#1
Hi

I'm looking for advice to do with my probably broken amp. It's a Blackstar HT20 which I've had for around three years (not sure of exact length of time so I don't know if warranty covers it). Two months ago it started playing up - severe crackling and drop in sound on both channels. Soon after it died completely, no sound whatsoever from any channel, regardless of cable, instrument, different wall sockets, volume, etc.

Unfortunately I only had time to take it to my local shop last week due to exams, and I spoke to the tech who generally has no idea what's wrong. It's not a valve issue however (I know it's not a real valve amp but I still checked to ensure this wasn't causing the problem). Only thoughts are that a transformer might have gone in there somewhere.

Any suggestions? I'm afraid that fixing it might be more expensive than the amp is worth. Is the best solution to contact Blackstar directly? Or cut my losses and replace it? Thanks for reading.
My stuff


Gibson Les Paul Studio
Ibanez ADC120
Tanglewood TGRF VS
Blackstar HT20
Roland Micro Cube
#2
Okay. you're making me feel suspicious of the amp tech. Please tell me he didn't say that he has "no idea".
Troubleshooting a circuit can be an involved (time consuming and expensive) process but even with a blackstar circuit there's a few really quick checks the tech can do to eliminate some obvious possible causes.

So how did he phrase your options? You didn't give a lot of details but I don't think I could rule out something as simple as a bad solder joint on the input jack, which is a quick and simple fix. If he didn't want to give you the wrong idea then I totally understand, because (no offense) some people think it should be easy to troubleshoot a circuit and get upset when we can't give a straight answer right away. And for all I know your amp might be smoked.
But if he didn't acknowledge that it could be a little problem as well...
#4
Quote by 311ZOSOVHJH
I'd still replace the tubes and find a new amp tech.

This.
And as said, solder joints should be checked, especially the input jack, and anywhere there is a wire.
And find a better tech.
Amp repair can be costly.
I charge $50 just to look at it (which includes basic troubleshooting).
Last edited by CodeMonk at Jun 30, 2015,
#5
If you don’t have the purchase receipt you won’t get any warranty service. That said, contact Blackstar and find out who the local warranty technician is. That’s the person you want servicing your amp, because that person will have schematics and be familiar with how to fix them quickly—and thus at less cost to you.
#6
I'll give you some help understanding why some technicians might not want to throw himself into this particular job.

Here is a 22 watt tube amp schematic:


And here are three pages worth of Blackstar HT-5 schematics.
http://music-electronics-forum.com/attachments/7092d1259344107-ht-5-preamp-pt-2.gif
http://music-electronics-forum.com/attachments/7091d1259344099-ht-5-preamp-pt-1.gif
http://music-electronics-forum.com/attachments/7090d1259344094-ht-5-power-amp-supply.gif

Blackstar doesn't want their schematics to be out in the wild, so this is what popped up when I looked for your amp. It's safe to say that your amp will not be simpler than this circuit.

So if you can track down a guy who is licensed to work on Blackstar amps it's probably going to be in your best interests.
#7
^Yeah, the newer stuff is overly complicated.

I've repaired a lot of amps over the years, both tube and solid state.
I try to avoid modelers, those can be a nightmare.

The most common failure I have seen in solid state amps is the power amp chip.
Those things can get really hot.