) and if it does, it will be eyewateringly expensive in comparison with AL or Poly cases.

Been using one of these for a good few years now and find it works with just about any amp I care to use. It works especially well where thers a tube in the amplifiers pre-amp. I initially bought it to use as a limiter but soon realised it can also do a very subtle compression that keeps the signal tight and under control without killing natural sustain. The enhance knob can also add a subtle crispness to the top end without it getting fizzy. Great all round pedal and I always have it last in the chain before the amp.

I probably ( definitely ) don't need another ABM but this one caught my eye recently. Apart from the current 750 EVO 5, i've never seen a Blackface ABM500 head before. I do remember years ago seeing a Whiteface Special Edition version but not the darker variant. Its basically EV0 III internal gubbins from what I can see and has a normal ice blue rear end. S/N 3585. Had had a hard life when I got it. It's been fully restored and all working well and sounding just like umm...an ABM. I never thought i'd like the dark finish but its grown on me. Curious if any BC users have a Blackface or Whiteface special edition ABM, are still using it and can share any history of these editions?

I will say diagnosing an issue without actually having the amp on a bench is always tricky. Expect the unexpected, especially if the amp is still working after a fashion. It will though be interesting to see if you can spot anything from a photo. There are a lot of high voltage caps in the SVT7 pro so be very careful when the lid is off not to touch or short anything and make sure it isn't plugged in 😬

Agreed, and sure I mentioned that when reffering to the driver chip circuit caps of potentially the value on the burnt remains of the component in the picture. C25 on the power board looks the most likely possibility to me, its a de-coupling cap and sits on its own between two parts of the amplifier. If it blew i'm sure the amp would still work as the driver circuits each have independent voltage feeds. As the cap would be gone, any harmful voltage wouldn't get anywhere else, you would more than likely just loose the de-coupling effect which might increase background noise rather than total amp failure. I'm pretty sure its not the pre-amp as I don't see any component value with a 47 or 25 on it. It's forum diagnosis at its best or worst if you like. The only way to know for sure would be to pop the hood and start taking high res photos of the SVT7 Pro mainboard. I don't recall coming across an amp guts reference library thread here on BC? Happy to attach schematics if you fancy a look at them🙂

Just for info, I had a look at the SVT7 Pro SMPS power board schematic and there are a few possibilities on it for similar spec caps as well. It's the age old issue of trying to figure out whats wrong from a forum post and the SVT7 Pro is also fairly complex bit of kit anyway. A Tech and some bench time are probably the best option when it comes down to it if you have an amp problem. I wouldn't write off class D, I've used Markbass kit as an example regularly and it was very impressive and reliable in my experience.

It's definitely the remnant of an electrolytic capacitor. Difficult to tell the rating but I can make out a 47uf or maybe 0.47uf rating and maybe 25V or 250V voltage rating. There isn't anything anywhere near those ratings on the pre-amp schematic. On the power amp schematic there are a few possibilities C141 0.47 250V C173 0.47 250V C25 47uf 25V I'm not familiar enough with these amps ( class D design possibly as it uses a pair of IRS209555 driver chips ). Whatever happened to the suspect cap, it must have let go in a spectactular fashion as the pressure cap is completely gone as are the leads that connected it to the board. Odds on if it came from your amp, there will be a couple of stubby wires protruding from the board somewhere. C25 looks the most likely candidate as the other caps C141 and C173 are integral to the driver chip circuits and i'm guessing the amp might not work at all if those failed. Class D amps by design require noise filtering because of the high frequencys involved in their workings. I know its probably not helpful but if I was to venture into non full blown tube SVT territory, I'd plump for the tube pre-amp class A/B power amp SVT3 Pro and give the class D SVT7 Pro a wide berth. I'm sure the SVT7 Pro is a capable enough amp, and a good replacement might be just what you are after. If its going back to where it came from at least you'll have an option to think about a replacement amp whether thats Ampeg or something else.

Sometimes the rig of choice for the weekend is the only rig available. An impromptu jam/gig at a friends party/barbecue saturday evening happened at his garden studio for the barbecue attendees. I once owned the ABM400 410H he now uses in the studio. It's changed hands over the last few years amongst the local bass playing population and has found its forte as a studio amp that doesn't get carted around anymore. Probably a good thing as it weighs about the same as a small elephant. Forgot how good the old school mosfet powered Ashdown ABM400's sound. Silky smooth tones with a hint of sparkle from the tube pre-amp and a very useable sub octaver.

Wise words from the BC community and would be first thing I would check. They don't always have a big obvious EV label on the back but should have a stamp of some type, often with a traceable OEM code. Like the TL606 cabs, the speaker chassis is fairly heavyweight. I played one of these for some years and it was the first decent cab I used my ABM's with. Must admit it never lacked delivering low end in anyway, if anything I had to moderate the amount of bottom end. It was one of the few cabs I've used that never complained or struggled with lots of bass. It was also one of the cabs I wished i'd never sold 😐

The mosfet version power boards in these early ABM's are prone to failure if the caps are past sell by date which is usually around 20-25 years with regular use. There's usually a bit of smoke and charring if they do and for some peculiar reason it's the mosfets on the left side( from front) that usually fail. As the good folks at Ashdown will tell you, it's best to replace all six mosfets if you have a failure as well as the four coupling caps. It might be easier asking if they would sell you a current pre-built APC033 (issue 4) modern Bi Polar power board as a drop in replacement. It may be cheaper than getting a tech to rebuild the original board for you. Of course thats if the power board is the issue 🤔 Had the caps fail on one I owned and elected to rebuild. It was messy but worked out in the end. scorched board caused by two shorted caps finished board