Blown valve?

quarky

I have a Blackstar HT-1RH and and Vox something or other cab. I can use the line-in with headphones, but I don't get any sound without the headphones. With just the guitar input, I get no sound regardless of whether I have headphones plugged in or not.

The cab looks OK (I opened it up and the speaker is connected), so does that sound a valve issue?

ICBM

Dave @ecc83 will probably be able to confirm, but that sounds like an HT supply failure not a valve.

If just the preamp valve had gone you would get sound through the speaker with the Line In.

If just the power valve had gone you would get sound through the headphones with a guitar.

It won't be a filament supply failure since the voltage for the headphone driver comes from the same circuit. Which leaves just the HT as something that will affect both valves I think.

Does the power light still come on?

quarky

Thanks ICBM. Yep, the power light still comes on.

If it is the HT supply failure, is it something that can be repaired? It would be good if it could, but I aware that it isn't really an expensive unit..

ICBM

I asked about the power light because I think it's also driven from the HT supply… so that makes the diagnosis more complicated!

Can you see if the valves light up?

It's not an "expensive" amp, but it can't be uneconomical to fix I don't think. A worst, give Blackstar a call - I've found them helpful.

ecc83

Sorry to be late on parade (but if peeps would ^&%ing SAY what make of &^%$img amp they are having &^%^!!ing trouble with I would have got here sooner! Only know about &^%$!ing Blackstars!)

Yup, HT gone. Can't think it is anything but the 80mA fuse popped. It has long been my experience that very low value fuses are prone to random blowing (might have had a 1kV mains spike?) . It would also be virtually impossible  to see if the fuse is intact.

80mils might be tricky to find and so I am going to stick out an unofficial neck and say fit a 100mA (T if fitted) . The HT diodes are 1A devices so can easily handle 100mA + fault current.

Oh yes! The pre amp loads are only 0.25W so do not fit an 82 and anything else but an 83? Check the anode volts.

Have not looked at the map for some time and did not realize that the heaters are AC fed? This means heater cathode issue could give rise to hum tho' neither of the cathodes are more than a few volts away from the heater.

If there is no sign of overheating on the PCB the fault is likely not serious (if there still IS a fault!) and so likely not going to cost a lot at Bs. AFAIK the amps are generally very reliable.

Dave.

quarky

Thanks for your help guys. I can't find much that looks like a fuse, but is it this black round thing in front of the two red wires?

Hope you can see the picture!

Or here:

https://1drv.ms/i/s!An1C7f0Qk0d1jLBzCk6AzBoHEKjQrg

ecc83

Nope. Is it as in this link but black?

http://uk.rs-online.com/web/p/non-resettable-wire-ended-fuses/3772203/

If so you will have to check its continuity with a meter and if O/C get the amp to Blackstar.

Sorry I don' have any internal shots of the HT-1. personally I don't like PCB mounted fuses but I have to say I never had one go in an HT-5.

BTW, did not know there was a holder for them, did you IC? Would make sense to me to fit one and replace fuse?

Dave.

quarky

Yep, that looks like it. Thanks. I think I have soldered once since school (with one of those little gas ones), so might look at taking it to Blackstar then. As I live in Northamptonshire, maybe it won't be a long trip!

ICBM

quarky said:

Thanks for your help guys. I can't find much that looks like a fuse, but is it this black round thing in front of the two red wires?

Yes, that's definitely the fuse.

ecc83 said:

BTW, did not know there was a holder for them, did you IC? Would make sense to me to fit one and replace fuse?

Very much, I also really dislike soldered PCB-mount fuses - unless they're an absolute 'last ditch backup' to prevent someone bypassing the proper fuse.

I didn't know there were those holders either but I will be getting some next time I have to replace one of those fuses.

quarky

So if I do it myself (my neighbour has a soldering iron!), I guess I need either one of these two:

http://www.ebay.co.uk/itm/0034-6003-Fuse-fuse-quick-blow-80mA-250VAC-TR5-MSF-/191908474972?hash=item2caea2f05c:g:SIgAAOSwEjFXcnkH

http://www.ebay.co.uk/itm/0034-6605-Fuse-fuse-time-lag-100mA-250VAC-TR5-MST-uk-stock/201606445827?_trksid=p2047675.c100005.m1851&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=36800&meid=a8a2a48a546c4040bf73bf220667bc04&pid=100005&rk=2&rkt=6&sd=191879663928

ecc83

If you don't OWN a solder iron you likely do not have the skill to remove a part from the PCB without buggering the print. I would leave the task to a good tech or Blackstar. Dave.

ICBM

ecc83 said:

If you don't OWN a solder iron you likely do not have the skill to remove a part from the PCB without buggering the print. I would leave the task to a good tech or Blackstar.

Seconded! This is not a reflection on your manual dexterity or skill with other tools, just a fact of modern PCB work.

It's *very* easy to damage the fine board traces if you're not experienced at regularly working on things like this - it even happens occasionally to those of us who are. If you damage the traces you're in for some very fiddly repair work to make a good job of fixing it.

quarky

Taking the great advice on here, I decided to take it to the professionals. I finally got around to taking it into Blackstar to get them to do it in maybe October. They had it for a couple of months, but it is fixed. And they did it free of charge!