Amplifiers that are a total pain in the arse to repair and reason(s) why ?

Telejester

The Peavey Classic 30 combo......( Retch )

Who in their infinite wisdom came up with that ridiculous folding circuit board that breaks connecting pins if you even stare at it . stupid idea of the century and no wonder amp techs despise them.

What others are out there and why ?

Danny1969

Engl Savage 120 .... crap PCB held on by plastic standoffs and getting at it properly involves desolding a whole bunch of wires that are direct to board rather than unplug-able .... there are other reasons it was a pain in the arse ...   it's  the hardest valve amp I've ever worked on  

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 ... 

martinw

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.

 

ICBM

Mentioned already in another thread, but Laneys are usually an absolute pig - for the simple reason that they seem incapable of making a chassis that fits the cabinet, using decent cabinet covering or gluing it down properly - with the result that it snags on the chassis on the way in and out, and it's difficult to get the screws to go back into their holes properly. It sounds like a trivial complaint, but wait until you've serviced a few and see if you think so… it can easily double or triple the time it would normally take to dismantle and reassemble one.

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.

Telejester

Engl inclusion surprises me, I thought German,efficiency, bmw, no sense of humour and all that. Sonically I think they stink, the sounds the Powerball farts out, dear oh dear.

DJH83004

Have to agree with previous, Peacemakers, 20, 40 & 60 (smaller ones are the worst) as per ICBM, but great amps IMHO. Mesa through-plated PCBs can be awkward at times and I had a pain the other day with a JCM2000 DSL 410, just getting to access to re-solder the input jack. Never worked on an Ultra Twin, but will give a wide birth! The worst for me personally was a Trace Elliot 715X bass combo,  class D with switch mode PSU, even if you are lucky enough to replace the PSU Mosfets and it holds together, getting to the Class D amp section, is impossible as it is sandwiched between the underside of the main PCB and the heatsink, with 20 or so SMT components to remove - one for the scrap bin!       

jpfamps

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.

ICBM

DJH83004 said:

The worst for me personally was a Trace Elliot 715X bass combo,  class D with switch mode PSU, even if you are lucky enough to replace the PSU Mosfets and it holds together, getting to the Class D amp section, is impossible as it is sandwiched between the underside of the main PCB and the heatsink, with 20 or so SMT components to remove - one for the scrap bin!       

Yes, that whole series is a nightmare. A while ago a practice studio gave me four dead ones, and by simply treating them as modular assemblies I managed to make two working ones. The rest of them was scrap, it's just too big a job to get at them at component level, and you have the usual SMPS/Class D problem that usually the only safe way of fixing them is to replace all the active devices, then turn on and pray it works...

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.

jpfamps

ICBM said:

DJH83004 said:

The worst for me personally was a Trace Elliot 715X bass combo,  class D with switch mode PSU, even if you are lucky enough to replace the PSU Mosfets and it holds together, getting to the Class D amp section, is impossible as it is sandwiched between the underside of the main PCB and the heatsink, with 20 or so SMT components to remove - one for the scrap bin!       

Yes, that whole series is a nightmare. A while ago a practice studio gave me four dead ones, and by simply treating them as modular assemblies I managed to make two working ones. The rest of them was scrap, it's just too big a job to get at them at component level, and you have the usual SMPS/Class D problem that usually the only safe way of fixing them is to replace all the active devices, then turn on and pray it works...

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.

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.

ICBM

jpfamps said:

My favourite amps to work on are 60s and 70s Fenders.

I actually don't really like these any more - they're often filthy, ratty and much-bodged basket cases that need so much work to make them really good again that it's difficult to charge enough, especially as if they have the board-conductivity problem they can be really very time-consuming and frustrating. Or maybe that's just a feature of the Scottish climate .

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.

jpfamps said:

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.

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.

DJH83004

I do agree about the Peacemakers, but I have a soft spot for them being UK designed and built in the UK by Clive Button and co. I also enjoy working on '60s / 70s Fenders and Marshalls also, in fact anything that has been designed with repair and service in mind. Though I currently have a Roland GR300 synth and guitar in for service, and I cant get a decent sound out of it 

ICBM

DJH83004 said:

I do agree about the Peacemakers, but I have a soft spot for them being UK designed and built in the UK by Clive Button and co.

Not a fan, sorry. There are far too many problems with too many amps that came out of that design school.

DJH83004 said:

I currently have a Roland GR300 synth and guitar in for service, and I cant get a decent sound out of it 

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.

Misty

How are the latest Fenders for quality and ease of repair, specifically the '68 Princeton, and Vibrolux? (Not the Custom Vibrolux Reverb, the newer one). 

DJH83004

ICBM said:

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.

Totally agree about the multi-pin connectors, I thought for once I'd have a bit of kit in that nobody had worked on before - should have known better  

jpfamps

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.

jpfamps

Misty said:

How are the latest Fenders for quality and ease of repair, specifically the '68 Princeton, and Vibrolux? (Not the Custom Vibrolux Reverb, the newer one). 

Fine.

Removing the PCB is straight forward.

jpfamps

Actually thinking about it the first version of the "pro series" channel switching Twin is a total sod.

ThorpyFX

How are mesas to work on? I've heard they won't release schematics and looking in my mark V it seems massively cramped indeed. 

Telejester

The early jcm800 heads were a cinch to work on as the PCB wasn't really that populated with componentry and wasn't this an example of using your head and making great amps at the same time. Some of those mesas by comparison are like the wopr in the wargames movie.

Voxman

Not being a techy I have no clue from an amp tech perspective of which amps are good and bad to work on - but reading these posts I was curious as to what amps you guys think are well built, well designed and easy to work on?  

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?

ToneControl

The chap who used to fix my amps told me that he once met Jim Marshall, and thanked him for providing him with a  continuous income (i.e. because there were so many faulty Marshall amps brought in to him for repair)