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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jul 27, 2016 11:26 am
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Congrats on a nice vintage tweed amp score! Some vintage TV Tweed for your first vintage amp is fantastic! Enjoy that puppy!

8)

T2

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jul 27, 2016 12:30 pm
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sfceric64, this is a cathode biased, Class "A" amp. Plate voltage will prolly be around 350-375VDC (accounting for increased outlet voltages, today) The idle bias will be about 9 watts per tube. Or around 25-mA per tube.

If the idle bias current is too high, first look at the cathode-tied 250-ohm, 5 watt resistor. And 25mfd/25VDC bypass cap. Then, the 250k-ohm + 7k-ohm grid-to-ground resistor network next. Finally, the 0.05mfd/600VDC coupling caps (for DC leakage).

Good luck with this great piece of history! :)


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jul 27, 2016 1:58 pm
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Quote:
Congrats on a nice vintage tweed amp score! Some vintage TV Tweed for your first vintage amp is fantastic! Enjoy that puppy!8)
Thanks, I'm starting to feel like a 3y/o on Christmas Eve. :D
Quote:
Plate voltage will prolly be around 350-375VDC (accounting for increased outlet voltages, today) The idle bias will be about 9 watts per tube. Or around 25-mA per tube.
Those are the numbers I'm expecting if everything is good.

On my earlier post, I was trying to hurry through the responses to miss the air station shift change traffic and get to the bank. I think the comment ref: 20uf to 16uf was leftover brain fluff from last nights reading, I think that's more Princeton #'s, was up reading til the wee-wee hours.
Also, on the tubes that are looking wonky. Any chance the 6v6s are of the vt-100 series variant and do you have experience with these?
Thanks,
Eric


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jul 27, 2016 3:59 pm
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Almost forgot to post this you-tube video I saw last night, yeah I know its 4y/o but it has a tone review of four tweed deluxes: TV, Wide-panel, (2)Narrow-panel
And he's playing a 55 goldtop LP and a fine 60's Strat
https://www.youtube.com/watch?v=niqzD-7cqYA


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jul 27, 2016 4:53 pm
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VT-107A and 107B are excellent tubes. 1940-50s era, with mil spec designations. But, are same tubes as commercial 6V6G and GT of the time. The coke bottle Sylvania VT-107B are most awesome tubes. The 6V6GT and 6V6G and all the VT types have same plate voltage and idle current bias specs.

http://cdn3.volusion.com/9yms2.j7rx4/v/ ... 1462990013

Best 6V6GT type are the 6V6GTY (esp Raytheon) and the Brimar CV-511. Esp in Class "A" apps. Very tough tubes.

http://www.hifido.co.jp/photo/16/870/87020/a.jpg

http://www.watfordvalves.com/images/pro ... 181004.jpg

Really, the best 6V6GT subtype is the Bendix 5992. SUPER tough tube. Great tone. very hard to find good ones, anymore. :(
http://cdn.shopify.com/s/files/1/0333/7 ... 1421343369


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 9:12 am
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I'm looking at a budget of around 150-175 for a complete set. So I'm gonna start my shopping list today, I'm leaning towards all glass type and gonna try and stay w/ unused. Appreciate all the pics and info.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 5:46 pm
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$150-175 for set of tubes is very reasonable for this amp. You can pst or email me, if you have questions on specific tubes or subtypes.

Good hunting! :D


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 6:06 pm
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sfceric64 wrote:
I'm looking at a budget of around 150-175 for a complete set.


I would think such a budget will be more than adequate. The pre-amp triodes and the 5Y3 are still reasonably priced -- it's the matched pair of power tubes that will consume the lion's share of the money.

Arjay

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 8:34 pm
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Well, I came in just under the top end of my budget. Depending on how things turn out, I may spend a little more.

I went with a single 6sc7gt, tungsol(these aren't cheap). Just to test in comparison to the installed 6sc7, electronically/sound wise. A CBS-Hytron 5y3gta, got a pair at a very reasonable price. And a pair of closely matched 6v6gt National Union(1951) black glass, also very reasonably priced.

I will probably end up getting another 6sc7gt tungsol and another set of 6v6 depending on the installed tubes and of course how everything sounds together.

I have a spare set of EH6v6gt for my drri, may see what those will do in this amp also.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 9:44 pm
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sfceric64 wrote:
Well, I came in just under the top end of my budget. Depending on how things turn out, I may spend a little more.

I went with a single 6sc7gt, tungsol(these aren't cheap). Just to test in comparison to the installed 6sc7, electronically/sound wise. A CBS-Hytron 5y3gta, got a pair at a very reasonable price. And a pair of closely matched 6v6gt National Union(1951) black glass, also very reasonably priced.

I will probably end up getting another 6sc7gt tungsol and another set of 6v6 depending on the installed tubes and of course how everything sounds together.

I have a spare set of EH6v6gt for my drri, may see what those will do in this amp also.


Sounds like very good set of tubes.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jul 28, 2016 11:28 pm
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I hope they work well together.
While continuing my research on National Union, I ran into this historical business report from (Lehmann Bros) and Harvard. A one page lineage of the company for those that like a little light tube related history.
http://www.library.hbs.edu/hc/lehman/company.html?company=national_union_radio_corp


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Fri Jul 29, 2016 7:34 am
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National Union made excellent tubes. I really like their gray-glass, black plate 6V6GT (or VT-107A). Is that CBS-Hytron a 5Y3WGTA? This is also an excellent tube.

CBS-Hytron, Tungsol, Raytheon never made a bad tube. Not that I know of. Getting a high testing, low-noise one is the key to a long life tube.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Fri Jul 29, 2016 10:42 am
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[quote] Is that CBS-Hytron a 5Y3WGTA?[quote]Yes the 5y3wgta clear glass rectifier and the 6sc7gty half black glass are brown base, but the 6v6gt are black base/glass. The JAN type 6v6 were a little more than double what I payed, unless I buy used/tested. That's where I may spend more later, after I get everything up and operational.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Fri Jul 29, 2016 2:50 pm
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Sounds good! Good luck.

Have any photos of the circuit? Thanks!


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Fri Jul 29, 2016 6:56 pm
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Have any photos of the circuit?
:o
Well, I wired my payment to the auction house late Wed., so I expect maybe by Mon. to get a package tracking #. They are only 500 miles from me so I'm hoping 2 days tops delivery by Wed/Thur at the latest next week.
Not sure how many items were sold during the auction, thinking around 225 pieces, and their package and handling is exceptional. I'll open it up and snap whatever pics are necessary as soon as I get my hands on it.

Tubes arrive Monday. There are a lot of variations on the National Union tubes, I don't believe the ones I ordered have jan-cnu(VT107's) on the tubes themselves but the packaging looked brown box jan type. I couldn't see through the glass to identify any tube characteristics and that's were it really counts. That and the 51 dates are sorta close to the end of the war stock years, maybe I 'll get lucky and have a few leftover mil spec parts inside.
They primarily used GE,RCA and TungSol patents so either way I feel they will be fine. And Sylvania buying them out in 54 just shows there was a perceived value there.

Gonna go to the local radidio shack tomorrow and pick up some little diy pieces. I need to fashion an electrolytic bleeder probe. I had thought they closed down the last store a few years back, but found one on google this morning.
Will look to order anything else needed by Monday also. Just gonna wait until I see it to spend any more money.

Good thing I grabbed this when I did, there is a 65/66 Twin w/JBL's and a 68 Bandmaster PB on my local craigslist. They want a little money for the twin w/ good reason and the other guy wants a couple bills to much for the Bandmaster.


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