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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 12:50 pm 
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I just noticed something with the amp.

According to the schematic posted in the first post the way the feedback is done a low impedance source may affect the feedback as the volume control is turned up higher.


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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 7:20 pm 
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Tube Radio wrote:
I just noticed something with the amp.

According to the schematic posted in the first post the way the feedback is done a low impedance source may affect the feedback as the volume control is turned up higher.



As soon as the 6AU6 gets here, I can test it out. Seems that it was a very successful amp back in the day.
I will build a set of test speakers for the work bench.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 9:31 pm 
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Yes although the output impedance of a source back then was a good deal higher than what a MP3 player will be.


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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 9:50 pm 
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Tube Radio wrote:
Yes although the output impedance of a source back then was a good deal higher than what a MP3 player will be.


Which brings us back to that transformer you suggested. Or, would be fun to design a buffer amp.
I will include two of them in my Edcor order for the 300B.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 10:07 pm 
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The transformer wont really solve that issue.

I'm working on an amp schematic with bass channel that we have been emailing about that will solve that issue.


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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Wed 30, 2017 10:21 pm 
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Tube Radio wrote:
The transformer wont really solve that issue.

I'm working on an amp schematic with bass channel that we have been emailing about that will solve that issue.



Great, what about the side amps?

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 12:20 am 
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I'm incorporating the Philcos as the side amps.


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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 2:09 am 
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John if you put the 12au6 in... it may work.. but may take longer to warm up.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 3:42 am 
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Pbpix wrote:
John if you put the 12au6 in... it may work.. but may take longer to warm up.



GREAT PETER
Wish I knew that. I will try it. Really want to test it out. Today, I started on the other chassis. Also plan to build a set of test speakers for the work bench.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 4:02 am 
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Starting my resistor storing system. Same as you suggested Peter.
http://www.ebay.com/itm/UNIVERSAL-Kraft ... Sw3YNXaj6X

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 4:48 am 
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john8750 wrote:
Starting my resistor storing system. Same as you suggested Peter.
http://www.ebay.com/itm/UNIVERSAL-Kraft ... Sw3YNXaj6X

Those are a bit too small.
I use either the 3-1/2 x 6-1/2
or 3-3/8 x 6

https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

https://www.ebay.com/sch/i.html?_odkw=c ... 2&_sacat=0

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 3:31 pm 
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Pbpix wrote:
john8750 wrote:
Starting my resistor storing system. Same as you suggested Peter.
http://www.ebay.com/itm/UNIVERSAL-Kraft ... Sw3YNXaj6X

Those are a bit too small.
I use either the 3-1/2 x 6-1/2
or 3-3/8 x 6

https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

https://www.ebay.com/sch/i.html?_odkw=c ... 2&_sacat=0



OK, I will get the larger ones. Thanks....

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 3:42 pm 
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IT WORKS.
Hooked up to one channel of the mp3, and one old Zenith speaker, it sounds good. Remember that I used the 12AU6.
With the other channel working, the volume will be ok. Tone control, there but not real responsive. Of course the speaker is just laying on the table and not in a box, so sound should get much better.
B+ 245.9, should be 240.
No 60hz hum at any level. A bit of IM distortion with no input. Some at different volume levels. That will be worked on later, after both amps are working, and the speakers are in a box.
Very pleased so far. Thank you Peter.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 3:50 pm 
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Here is a thought about the original Zenith speakers.
When I got the console, all wiring to the speakers was cut out for some reason.
So, I installed a crossover to connect the 6X9 and the tweeter. Not thinking that the 6X9 was
a full range speaker. Naturally the system did not sound good. When I connecter it to the Philco
without the crossover, it sounds ok.
I will mount the speaker and tweeter in a nice padded box. It will need a capacitor in line with
the tweeter. What type and size? Anyone know?

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 4:22 pm 
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john8750 wrote:
Here is a thought about the original Zenith speakers.
When I got the console, all wiring to the speakers was cut out for some reason.
So, I installed a crossover to connect the 6X9 and the tweeter. Not thinking that the 6X9 was
a full range speaker. Naturally the system did not sound good. When I connecter it to the Philco
without the crossover, it sounds ok.
I will mount the speaker and tweeter in a nice padded box. It will need a capacitor in line with
the tweeter. What type and size? Anyone know?



Maybe I could connect the 6X9 directly, and use the crossover only for the tweeter.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 4:26 pm 
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john8750 wrote:
Welcome aboard Brian..................
APB Where can I get these old plugs? These are on the chassis of an old Philco tube amp for a phonograph of about 1960, or so. I need them to restore this in vintage condition. HELP
Attachment:
The attachment plugg.jpg is no longer available


Hens teeth - I got a dozen back in 2008 when I working on bank teller interphone systems - and they ran pricey back then too. Cinch, EHC and EBY all made them - mine are marked with RMA/EIA number of 160, for EBY.
Attachment:
5-pin.jpg
5-pin.jpg [ 44.96 KiB | Viewed 1942 times ]


The interphone systems I worked on used them for detachability ( in case some idiot driver hit the pedestal in the drive thru teller lane, the connectors would break away, disconnecting the pedestal from the power source.

I still have 6, $6 each, plus shipping.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 6:05 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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john8750 wrote:
john8750 wrote:
Here is a thought about the original Zenith speakers.
When I got the console, all wiring to the speakers was cut out for some reason.
So, I installed a crossover to connect the 6X9 and the tweeter. Not thinking that the 6X9 was
a full range speaker. Naturally the system did not sound good. When I connecter it to the Philco
without the crossover, it sounds ok.
I will mount the speaker and tweeter in a nice padded box. It will need a capacitor in line with
the tweeter. What type and size? Anyone know?



Maybe I could connect the 6X9 directly, and use the crossover only for the tweeter.


My advice would be to use a choke in series with the woofer and a capacitor in series with the tweeter.

If the 6 X 9 is a multi way speaker then you won't need the tweeter, but if it only has a cone or a cone and whizzer then yes you will need a tweeter.

Now concerning the amps I'm drawing up I did not include any tone controls.

If there are tone controls used I'll need some sort of schematic showing how they connect up unless you used the original tone control circuit that Philco used.

I'd suggest ditching the tone control on the Philco amps and I can include the tone control circuitry from the Motorola schematic on the schematic I'm making if you want tone controls.


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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 7:46 pm 
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Findm-Keepm wrote:
john8750 wrote:
Welcome aboard Brian..................
APB Where can I get these old plugs? These are on the chassis of an old Philco tube amp for a phonograph of about 1960, or so. I need them to restore this in vintage condition. HELP
Attachment:
plugg.jpg


Hens teeth - I got a dozen back in 2008 when I working on bank teller interphone systems - and they ran pricey back then too. Cinch, EHC and EBY all made them - mine are marked with RMA/EIA number of 160, for EBY.
Attachment:
5-pin.jpg


The interphone systems I worked on used them for detachability ( in case some idiot driver hit the pedestal in the drive thru teller lane, the connectors would break away, disconnecting the pedestal from the power source.

I still have 6, $6 each, plus shipping.



If you would like to sell any of them, I am interested.

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If I did something right, I made a mistake.


Last edited by john8750 on Sep Fri 01, 2017 6:23 am, edited 1 time in total.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 7:52 pm 
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Justin
The original schematic. The Philco must be kept original.
download/file.php?id=187445



The Zenith 6X9 is one cone full range from the 60's. Works good.

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 Post subject: Re: Philco amp re-build.
PostPosted: Aug Thu 31, 2017 8:15 pm 
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So the tone controls of the philco have to be there for the feedback circuit or is it just something you want?

Concerning the tone controls not doing much it is because of a lower source impedance


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