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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Thu 19, 2020 9:17 pm 
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It appears you are correct but either way , it will work , the dogs are demanding to be taken for a walk will look at it more in a half hour .

I never made it back to the computer .

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Last edited by battradio@ on Mar Sat 21, 2020 12:46 am, edited 2 times in total.

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Thu 19, 2020 9:23 pm 
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OK.

Larry

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Fri 20, 2020 9:04 pm 
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I thought for sure when I replaced parts that I went by schematic but when powered
up R25 blew. Now I'm confused as to components that were grounded now are not
supposed to be????
As shown original cans were grounded to chassis


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Fri 20, 2020 9:18 pm 
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Just because the outer shell is soldered to the chassis does not necessarily mean the interior caps are grounded to it. Post a photo of the bottom of that cap.

Larry

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Fri 20, 2020 9:23 pm 
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pic2 I believe


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Fri 20, 2020 9:24 pm 
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pic 3 I believe


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 12:32 am 
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It appears the cans were connected to metal part of the chassis , so that is OK as long as you wired them all correctly .

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 1:19 am 
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Is this how that 4 section can was fastened under your chassis?

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 4:02 am 
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Those capacitor cans are covered in cardboard specifically because they are not connected to chassis ground. They are typically mounted to a phenolic wafer to insulate them from the chassis.

-David


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 5:06 am 
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The photo I posted above is of a 1347 chassis which is why I was asking if that's what his looked like. I know how they're fastened.

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 2:21 pm 
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Yes that is how the 4 section was mounted which is where a mistake was made
in grounding that cap but what about C20 to the left of that pic that was mounted
outside and grounded to the chassis


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 2:43 pm 
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C20 does not get grounded to chassis, only C4 is grounded to chassis. Those two wires coming off of plug W1 are Hot and Neutral, neither is Ground.

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 6:01 pm 
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ok, caps that I installed were checked and are ok
diodes also checked ok
wires that were grounded are now as they should be
so does it still stand that R25 should be increased to 200 ohms?
or should I start with that value and adjust to the 240v target ?


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 6:02 pm 
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ok, caps that I installed were checked and are ok
diodes also checked ok
wires that were grounded are now as they should be
so does it still stand that R25 should be increased to 200 ohms?
or should I start with that value and adjust to the 240v target ?


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 6:26 pm 
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I would use the resistor values in the schematic. You have plenty of margin in the capacitor voltage rating to accommodate a few more volts of B+.


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 9:37 pm 
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stratozen wrote:
ok, caps that I installed were checked and are ok
diodes also checked ok
wires that were grounded are now as they should be
so does it still stand that R25 should be increased to 200 ohms?
or should I start with that value and adjust to the 240v target ?



You need to compensate for removing the two selenium rectifiers , i would buy two 200 ohm 5 watt resistor .
Install the first one and check the voltage , if the voltage is low parallel the second one with the fist one , to get 100 ohms.
check your B+ and go from there .

You should realy consider a fuse in series the R 25 .

https://frank.pocnet.net/sheets/049/5/50L6GT.pdf

The plate voltage rating is 200 volts DC for the 50L6's , like most manufacture's it is pushed past the limits all ready , lets not ruin your output tubes

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Last edited by battradio@ on Mar Sat 21, 2020 10:11 pm, edited 1 time in total.

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 10:07 pm 
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Why? The B+ difference between selenium and silicon rectifiers is about six volts. Hardly a big deal unless the capacitor voltage rating is right on the edge, which they are not on this set.

-David


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 10:17 pm 
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I replaced a lot of selenium rectifiers in sperry steering amplifiers and most of the time a 30 volt increase increase was measured , in this case two selenium rectifiers need to be compensated for .

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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Sat 21, 2020 11:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Boston, MA USA
30 volts would be the difference between an aged selenium rectifier and a new silicon rectifier. The forward drop of a typical new selenium rectifier is about 7 volts, for a silicon rectifier about a volt. Hardly a big deal. OTOH, when you replace a vacuum rectifier having a typical forward drop of about 20 volts with silicon rectifiers, you might have to make some changes.

-David


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 Post subject: Re: Philco D-1347 Selenium Replacement Problem
PostPosted: Mar Tue 24, 2020 11:10 pm 
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Joined: Apr Wed 03, 2013 2:38 pm
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After making the changes with the wrong grounds I connected meter to the plus side of C19a
and the negative side of all caps and shows no voltage.

Just so I'm on the right page, the neg side of C20 is now connected to R25 and nowhere else(ie ground)

The neg side of CR1 is now connected to the one side of the on/off switch on the vol control plus all neg
sides of C190, C190a, C190b, and C190c and on up to T1 Green wire

Again all caps have been checked and diodes

I hate to bring up a dead horse question again
The multi cap electrolytic I understand because it was not chassis mounted
but C20 was chassis mounted and when I checked continuity between can and chassis they were connected
but now I do not have C20 connected to the chassis(still confused)


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