Vendor selling 7907 voltage regulator !!!

[newbiesat]

Hello all,
Having question to look for 7907 voltage regulator but could find any vendor selling it (already try mouser, digikey, mcmelectronics but do not get any return). Please help and thank you in advance.

[budm]

Re: Vendor selling 7907 voltage regulator !!!

May I ask to what kind of circuit it is being used in?

[newbiesat]

Re: Vendor selling 7907 voltage regulator !!!

Hi budm,
The regulator use on Sony Receiver STR-DG820. Thanks.

[LLLlllou]

Re: Vendor selling 7907 voltage regulator !!!

Hello all,
Having question to look for 7907 voltage regulator but could find any vendor selling it (already try mouser, digikey, mcmelectronics but do not get any return). Please help and thank you in advance.

Are you sure it's a negative 7V regulator? I don't even see any on ebay, and I don't remember ever seeing one in the 79xx series data sheets. You could use a 7905 with 3 silicon diode in series with the ground leg. Each diode should drop about .7 volts bringing the regulated output up by the same amount.

[mariushm]

Re: Vendor selling 7907 voltage regulator !!!

Me too, me too... saying something's fishy.

You sure it's not a 7909 with poor engraving?

Anyway, instead of diodes, you could probably just use a LM337 , the pinout is the same, you can get it in to-220 package so you can reuse the heatsink if the original regulator was in to-220 package.

You would just have to solder 2 resistors on the leads of the regulator to set the voltage to -7v which should be very easy.

http://www.newark.com/on-semiconduct...0ab/dp/45J0747

[budm]

Re: Vendor selling 7907 voltage regulator !!!

Adding the Diodes to the Ground pin of the 7905 as suggested by LLL will be the easiest.
Data sheet does not show 7V version.
http://www.datasheetdir.com/LM7907+Regulators

[mariushm]

Re: Vendor selling 7907 voltage regulator !!!

How do you figure that?

You'd have to pull one of the legs of the regulator off the board, connect the diode in the pcb hole, then solder the diode to the leg... not to mention the diode won't be exactly 1v so you'd have to use several diodes..

With the LM337 you solder the resistors to the legs, then put the three legs in the pcb and solder them.
If you can't solder them on the legs of the regulator, you can solder the two resistors on the back of the pcb, they're tiny and easy to solder there.
Again, the pinout is the same so no other mods necessary.

[budm]

Re: Vendor selling 7907 voltage regulator !!!

3 diodes (IN4XXX series will do) in series, Anode to Ground, @0.6v each will get about 1.8V, close enough to 7V (6.8V) he needed. He is going to replace the IC any way, so just connect Diode to pin 1 which is the Ground pin for the 79xx IC. To make it more stable, add 0.047 cap in parallel with the Diode string, no big deal.
Pin1 (adj) of the LM337 will have to lift off the board anyway.

[Khron]

Re: Vendor selling 7907 voltage regulator !!!

Newbiesat, what's the marking of this regulator, on the silkscreen / board, and which board is it on?

Edit 1: Nevermind, i found it (in the service manual).

Seems the original part number is TA79007SB, made by Toshiba Semiconductor (so no wonder you couldn't find the equivalent "jellybean" 7907 ), and it's "not recommended for new designs".

But after a quick perusal of the schematics, it seems to me that if you replaced both that -7v and the associated +7v regulator with, say, the +/-8v versions, it should make little to no difference, since they're used for the analog stages (a bunch of opamps).

I *DO* invite the brighter-than-mine minds to correct me if i'm wrong, though

Edit 2: Ah, damn - the input select / volume control chip has absolute max supply rails of +/-7.75v...

[Khron]

Re: Vendor selling 7907 voltage regulator !!!

On second thought... Another (possibly easier?) option would be to go down to +/- 6V rails, with a 7806/7906 pair...

[budm]

Re: Vendor selling 7907 voltage regulator !!!

I agree.

[japlytic]

Re: Vendor selling 7907 voltage regulator !!!

How many pins does it have?
A clear picture of it would be helpful.

