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Author Topic: Ever heard of a 1948 Symphony Porto-Amp?  (Read 7430 times)

K Man

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Ever heard of a 1948 Symphony Porto-Amp?
« on: November 02, 2011, 07:00:19 PM »
Looking for any info on a Symphony Porto-Amp made in 1948.  Small 3 tube practice amp @ 12" x 12" x 5".  One knob labeled "Volume" and two inputs labeled "Instruments", runs on 110 Vac wall power,  8 inch speaker.

Has a removeable front cover that is covered in it's original fake alligator skin material, back cover is covered in the same material.




joecool85

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #1 on: November 03, 2011, 09:32:59 AM »
I've never seen anything like it.  Could you provide us with some guts shots?
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K Man

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #2 on: November 03, 2011, 09:57:03 AM »
Sure thing,  I'll update with internal pics hopefully later tonight @ 10 pm EST.  What I remember of the components is the speaker is a "Utah",  made in Huntington, Indiana.  It has a little lightning bolt for a logo.  The rectifier tube is a 7Y4, power tube is a 6V6GT, both are Sylvania brand...can't recall the pre-amp tube number right now.  The tube sockets are made by Admiral.  The tubes don't look to be 60 years old but who knows.

K Man

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #3 on: November 03, 2011, 05:22:59 PM »
Okay, more pics and data...
The cap can is an Aerovox, made in New Bedford, Mass.  The company is still in existence.  I've talked to their customer service.  They have no record of this model.  The rest of the components I haven't researched yet.

The fatter orange cap is a Cornell Dublier

The larger wax coated orange cap...I can see some numbers but not a maker name.

The small yellow cap is an Astron.

The thin blue green cap is a "Solar Sealdtite Wax-Molded Paper Capacitor".

The smaller orange wax coated cap is a "Tube - U - Lar Wax-Molded Paper Capacitor" made by Pyramid Electronics.

The preamp tube is a 6SN7GT.

The black transformer has 32 ? - 2 stenciled on it...the third digit is fudged up...could be a 4, could be an A.  Can't see any markings on the small silver xfmr.

The cap can and black xfmr are both electrically connected to a flat brown bar shaped component that's held down by a metal bracket.  The metal bracket is stenciled:
K59J131-5
Res 625

The "Utah" speaker part number is B104759-1

Other than dust, dirt and a very poor attempt at adding an extension to the AC power cord, the entire amp looks to be original. 

The 1948 date may or may not be accurate.  The date came from a vintage guitar equipment dealer located in Amsterdam, Netherlands via a web search.  He knew nothing about the history, manufacturer, etc of this type of amp and had gotten rid of his some time ago.  His listing is apparently trapped in the MATRIX and still shows up via web search.

K Man

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #4 on: November 03, 2011, 05:25:17 PM »
More pics

joecool85

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #5 on: November 04, 2011, 08:14:04 AM »
Have you tried playing the amp at all?
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J M Fahey

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #6 on: November 04, 2011, 08:23:14 AM »
Never heard either, doubt anybody has.
Cool looking anyway.
Just turn it on carefully, wait a few minutes watching for smoke, sparks, etc. , then touch the chassis with a neon screwdriver to check whether it´s electrically "hot" or safe.
Then invert the plug in the wall and try again.
Only after being ABSOLUTELY SURE it is not "hot" plug a guitar and try to play.
Good luck.

K Man

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #7 on: November 04, 2011, 08:51:15 AM »
No, I haven't plugged it in yet.  Thanks for the "hot" advice.  I was thinking I'd also pull the tubes before I plug it in to see if anything smoke checks...then try it again with just the rectifier tube and then the preamp, etc.  Based on the condition of the homemade power cord extension, it hasn't been plugged in for some time.  That mess would have popped a breaker or two.

