Epiphone Galaxie 10 rebuild - trannies & choke questions

[RogerWilco99]

I have a "dead" Galaxie 10 that I'm going to replace the transformers on and build it with new components (caps, resistors, tubes, sockets, etc.). I'm trying to decide what PT to put in it. I'm thinking of using a Hammond 260J PT and a Hammond 125E-SE output transformer.

I've purchased new tubes for it, too. Basically I'm building a "from scratch" amp in the chassis. I am changing over to tube rectification using a 5V4 tube (or a GZ34).

I know the current out of the 260J is overkill but I like that I could stick a KT66 in it if I wanted to.

I'm also thinking of replacing the 1K ohm 3W reisstor in the power supply (along with other cap changes) with a choke. Any recommendations for that? Radiodaze has a "universal" choke that can handle the current and voltage. I really don't understand how to figure out what choke to use since I've [never] used one before.

Anyway, do the trannies I've mentioned sound like good choices for this application? I'm pretty thick skinned and freely admiit I'm still an "apprentice" at working on/building tube amps. I've worked on electronics for decades but it was nearly all digital and op-amp/optical switching type stuff.

Cheers,
Bruce

[RogerWilco99]

Okay, nevermind then. Sorry to bother you!

Not one reply in three days. Well, I guess I'll just figure it out myself.

[echuta13]

My buddy had one of these, and my $.02 is to gut it, and start with a better circuit. The voltages on the 6L6 are huge, and the screens are getting way too much of that (stock tube is a sovtek which doesn't sound that great either). The stock speaker is poop, O/T is anemic. Preamp voltages were ranging in the 250-300v range and it also sounded terrible because of this.

After my buddy wasted a bunch of time tweaking his amp, it only sounded mildly bad (a big improvement!).

If you're keeping it single-ended, a tube rectifier would be a needless expense.
Can't comment on the 260J as I've never used one, but it looks like the voltages might be pretty high with that one. What about a 270DX/EX? 125ESE is fine.

[RogerWilco99]

Thanks for the advice. My intent is to completely rebuild the amp with all new parts and to fix issues like that. I've even thought of building a Marshall Studio 15 in the case. But I'm not sure I could get all of it in this chassis since that would need a preamp tube, a driver tube and the two 6V6 tubes. That's a lot for that small chassis.

I intend to build a Studio 15 eventually but probably not, now. This one might turn out to be more like a Gibsonette (or not) but with a tone stack and a master volume (which gave me the Marshall idea anyway). I could just leave out the master volume. I'm definitely going to overhaul the power supply to clean it up better and switch the heaters to DC.

This amp really needs more kick from the pre-amp to get the 6L6 to overdrive. I'm even thinking of adding a 12AT7 (or 12AU7) as a driver tube after the tone stack to put back some of the gain from the pre-amp by putting the gain control between the two 12A*7 tubes and volume control between the driver and the 6L6. Maybe add a switch to switch the second triode of the driver tube in and out as a "boost" or "overdrive" switch.

There is enough room in the chassis for another noval tube for another gain stage. I think that's what I'll do and get the pre-amp voltages down to about 225 to 240. That should smooth them out from the torture they normally get in this amp.

[tyru007]

Goto the AX84 site and and use the schematic for the P1-Extreme to rebuild your galaxie. The Hammond 270EX and the 125ESE is a great tranny set to use.

http://www.ax84.com/static/p1x/AX84_P1x_080623.pdf

If your want a cleaner sounding amp, build a champ (tweed or BF tone stack). I build a nice sounding BF Champ capable of taking 6V6, 6L6, EL34, KT66, etc

http://music-electronics-forum.com/s...ad.php?t=10213

[RogerWilco99]

I have a Hammond 270DX PT and a 125DSE OT that are available. I bought the 260J for this but it's a _monster_ tranny and I wouldn't waste it on this amp. I think I'll try one of the BF Fenders and put a tone stack in it like Blues Jr. I have all of those power tubes. I'll just have to be sure to wire it so that it will work with any of them which will (I think) mean changing the tube wire a little.

This amp looks a teeny bit like the Blues Jr. It would be nice if it sounded as good. I have a Celestion G10 Vintage I can put in place of the Tube 10. The Tube 10 is somewhat inefficient at 94db. The G10 Vintage is better at 97db. But a Jensen is perhaps a better choice to get that "Fendery" sound. Or perhaps a Blue Coat Eminence like a Delta Demon or Ragin' Cajun'.

I'm certain I want two preamp tubes in there. The tone stack sucks too much of the signal up to use just one preamp tube, even at 12AX7 and have a gain and master volume, too. I could put a "fat" or boost switch in there to cut the second half of the second 12AX7/12AT7/12AU7 (depends on what sounds and works best) in and out. Perhaps a High/Low Impedance switch, too, since it has only one input jack and there's not enough room for another.

