info needed on this amp

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xbox_540
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Joined: 2010-04-06
info needed on this amp

just scored a earth 1952 revival 2x12 amp for free but only the amp section (no box or speakers) so i have turned it into a head but i need to know what impedance this amp runs at and if i can run two cabs with it. and also does anyone know what the jack next to the reverb inputs does? is it some kind of footswitch jack?

Lucent
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Joined: 2007-06-17
The jack next to the reverb

The jack next to the reverb is for a foot switch to control the reverb (On/off) My 1961 112 Revivals have the same jack.

Not sure on the impedance, maybe somebody else here knows. or look through the older posts. There is a schematic posted in one of them.

I run with the 1st jack powering the single internal 12" speaker and the 2nd jack connected to a Peavey 4x12 cabinet. Seems fine.

L

xbox_540
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Joined: 2010-04-06
i see, i think i saw the

i see, i think i saw the schematic that was posted but the link was broken so i couldnt open it. what ohms does your peavey cab run at?

Lucent
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Joined: 2007-06-17
It is a 4x12 @ 4 ohms.

It is a 4x12 @ 4 ohms. Scorpion Speakers. Peavey 412FC.

xbox_540
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Joined: 2010-04-06
so does that mean that the

so does that mean that the speaker inside your amp is a 4 ohm?

Lucent
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Joined: 2007-06-17
I don't know. Seems likely.

I don't know. Seems likely. It is the original speaker but I don't think it is marked.

Vince
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Joined: 2010-04-08
Speaker Impedence?

Could you check it with a meter? No one has been able to confirm what these amps run at and I have a matching cab that I have been trying to figure out which speakers to put in it.

Mine is a Fenderish looking head in tweed... it runs 2 6L6's and no preamp tubes... preamp is solid state. It has reverb.

Thanks!

Lucent
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Joined: 2007-06-17
OK I found My meter.

Edit: So I set the meter at 200 and measured the resistance of the single speaker. Meter was running between 14.5 * 15. I think that means the speaker is running at 16 ohms. Seems high to me. Do I need to measure differently?

Looking at it again it may be a reading of 1.5 which would seem to indicate a 4 ohm load.

Somebody who knows more about ohms and meters needs to chime in.

L

Vince
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Joined: 2010-04-08
1.5 would almost be a dead

1.5 would almost be a dead short! I got 20 out of a 16 ohm speaker.

I don't know.... I wish I could determine the load from the schematic.

Lucent
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Joined: 2007-06-17
The speaker is marked:Track

The speaker is marked:

Track 12-16
29173
285763

I guess it could be a 16 ohm speaker. It is a 12 " speaker. I couldn't find any info on it on the web.

Not sure how to read the meter but it lookis like I am getting 14.5 - 15. Which would seem to indicate a 16 ohm load.

Update: I just checked my other 112 that is not running but has the original speaker in it from when I bought it back in 1976. It gave a readout of 8.5. Seems I have two amps with different speaker loads.

How can I measure the amp instead of the speakers?

L

Vince
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Joined: 2010-04-08
I don't know anyway of

I don't know anyway of testing the amp itself. You could look at the output transformer for any indication of which tap it is using or maybe cross reference some numbers off of it. I think I may just try running at 16 Ohms. I was running it at 8 ....

xbox_540
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Joined: 2010-04-06
it seems likely that it IS 16

it seems likely that it IS 16 ohms based on what your speaker was labeled as. I used it with my 16 ohm cab and it sounded amazing but even if it was lower ohms i guess it wouldnt hurt to run it with a 16 ohm load would it?

Vince
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Joined: 2010-04-08
It very well may be 16 ohms.

It very well may be 16 ohms. I don't have allot invested in the amp buy it sounds so good that I don't want to blow it up due to running it wrong. So frustrating.

More resistance is going to add heat and stress the transformer.... the same with less... it will put a strain on the whole output section.

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