[Khron]

Re: Vendor selling 7907 voltage regulator !!!

Service manual shows it as a 3-pin device, and the datasheet i've found shows it to be in a box-type TO-220 size case (no tab / screw hole).

http://www.semicon.toshiba.co.jp/inf...&pid=TA79007SB

[999999999]

Re: Vendor selling 7907 voltage regulator !!!

I also agree, pull the +7V regulator out and replace both with (a same voltage pair of) 7806 & 7906, "assuming" they have the same pinout and mounting tab polarity vs heatsink electrical connection if any.

[newbiesat]

Re: Vendor selling 7907 voltage regulator !!!

Thank you all for your comments/ideas. However, does it make difference to replace both with +/-6v or +/-8v? I mean which one is better and more safer... not to destroy other components... By the way, there is other parts KIA7907PI that sold on amazon... but currently not available ..

[mariushm]

Re: Vendor selling 7907 voltage regulator !!!

Right now your thing is designed to use +7v and -7v, so there's a 14v difference.

If you put -8v and +8v regulator you might damage the opamp or whatever's powered from +/-7v because now instead of 14v, you have 16v.

If you put -6v and +6v there's 12v , which is less than the original 14v. Chances are the device will work fine with less voltage. But it's also possible that they receiver may behave erratically or distort the sound or whatever uses that split power supply.

However, some opamps are not rail-to-rail as in they need input voltage to be a few volts higher than the maximum output voltage they're supposed to amplify.
So for example if the opamp needs 2v above maximum output but receives a 1v signal and is supposed to amplify it to 5v, it will distort the output because your maximum voltage is 6v, just 1v above the output instead of 2v.

I still don't get it why the reluctance to just use an adjustable regulator with a couple of resistors soldered at the bottom to get the regulator to output -7v. This way you don't have to debate what kind of regulator to use or the risks.

[999999999]

Re: Vendor selling 7907 voltage regulator !!!

Get the 6V regulators and try it. IF it turns out that you really need the extra 1V, you can turn them into 7V regulators as easily as a typical "adjustable regulator". Instead of posting pics and a lot of text I'll let the following webpage explain, but I think +-6V should work out ok.

http://www.rason.org/Projects/regulator/regulator.htm

If you order from some place that has both a large selection of resistors and low cost (~$2) USPS shipping for orders so small, you could just go ahead and calculate out the resistor values you'd need for the extra 1V, and order them simultaneously to the two regulators... resistors are only 10 to 20 cents each addt'l, then you already have them if it turns out you need them.

Personally, I already have some LM7905 and LM7805 lying around, if it were my project I'd even try those first, the reason being that voltage regulators don't usually fail unless there was some other problem, so I'd know if the amp seemed to work before throwing any more money into it... and of course, I could use a couple resistors to raise the value of those up to +-7V too.

[tom66]

Re: Vendor selling 7907 voltage regulator !!!

Well, what opamps are used in the circuit?

I have heard of 7.5V and 8.5V 78xx/79xx regulators but I'm guessing they're even harder to source!

[999999999]

Re: Vendor selling 7907 voltage regulator !!!

Here is the service manual download:


It has a number of NJM4565 opamps which will tolerate up to +-18V rails (and down to +-4V), but the BD3471KS2 voltage and input selector IC Khron666 referred to has the +-7.5V limit, but it also isn't guaranteed to work below +-6.5V.

Interestingly on pg. 22 of the manual, that BD chip appears to have 2.2 Ohm series resistors (# R487 & R488) on the VCC & VEE rails, bringing them down to +6.9V & -6.8V. If a diode were put in series with each of those, it would pull down +-8V regulators to within the +-7.5V max for the IC, OR the resistors themselves could be swapped for a higher ohm value .

[newbiesat]

Re: Vendor selling 7907 voltage regulator !!!

Hello all,
Thanks again for all of your contribution to this topic. I finally able to get those -7v regulator (KIA7907PI) from encompassparts.com and bring back alive the sony str-dg820 receiver without the "protector" message display.

ns