MT200

[Systematic Chaos]

Mesa 20/20 Deep Mod:
http://forum.grailtone.com/viewtopic.php?f=5&t=31723

[rnolan]

Hey SC, just wanted to say I really appreciate you finding all this stuff for us all  :thumb-up:

[Soloist]

I put a pair of Tung Sol reissues in the MT200.. and WoW!! Nice warm tone! :thumb-up:

Now, on the Mesa 50/50 I was reading that V2 and V3 are both phase inverters :facepalm:. V1 splits the signal to each side. Can someone confirm this? MJMP? SC? rnolan? Anyone?

[Systematic Chaos]

Correct! Is that the old 50/50 or the new one?

[Soloist]

I think it's a newer one. Blue power light on it.

[Systematic Chaos]

I'll mail you some MB docs

[Soloist]

Thanks SC!

[MarshallJMP]

Hey Soloist,do you got what you need from SC?

[rnolan]

Well that's an interesting way to do it, so V1 is the buffer tube for both channels (one triode each) and V2 and V3 are the PIs, one per channel to drive the output tubes (which I assume there are 2 per channel in push/pull)

[Soloist]

Hey Soloist,do you got what you need from SC?

Yes I do! Thanks Guys :thumb-up:

[Systematic Chaos]

Hey SC, just wanted to say I really appreciate you finding all this stuff for us all  :thumb-up:

All cool bros!
I did some mods and maintenance on some Boogies ;)

[DorsetRatt]

Mesa 20/20 Deep Mod:
http://forum.grailtone.com/viewtopic.php?f=5&t=31723

Thanks for the link SC. I've got the deep mod on the 20/20, it was done by the previous owner ... I have no idea what the 20/20 sounds like as standard, but consensus of opinion seems to favour the modded version.

I'll try some different tubes for the PI positions, probably the 12AX7LPS that you've mentioned previously. If it doesn't work out for me I'll try the 12AT7, I can reuse the 12AX7LPS and install them in my SP-77 (I seem to remember Soldano recommending the Sovteks).

MJMP, under-biased power tubes are a concern ... it wouldn't surprise me if they were, I think perhaps it's a Mesa tube strategy. It's a little frustrating that the bias is not easily adjustable (trimpots, etc), so I'd be really out of my comfort zone.

[Systematic Chaos]

I don´t have the schematics of the 20/20 DynaWatt, but there´s a 33k resistor in the fixed bias circuit... Replace that with a 15k resistor and a weber WP503L 50k bias pot in series  :thumb-up:

[Dante]

Hey SC, just wanted to say I really appreciate you finding all this stuff for us all  :thumb-up:

All cool bros!
I did some mods and maintenance on some Boogies ;)

I can't thank you enough for the advice on re-tubing my DC-5 combo  :bow: