Gibson EH-185/EH-150 Layout

[reddead83]

Hello,

Planning on building an EH-185 from the attached schematic. Any one care to check my layout. I'm planning on using the Mercury Magnetics replica transformers, any recommendations on what to do for the replacement for the field coil, choke (recommended model?) and resistor(what value?), two 20 watt 1.5k power resistors or another suggestion?

Thanks,

Jesse

[Colossal]

Hello,

Planning on building an EH-185 from the attached schematic. Any one care to check my layout. I'm planning on using the Mercury Magnetics replica transformers, any recommendations on what to do for the replacement for the field coil, choke (recommended model?) and resistor(what value?), two 20 watt 1.5k power resistors or another suggestion?

Thanks,

Jesse

I can tell you from firsthand experience the field coil is 730-750Ω and the choke is a 5H Thordarson . You can replace the field coil with a resistor with suitable power rating or have a choke wound. One thing people see and think is wrong is the PT secondary voltages. The PT is 408-0-408VAC (nominal, +/- 10% at least). This rectifies to 403V with a 5U4G and under load, but the key to getting it right is the 20k bleeder resistor to ground right after the field coil. That acts as a primitive regulator and dumps a lot of voltage. At that point, the voltage should be 310VDC. On the 6L6 plates, a mere 301VDC or so. 22V on the cathodes. The amp runs in Class A push/pull.

That is a killer sounding amp. Great for gypsy jazz and a smokin' bluesy tone through the Mic input.

EDIT: p.s. I still have a set of transformers and all 1940s glass for an EH-150 build. One of those amps I keep hoping to have time for one of these days!

[pompeiisneaks]

I frequent the EL34world forums as well as moderate this one, so I'm pretty sure you're going to get similar responses here as I and Sluckey gave you there (Sluckey is here as well).

Maybe someone else here will know more.

I do love mine, sounds amazing, i even had to do a split plate load on the mic input to try to tame it a bit more for guitar, and even at that the gain is insane at about 3/4 volume and if I go to max volume it's really hard not to get it squealing and wailing.

~Phil

[reddead83]

Thanks for the insight Colossal, good information.

Hi Phil, figured it was worth a shot to ask. Looked through a couple threads here and it seems like a few people have built one.

I've been listening to recordings with the amp and getting hyped about building one. What kind of pickups are you using?

[Colossal]

That 185 and 150 are rare birds these days. A while back, I was lucky to work with a couple of gentleman that had originals. I also did a lot of research on the EH-150 Types I, II, and III models.

Phil you are indeed right about that Mic channel! A raging beast! Mark Fowler can attest to that too, back when we were building these. Coax is your friend

Probably some five or more years ago now, I scored some lovely 5U4Gs and 6L6Gs, the ST coke-bottle type and some very minty 6F5 and 6C5s for that rainy day EH-150 Type III build I keep promising to build. All 1940s stock. Beautiful original JAN cardboard sleeves too. Great old lore. For fun, I tried one of those 6L6Gs in a SE build and it was sweet.

I built one for a gypsy jazz player (Type II with the 6SQ7 preamp) and he played his homemade archtops through his. A really warm jazz tone but not clean. Definitely some warm, lovely fur on the edges. Touch sensitive too. And when you want to rage on some blues, plug into the Mic channel!

Dammit man! You're gettin' me fired up again. I gotta stay focused and finish what's on my plate before dessert.

[reddead83]

Colossal thats awesome, sounds like you're the go to guy for knowledge about these amps.

Good to know, shielded it is.

With all those sweet tubes laying around sounds like you should build one as soon as possible haha.

Alright, so looking at running a Hammond 158Q choke with a 50 watt 680R resistor in series which will give me 785R to emulate the field coil. Will this work? Choke is 150ma, 5H, 400 volt max DC. 105R resistance.

Thanks,

Jesse

[M Fowler]

Dave (colossal) we also played with that voltage divider for that hot channel on the EH150 it is indeed an aggressive channel and can be quite a lot of fun!

Love the octal preamp tone.


For the EH150 I went by the build book by Tino Zollola amp book 2 I think.


Mark

Modified EH150

Gibson EH150 schematic.gif

schematic replace field coil with choke.

[Stevem]

The only thing you might want to do different build wise is to use that standby switch set up that Gibson later Used where in standby the switch places a 22k resistor in series with the output tubes cathode to lift it way above ground and then in the operate postion places a short across that 22K .

[pompeiisneaks]

Thanks for the insight Colossal, good information.

Hi Phil, figured it was worth a shot to ask. Looked through a couple threads here and it seems like a few people have built one.

I've been listening to recordings with the amp and getting hyped about building one. What kind of pickups are you using?

Oh gee, don't recall now,

ok, just listened, and I can tell you it's my epiphone es 339 with P90's it's the only guitar I have that has switching problems and makes noise switching (and it's only a few year's old) But my thoughts were that having an archtop semi hollow style guitar fit this amp best. It does do it service

~Phil

[Bennosteve]

I recently bought a Gibson chassis without the cabinet from what I suspect is a transitional period between EH-150 and EH-185. The nameplate was made as EH-150 but has been overstamped to say EH-180. Anyone heard of an EH-180 and if so know anything about it? I have a Jensen A12 with field coil that I picked up in hopes of someday finding a BR-1, which was my first amp as a wee lad. I still have a spare field coil or two from back when CMI reconed mine off-center and it sounded like shit at low volume. It took them a year to do that and send it back to me, that was around 1970 but I digress..........................