Need 4-pin 15V regulator for Philips tuner

Hello tuner fans,
I have a Philips AH-673 tuner that I belive has a defective IC1 4-pin 15V regulator that is defective. The regulator has four pins on it. On the part it says F 7717 and below that the Philips #: 612153-1, made in Korea. Can someone help me find a comparable part to replace it with? Thank you.

Hmmm... the service manual says IC1 is part of the IF amplifier, and it's an 8-pin device. No sign of a 15V regulator that I can see. Maybe more than one version of this model?

Can you post a decent picture of the device, and the board where it's mounted?


John

The IC1, a 4-pin positive regulator, is located to the left of the power supply board photo, screwed down to the chassis. It is connected to the power supply via a harness with four wires. The regulator has four pins extending from it. From what I understand, 30vdc goes into the regulator from the board and the regulator sends out 15v back to the power supply and to the if board.

Got it, unlike other makers they apparently re-use that component locator from board to board, as there is also IC1 on the multiplex board and yet another on the touch control board, probable other places too. Makes the part references a PITA, but I found this regulator in the manual with your added info & picture. Not that it helps much, but the manual has 4822 209 80442 as the Philips part number.

I'll poke thru some datasheets and see if I can't turn up an equivalent part.

We have some Philips guys on AK, may be a better chance that one of them sees this if it's posted on Solid State or DIY forums but cross-posting makes the moderators cranky sometimes, so let's see if we can't solve this one here before you try the question on another forum.

John

Thanks. I'll do some more research myself based on that number from the manual.

So, this looks like an adjustable voltage regulator (positive). It's in a TO-220-4 case, also called TO-220F/4 by some makers.

Found some similar devices, but not sure about whether they'll handle the current requirement for the +15V out.

This first one isn't in the same heat-sunk TO-220 case so it may be rated for lower current than your original, but the pin-out looks consistent (you might have to play with the associated components to get that +15V dialed in, look at the application note for "normal regulator circuit vs. what the schematic for your gear shows):

http://www.semicon.panasonic.co.jp/ds4/AN6531_E_discon.pdf

Here's another one from Fairchild that is in the TO-220 package, the UA78G is the positive output version:

http://html.alldatasheet.com/html-pdf/128965/FAIRCHILD/UA78G/484/1/UA78G.html

Here's some 2A parts for sale, looks like they're close though that +35V max input voltage rating and lack of a heat-sink tab makes me a little nervous:

http://www.digikey.com/product-detail/en/KA278RA05CTU/KA278RA05CTUFS-ND/1055400

Here's another brand, from Mouser:

http://www.mouser.com/ProductDetail/NJR/NJM2397F/?qs=/ha2pyFaduiNvS5YLOLbjvBs9niVm57n1kkWsvCFwmA=

It might be easiest to simply replace this part with a fixed 15V regulator, which you can find almost anywhere. Not sure what side effects that might have, but you'd just connect the +30V input, the +15V out wire, and ground. The +5V control wire would be left disconnected. It's easy to rewire that connector to match the pinout of a new device BTW, just move them around in the plug as needed. The schematic identifies which wire is which.


John

John, thanks for the nice links and suggestions. On the Fmtuner group site one member said this based on his preview of the tuner schematic:

" According to the schematic, this regulator takes a nominal 30-volt input
on pin 2. Pin 1 is ground. Pin 3 is the output (feeds a 100 uF bypass
cap C511). Pin 4 is the regulator feedback - the schematic notation
says "5V" and there's a 10k/4k7 voltage divider from the output feeding
it, so that makes sense. R561/C517 seem to be an output compensation
network to ensure stability."

This company claims to have the part.

No affiliation. Just for for your information.


Voltage regulator.

They list it as a spare part for your tuner.

However they are UK-based. Shipping to the USA is not too bad if this turns out to be your only option and you want to stay with original parts.

They claim it is an original part, but counterfeit parts are not uncommon.

Again, this is just for your information.

Thanks for the UK link, however, just for the heck of it, I put in a shopping cart to buy and it came up with a note that this part was unavailable and could not be shipped to the USA, I would imagine since it's design is for a 220-240V tuner model. I don't see why this would make a difference since the transformer takes that down to dc voltage.

http://www.buyspares.com/basket.pl?webkit=1

I have a question. I'm getting suggestions for adjustable and fixed regulators. Which one is correct? I would think that it should be fixed as the input voltage going to the regulator is 30vdc while the output is at 15Vdc.

