Marco Polo Amp Tubes

[12string]

Hello,

I just acquired a Marco Polo amp (late 60's Japanese import as best I can tell) dirt cheap. I am stunned at a) how well it was assembled and b) how quiet it is and how great it sounds.

But I can't find any information on the amp. Particularly the tubes. This amp uses 7 pin tubes for the preamp, tremolo, and power section. Does anyone know anything about these tubes?

Preamp/tremolo tubes: NEC 4Y
Power amp: NEC 4X
Power amp: NEC 48

Note that the 4X and 48 tubes appear the same.

Any and all help would be greatly appreciated, thanks!

[Rob Mercure]

12S,


By the 1960s Japanese tube manufacturers - who were mostly owned by USA firms - confirmed to RMA/EIAA tube nomenclature, i,e, they used the same tube numbers we did. So while NEC probably stands for "Nippon" Electronics Corporation" or such the "tube numbers " you supplies don't mean anything! Look elsewere on the tubes and be aware that tube branding ink washed off easily with water.

You might want to do a web search on Marco Polo - the fact that all your tubes are 7 pin makes me "sorta remember" an amp with a similar name that was line connected. Do you have a power transformer?

Rob

[12string]

Rob,

Thanks for the input. I've been huting for Marco Polo and the best I've been able to find so far is a reference to a US importer by that name that imported guitars and amps from Japan in the 60's. Unfortunatly there is no schematic in the amp, though the work inside is amazingly well done, point to point, extremely clean, twisted, etc.

There is a power transformer and a small output transformer, this amp can't be putting out more than 1 or 2 watts. I'll check the tubes again for faint text.

Thanks for your help.

Mark

[Enzo]

Yeah, those sound like lot codes.

[Jag]

I've heard it said that you can do a little "huh" on the tube and sometimes the wiped out printing will show in the condensation. It's never worked for me though.

[pchilson]

Hey 12string, can you post some pictures of this amp?
Have you learned anything new about it?
I'm trying to ID something along those lines myself here.

[Gtr_tech]

Preamp tubes: 6av6, pwr tubes probably 6aq5, unless it doesn't have a pwr transformer...then who knows.....