Hiwatt G100R acting up - no "power" on gain and garbling on clean

21Fretter

Sorry if you guys feel this is a bit spammy, I posted in my previous topic about the amp I was looking to buy/bought but thought a lot might not be giving it a look thinking I am simply posting about the tone/price/foot switch etc.

I've copied from my other topic:

I've run into a problem with the amp. Happily played a show with it on Saturday night, ran like a charm, master and channel volume no louder than 12' o clock each, haven't had any bumps that i can recall with it, been very careful with putting it down softly after carrying etc but suddenly when I turned the amp on at practice today ( the amp was unplayed until today from the show, simply sitting in my lounge), it could barely get any volume on the gain channels, basically bedroom levels at 12' o clock both channels, a lot less gain and the clean like has almost a terrible tremolo to it and had random volume pops/jumps depending on which notes I picked, hard to describe. I used the line out of the amp into my UX1 and I was able to record the clean channel without any of the previous problems I can recall (was a bit of popping but that was because it was clipping, recorded too high/idk, could be part of the problem, seems i had to drop the volume ridiculous amounts to get it to stop hitting the red). Any ideas?

Edit: Did some more recordings, I can definitely record fine which means nothing wrong with preamp and connections? My new description of the clean is like a bunch of farts and distortion is better described as more harsh and digital sounding like one would have when using a line out but forgot to add cab simulation but not AS harsh and digital. Maybe the volume I played at the show managed to rattle one of the speaker connections a bit loose?

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Morning update: I played through the headphone jack this morning, a engineering friend suggested it and I get the same issues. I believe the line out is simply the preamp and the headphone jack is preamp + power amp which is not starting to sound too good?

guidothepimmp

Strange dude, maybe that's the reason the other guy sold.. Time for an amp tech? Really wouldn't know where to start, in 8 years I haven't had 1 single issue with mine and the amp has had heavy use..

That's sad news man.. I love these amps..

21Fretter

guidothepimmp wrote: Strange dude, maybe that's the reason the other guy sold.. Time for an amp tech? Really wouldn't know where to start, in 8 years I haven't had 1 single issue with mine and the amp has had heavy use..

That's sad news man.. I love these amps..

I would hope that people are better than that but you do unfortunately get those few. It was a legitimate shop holding it for him though (JT's Instruments) who apparently gave the internals a look when they first took it in (they held the amp for about a month before I bought it). I'm also unsure of what approach to take, is repairing a solid state often not more of a mission than the value? I highly doubt I have an recourse against the seller either, it is a 2nd hand deal. Let's first try get some guesses as to the issue though because I do have a friend who studied robotics at UCT so he does have electrical experience and said he would be willing to help.

AlanRatcliffe

Sounds to me like it could be a power supply problem (I've had that same problem before and it was just a few dry joints in the power supply section) or possibly something to do with the power amp.

Anything is fixable to someone with the knowledge, the tools and, most importantly, the time. The reason a lot of newer stuff is so expensive to repair is labour is expensive and properly tracking down a problem takes time - so it's quicker and cheaper to replace the whole innards or the whole unit than spending the time to find the specific fault.

21Fretter

The possible problems you described, are they problems that can pop up suddenly or would the seller possibly have known?

AlanRatcliffe

Impossible to say - depends on when they started.

21Fretter

Spoke to the seller, obviously he has never had the problem but he was selling because he hadn't been using it for a good while, might have been there and simply didn't know (who knows). At least we have a rough idea of where the issue might be, can't find any schematics unfortunately but my friend said he would take a look because I don't know if it is worth having a pro look at. Now if I could get the bloody footswitch from him that would also help to offset the costs if we can't get this going again, sigh.........

21Fretter

My friend took a look at the amp and managed to get it working again thankfully. The only worry is that he didn't really "do anything". He said he literally opened it up, looked around and nothing looked out of the norm (he did say there was a transistor of sorts in the heatsink area which did not look seated properly which he put in place). Disconnected the speak and ran the amp through an external speaker (which he said sounded fine) and reconnected everything. Any ideas?

epictring

For now... Don't fix it if it ain't broken ?

Wait till something weird pops up again, maybe your friend's magic fixed her.

guidothepimmp

+1,

Give a right ol jam and see what happens.. Could be that there was dirt or gunk stuck somewhere that dislodged when he opened it?

Really difficult to say.. Hey at least its working and that's the main thing

Nicholas-L

Sounds like a dry joint , which could have caused an intermittent connection. Just my 1c worth. If it's seated properly now then you should have a need for worrying anymore. ? I had a G50R and man that thing ran like a tank.

Norman86

The CPA would have covered you to take it back to the store!!!!

Personally, thats what i would have done!

21Fretter

Unfortunately the problem reared its ugly head again, its intermittent this time though. Need to get it fixed obviously, can't have an unreliable amp. I was with my friend this time when he opened it up, not that I have any experience whatsoever and even know what I am really looking at, and we couldn't see any blown/'bloated' capacitors, blackened components etc. Nothing looks out of place, soldering still looks good and shiny. The only thing that stood out was this (http://imgur.com/a/HPDP7 - two pictures, one of the power section and one of the only component that looks out of place). Firstly, do you guys have an idea what component it is? The label on the PCB is RT1. My friends says he thinks the component should be in that little hole on the heatsink, not sure what it does though and it looks like it is covered with thermal paste.

Ideas?

AlanRatcliffe

21Fretter wrote: Firstly, do you guys have an idea what component it is? The label on the PCB is RT1. My friends says he thinks the component should be in that little hole on the heatsink, not sure what it does though and it looks like it is covered with thermal paste.

I'm not sure what it is, but it looks like it should be in the hole (same as the part labelled QB, between the two driver transistors in the middle of the heatsink). If there is a hole in the heatsink and both the hole and the component have thermal paste on, I'd say it's pretty much a no-brainer. And if it's a part that gets so hot it needs heatsinking, then it is likely to cause problems when it is not.

Someone probably had the heatsink off for other repairs and missed getting the part back in place when they reassembled.

That's best guess at the moment. But if you get it back where it should be, then you might have to resort to a qualified tech to investigate further.