Blackstar HT-100 volume/power issue?

Discussion - HT Venue amplifiers. Inspiration from Studio to Stage.
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twilliam
Posts: 2
Joined: Fri Sep 13, 2013 5:50 pm

Wed Sep 18, 2013 11:48 am

Hello all,

Hoping for some help/advice regarding a slight conundrum with my Blackstar HT-100 amp head. Already taken it to a tech who has found no issues, tested all the tubes and apparently all OK. Had to part with £20 for this… not that it’s an extortionate amount of money, but it’s a little disappointing paying for someone to tell me there is nothing wrong with my amp! Ah well, such is life. After getting my amp back, it turned out that said conundrum was still there. So, before I take it back to Mr Tech, I’d be interested to know if anyone else has had the same problem.

I guess it would help if I told you what issue I’m having. I bought the amp new just over a year ago, and it gets relatively light use – I never have the volume past about 10 o’clock. The last few weeks, about an hour after I start playing, the volume starts popping in and out (like a dodgy cable might sound if you wiggled it) and eventually it just goes so quiet that it may as well not be on. Only on the overdrive channels though – the clean channel is fine! I can still get overdrive if I use one of my Boss pedals on the clean channel, but I rather like the warm tubey overdrive on the Blackstar so, although a good quick fix, I refuse to accept it as a permanent solution. Plus, my amp is clearly broken and needs fixing.

I have tried everything I can to eliminate the possibility that it could be anything else malfunctioning. I thought it could have been my guitar (the jack or pots) but I get the same result if I unplug from the guitar and touch the jack - distorted, broken up sound with sharp fluctuations in volume. If I do the same on the clean channel, it’s a constant noise, as you would expect. I’ve tried taking my pedals out from the effects loop – no change. I accused my (admittedly rather old) 2x12 cab of finally showing signs of death, but after trying different leads and a different cab, still no change! There is nothing wrong with the pots on the amp either, but even with the volume off on my guitar I occasionally hear a weird scraping/popping, like you would hear if the pots were bad! I don’t understand.

I would appreciate it if you could throw some ideas around about what this might be, and if there’s anything else I can do to troubleshoot the issue further. Many thanks in advance!

Stiggie_9
Posts: 77
Joined: Mon Jun 14, 2010 12:00 am
Location: NW England

Wed Sep 18, 2013 12:41 pm

Hi. The fact that your probem doesn't seem to be there when the amp's cold, but only appears after an hour or so when it's thoroughly warmed up, might be a clue to what's going on. It could be that there's a bad connection somewhere in the amp - a bad or cracked solder joint, or a dirty or dodgy connector - that's fine when it's cold but eventually opens up with heat.

I'd start with the valve bases, as they're closest to the most obvious sources of heat, the valves themselves. After that, it's probably a case of working your way round the circuit boards with an insulated 'prodder' (a wooden chopstick or bamboo skewer is good), gently pushing and tapping connectors and components until you get similar sounds to the problem you're experiencing. The issue affects only the overdrive channels of the amp so you're probably best looking in areas of the circuit that are only involved in the signal path when those channels are selected.

One other thing you might look at: the front panel pots. You mentioned in your post that you think they're all ok - how do you know for sure? The reason I ask is that I had a problem with my Stage 60 when it was fairly new where a faulty Presence pot caused a strange crackling/break-up noise from time to time - but only when the amp was thoroughly warmed up and when I played specific notes (there must have been some resonance effect coming into play). Blackstar kindly sent me a replacement pot, which I fitted myself, and the problem was sorted.

Obviously any exploratory work you do inside the amp is going to have to be done with the amp opened up and switched on, so if you're not experienced in delving around inside valve amps and working around the high voltages they contain, don't even think of trying it yourself!

Hope it's of some help, anyway. It's probably worth giving Blackstar themselves a call - they're usually very heplful over the phone, I believe.

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MikeD
Posts: 78
Joined: Fri Sep 16, 2011 12:00 am
Location: Sweden

Wed Sep 18, 2013 2:36 pm

Like the man said..."if you don´t know hwat your doing...don´t"....theres enough ampage stored away in there to give you a really good shock....not worth 20 pounds

http://www.youtube.com/watch?v=Vv2tQYl3 ... SRy3vtIHoY

and my other tip.....next time it happens, grab you smartphone and film it.....then you have something to show your amp Tech and hopefully he will recognize the fault......and if he´s any good he should realize he missed something first time around and hopefully won´t charge you cause of his mistakes ;-).....or just send the video to the guys at blackstar and they might have some answers

//Mike

twilliam
Posts: 2
Joined: Fri Sep 13, 2013 5:50 pm

Sat Oct 12, 2013 12:24 pm

Thanks for the advice. I think I can pretty much confirm that it is a circuit board issue, as the most recent problem I'm having is the amp deciding to turn reverb on all by itself! Again, it only seems to be happening after about an hour of playing. I suspect that the amp is getting too hot and something is then touching something it shouldn't. I noticed when I turned it off and we packed away after last rehearsal that the metal vent plates on the top were scorching hot... I expect some sort of heat off them, but they were seriously hot, is that normal?! Going to take it back to dealer at some point soon when I have time, as I think this might be something Blackstar need to take a look at.

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