[RogerWilco99]

As has been suggested, I have a Hammond 270DX transformer that I'm going to use for the PT. I'm going to basically build a Princeton 5F2-a in it on a custom turret board and add a 12AY7 (the EH-12AY7) as the first gain stage followed by a gain control, the second gain stage from the second half of the 12AY7 then a full tone stack (based on the Blues Junior's) then the first half of the 12AX7 (a Tung-Sol 12AX7) then the master volume control. Then follow that with the rest of the 5F2-A circuit for the octal tube but using a Tung-Sol 6L6GC-STR instead of the 6V6. Output tranny will be a Hammond 125ESE.

I've got a Celestion G10 Vintage speaker that I can stick in the cab or I can try a Jen C10Q. I think they both sound pretty good but the Jensen might sound a bit better with the (basically) Fender Blues Jr/Princeton Tweed circuit. I could go with an alnico Jenson P10, but I don't have any of those and I don't want to buy one to speculate with.

I'm wondering what to do with the second half of the 12AX7. I know how to hook it up to let it idle. But, I'm thinking of the possibility of making that siwtchable as another gain stage after the master volume. If I did that, I'd probably be better off using a 12AT7 instead. Otherwise, it might come out with too much gain and sound pretty crappy and clipping like crazy. The idea I have for this is to perhaps add this with a "Gain" or "Overdrive" switch so that it behaves like a two channel amp. Of course, the overall target is more of a blues amp, so the whole overdrive idea might make no sense. Any comments/suggestions, there?

[PremiumPlus]

If it were me, I'd build a stock 5F2A circuit and try that first. I own a tweed Princeton and it is really sweet. I bet it will really do well with a 10" Celestion. I've got a Marshall 4x10 with those 10T-35 (I think that's the number, I know the 35 part is correct) and it loves small amps.

[Dobro7]

Epiphone Galaxie 10 rebuild

Ok, I was very thankful to come across this post. I am about to rebuild my Galaxie 10. I think this amp has some potential to be used in the studio or even live.
After some research I am going to use the 125ESE OT, change some of the caps and resistors, speaker, etc. I am not sure on the whole choke thing though. Or what tubes I should use.

If I use the AX84 schematic shown above, will this still allow a good clean sound with some raunchy blues when cranked?

Should I install a choke? If so, where and what model?

What tubes should I use? I have read the KT66 and a 5751 work great.

I have also thought about putting a switch to bypass the tone stack if wanted.

Any help would be greatly appreciated. This is only my second amp to modify, but I feel it will allow me to learn a great deal and come out with an impressive sounding little amp. I do have electrical background, just never messed with my amps much.

[pacAir]

Epiphone Galaxie 10 Mods
I know this is a "dead" thread but I wanted to post a relevant update.

I purchased a couple Galaxie 10 amps about 8 years ago to mess around with (like a lot of other people). The first thing I did when they arrived was to unpack one, connect my Fender Strat and play the amp with all knobs cranked to "10". Five minutes of having some lead guitar fun the amp went silent, no fuse blew and no smoke was evident. I confirmed that the output transformer blew (I had assumed this to be the amp's Achilles' heal and this confirmed it).

Fast forward to 2013... I finally got around to working on this amp! My goals were to replace the blown OT with a heftier unit, increase the gain a little bit and do something about that annoying and ever-present hum. Here are the mods I did:

Filter Caps: I paralleled two 100uF, 450Vdc caps and connected them from the output of the bridge rectifier (pre-Standby switch) and the adjacent chassis ground connection. I also paralleled a 47uF, 450Vdc cap across the existing C5 (22uF). These values were a mixture of empirical design and caps I had on hand. They were very effective at squashing the amp's hum level.

Preamp Gain Bump: I paralleled an additional 10uF, 50Vdc cap across the existing 10uF at C4.

Output Transformer: I removed the original transformer (this also helps to make room for the additional filter caps) and installed an oversized Hammond 125ESE transformer (I used the 4-ohm secondary winding as determined for a 5000 ohm primary impedance... see the Hammond specs that come with the transformer).

This transformer is rated as an "honest" 15-watt unit but is greater than 4 times the physical size, mass & weight of the original! There truly is no substitute for "iron" in your tube amp diet! I mounted the transformer to the cabinet using threaded inserts install through the bottom of the cab.



When I was done I set up the modified unit next to an unmodified Galaxie 10 and played my Strat through both to compare them.

The stock unit sounded tinny, tiny and lifeless when played clean. When gained-up it sounded like a single bee in a jar. This reminded me why I purposely tried to blow the amp up originally (to see what would fail first). The amp was a humming toy with little to recommend it.

The modified amp, however, was a totally different animal... it had BALLS (for its size)! It was very jazzy when played clean on the neck pickup with plenty of authority, headroom and warmth. The amp was very chimey when gained up to the edge of distortion with an obvious boost in output level over stock. When cranked and using the bridge pickup it screamed WITHOUT sounding stressed out and wimpy. It is now a BLAST to play through, easily good enough to record with or to mic and play small gigs with!

The hum level was at least 3 or 4 times lower than stock and was quite acceptable. These mods took a toy and bulked it up into the "REAL tube amp" category, a fun to use tool that sounds a TON better than stock!


Steve
Pacific Music Services