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Should I bother? Beginner tube amp question...


jtnfoley

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Yes, I seen nice while browsing but, an oriental ebony lacquer finish.

The Silvertone was an lower end from Sears, Western Auto,etc. Still would be nice to have pics. May workout better than others? Seems like got to be sure to get one that can be extracted for the whole, with not exertion to the point of damage of the prize, inside.

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The Cumberland CL ad for the Magnavox console is dated 1965. It could very well mean that it's a Astro-Sonic, which means it's a transistorized console stereo. Or a combination of a tube pre-amp/tuner with a SS power amp.

You would have to ask the seller if it's labeled Astro-Sonic, or if the back panel seals off the the whole back of the console stereo. The tube units had either no back panel, or panels with access to the tubes and for ventilation.

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Here is a pic of the "Classic 1965 (dated on cabinet) high-end Magnavox stereo console. In same family since new! (we need the space) Looks and works great. Has controls for volume, bass, treble, "timbre," AM/FM/phono/aux, plays 33/45/78 rpm records. One side has storage for records. This is a really cool piece of furniture that also makes music! Dimensions 48x19x28 inches"

BRAC-

Any chance you could send me a pic of the back where its opens to access the tubes?

SELLER- OK, attached are 2 pics. One is the back of the cabinet, showing vent holes and the outputs for external speakers. The other is the underside of the cabinet where there is a cutout and you can see the chassis. I can see the tubes through the vent holes and around the edge of the chassis, way in there, when I look in with a flashlight, but I can't get them to show up in a photo.

post-28352-13819373464482_thumb.jpg

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There were two reasons for my interest in the Stromberg when console hunting: First, they had some extrordinary models and I may have hit the lottery and second, the Made in Rochester site (or a related site) stated that the only SS Stromberg ever made was an FM tuner, so i would not waste any time running down SS consoles.

I don't know if there are others that may hve the same cache'.

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Its working! Silly little Cambridge Soundworks speakers in my office for now, but still!

I brought it up slowly on a variac while watching, listening, and sniffing for trouble, and while measuring chassis potential relative to ground. (About 10.5VAC as it happens, probably a transformer leaking to ground???)

It sounds great (after having found a cracked solder trace on the RCA inputs causing a channel to drop out) and I can't wait to test it on my Cornwalls and LaScalas!

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"(About 10.5VAC as it happens, probably a transformer leaking to ground???)"

Really? That might be something you'll want to watch.

Did you check plate voltages on the input and output stages against a schematic or perform resistance checks?

I'm glad it's come to life and passed the first smoke test.

Erik

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"(About 10.5VAC as it happens, probably a transformer leaking to ground???)"

Really? That might be something you'll want to watch.

Brother, you said a mouthful!

Did you check plate voltages on the input and output stages against a schematic or perform resistance checks?

I'm glad it's come to life and passed the first smoke test.

Erik

Negative on the plate voltages... I'm going to check the capacitors with an in-circuit ESR meter probably today (I'm in my office with access to LOTS of toys!) While I'm at it I'll walk the schematic... This IS a learning experience after all!

The "mouthful" referred to earlier? Reverse the polarity on the mains plug (it's non-polarized, of course) and that potential to ground is 110-115VAC

So, dear future reader (should this thread indeed be scrounged up by the next toob noob) TREAD LIGHTLY!
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I hope you took that comment in the right light, just as a 'light' suggestion to maybe proceed with a little healthy cuation. It's how I am, probably because I'm a teacher by trade, or something. I mentioned earlier on in this thread that it was an amplifier very similar to this one that once lit me up like a mercury vapor rectifier when I picked it up. On vintage stuff, it's just hard to tell sometimes if insulating materials are in good shape -- that sort of thing. One never knows what sorts of 'events' or mishaps such an antique may have been exposed to, or what damage may have been done to power supply elements that can't be seen (but possibly really quickly felt).

I'm curious to see how things progress. Thanks for reporting some of your findings.

Erik

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I just wanted to mention again the other alternative of an inexpensive kit with instructions and new parts. Or possibly a competently restored vintage power amp that can be used as training ground for study, measurement, and minor modification.

A chassis looking down at the ground from a height of 115 VAC needs to be encouraged back to earth very soon. I sincerely hope that discovery was made by way of a volt meter, only.

Take care and good luck!

Erik

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I meant to leave a link for this well-known Dynaco site:

For someone who is interested in learning, the kit prices are really quite good, IMO. The Dyna 70 is great looking, I think. Kit building is a blast, too! Wake up early on a quiet Saturday morning with a hot mug of whatever like you like, and heat up the iron for a few more connections, check them off as you go along. It is really enjoyable. People readily pay these prices for crossovers, which is fine and a personal choice, entirely. Just for the record, the same amount of money can buy a working amplifier that you can be proud to have built and tested yourself. There is always lots of support as you go along, too.

http://store.triodestore.com/diy35kit.html

Erik

edit: search Dynaco on ebay. The ST-70 kit with an inside shot of some very nice wiring can often be found. In my case, totally worth the expense. I didn't want what someone else may have made for the same price; I wanted to learn for myself.

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