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Drken
February 2nd, 2011, 07:00 AM
I purchased an AE RAMFactor card from someone on eBay, and the card I received is non-functional. It appears that one of the components on the board is fried. I have no idea as to what this component is but would appreciate any help anyone can give me in terms of details so I know what part to order. (If you can't tell, I'm not an electrical engineer by any stretch of the imagination!) Many thanks in advance.

The part fried is circled in red:

5171

The component is approx 5/16" long (sans legs) and consists of two blackish bulbous ends with a narrower center post which looks to be wrapped in a reddish wire. There are two of these, one to the left of the battery, the other (the fried one) upper right of the battery.

deathshadow
February 2nd, 2011, 07:27 AM
Looks like a coil resistor -- unsolder one leg on the surviving one and measure the impedance, you should be able to replace it with a more conventional one.

It could also be a RF crystal coil, but there is no reason for a Ram card to need one much less two of those... oh, and that's a power conditioning capacitor, NOT a "battery"

glitch
February 2nd, 2011, 08:18 AM
That might be a filter choke, instead of a resistor. I'd measure across its end leads (with one desoldered) and see what the resistance is. If it's open or 0 Ohms, it's dead...if not, it's probably just a little scorched. and OK.

RetroHacker_
February 2nd, 2011, 09:37 AM
That is not a resistor, it's an inductor. And it is only in the circuit that goes to the external battery pack, and may not affect operation of the card. It has been a while since I used a RamFactor, but I *think* you need to do something special to use it without the RamCharger (battery pack). What are the symptoms? Will the machine boot with the RamFactor installed?

-Ian

RetroHacker_
February 2nd, 2011, 09:50 AM
Just checked with my RamFactors. You need to have the jumpers installed or else the computer won't even boot. (On a IIe, I get a garbled screen). The jumpers allow the computer to power the card. The red connector in your picture needs two standard jumpers installed, shorting the first and second pins together, and the third and fourth pins together. Then, plug the card into the computer and power it up. The computer should boot as normal. From BASIC or DOS, do a PR#x, where x is the slot you plugged the card in. That should bring up the RamFactor configuration menu.

-Ian

RetroHacker_
February 2nd, 2011, 10:00 AM
Also, looking again at your picture, you do not have any RAM in your RAMFactor. You need that.

-Ian

Drken
February 3rd, 2011, 11:51 AM
I took the RAM off the card to check it on another card known to work, just to make sure that the RAM were good (they are). If this component is only there for the external power pack, and I don't have the external power pack, will jumping pins 1-2 and 3-4 bypass that fried component and allow use of the board in the Apple? I know I'm probably being overly cautious, but again not being an electronics expert, I find that caution is best.

Thanks for all the responses & help to all!

Ken
www.Apple2Online.com

Drken
February 3rd, 2011, 12:52 PM
From what I can tell looking at the Jameco catalog, ita a High Current Axial RF Choke http://www.jameco.com/Jameco/catalogs/c111/P57.pdf. I have no idea which one, though, as I haven't a clue as to what "L" ("micro H") units are or how to measure them. Anyone here much more knowledgeable on these chokes who might provide some guidance?

Ken
www.Apple2Online.com

RetroHacker_
February 3rd, 2011, 02:05 PM
It is definitely a choke. I do not know the value, however I do not believe it is critical to this circuit. The board may fail to operate if this part is open circuit, but I don't think it actually needs to be a choke if you are not using the batteries. Check the resistance of the part with a multimeter, and check the resistance of the other one.

Does the board work when you install the first bank of RAM (the row of 8 RAM chips along the top) and the jumpers?

-Ian

Drken
February 4th, 2011, 09:08 AM
No, the card did not work with the RAM installed, but I believe it was because the pins were not jumped on the battery connector. I'm awaiting on a replacement capacitor since the one on this card needed to be replaced. Once I get that soldered in, I'll add the RAM back, jump the pins in the battery connecotr & see if it works sans choke. Unfortunately, that choke broke when I attempted to remove it - probably from the ferrite core being overheated & becoming brittle (or outright cracked in two) so I can't do anything with it and I'm hesitant to take the other one out to measure the resistance until I see if the card will work without the other choke in place.

