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Old 13th Jul 2017, 8:35 pm   #1
Dick Glennon
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Default Philco 48-2810

Hi,The mains dropper has gone open circuit on the Philco 48-2810, I want to know if a dropper from a Dac90a will fit. Thanks Dick.
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Old 13th Jul 2017, 8:58 pm   #2
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Default Re: Philco 48-2810

Now let's try again my last post was removed for some bizarre reason !

do you have a circuit with all the valves listed .
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Old 13th Jul 2017, 10:44 pm   #3
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Default Re: Philco 48-2810

14S7 7B7 14B6 50A5 35Y4

It's a 150mA heater chain so it's unlikely that a 100mA chain DAC90A dropper would be any use- it would be overloaded 100% even if the resistances were correct!

The circuit shows a 320R resistor upstream of the rectifier heater and a 290R one between the rectifier and output valve heaters. 10W rated W/W resistors should be OK, 330R and 300R would probably suit for 240 rather than 230V operation.
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Old 13th Jul 2017, 10:56 pm   #4
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Default Re: Philco 48-2810

I do not have a circuit diagram. Please let me know where I can get one. Thank you Dick.
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Old 14th Jul 2017, 12:32 pm   #5
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Default Re: Philco 48-2810

Quote:
Originally Posted by vinrads View Post
my last post was removed for some bizarre reason !
No posts have been deleted or edited.
The circuit is available from Radiomuseum: http://www.radiomuseum.org/r/philco_48_2810.html, but also may be anglicised as the B2810, which is on Paul's DVD.
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Old 15th Jul 2017, 9:18 am   #6
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Default Re: Philco 48-2810

Thanks for clearing that up Bill, don't know what happened to it then. Mick.
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Old 23rd Jul 2017, 8:08 pm   #7
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Default Re: Philco 48-2810

Hello again,I have the B-2810 circuitry but it is not the valve line up of the 48-2810. I cannot download the radio museum just yet. Should I wait until I get the circuit for it?

Regards, Dick.
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Old 23rd Jul 2017, 8:42 pm   #8
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Default Re: Philco 48-2810

Hi Dick

Are you saying you have reached your Radiomuseum daily or 30 day limit as a non-member for downloads?

If it the resistor in the filament chain its 290 Ohm it will need to be 20W its dropping 115V

There is also a power resistor in the rectifier circuit do you know which one is faulty?

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Old 23rd Jul 2017, 10:25 pm   #9
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Default Re: Philco 48-2810

I am a member at the radio museum but I have mislaid my password so I must wait until my son comes to help me out. Dick
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Old 23rd Jul 2017, 10:31 pm   #10
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Default Re: Philco 48-2810

Hi Dick pleased to hear your a member.

If you have an 115 V transformer and you set the radio to run on 115V both resistors are out of circuit so you could asses the rest of the set whilst you wait for your password to be sorted.

If it going to take a while to sort your password drop me a PM.

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Old 24th Jul 2017, 12:12 pm   #11
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Default Re: Philco 48-2810

Quote:
Originally Posted by Dick Glennon View Post
I am a member at the radio museum but I have mislaid my password so I must wait until my son comes to help me out. Dick

You can still download limited amounts of info as a guest. It's a bit of a rigmarole, but just the circuit shouldn't take too long.
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Old 24th Jul 2017, 4:20 pm   #12
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Default Re: Philco 48-2810

Quote:
Originally Posted by Cobaltblue View Post
If it the resistor in the filament chain its 290 Ohm it will need to be 20W its dropping 115V

There is also a power resistor in the rectifier circuit do you know which one is faulty?
I would use a capacitor-reactance dropper for the valve heaters. To me, it's the best way to do it. It has a surge-limiting effect on the heaters and runs perfectly cool. The resistors in the rectifier circuit can still be power type resistors.
The set uses the same circuit as the U.S. sets but uses a 7S7 instead. All the Philco's sold here use the 7A8 FC valve.
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Old 24th Jul 2017, 10:07 pm   #13
Dick Glennon
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Default Re: Philco 48-2810

Hi, would it be too much to ask for someone to send me a diagram incorporating the mains dropper as for show but with an appropriate capacitor/resistor dropper showing values and place in the circuit.It would be very much appreciated. Regards Dick.
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Old 25th Jul 2017, 5:03 pm   #14
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Default Re: Philco 48-2810

Quote:
Originally Posted by Dick Glennon View Post
I am a member at the radio museum but I have mislaid my password so I must wait until my son comes to help me out. Dick
I'll wait until you can print a readable diagram!
I calculate a 2.2 mfd A.C. type capacitor for the voltage drop.
Sorry, I can't provide a schematic of the way the cap should be connected.
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Old 26th Jul 2017, 9:59 pm   #15
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Default Re: Philco 48-2810

Hi again, I have taken a look at the valve lineup in the Philco, I have Four numbers as follows 14S7. 12Q7. 35L6 and 35 Y4. The other valve has the number missing. The dial bulb is quoted at 35 volts. Would this lineup work. Regards Dick
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Old 26th Jul 2017, 10:41 pm   #16
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Default Re: Philco 48-2810

The lineup is plausible, though odd, with that mix of Loctal and Octal valves.

The missing one could be a 12K7 or 12SK7 (top cap or single ended) if Octal, or something else again if Loctal. The total heater volts is 108V plus panel lamp?

This is a different lineup from the RM circuit which has the 14S7 7B7 14B6 50A5 35Y4 lineup I quoted earlier. That uses the odd US arrangement with the panel lamp wrapped round the rectifier filament tap and adds up to about 117V.

Snip of heater chain circuit attached.
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Old 27th Jul 2017, 8:07 am   #17
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Default Re: Philco 48-2810

I was not aware you could download anything as a non member of Radio Museum?

Sorry,I have drifted with others a bit.
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Old 27th Jul 2017, 8:21 am   #18
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Default Re: Philco 48-2810

Hi HB

Non members can download up to 3 pages a day or 10 per month.

It's a bit of a faf much better to be a member

Dick is a member just having login trouble.

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Old 27th Jul 2017, 8:33 am   #19
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Default Re: Philco 48-2810

Quote:
Originally Posted by Cobaltblue View Post
If it the resistor in the filament chain its 290 Ohm it will need to be 20W its dropping 115V

There is also a power resistor in the rectifier circuit do you know which one is faulty?
This has niggled at me for a while- I've worked out why:

The 290R resistor is in the heater chain, but it only carries the heater current (150mA), it doesn't drop 115V. So about 6.25W.

The 300R resistor in the rectifier circuit is also part of the heater dropper chain- that one carries both the heater current and the half wave HT pulses so it dissipates rather more.
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Old 27th Jul 2017, 8:57 am   #20
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Default Re: Philco 48-2810

I blame sleep deprevation

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