A fixed voltage voltage regulator directly provides the required output voltage without any external parts to tell it what its output voltage should be.

A adjustable voltage regulator can be programed to supply the required voltage. It needs external parts (resistors) to tell it (program) what its output voltage will be.

This can be seen in the application notes of the voltage regulators referenced by jdurbin1.

Once the voltage of an adjustable voltage regulator is set by the external resistors it is then constant or fixed.

Either an adjustable voltage regulator with the correct output voltage programing resistors or a fixed voltage voltage regulator with the correct output voltage (15 volts in your application) should work.

So you could use a 3 terminal 15 volt positive regulator and not use the connection that is currently connected to pin 4 (per the service manual schematic) of your original voltage regulator.

Or you can use one of the 4 terminal adjustable voltage regulators referenced by jdurbin1. You may have to recalculate the values of R517 and R518 per the application notes provided in the links for the particular voltage regulator that you choose to use. This will be necessary to program or adjust the output voltage to 15 volts.

Note that Fairchild makes both a 4 pin adjustable voltage regulator and a 4 pin fixed voltage regulator. The addition pin is for Vdis or output voltage voltage disable (on or off). This functions the same as a fixed voltage voltage regulator with the additional function of being able to turn the output voltage on or off with a control voltage to the 4th pin.

Both types are shown in the reference to the KA278RXXC as provided by jdurbin1.

See the picture below. In figure one the two resistors R1 and R2 are internal to the voltage regulator and preset the output voltage. Pin number 4 is just used as a means to turn the output voltage on or off.

The two resistors in figure 2 are external to the voltage regulator and there values are chosen to program the desired output voltage. These resistors would be your resistors R517 and R518, all though you would have to calculate the value of the resistors depending on which adjustable voltage regulator you choose.

As already mentioned, it may be easier for you to use a 3 terminal (one pin for input, one for output and one for ground) 15 volt fixed voltage regulator and just not use the wire that is connected to pin 4 of your current voltage regulator.

If you want to use a simple 3 terminal voltage regulator the MC78T15CT would be a good choice. Output current of 3 amps maximum and a maximum input voltage of 40 volts for the 15 volt output version.

There are many other three terminal 15 volt TO220 case voltage regulators available. As long as you do not exceed their maximum input voltage, their maximum output current rating or total power dissipation , any of them should work OK.

You might want to choose a low noise type of voltage regulator, since this is for the tuner section, although it may not be necessary.

Again pay attention to the pin out of the replacement voltage regulator.

:thmbsp:

(what he said)


John

Thank you both for your excellent suggestions. It is greatly appreciated.

"The two resistors in figure 2 are external to the voltage regulator and there values are chosen to program the desired output voltage. These resistors would be your resistors R517 and R518, all though you would have to calculate the value of the resistors depending on which adjustable voltage regulator you choose."

JBLguy,
I was thinking about this and not being technically oriented, I was thinking about the resistor values at R517(4.7k) and R518(10K). If these are the two resistors which determine what the output should be( in this case +15V) then according to the formula in an adjustable voltage regular to determine output voltage, it should be R1 + R2 divided by R2 x 5. So if R1 is 10K and R2 is 4.7K, then the output voltage would be 15.64. Is this right? Is this how the Philips techs set this up?


Update(Sun.,7/13)

I connected a Fairchild KA78R15CTU fixed positive regulator. I had to change the wires on the harness to match the different pin-outs. With the harness connected, I tested 22.5v on the input and 15v on the output. Pin 4 was seeing an off spec voltage so it shut the regulator down. I disconnected pin 4 and all seemed fine. The tuning meter and signal meter are now functioning normally. I hooked the tuner up into the system and it is playing music once again. Thank you all for your suggestions. I will check the temperature on the new regulator later.

Excellent!


John

I am glad that you have been successful.

The Fairchild KA78R15CTU is a fixed voltage regulator and pin 4 is the Vdis pin, that is the on and off control pin. It is not used to set or program the output voltage.

There are, as I posted, other versions that are adjustable and require the use of the voltage divider network connected the correct pin.

Some application notes suggest that it is OK to leave the Vdis pin disconnected and some suggest that it is better to program the pin for on operation.

Leaving it disconnected may result in erratic operation in some situations.

Since it is working for you, it may be OK.

The correct method is shown in the specification sheets.

Had you used an adjustable voltage regulator such as the AN6531 referenced in a previous post, then you would have needed to program the output voltage with the 4th pin.

Your calculations for programed output voltage are correct for the AN6531 voltage regulator.