Seek OT-215 Substitute

[ktritty]

Hi Y'all

First Thread EVER made anywhere on Al Gore's curious internets. Feels kinda tingly, smells like almonds...

Anyways, I'm wondering if anyone out there can help me find a substitute for an OT-215 Output Transformer (From an Ampeg G-15 Gemini-2).

I have located a few OT-215's but they seem so scarce and expensive. I'd be happy with any Transformer that has close enough specs to work. Don't mind if it gets a shade distortey (rather than boringly clean as this amp was originally) as long as the replacement will not overheat.

I am comfortable making a few basic mods to the output stage as needed to make your recommended transformer work. Currently using 8ohm speaker; OT-215 Center Tap at 430V; 7591's Cathodes at 0V. Plate Bias I think is normally 40mA Anode current per 7591.

Any advice greatly appreciated, THANKS!

[Enzo]

Hi, welcome to the forum

Use the search function at the top here and enter "OT-215"

It will return this thread and the one we just had on the same topic. Open that other thread and read through it. I think it will answer your needs.

Pretty much any transformer intended for a pair of 6L6s would work well enough. AMpeg used the OT-215 for both 7591s and 6L6s.

[ktritty]

OT-215 Alternate Found

It's been a while, but I found some extra ching and bought a Mercury Magnetics APO-RR2 transformer to replace the bad OT-215. I am very happy with the results. Does not have the original Ampeg sound at higher volume, but has a sound that I find to be much more fulfilling. A warmer, broader distortion, but the distortion is still fairly mild as one might expect from otherwise stock Ampeg Gemini 2 G-15.

Required Drilling a single hole in chassis to accommodate the different size tranny, but it is easy to locate the hole so that replacing with an APO-RR2 is easier than it would have been with a new OT-215.

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Mercury APO-RR2 replacing Ampeg OT-215... Recommended!
***

[pecorporation]

Have an Ampeg Gemini VI GS-15R with an opened primary on the output transformer. The number on it is OT-215. Aside from Mercury Magnetics, are there any viable substitutions that may be more cost effective?

Thanks!

[Leo_Gnardo]

Have an Ampeg Gemini VI GS-15R with an opened primary on the output transformer. The number on it is OT-215. Aside from Mercury Magnetics, are there any viable substitutions that may be more cost effective?

Thanks!

I use Deluxe OT's for most of those shower-curtain Ampegs. Available for dirt cheap (compared to Mercury) at Antique/CE.

[pecorporation]

I use Deluxe OT's for most of those shower-curtain Ampegs. Available for dirt cheap (compared to Mercury) at Antique/CE.

Thanks! That did the trick!

[Leo_Gnardo]

Thanks! That did the trick!

Its' nice when things work out - even better if it's cheap!

[pecorporation]

Hi Leo,

One quick question, when you swap out the Fender HT OT for the old Ampeg OT, do the primary coil colors match up, blue and brown, to the old OT or are they reversed. Reason I ask is the brown and blue on the old OT schematic is reversed to the newer Fender HT schematic.

[Jazz P Bass]

A word of caution: sometimes the winder gets it wrong.

With a negative feedback circuit it matters.
If you lift the NFB & the output signal rises, then the OT is wired correct.
If the output goes lower, then it is wired incorrect.

[pecorporation]

Thanks, Jazz. The winder got it wrong. Fired it up and boy what a squeal, reversed the leads, all is well.