Help, not truly urgent, requested

This is my first post here. I'm in rural France with a 212 HD-130 that I bought in the 70's and never used that much and then sent to France when I retired here. I had smaller amps for practicing around the house, put the Musicman in the basement, where there was room for it, and never played out that much in the States. I have to run the Musicman through a power transformer, since it only runs on 110V as currently configured. And I know literally nothing about electronics, I'm just a guitar player, until recently primarily an acoustic guitar player.
My main problem now is that the amp produces low-level background hum at a level that seems too high to me, but maybe it's always been like this, I can't remember. How much hum is normal? The hum is there when all volume knobs are at zero and is not affected by turning volume knobs higher or by anything else. It's there when the power tubes warm up. It does increase slightly at 130W, as opposed to 65W.
What are the filter capacitors for a solid-state driver HD-130 (2475-130 chassis, *not* 2275-130 [these are listed in another thread in the Capacitors topics])? And what are the other capacitors? I ask about capacitors, because Mike already suggested that old/bad capacitors could be causing the hum, when I contacted him to sign up for the forum. Two 100u/450V capacitors were replaced in 1992, the last time I had this amp serviced. Should all capacitors throughout the circuity be replaced?
Assuming I can get over this hum problem, what would be involved in converting this amp to one that will run on 220V? Is the original internal transformer equipped for this? A tech here has asked me this via email. He also proposed somehow fitting an external step-up transformer into the unit, in the event that the internal transformer cannot be altered to accommodate 220V.
Thanks in advance.

Well, I'll give you the first opinion! There are more than two but that amp should have 4 caps in the PS section. Could be the problem. 1992 is still 22 yrs ago so even THEY could be bad, depending on the quality of the replacements. Does this amp have the 12ax7 PI tube or SS driver? Just trying to date it. As for converting it, my opinion is to get a STEP DOWN transformer, since you are wanting to run it on 220 and it's set up for 110. US amps did NOT have provisions for 220. It's not necessary to replace ALL caps, just electrolytics from back in the day. OOOPPPS. Just read better. SS driver. OK. Still, electrolytics on the PS, bias board, and any on the driver board. There are like 5 electrolytics on the driver board. Mike. Any other opinions? I don't want to be the only mouth here! Lars-you're the export guy! Mike.

This amp has four 6CA7 power tubes, the phase-inverter tube (it's a small tube, probably 12ax7), and a solid-state preamp, at least that is my understanding. And this phase-inverter tube is probably original. (I bought the amp second-hand in the 70's and never changed this tube, to my knowledge.) I don't really know what the "driver" means, so I was just trying to sound like I did know. Same goes for "step-up" transformer. I thought if one were going from 110 to 220 that that would be a step up, not a step down. Hey, it's all arbitrary, at least the nomenclature part, right?

Yeah. Not meaning to be a smart ass here. Just want to make sure you get the right info. The driver is actually the Phase inverter or driver. That tube is IMPORTANT in MM's so if you replace it, get a good one. The SS DRIVER versions have another board in the back with SS devices taking the place of the 12ax7 and the amp is Totally different as far as the way it functions. No bias setting but a CURRENT setting that controls how much the tubes are driven. Also, the amp is kind of backwards in that it it cathode driven and the so called "bias" voltage is ppositive instead of negative. Confusing? Yeah, they are. I would look into a step down transformer rather than looking for a MM export tranny since they are few and far between and REAL expensive, from what I remember. Also, the 220 v transformers had extra fuses, if I remember correctly on the mains. Lars would know for sure. Mike.

Hi Harvey,
if I understand it correctly, you have a standard US version of the HD-130 amp. Like Mike said, those are not equipped for 220V conversion. However, you can obtain a replacement power transformer form tubeampdoctor.com :http://www.tubeampdoctor.com/de/shop_Net ztrafos_Netztrafos_fuer_Music_Man/Netztr afo_fuer_Music_Man_130_Watt_Model_2275_1 30_2475_130_132
(you may have to cut and paste through Notepad to get the link to work).
The hum could be a faulty tube, a problem in the power supply or be caused by the fact that you are using a step-down transformer.
The 12AX7 tube could be causing the hum - one half of it (the actual phase splitter part) is directly coupled to the output section so even with all knobs at zero, could cause hum in the speaker. A correctly working MM amp will have no hum and only perhaps a tiny bit of white noise in a no signal situation.
If you decide to replace the power transformer, I would strongly suggest that you get your tech to convert the power wiring to European standard: The ground lift switch is removed and replaced by a dual pole master power switch. Whether you want to add the extra fuses inside is up to you. The main power fuse may also need to be replaced (I don't remember off the top of my head) so it provides the necessary protection.
Sincerely,
Lars Verholt

Thanks Lars. Knew you'd have the skinny! Mike.

Ledocs,
I am French, located in PAU, I have a 210HD130 SS driver I got brand new in 1979. No hum at all, but I replaced all the electrolytic caps in 2010.
feel free to contact me at sobole@live.fr