JRC 7915A or NJM4558LD failure, replacements?

[bitcore]

So I have a Numark CM200 mixer, and it's output stage is toast. It's BEYOND gone. It just outputs garbage that can only be regarded as 'well I may be able to tell what's playing...' With my entry level knowledge of electronics, I'm not positive if it would be the op-amps that are tied to the outputs of the mixer, or the two JRC 7915A transistors that have gone south. The PCB around the 7915A's looks baked as if they have gotten too hot and are damaged.
Can't test with a multimeter as I can't locate it right now. My money is on the JRC 7915A's being blown. Does anyone know of a suitable replacement? I can't find any datasheets on them and I've looked for hours
I'd love to get the best replacements that are <10$ each if possible.

Pic doesn't tell much of a story, however you can see the NJM4558LD's are SIP-8


Any recommendations? I would greatly appreciate any help or at least some direction since this is currently a 250$ pile of scrap on my desk

[wg_ski]

The 7915 would be a voltage regulator, not a transistor. If one of those goes south, you would get garbage for sound. Especially if one goes out and the other doesn't. They usually come in pairs, a 7815 on the + side and a 7915 on the - side, but there crazy designers out there. One pin should be some voltage greater than 15 (or -15 for the 7915) , one at ground, and the other at 15 (or -15). If you get no regulated output from one of them, there's the problem. You should be able to find data sheets - if you look for ICs instead of transistors.

[bitcore]

Excellent, Thank you so much for your help! I've been meaning to get a new multimeter to check this, so this is the perfect excuse. I also need to stop assuming what a component is based on it's packaging and pay attention to subtle differences.... like numbers off by 1. Sure enough, there are both a 7815 and a 7915 on the circuit. Oops.

I was entering the model number and manufacturer into google with a few other search terms like 'datasheet' to try and dig up something on it, and I had a hard time finding anything conclusive. So, you can guess that I do not know of many resources for datasheets. Are there any you frequent when looking parts up?

[dave_gerecke]

Hello bitcore, here's a couple sites I use

ALLDATASHEET.COM - Datasheet search site, Datasheet search site for Electronic Components and Semiconductors and other semiconductors.
Datasheet & Application Note Database, PDF, Circuits, Datasheets | Datasheet Archive

There are others, you just have to look around.

Peace,

Dave

[jean-paul]

First measure what supply voltages you have. If they're off then replace the 7815 and 7915. Recheck if you have + and - 15 V at the outputs. If the device works OK now you are a lucky guy. If not you will have to replace the opamps.

When you are at it just replace the NJM4558 for NJM4580 ( sounds/measures better and it is available in the same form ) and the caps surrounding the semiconductors. Something went wrong and I wouldn't trust the surrounding components.

Please be aware that the device could have blown form "latch-up" of the 7815/7915 regs. This is when the supplies do not come up equally at power on. It would not harm to place protection diodes to prevent this. I think it would be OK to check yourself what is meant with protection diodes... hint : you will need 4 of them ( 1N4004 or equivalent ).

[bitcore]

I was using alldatasheet earlier and could only find the datasheet for a motorola 7815:
7815A pdf, 7815A description, 7815A datasheets, 7815A view ::: ALLDATASHEET :::
Now, I have JRC IC's, and the model numbers for each manufacturer can't match up, that would be just too easy - or is it?

So, I need a linear voltage regulator, one for + and one for -, that is 15V and can handle at least 1A of current, correct?
I found this one on newark, but I am unsure how to find it's negative voltage mate that I also need for this project. STMICROELECTRONICS|L7809CV|Voltage Regulator IC | Newark.com

I feel bad asking for so much assistance, I'm hoping someone who has had to replace these before, may stumble upon this and share what he or she wound up doing.

[dave_gerecke]

Hello bitcore, no problem on asking questions, everyone has to learn at sometime. We all were asking questions at some point in our lives.
In regards to finding the datasheets for the Motorola versions, they should be interchangeable. The 78xx & 79xx voltage regulators were originally developed by National Semi (I think, correct if wrong) and many have many copies since. There are various different versions of 78xx and 79xx, with the ending xx's replaced with two digits that represent the nominal voltage at the output if the conditions spelled out in the datasheet are followed. You should be able to replace the JRC voltage regulators with ones from another company with no problems.
And I would recommend following Jean-Paul's advice. If the vregs failed, it's likely other components failed, and they are relatively cheap. And if you can get better opamps that fit the design, that's good too!

Peace,

Dave

[dave_gerecke]

Hello again, did a quick search for JRC semiconductor on google, and here's the webpage for the voltage reg stuff. The name of the company is slightly different, but it's JRC:

????[??????????????????]

Now you can do a direct comparison between the Motorola and JRC datasheets. I would suggest going to the National Semiconductor website:

www.national.com

and checking out their datasheet, App Notes, etc. for the 78xx and 79xx devices. Then you can compare multiple ones and see for yourself!

Peace,

Dave

P.S. sorry that the JRC link looks funny, for some reason it shows that way, I think it's because they are a Japanese company, so different characters.

[sandyK]

bitcore
Don't forget that if you do not get the correct voltages out from one or both of the voltage regulators, that it would be best to remove the voltage regulator(s) with the low voltage output reading, and check for a short circuit to earth/0 volts , (very low resistance reading) and locate the fault and remove the fault. It could be anything from a faulty bypass capacitor to a faulty NJM4558.It seems highly unlikely that the voltage regulators would fail/overheat without a good reason.

SandyK

[bitcore]

Ok, it's been a while, but I've finally gotten some replacement parts.
I'm going to try replacing the larger caps around the power input for the unit. I'll be replacing two 25V 1000uf caps with 1500uf caps, and 3 1000uf 16v caps with the same rating. These are some of the lower ESR caps on newark made by rubycon, 0.02ohm & 0.017ohm respectively.
I'll report back if this fixes it If not, I'm back to square one, trying to determine if it's an op-amp or voltage regulators that went out.
Thanks for the tip SandyK, I have a feeling that you are right about the bypass caps going bad.