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Base theme by DesignModo & ported to Powered by Vanilla by Chris Ireland, modified by the "theFB" team.
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I've worked on more badly designed solid state amps than I can list, most of them built using IC output stages originally designed for general home stereo light usage ...
The more modern Ampeg SVT bass amp.
Firstly it's F. heavy. Never managed to wok on one without hurting my dodgy back.
Then there's the separate preamp and power amp, making getting it out of the box a palava.
Then there's the 6 expensive output valves, mounted on a double layer PCB so it's nigh on impossible to get at the back of the valve sockets to measure anything.
There's the 'protection' system that shuts the amp down if it detects a bias imbalance, but doesn't tell you where the problem is, so you can't find it.
Finally there's the fact that every one I've had in doesn't match fully any of the available schematics.
Finally, it's clear it's been designed by someone who doesn't really understand valve amps. Lots of little things that could be so much better at no cost and with a bit of thought.
There are ways round all of the above, but they're a mess to work on. And it's not like they're reliable.
I agree with Telejester about the Peavey C30 - just a poorly-designed and built amp, unworthy of Peavey - and Danny about Engls - not just the Savage - neither as well-made nor as easily worked on as their 'German engineering' would lead you to expect.
Ashdown Peacemaker (Partsmaker) and Fallen Angel (Failing Angel) are another couple - a huge amount of dismantling of stuff you shouldn't have to, just to get into the thing. One of them needs the reverb tank taken out and the speaker baffle loosened and tilted forward just to get the chassis out… can't remember which one but they're both nearly as bad.
But the worst ever has to be the Behringer Ultra Twin - the first and so far the only amp I've ever worked on that *cannot* be got into to repair and then put back together - the screws that hold the front panel boards in are hidden under the glued-on panel front, which can only be removed if you accept destroying it in the process. Hence the amp was a write-off for one broken pot.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I would generally concur with most of the above, although I would never describe an Ashdown Peacemaker as a great amp......
Remarkably even ENGL couldn't supply me with an accurate schematic for the Savage 120. For most repairs this would not be a problem, however I once had the job of unmodding an eBay purchase back to the original circuit......
ENGLs generally aren't my favourite as often the OT is mounted on the PCB, which makes dissembling the amp "interesting".
The main issue is of course cost; if you are working on a high value item then you can charge for the extra time the repair takes due to the total lack of consideration the manufacturer has given to the possibility of their product needing a repair.
Thus, I would never complain about working on SVTs!
The worst amps are essentially inexpensive overly complicated amps. The Fender Frontman series are pretty bad as they have an overly complex output stage (why?), and the mute circuit actually turns off the input stage to the power amp by switching off the current source on the tail of the diff amp.
I've had several of these in that would either show weird oscillations or randomly latch up, which no obvious remedy other than disabling the mute circuit.
The Peavey Classic 30 is a known weakener, although I don't mind working on these that much. The Valvekings are a pain though.
My favourite amps to work on are 60s and 70s Fenders.
The older ones are relatively repairable though.
Did I mention Marshall MG-DFX/AVT/Mode Four yet? Easy to get into and replace the parts - almost always the fan-cooled power modules - but risky, since they have a habit of just coming back again… sometimes within the repair warranty period so you end up doing it again for nothing. I won't work on them any more unless the fault is definitely not related to the power section.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I had my first ever Mode 4 in a couple of weeks ago.
It certainly fulfils my overly complicated inexpensive amp criterion.
This had a fault in the channel switching that was "interesting" to diagnose, but turned out to be a permanently shorted switch. Both the fans had died too, but fortunately (and surprisingly) the power modules hadn't.
A 350W SS amp based on 4 integrated power amp chips is a disaster waiting to happen.
Some of my favourites to work on are the 70s Traynors which are similar, but actually much higher-quality and don't suffer from the same problems. On the other hand modern Traynors are a nightmare… horrible construction from an access point of view.
You're braver than me if you would even look at it. I simply won't now, on the offchance that the power chips decide to catch fire after I've done something to it, whether or not it was anything to do with the work I did. I've only seen three of them I think, but they were all completely fried. I suggested the owners sent them back to Marshall and then sold them as soon as they came back.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Ah, those are brilliant! I recently had one to service… it was 'interesting' considering that when I got it, only one string was making any sound and even that was all wrong. Most of the problems were in the ludicrously huge multi-pin connectors on the cable, of course - once I'd got that sorted out it all more or less became obvious.
The actual sounds and tracking are miles ahead of any of the later ones with the GK pickup. The biggest problem is that when you do get a great sound, there's no way of storing it other than writing down the settings, so changing sounds is not for the fainthearted.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I've had a couple of GR300s in.
They are an amazing piece of engineering really, although sonically it was not to my taste.....
The connector is an issue as it was bespoke for that unit, and not an off-the-shelf item. Fortunately I've only ever had to resolder one rather than trying to swap it out for a more sensible unit.
The last one I had was all working accept you couldn't tune the D string.
Removing the PCB is straight forward.
Actually thinking about it the first version of the "pro series" channel switching Twin is a total sod.
Also, I was just curious. If a customer brings in an amp that you know is going to be awkward to work on (Laney perhaps!) and take three times the time, do you quote three times the cost, or charge just a bit more, or just accept that some amps take longer than others and base charges on a set scale linked to what the fault is on a 'swings/roundabouts' basis?