Marshall Avt150H

[Dennyps4]

The Mica washers are still there. Definitely looks like, a tried and gave up job, is also missing the input jack. Maybe frustrated and threw it? My school of thought on the paste, from rebuilding and building custom laptops and computers, (CPU"S), is that any over abundance of thermal compound, actually causes more heat than it dissipates. I've used artic silver forever and always applied just enough, with a razor blade, to apply a thin layer between the chip and the heat sink,to maximize the effectiveness of the sink. I have then overclocked the chips with no issues. Not the case with these IC's? I have probably have a 100 of those fans, so that's good. I just find it hard to accept that if this is such an abundant issue, why hasn't the chip been revised or replaced by one with better durability? These amps seem to be that of a, "throw away", and the chip is probably that way, on purpose. I know one thing, I will never buy another solid state, ic, based amp again. Now I know why a lot of techs, wont touch these mass produced amps. I have a old Gateway 2000 motherboard that is better than this, sorry excuse for a pcb. Makes me sad, that this is where technology has gone. Although job security, for techs.

[Dennyps4]

Thanks, ENZO, don't ever get the impression that I'm not listening to you. I have just had WAY too much time to think about stuff, being stuck at home. Lol I have yet, to meet a more competent tech online, I have read a lot of your posts, and think you do great job, all for not. Glad to see someone that is not all about the almighty dollar, willing to teach people. You're a dying breed.

[Dennyps4]

Thanks Enzo, you have great insight, (and the rest of you on here). I have WAY too much time to think and analyze crap. I admire you're willingness to help people with such mediocre equipment. I have read many of your posts. Most techs wouldn't give you the time of day. Where I'm from, you'd hard pressed to find someone that will even look at one of these cookie cutter amps. I will get some work done, before I bother you guys again. You're a dying breed.

[acorkos]

Why is this particular amp so fragile? I have seen all kinds of issues, from researching, with the power section, it seems.

my opinion....a 100 or 150 watt solid state amp, even when played through a 4x12 (100-watt marshall half stack...every young wanker's dream), doesn't have the punch required to hang in a live band setting. the young owner can't figure out why he can't hear himself over the gorilla drummer's crash cymbals and the 2nd guitarist's 40 watt hot rod deluxe...so he cranks it up to maximum volume, maybe even pushing the front end with a metal zone...it's a matter of time before he fries the output transistors.

i think you need 300-400+ watts from a solid state amp to keep it running cool enough to avoid frying at rock band levels. anything less realistically limits the amp to recording or bedroom practice purposes. or micing it and using sound reinforcement to bring up the volume to "competitive" levels...but doing that would mean your 100-watt marshall half stack is inadequate...oh, the shame

[Ronsonic]

IMO the problem is they used the TDA instead of an LM3886. You can blow up the 3886, too, but it's a lot better protected. The 7293 seems to survive pretty well in self contained gear, powered monitors and the like, but does less well exposed to the elements.

There are bazillions of those amps out there and they're sold to a market segment that's particularly rough on gear, so I wouldn't say the failure rate is all that disproportionate.

Enzo made some good trouble-shooting points. Check. Also, and this is guitar amp T/S 101, suspect FX loop jacks.

[Dennyps4]

I'm with you that's why I have a Rivera. Thing is built like sherman tank. I can't even pick it up anymore. Someone said that this Avt was heavy, I laughed when I picked it up, the only thing heavy is the transformer. I just can't believe Marshall makes such junk, the kids are better off with an old JCM 800, with a Metal Zone in front of it. Blah, but still better. It's all about making a buck, no one cares about craftsmanship and reliability. That's the ugly side of technology.

[Dennyps4]

Thanks ENZO, for being so helpful and willing to spare your time and knowledge. You guys are the best techs I've ever come across online. I appreciate that very much.

[acorkos]

...the kids are better off with an old JCM 800, with a Metal Zone in front of it.

unfortunately, dad (with his credit card) usually wants a warranty. and a decent 100 watt tube head costs 3x what a solid state head does ("but son, this one is a hundred watts, too, and it's a lot cheaper").

[Dennyps4]

Bulb Tester

Well, I made my bulb tester and checked the amp, w/out power section, and all is well. I'll post pics tonight, when I test the effects loop with my, Mosvalve 1500, which is undeniably the best solid state power amp ever, IMO. Once you mod the torridial tranny, to stay put, anyway. Marshall should take notes. LOL I ran the amp for about and hour with the bulb in line, to reform the caps, etc.. and no blown fuses. The circuit itself is pretty stable. Until then.......

[Dennyps4]

Here's the pic of the dim bulb tester. Pretty Cool. You can see the filament do the hula.