A couple of weeks ago, I started to get strange noises on the "drive" channel of my HT20 Head (volume fluctuations, feedback type squeeling, fizziness, etc.). I suspected the power tubes as the culprit, due in part to the symptoms and due to the general 'bashing' that the stock TAD tubes get here on the forum. I changed out the pwr tubes and the V1 pre-amp tube to Tungsol brand (I had changed the V2 out previously to an EH12AY7 for some gain reduction). Didn't correct the problem, so took the amp to the closest Blackstar warranty repair tech.

When we plugged the amp in upon arrival, it demonstrated the problem, so I left it for repair and biasing. It took the tech. a little longer that he usually takes because when he went to troubleshoot the problem, it would not repeat. Finally it did and he traced it to a defective solder joint of a surface mounted component on the PCB. He replaced the component with a new soldered joint, and tested the amp several succeeding days in attempt to insure that the problem is corrected.

So far, I've played it around 2 hrs. and all is OK....Hope it is permanently fixed

The tech affirmed that even though the HT20 is cathode biased, it must be checked and re-biased for pwr tube changes. This topic has been bantered about and argued frequently on this forum, so here's another expert's viewpoint on the issue. Trust me, this man is worthy of the title "expert" due to his credentials and main vocation.

Regarding the tungsol tubes, I see no difference in tone, but there is no question that there has been an increase in the volume. My master volume and clean chnl. settings both had to be reduced for approximately the same volume. I kept the TADs for emergency spares.

I questioned the tech on his preference for tube manufactures and he was very non-specific. He said when he needs to replace a tube, he just "fishes around" in his bin of many, plugs it in, checks bias (if a pwr tube), and then if it sounds OK, it is. Didn't seem to have a preference.

I had promised an update upon resolution on another thread, so there you have it.

good to hear the issue is resolved - bet that was a bitch to track down...

"The tech affirmed that even though the HT20 is cathode biased, it must be checked and re-biased for pwr tube changes. This topic has been bantered about and argued frequently on this forum"


a while back in another thread i had posted a response directly from B/S concerning the bias question on the HT-20
and your tech validates the B/S recommendation - there should not be any confusion about that anymore

no kidding Tone...misinformation is a constant battle

it really pays to have a good tech - you and i should consider ourselves lucky

Bob,

Sorry didn't get back to you before you got done here. Wasn't able to get away during the week at all.

Glad you got it resolved.

Considering the tech ya took it to, there's no further question on the biasing issue for me.

Did he mention any thoughts on the amp?

Sorry we couldn't connect, hopefully another time.

Yes, I questioned him on what he thought about the construction of the amp. He said it looked pretty good, thinks current Chinese manufacturing quality is pretty good, but that the Chinese are now subcontracting a lot of work out to Vietnam (that, to me means another learning curve). The only somewhat negative comment was regarding placing the tube sockets on the pcb, which most critics view as an undesireable (yet cost cutting) practice. He felt that it is very quiet for a tube amp and attributed that to the SS components in the circuit which he likened to putting a tube screamer in the circuit.

He also said he hasn't had many come to him for repair. So either they're not selling well in this area, or they're very reliable.

I played the amp another couple of hours this afternoon, and I'm struggling to get the same tone at the same volume with the new Tungsol pwr tubes. Seems like I have to play louder (but the same dial setting) to get my favorite tone on the lead channel. I'd prefer it was like before, but we'll see what happens w/ additional trials.

Ya, hope so. Considering booking some things up that way (Erie, maybe Bradford, lower NY...Maybe see how things go in the NY casino area)...once Spring gets here.

Thanks for his impressions. There are no sellers near here. BUT, there are three of us around who have them, that I know of. All of us have used a lot of different amps and played for...eeesh...long time... All of us have gotten them online, except the one guy got his HT100 in, I think Harrisburg. Then ordered an HT5H online.

Regarding the volume, might take a little to break the tubes in to get to their optimal sound.

my tech said the same thing about the tube sockets...in fact when i changed the preamp valves it almost
felt like it flexed or moved a little bit when i pushed them in - didnt seem to affect anything but it worried
me for a moment - its still working fine and we have a show tomorrow nite at the beach so time to add some hours
on the beast

Argh. Killing me that we're not out playing. Looking forward to the new thing being ready...but this is the longest have been off in 8 years... And can't wait to use this thing live (Only times did, just used the clean channel with the TK in front). Use the HT5H for practice, but every time I go downstairs the HT20 is sitting there on top of the "stack of heads".

"show tomorrow nite at the beach"

'At's so great. I just scraped ice off the car window.

IM4 should be shoveling out from under a blizzard by now...or getting ready to hibernate.

poor guys

my better half is from those parts sorta - (bucks county PA)
and needless to say doesnt miss the frozen car doors

Ah, that's cool.

Actually, I do like winter, generally. Not like they used to be...but always seem to get the lousy ice storms when I'd be traveling 100 miles to a show. Get to skate there, whiteknuckled, on PA's backroad rollercoasters.

Sides carries BS? Had no idea. They didn't show up in the listing when I checked on Blackstar's site. We practice across the street from there. Might drop in and look at the Artisans.... That can't be a good idea...

I generally go to Rainbow since it's locally owned and I know the guys there.

My WGS' seemed to break in pretty quick, but ya, that could be a part of what you're dealing with as well. SEND EVERYONE AWAY FOR THE DAY, CRANK IT AND HAVE SOME FUN!

I say that...but my gear at home sits dormant. I also have a "new" git that needs torn apart and modded up. The new parts are in a box waiting. EVERYBODY OUT! DAD'S SOLDERING!!!!