Swapping 110v to 220v Transformer on 65-212
Hi all,
I've got a pretty, mint condition 65 watt 212. Chassis is 2475-65. PI tube. It sounds amazing. It is my main rig. I'm from the US originally but have called New Zealand home for many years. I'm not planning on returning to the US, so it's time to swap out the Power Transformer as I'm not interested in lugging around an external one if and when I start gigging. To that end I've purchased the only replacement 65 Watt PT available today from Mercury Magnetics. The info below is for all those dealing with PT replacement and should be taken with a grain of salt in that: 1. I'm not an amp tech 2. I have yet to install my replacement PT.
The following is what I've gathered over the past few days about the Transformer situation with Musicman amps of this time period
History:
Musicman amps (like mine, ie mid to late seventies with a PI tube) had one type of Power Transfomer stamped 1-65 early on. This supplied Hi/Lo power, switched in the transformer's primary. Later they changed Hi/Lo switching to the Secondary. This later model transformer is stamped 100-65. This swap of transformer required rewiring the front switch to ON/OFF and the rear Standby become HI/Standby/Low and was detailed in Service Bulletin #4, available in the Downloads section of this site along with Schematics. Many people however (like the previous owner of my amp) never swapped the transformer. Why would you if the amp worked perfectly well?
Interesting to note: I used to jam with a guy in the late 90's who bought a 4-10 (don't remember 65w or 130w) that had undergone the rewire and swap. His amp had a metal badge stamped on the front switch that said 'On/Off' covering the old 'Hi/Off/Lo' markings. Same thing on the rear standby switch, with 'Hi/Standby/Low' printed there. Yet I've never seen another Musicman like it, ie one that has had the PT replaced and switches rewired.
What Musicman Transformers are Available Today:
Apparently Mojotone used to build replacement versions of the PT (not sure if they were 1-65 or 100-65!) but that ended years ago. Other threads mention TAD (Tube Amp Doctor) as a potential source - but unless they have products not listed on their site, the only Musicman transformer they build these days is at Output Transformer for the 2275-150 variant. They used to offer a PT for the HD130 (accommodated Hi/Lo switching) but not anymore.
Currently, in 2026, Mercury Magnetics offers both Output and Power Transformers for the 65 watt and 130 watt variants. It is important to note, however, that these have only ONE power setting available.
Mercury Magnetics website lists a 2275-65 Power Transformer (both 110v and Export) labeled 'Drop-in Upgdade!' - which is not entirely accurate. I have yet to install mine, but the first thing I noticed on arrival was there aren't enough wires to offer Hi/Lo switching. Oh well - I would have purchased in anyway. My main concern isn't Hi/Lo switching, it's not having to carry around an external transformer!
There is one main output voltage (red and red/yellow) on the secondary and it is 245V. There are also 2 oranges (labeled 'Accessory') and 2 green wires labeled 6.3V filament.
Also important to note, Mercury Magnetics also sell Output Transformers for both the 65w and HD-130w models.
Install:
At this stage I'm confident that I (or an amp tech, haven't decided yet) will get the new transformer installed and running. But this amp will always be in what used to be considered 'Hi Power' mode, ie 65 Watts. That's fine by me - though I'm not sure I'd want Hi Power mode in an HD 130 all the time! I've got an HD130 as well, which I may also convert at some stage but I may see if it's possible to use a PT meant for a 65w. Not sure if that will work yet. I'd prefer if the HD-130 was at the same output level as the 65w. Mysteriously, Mercury Magnetics spec sheet for the HD130w PT outputs a single secondary power tap rated at 265v. Not sure how that works as the 65w and 130w PT's are only 20V apart in their output!
Also important to note for those seeking to install a replacement PT (either 110v vs 220v) - you don't need to pay attention to Service Bulletin 4 as far as I can tell. Service Bulletin #4 was about moving Hi/Lo switching to the Secondary and the rear of the amp. No point if there is no Hi/Lo switching! Having said that, the most I've done on an amp is recap it!
It seems when Mercury Magnetics engineered the replacement transformer they decided to simply skip Hi/Lo switching altogether as the simpler alternative. So if you're amplifier, like mine, has a 1-65 OT and never underwent the SB #4 rewire, you can just keep your wiring the same more or less. Obviously the front switch has to be adjusted to on off, but the rear Standby can remain Standby.
The forum isn't terribly active at present as far as I can tell, but if anyone has a piece of advice or a suggestion to make before I proceed with the install I'd be grateful for it.
Member for
12 years
Late 70's 210 HD 130w
Member for
7 years 6 monthsHey Mike (I think it's Mike?…
Hey Mike (I think it's Mike?)
Good to connect again. You helped me out a few years ago when I recapped both amps from memory. Here are the spec sheets from Mercury Magentics for both the 65 and the 130. The 130 lists the orange 'Accesory' wires output as 37v. I haven't opened my amp yet as I' need to get a proper workspace set up, but I watched a few Musicman repair videos online and they all seem to have 2 orange or brownish wires going to the rectifier board as per pic.
Regardless, I emailed the Mercury Magnetics rep as to that the Orange wires were on the 65w they told me:
Member for
12 yearsIf it were me, I'd use the…
If it were me, I'd use the stock switch and just use the primary inputs to both sides of the power switch. Just gang the switch high and low together and that way it's always on the side for the primary. You don't have a second winding so what the hell, make it simple. On either way is going to go to the primary tap. JMHO of course.
Late 70's 210 HD 130w
Member for
7 years 6 monthsSounds good to me. No need…
Sounds good to me. No need to get fancy with switches etc in my book. For me this is a lifetime amp so as long as it works correctly no need to add tags etc to the chassis to show the fact it's no longer Hi/Lo. I haven't taken a serious look yet inside the chassis in terms of wiring yet but hopefully it will be straight forward enough not to have to involve a tech. I can't see why it won't be as simple as copying the secondary wiring exactly and ganging Hi and Lo together off the primary. I may post on some electronics forums beforehand to make sure I'm on the right track.
I'd like to see the wiring…
I'd like to see the wiring schem for the Mercury transformer to give any kind of opinion. Don't know what they are referring to accessory unless maybe a tube rectifier. Maybe post both schematic here and we can opine. Can't imagine it's that big of a deal. The 130's four tube amps obviously so the current requirements are different for the amps so one transformer for the 130 just wouldn't have to work as hard as long as the voltages are correct.