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Posted: Fri Sep 10, 2010 12:08 pm
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Here are some shots of the transformers. I looked it up here Transformer company EIA codes and says the codes are for a Fender Concert. Is that right? Or is this a reissue transformer for another amp?


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Last edited by Truetone6 on Fri Sep 10, 2010 12:42 pm, edited 1 time in total.

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Posted: Fri Sep 10, 2010 12:17 pm
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"022855" shows it to be an output tranny for a Super Reverb, a Concert, or (possibly) a 5G6 tweed Bassman made in the 51st week of either '65 or '75.

https://taweber.powweb.com/store/xfmrcr.htm

All of them with 2Ω secondaries.

It's the wrong impedance for that speaker.

Arjay

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Posted: Fri Sep 10, 2010 12:53 pm
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Retroverbial wrote:
"022855" shows it to be an output tranny for a Super Reverb, a Concert, or (possibly) a 5G6 tweed Bassman made in the 51st week of either '65 or '75.

https://taweber.powweb.com/store/xfmrcr.htm

All of them with 2Ω secondaries.

It's the wrong impedance for that speaker.

Arjay


Wow! Thanks I didn't know that. The speaker is a 93 Eminence 15 inch 4ohm.Think it is ok to play it like this? I only play it at home and I never go over 4 or 5 on the volume. I could bring it back to the store that I bought it from but I'd rather keep it.

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Posted: Fri Sep 10, 2010 1:37 pm
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The 4Ω speaker should not present any deleterious operational effects to your amp. Leo "back in the day" insisted that his tranny vendors (Triad, Schumacher, and Better Coil & Transformer) wind their iron such to permit a 100% mismatch between amp and speaker lest some catastrophic event occur during the amp's service life. You've only got a 50% mismatch so I wouldn't give it a second thought. Bear in mind though -- you have the capability to safely add a second 4Ω load to the amp via the extension speaker jack anytime you feel the need (such as a 2 x10 Tremolux or 2 x 12 Bass/Bandmaster enclosure).

HTH

Arjay

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Posted: Fri Sep 10, 2010 1:51 pm
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Retroverbial wrote:
The 4Ω speaker should not present any deleterious operational effects to your amp. Leo "back in the day" insisted that his tranny vendors (Triad, Schumacher, and Better Coil & Transformer) wind their iron such to permit a 100% mismatch between amp and speaker lest some catastrophic event occur during the amp's service life. You've only got a 50% mismatch so I wouldn't give it a second thought. Bear in mind though -- you have the capability to safely add a second 4Ω load to the amp via the extension speaker jack anytime you feel the need (such as a 2 x10 Tremolux or 2 x 12 Bass/Bandmaster enclosure).

HTH

Arjay


Oh that is awesome! Thanks so much Arjay!


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Posted: Fri Sep 10, 2010 2:00 pm
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¡De nada, señor!

:mrgreen:

Arjay

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Posted: Fri Sep 10, 2010 9:21 pm
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Que paso amigos ! I'm not interested in bursting bubbles, but there is the concern of flyback voltage in the output section. Maybe Arjay can give you a better explanation, speakers are his territory. But when the speaker voice coil returns to it's home, the magnetic field collapses and induces a high voltage back into the output trans and the power tubes. The OT multiplies this voltage. The result can be arcing at the tube sockets. This condition is increased when the impedance load(speaker) is higher than the OT is expecting to see, and even more so if the tubes are under biased. Didn't see an interior shot of the chassis, but this amp may have had flyback diodes installed on the power tube plates. Six in4007 diodes at .25 cents, is cheap insurance. I put them on my amps, and three in series to ground off the plate socket terminal, will not affect the amp's tone whatsoever. Hey Arjay, 50% ? Arturo

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Posted: Fri Sep 10, 2010 9:59 pm
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Doh!

De acuerdo, compa......it's a 100% mismatch.

"CRS syndrome" rears its ugly head yet again.

:mrgreen:

See what you have to look forward to when you hit my age?

"I just wish I hadn't drank all that cough syrup."

Arjay

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Posted: Fri Sep 10, 2010 10:39 pm
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aclempoppi wrote:
Que paso amigos ! I'm not interested in bursting bubbles, but there is the concern of flyback voltage in the output section. Maybe Arjay can give you a better explanation, speakers are his territory. But when the speaker voice coil returns to it's home, the magnetic field collapses and induces a high voltage back into the output trans and the power tubes. The OT multiplies this voltage. The result can be arcing at the tube sockets. This condition is increased when the impedance load(speaker) is higher than the OT is expecting to see, and even more so if the tubes are under biased. Didn't see an interior shot of the chassis, but this amp may have had flyback diodes installed on the power tube plates. Six in4007 diodes at .25 cents, is cheap insurance. I put them on my amps, and three in series to ground off the plate socket terminal, will not affect the amp's tone whatsoever. Hey Arjay, 50% ? Arturo


OK,thanks for the heads-up man! I will have Reverb Ray,my local tube tech,check it out when I bring it in for a tuneup.


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Posted: Fri Sep 10, 2010 11:43 pm
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Like Art mentioned, look for evidence of arcing around the pins of the power tube sockets. Also, be sure to check the 470-ohm 2-watt resistors there for any tell-tale signs of thermal abuse and/or overload. Replace as necessary. I've seen the effects of flyback voltage before but this symptom generally occurs with tube bass amps that are routinely driven hard for extended periods -- Dual Showmans and Bassmans were notorious for this, primarily when used with more than one cabinet (ie: a 100% under-loaded impedance mismatch).

Arjay

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Posted: Sat Sep 11, 2010 11:00 am
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OK,Thanks guys. I talked to my friend Jim Harms yesterday.He owns the store where I got this amp. He told me that amp came out of a Studio in Nashville,where the last owner bought it about 30 years ago. He said the speaker was changed to the Eminence about 15 years ago and the grill cloth was probably replaced at the same time. I don't know what kind of speaker was in it before. This is the speaker in it now.

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Posted: Sun Sep 12, 2010 3:09 pm
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The OEM speaker for that amp was most likely a Jensen C15N or an Oxford 15M6 but it could also have been an alnico Jensen P15N or an early ceramic CTS.

HTH

Arjay

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