Mark III Tube Identification - Help Needed

[fretout]

Hi guys! I've been away for quite a while. I was looking for a Coliseum amp (preferably a GEQ-Equipped model) and ended up purchasing what was SUPPOSED to be a Mark IIC+, but it turns out to be a Mark III. I definitely overspent for a Mark III, and the condition isn't so great, so I might have to return it.

Anyway, this Mark Coli (dated 09/85) came with stock tubes. I'm not quite sure what these preamp tubes are, so if anyone can identify them, I'd appreciate it. They have no other information other than "MESA STR-12AX7-A (ECC-83)". I feel like I've seen these before in my other amps, but I'm not sure what exactly they are. Here's a pic...



Now you want to see something really sad? The amp came with what appears to be all stock original STR-415s! Unfortunately, the seller packed the sextet in bubble wrap UNDER THE AMP (instead of inside the headshell), and they have all been destroyed. Yep, all six STR-415s, presumably working, were all crushed inside the bubble wrap. Here's your guy wrenching pic of the day. Here's what approximately $660 looks like when they're ruined...





So, does anyone know what 12AX7-As these are? Anyone know someone that repairs Power Tubes? :-/

 

[dodger916]

That seller should be arrested! There's a special place in hell.....

 

[thunda1216]

from the clips on the plates, the preamp tube appears to be Chinese. so sorry about the power tubes...:-(

 

[Buddy]

from the clips on the plates, the preamp tube appears to be Chinese. so sorry about the power tubes...:-(

+1 I still have a set of those tubes from '87. Chinese manufacture was how they were described by Mesa support back then.

Sylvania big bottle massacre. That is near reason to cry.

 

[McBarry]

Love those preamp tubes in my Mk I, but unusually they don't sound as nice in my MkIII - too grainy/gritty..

Re p/tubes.. have him replace them- it was his error that causes the problem, he should rectify it..
It's not about being nasty, just rectifying a problem..

And maybe he could pay for your therapist fees, for your "loss".....

 

[fretout]

HAHAHAHAHAHA!! Thank for all of the support through my loss. I really don't think the seller was knowledgable about this Mesa, let alone how fragile tubes are. After I saw the blue stamping of "STR" on a broken piece of glass, I knew these tubes were something special. After I looked up the price of what these STR-415 are selling for (around $200 a piece), I realized that I'm looking at $1,200 worth of damage. Ouch.

Thanks for help identifying the preamp tubes. They are all in decent shape. I decided to start swapping preamp tubes out of my Mark III Blue Stripe to see how the tone was affected. I started with V3 and pulled the Sovtek 12AX7LPS and tried the Mesa-Branded ECC83, and I noticed that the ECC83 seems to be much quieter, and seems to have more low-end-girth than the Sovtek.

Next, I tried swapping the V1 position tube to see how the overall amp is affected. I pulled the Mesa-Branded 12AX7-A "Russian 2" and replaced it with another one of the Chinese ECC83, and the tone seemed more balanced. It was also quieter, but had more of a "Hi-Def" type of tone that seemed like it had additional harmonic overtones, but I was definitely a "softer" sounding tube.

In all honesty, if like to replicate the tone of my Mark III Coliseum (which is also a blue stripe), but even with the same tubes, the Coli has a much more pronounced and deeper low end.