Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dunner84 on July 11, 2015, 02:30:38 pm

Title: Transformer replacement
Post by: dunner84 on July 11, 2015, 02:30:38 pm

Hi all,

I had a post on another forum last year regarding a cool old Masco ME-18 that I found in the trash. Well I cleaned it up, replaced the caps and got it all working. It sounded pretty neat.. Sounded. The Iron was in rough shape to begin with, and has worked well for the past several months, but the transformer has just died.. I need to replace them and have some questions about my options..

Here are the specs (from the spec sheet) for the current transformers:

Output - 3k pri 2-4-8-15-500 taps, wattage not listed
Power - wattage not listed, 330-0-330 6.3v/2.5A 5v/2A

I have dug around and found these transformers below. They seem to be ok replacements. I am not worried about size. Just function. I also want to consider replacing the circuit someday. It sounds neat, but I don't love it. I am considering fitting in a 1 channel baseman, or Super Reverb without reverb or trem someday. So they would also need to accommodate my future considerations.

Output - h018343 - 50 watts   4k pri 2-4-8 taps
Power - h041316 -25 watts 330-0-330   120ma   6.3v/3a   5v/3a
Power - Mojo762 - 40+ watts   354-0-354   250ma   6.3v/4a   5v/4a

So, have I missed anything with these choices?

Also, I am not stuck on a simplified baseman or Super. Any other good 2-6l6, 5y3 amps with simple tone sections? I have room on the chassis for a 3rd preamp tube if necessary, and have 9pin sockets that fit the current holes.

Here is a picture of the schematic, if it helps.

Thanks,

Title: Re: Transformer replacement
Post by: sluckey on July 11, 2015, 02:52:17 pm

Quote

Power - h041316 -25 watts 330-0-330   120ma   6.3v/3a   5v/3a

This one seems kinda light weight for where you're headed.

Title: Re: Transformer replacement
Post by: PRR on July 11, 2015, 03:52:00 pm

Which transformer failed? I don't see a compelling need to replace both right away.

If I am reading the blurr right, you need 120mA to just idle and 170mA at full roar. The 120mA part may be fine for the parlor radio, but serious guitar beating will need a larger PT.

Title: Re: Transformer replacement
Post by: dunner84 on July 11, 2015, 08:32:52 pm

Thanks for the feedback!

It was the PT that went, but I have a feeling the OT is close as well. This thing was in miserable shape when I started restoring it. So it looks likes the Mojo762 is the way to go? Does the OT look ok too? It has a 4k primary vs 3k on the original.