J M Fahey

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #8 on: November 04, 2011, 09:12:58 PM »
Fine.
What I said is the bare minimum to check whether you have a playable (or at least a reasonably repairable ) amp or just a beautiful "Show but do not plug" piece.
After checking that, with tubesand all, leave it on a couple hours.
Old electrolytic capacitors might decide 2 hours later that this brave nrw world is not for them and give up the ghost.
If they survive, next job will be to add a properly grounded 3 pin plug power cord.
Only then it´splayable.
But check step by step.
Initial testing should be plugging it into a fused extension.
A 5 or 6 A fuse will protect you from cursing in the darkness.

K Man

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #9 on: November 05, 2011, 11:07:52 AM »
By 5 -6A fused extension, the amp does have an internal fuse.  Not sure if this was stock or added by a previous owner.  Depending on where the fuse is in the power path and the value of that fuse, is that an alternative to having to come up with a new dedicated fused extension?  I've got enough power strips laying around, probably makes sense to swap a lower amp breaker into an old strip to give me a ready made go-to for future use

J M Fahey

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #10 on: November 05, 2011, 01:40:10 PM »
The external one is an extra safety measure.
I´ve seen more than one amplifier *showing* a nice fuse holder, which was bypassed or wrongly re-wired by an earlier user or simply cracked or broken in some other way.
« Last Edit: November 05, 2011, 01:42:00 PM by J M Fahey »

Kaz Kylheku

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #11 on: February 08, 2013, 09:39:59 PM »
The amp is clearly supposed to be called Symphony, but the front plate actually says Gymphony.

The treble clef is a fancy G, not an S.   xP
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Roly

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #12 on: February 08, 2013, 11:32:08 PM »
Extremely cute.  Older than I am (just).

I wouldn't give you two bob for the electrolytics, and those waxy brown tubes are waxed paper which have to go.  You are also bound to find some drifted-off-value resistors in there as well.

I'd go a bit further and say power it up initially via a limiting lamp.
http://www.ssguitar.com/index.php?topic=2093.0

But what really has me worried (and I suspect JM too) is the "7Y4" rectifier.  This suggests to me that it may be a series heater chain, or some other oddity, and therefore have a live chassis, in spite of having a transformer; one like this almost killed me once.

I would first check very carefully (you life depends on it) with an ohmmeter that one side of the mains isn't somehow connected to the chassis.  Make sure you have a grounded lead with the ground connected to the chassis before you power it up. {better to blow it up than get electroluxed}

And hopefully we'll hear back from you.
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #13 on: February 11, 2013, 05:46:50 PM »
The 7 tubes are all Loctal bases.  (also Loktal) The 7Y4 is a 6X5 in a different package.  6v heater.   Loctal bases on tubes have the same pins arrangement as octal, but the pins are wire, like a 12AX7.  The center locator peg has an indent, like a guitar plug, and the center socket hole has a spring, so the tube snaps in securely.


I think it unlikely that a 6V6, a 7Y4 and a 6SN7 are run series string across the mains.   He reports two transformers, a black one and a small silver one.  SOUnds like power and output to me.  Three 6v tubes is consistent with that.  The flat brown bar thing that says 625 is a power resistor, 625 ohms, I'd suspect it was the cathode resistor for the 6V6 at first glance.


Forgive them spelling SYmphony with a G-clef, it is the same thing as some artist spelling his name with $$ instead of SS.  Artistic license.

Roly

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Re: Ever heard of a 1948 Symphony Porto-Amp?
« Reply #14 on: February 13, 2013, 06:46:18 AM »
Thanks Enzo, it's been ... (never mind) since I've even seen a Loctal.  I think they were originally devised for military use and seem to be rarer than hen's teeth these days, at least here in Oz.

I agree it's unlikely it's a hot chassis, but a radio clearly marked "AC only" with a "power" tranny that turned out to be for heaters only, as I said, nearly put paid to me, so I'm a bit cautious with these really old amps.  When I was in the UK (a long way back) encounters with AC/DC gear was all too common, but such horrors thankfully seems to be pretty well unknown here.
If you say theory and practice don't agree you haven't applied enough theory.