CurtPalme.com Home Theater Forum

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

Greetings!

Yes, it does have a 4 pin device there. Looks like it says KIA 578 but nothing comes up for me when I search it. Also in the second pic you can see a bridge rectifier KBU 804 below the fuses, FWIW.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Ok, so it does have it. Then you should of had +5v on pins 4 and 5 at BN94 which, according to your chart you did not. Set your DMM to diode scale and see if there is a short between any pins of that ic91.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Yes, test in circuit for now. Set you DMM to diode scale. Touch the 2 leads together and look at the meters display. That is a short reading. Now, testing the ic leads look for a reading close to the meters short reading.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Then it's probably bad. If you want to double check pins 4 and 5 on BN94 again for 5v you can.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

I'm willing to just replace it while I have the thing apart. It's relatively easy to get to.

However...

The part number is KIA578R050FP/PI. I haven't found it anywhere yet. NTE has no direct cross-reference. I have the data sheet from the manufacturer KEC. (The unit was made in China).

One issue is that it's a 4-pin T022 package where most equivalents are 3 pin.

Can you recommend a source?

Thanks

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Call Marantz parts at: (201) 762-6392

Select parts dept..

Give them this part number: 90M-HC300990R

They do have stock and they are $12.80 each and $7.00 shipping.

Also be aware that you may have another problem that caused this part to fail. I usually order more then 1 part but these are a little pricy. Of course you could probably Ebay any left over parts, especially since this is such a rare part.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Oh, I forgot. I put in a request to 1 of my China suppliers but I wont have an answer until later today. If they have stock it may be cheap but it takes around 2 weeks to get parts.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

Thanks for the research. I've been doing likewise. I just chatted with Mouser over a substitute, and they have a 4 pin T022 with exposed heat sink by Sharp still in stock. 5V, 7A output. The original was 5V 5A.

I'll try to attache the html file for it, see if it works.

They're $3 each. I have other things I can order as well to accommodate shipping costs. If it will substitute, I would feel a whole lot better blowing a $3 part than a $13 part.

What do you think? There's also a 5V 3A part made by Fairchild, but I'm concerned with going low on the current.\

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

Here's the actual datasheet. Doesn't look like the Sharp accepts as high an input voltage as the KEC (original).

But the point is to use it to make sure that there aren't other issues causing a problem, so if it lasts long enough to power up and test the unit for a while then the exorbitantly priced original can be ordered from Marantz.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Actually they are not the same pin number either. At mouser the pic shows 4 pins but I also found the same data sheet and it has 5 pins.
One is for Voltage adjustment. The KIA is a set voltage. So it might work but you'll need to play with resistors most likely.

Athanasios

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

The 3 amp device is no good. You can up the amps but not lower.

The Sharp device is 7 amp but the input voltage max is 7v and that's not enough. The circuit supply is +8v.

Funny thing is that because of the circuit design you can use a standard 3 leg regulator. The on/off leg is just tied on all the time. You just have to get the correct leg on the right hole and be able to mount it to the heat sink.

Or you can wait until I hear back from my China supplier.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

OK, next possibility!

I removed IC91 and took it and the data sheet for it to a local electronics surplus store. The proprietor is pretty sharp and has always been helpful. I removed it to test it more thoroughly. It does show values in one direction but open in the other direction, FWIW.

The proprietor checked out the IC91 data sheet and then looked up the data sheet for this regulator: SG29055A by Microsemi. It's a 5 pin regulator, but by removing the 5th pin, it appears to have very similar tolerances to the original IC91.

Data sheet is attached. I thought it would be wise to have a consensus before I installed it.

Thanks for checking this out!

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

First I'm going to ask if he verified that ic was bad.

Second I'm going to ask if you see a problem with that replacement.

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

I asked him if he would check it for me, and he said that it couldn't be checked out of circuit without a specific kind of testing circuit, since it was an IC.

Did I see something wrong with it? The input and output voltage seems to be in range and the pin-out matches the old one. One issue is that it has a metal-backing for ground, so it needs to be insulated from the heat sink. I do have an insulator.

I'm not totally sure the old one is bad. That's why I took it with me in the first place. I'm not sure the readings I was getting are consistent. I took readings of both the original KEC and this SG for comparison. The readings don't make lots of sense to me on the new one. They match the old one when the black lead is on pin 4, but nothing when reversed. I did put a fresh battery into my meter, fwiw.

OLD KEC
Pin 1 & 4 (black) = (open) Pin 1 & 4 (red) = (open)
Pin 1 & 2 (black) = (open) Pin 1 & 2 (red) = (725)
Pin 1 & 3 (black) = (open) Pin 1 & 3 (red) = (920)
Pin 2 & 3 (black) = (open) Pin 2 & 3 (red) = (925)
Pin 3 & 4 (black) = (1050) Pin 3 & 4 (red) = (open)

open =1

NEW SG

Pin 1 & 4 (black) = (open) Pin 1 & 4 (red) = (open)
Pin 1 & 2 (black) = (open) Pin 1 & 2 (red) = (open)
Pin 1 & 3 (black) = (open) Pin 1 & 3 (red) = (open)
Pin 2 & 3 (black) = (open) Pin 2 & 3 (red) = (open)
Pin 3 & 4 (black) = (1050) Pin 3 & 4 (red) = (open)

Could that be right for the new one? Seems odd that so many open readings.

Meter shows a short between pin 3 and the metal tab, which should be ground. Meter shows reading between tab and pin 4.
But no reading between pin 3 and 4.

Comment, please?

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

You called me Curt in that email you sent, lol. Was it meant for me or for Curt?

Zerog · Joined: 05 Jan 2013 Posts: 35 Location: Southern California

Oops, Sorry - I thought your name was Curt. Apologies for the mistake to both of you.
In the email I was trying to that verify with you the line between being helpful and hindering the expert. Smile

I appreciate your help and would like to facilitate matters if at all possible.

As far as the
Marantz is concerned....Do you think the original IC91 might still be good?

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

How about this part?

http://www.datasheetcatalog.org/datasheet/fairchild/KA78R05.pdf

http://www.ebay.com/itm/KA78R05-Manu-FAIRCHIL-Encapsulation-TO-220-Low-Dropout-Voltage-Regulator-/120922014872?pt=LH_DefaultDomain_0&hash=item1c27838498

Nashou

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Both the SG29055A and the KA78R05 are only 1 amp devices. We need 5 amp. Even with no problem at all it would blow those 1 amp parts.

However, we need to do some more testing before any parts are ordered. It has not been confirmed that the ic91 is bad. Those number are not bad but still doesn't mean it may be failing under load.

What I would do next is check for a short to gnd on the reg board without ic91 being installed. You would need to test between contact points of pin 2 and 3 on the board where the pins would be. DMM on diode scale. But, all wiring harnesses need to be connected but do not plug in the receiver.

Just give me the numbers. i don't need to know what lead was where.