RetroHacker_
February 4th, 2011, 09:23 AM
Why does the capacitor need to be replaced?

You can measure the choke without removing it from the board. I'll have to check one of my boards, but I do not believe the circuit is complete if the jumpers are not installed, so the reading would be accurate.

Something tells me that the board won't work with the choke removed completely. It's in the power circuit to filter out noise from the external power supply/battery unit. Since you are not using the battery unit, the jumpers must be installed. But there will also be very little noise, being that the card is powered from the II instead of the RamCharger. With the choke removed, that power circuit will not be complete. Simply measure the resistence of the other choke (shouldn't be very large, less than 10 ohms would be my guess), and replace the missing one with a similar value resistor, or even a piece of wire. I will double check the circuit on my board at home.

-Ian

RetroHacker_
February 4th, 2011, 01:07 PM
OK, I just got home and I checked the resistance of the inductors on my card. They're less than half an ohm. And by looking at the circuit, I can see that they are right in the power line from the battery pack connector. Thus, you NEED something there, or else the card won't get power. I see no reason why they need to be active components though, since when you power the card from the Apple's bus, the filtering provided by the electrolytic will be sufficient. You can replace that inductor with a piece of wire and have the same effect. I just confirmed that by jumpering out that inductor on one of my RamWorks cards, and it worked fine.

-Ian

Drken
February 4th, 2011, 02:05 PM
Thanks, Ian, for checking out your card for me. What does "less than half an ohm" equate to in terms of L value? (I'm referring back to the Jameco page I cited earlier listing the available chokes, and they're differentiated by L (micro H) values.)

The capacitor needed to be replaced since one of the arms was broken. I'm sure I broke it while tooling around with the choke. So I have ordered a replacement capacitor from Mouser.

BTW, when I measured the resistance of the other, non-damaged choke, I came up with 0 ohms, so I don't know if it was operator error (me) or if there really is something wrong with that 2nd choke. I'd like to replace both chokes if I can figure out which part number I need to order!

Ken

www.Apple2Online.com

RetroHacker_
February 6th, 2011, 06:16 AM
It might show up as 0 ohms, depending on your meter, it's sensitivity, and what setting you had it on. I got 0.4 ohms. But DC resistance tells you nothing about it's inductance, and I do not have the equipment to measure that. But, again, this is just part of a filter circuit for the batteries. You don't need it. Replace the broken one with a piece of wire.

The cap you broke off is needed though - it's a 1000uf filter on the 5v line. The card *might* work without it, but it should really be there. Any 1000uf electrolytic at 6.3v or greater will be fine - you should even be able to get one at Radio Shack. Remember, those caps have polarity, the positive side goes to the pin closest to the red connector.

-Ian

Drken
February 6th, 2011, 07:20 AM
Thanks, again, Ian. I'm finding this really educational, to say the least.

I am going to simply solder a piece of wire in place of the broken choke, since I have been unable to find what looks to be a replacement choke. I don't understand inductance and L values at all, and have no way to measure them, so selecting a proper replacement choke, even if I could find one that is the correct physical size, would just be a poke in the dark for me. (The only ones I could find are about 2-3 times the physical size.)

I'll let you know how I make out when the cap arrives. And again, many thanks for all your help - much appreciated!

Ken
www.Apple2Online.com

Drken
February 13th, 2011, 06:09 AM
Success! I was able to repair the card by replacing the damaged cap and, rather than continue to spend hours trying to find an appropriate choke replacement, I took the suggestion & simply jumped the circuit with wire. Added RAM, booted & did the PR#x & got the RAMWorks configuration menu. All seems to be working fine now, thanks to all the help I received here. Many thanks!

Ken
www.Apple2Online.com