New Matamp Site

[weasel_face]

I've been told there is a simple adjustment we can make here to bring the voltage down. I'm still waiting to hear back from them for the approval to do so or if it's not worth it. Fingers crossed I guess haha.

[Dr Tony Balls]

It had red plated and took it back to my tech and we found out that the screen voltage is very high which could have done that or it was a shit tube. The company weren't surprised by this and said the way it's designed it eats tubes and if they altered it they said people wouldn't be happy as it's not authentic.

This sounds like hogwash to me.

Unfortunately it's the case man. The email from them to my tech says they weren't surprised it red plated because the tubes can't take the power going through them and if they change the circuit it wouldn't be authentic, just relaying what's been said. They've been considering dropping the voltages themselfs. Like I said could be a shit tube but I'm told those voltages shouldnt be that high, just worth being aware of.

I mean that what sounds like hogwash is that its "authentic" and "designed" to redplate. The original GT120s put ~500V on the plates, which is NOT extreme by any stretch. Old datasheets said that max plate for an EL34 was 500V but thats super conservative, and modern ones list 800V. Hiwatt 200s designed for 650 on the plates of an EL34. So its neither authentic to design in some crazy high plate voltage, nor is it realistic for that to kill a tube.

Improperly designed *screen* supplies can cause the screens to light up red, but the original designs has the screens running in standard FMV "at or near the plates" voltage.

What *is* possible is that the original bias circuit is designed like shit to not provide proper negative voltage and keep the plate current in check, but a) its the exact same as the Orange one which worked just fine and b) NOBODY gives a shit if you tweak the bias circuit to make the amp work right.

So yeah....what im saying is hogwash is their excuse.

Do you have the schematic they sent your tech? I'd love to see what theyre trying to say is the problem.

[1bottlerocket]

Send your amp to the Doc and get it straightened out.

[Dr Tony Balls]

Send your amp to the Doc and get it straightened out.

LOL. I'd gladly set it right but the shipping from Oz might be a *tad* inconvenient.

[weasel_face]

Oh right! I apologise I read that wrong haha. It seems like bad design but I'm really only repeating what we've found out in testing an so on. The schematic they sent doesn't match the amp haha, they were cautious about sending it in the first place but it was pretty much no help in the end. I was told they'd contact me directly about the whole thing which was last Friday...

[weasel_face]

This might be of interest, more or less explains my issue. His was an old one but I guess they're direct clones and have the same problem.

http://music-electronics-forum.com/t34052/

[Dr Tony Balls]

This might be of interest, more or less explains my issue. His was an old one but I guess they're direct clones and have the same problem.

http://music-electronics-forum.com/t34052/

Yeah but that doesnt really solve much. In that person's case it seems to have worked but we dont know the end of the story, AND its certainly not indicative of the amp design itself. If it was, every vintage Orange or Matamp (and a lot of other British amps) would eat up tubes without that mod.

[jerms]

Ii've had nothing but probs with old orange amps...... I had a OR 120 and a matamp cinamascope 120 and when cranked both would go unbalanced, and one side (2 tubes) would redplate and blow the fuse.... I couldn't figure it out, so i took it to the tech soldano..... He told me in the 70's they changed the phase inverter and that under drive it would go unbalanced and drive one set more than the other set of tubes..... He did a mod to the phase inverter on the OR 120 and it worked great after that......

[weasel_face]

Oh right yeah haven't heard about that sort of issue. I spoke to much tech about it and that might not be what's happening to mine but good to check out anyway. I think I'll be leaning towards a full refund now unfortunately. Two months in and I haven't got what I've paid for, they've been pretty unhelpful in they way of reasonable soloutions (NOS tubes isn't one) and my tech is doing all problem solving for them. It's a lot of money to have spent for something so unrealiable at this point. I'm out $330 import fees and probably the return shipping, I dunno live and learn I guess haha.

[welshchris]

Sucks to read you’ve had so many probs and an extra balls you’re so far away from them for getting it sorted. Any merit is sending it up to TYM in Brisbane to look at it? Pretty sure he has a lot of Matamp experience.
Prob cheaper than the shipping back to the UK. Though maybe one it’s boxed up you’ll just want rid of it.

Me and my bandmate both run GT120s and the only issue bar run of the mill the valve replacement I had was replacing some screen resistors a few years ago. (our amps were build late 90s and early mid 2000s).