Faulty Blackstar HT40 mk 2 help required please

dakwah

Hi 

Need some help please.

I bought a used HT40 6L6 for a good price

Was working great. Now stopped working.

The symptoms are just a hum which increases on either channels as volume turned up, no guitar sound at all. Tried the XLR output same hum.

All valves are glowing.

Where shall I start diagnosis?

If valve then can change. If circuit board issue, probably not worth the cost of repairing?

Any suggestions much appreciated

regards Stan

ecc83

Hi Stan, virtually impossible to diagnose and especially for a S/H amp that might have been bounced or messed with! I doubt it is a valve problem so don't buy any.

If it was working ok and you liked the sound then yes, very much worth fixing. Try to get it to Northampton because Blackstar's service charges are very reasonable.;

Dave.

dakwah

thanks Dave

not worth the effort or expense as I live in North Wales

did read that these amp do show problems

regards Stan

Danny1969

You could at least find out if it's a pre amp or power section fault ... plug something into the effects return socket so you are bypassing the pre amp section. 

impmann

Danny1969 said:

You could at least find out if it's a pre amp or power section fault ... plug something into the effects return socket so you are bypassing the pre amp section. 

Deffo try this but on a Blackstar you need something plugged into the guitar jack as well  (such as a shorting jack) to lift the protection circuit on the amp - it just sits in standby otherwise.

Tbh, there isn’t a golden Bullet issue with the HT40 mk2  - genuinely they’re actually pretty reliable. If you get stuck, call the service team at Blackstar - whilst you’re not local to Northampton, there will be other options.

Good luck.

dakwah

thanks everyone

will try all your suggestions

much appreciated

Stan

Hydra

Blackstar collected an amp from me for repair work in the past.  Very same issue as yours on a V1 HT20, lights on no one home.  It was still under warranty and their diagnosis was a blown power tube/s.  Who knows for sure though?

dakwah

thanks Hydra

something to look at. one valve looks a little dimmer, but could be my eyes.

Stan

DartmoorHedgehog

Hydra said:

Blackstar collected an amp from me for repair work in the past.  Very same issue as yours on a V1 HT20, lights on no one home.  It was still under warranty and their diagnosis was a blown power tube/s.  Who knows for sure though?

My HT20 head did that once - all valves looked to be glowing normally but no sound.  Somebody on here (probably @ecc83 ;
) suggested a faulty power valve and sticking a spare one in each position in turn proved they were right.  So definitely worth a try OP before you take it to a tech.

dakwah

thanks Hydra 

will source a valve, as I said all I get is a hum on either channel that gets louder with the volume controls...

Stan

impmann

If you are replacing the power valves 1) they need to be replaced as pairs and 2) they will need biasing. The HT40 Mk2 does have a bias light system fitted but unless you *REALLY* know what you're doing, there are lethal voltages in there so you ought to get a tech to do that. 

dakwah

thanks Impmann

will take that into consideration

as I am note using the amp at the moment will leave it alone for now 

thanks for the advise 

Stan

ecc83

"The HT40 Mk2 does have a bias light system fitted "

Does it by crikey! What does that look like/work then?

Dave.