Epiphone ea-50 8ohms or not???

edadmartin · Posted: Mon Nov 26, 2007 7:41 pm Post subject: Epiphone ea-50 8ohms or not???

My 63 EA-50 has the stock cts 8 ohm speaker in it and its toast.
I measured the ohms of the transformer at a weird 3.4 ohms.Does this mean the ot is failing? or that a wrong ot was substituted at some time in the past(it doesnt look like an after market change out)??
should I run a 4 ohm speaker? would it hurt??,or throw another 8 ohm speaker in there??? Laughing

tw001_tw · Posted: Tue Nov 27, 2007 8:09 am Post subject:

Describe what you mean by "...I measured the ohms of the transformer.."
please.

As of right now, I'd replace the speaker with one of the same resistance.
How many problematic amps do you have?? Shocked

edadmartin · Posted: Tue Nov 27, 2007 6:33 pm Post subject: problematic amps

I buy amps and guitar type items and spend my time figuring out whats wrong.some are saved some are resold.I enjoy fixxing things and it always teaches me something new.The forums are a great source of interaction ,and I enjoy all the great info as well.I have 3 kalamazoos Im recapping and this EA-50 right now.Ive built a jtm-45 and a 18 watter last year from help on various forums.Ive also got a supro 24 kit waiting in the wings and 2 old kay amps,and a almo or 2 collecting dust.
I used a multimeter on the speaker wire to check the ohm reading.This may have been wrong,because of your comment .If it is wrong Im all ears,I want to learn Laughing

tw001_tw · Posted: Tue Nov 27, 2007 8:43 pm Post subject:

WOW! I wish I had your kind of time. Very Happy

I've been working on my
Bogen rebuild for what seems months.. and it probably has been (2 to 3)
Although I am closing in on that one.. and fast
I got an 18watt I built from scratch that works, but its not as loud as it
should be - it has to do with the reverb stage I added (works fine if I bypass
the reverb stage). thats been sitting for about 4 or 6 months. Maybe one
of these days, when I get back to that one, I'll send you the layout I'm using
and see what you think!

To my knowledge, I don't know of a way to determine what ohm speaker
an output transformer is expecting. You either know it, or you don't.
There is a way (rather complicated) to determine the primary impedance,
but other then that.... As an experiment, I measured the OT leads that
go to the speaker (speaker unattached) and I measured 0.7 ohms on my
Bogen rebuild. I do know that it is wired for an 8 ohm speaker. Am I
following you ok on this one? I'm getting the feeling I'm not
understanding your question very well.

Still haven't got the pm I sent you?

Dilapidus · Tadpole Joined: 02 Apr 2007 Posts: 20

edadmartin · Posted: Sun Dec 09, 2007 1:48 pm Post subject: a need to know

How do you know what speaker to use normally,with out specs???And what if you have old iron and dont know the ratings or specs,I need to know if the ot is performing correctly or not,how do you all test transformers??? Confused

_________________
" make things as simple as possible-no simpler " Albert Einstein

Dilapidus · Tadpole Joined: 02 Apr 2007 Posts: 20

I don't know.. I'd guess you put up two traces on a scope and do some calculating.

The EA-50 is definitely an 8 ohm transformer. It's the exact same circuit as the Gibson GA-5 (crestline)
_________________
See me fumble with tube amps at http://www.paleoelectronics.com/blog

tw001_tw · Posted: Sun Dec 09, 2007 3:35 pm Post subject: Re: a need to know

edadmartin · Posted: Mon Dec 10, 2007 2:25 pm Post subject: wowww!!

Ok yea my brain hurts,Ill have to digest this info slowly.But I do have a variac and a multimeter so it seems doo able.thanks for this great info
Ive finished my kalamazoo amps for now,but havent gotten into the epiphone ea 50 yet.Ive got new caps coming and it needs a pot or 2 Smile

I just picked up an old olsen 4 track tape recorder9Its got tubes) and an old zeinth radio,probably mid 40s.new projects for 08
_________________
" make things as simple as possible-no simpler " Albert Einstein