ibm thinkpad t20 capacitor identification

[sluggy]

Hey all I was hoping somone here could help me. I need to identify 4 capacitors all with the same marking. The placment of these capacitors can be seen on this picture here.

http://www.linuxfocus.org/~guido/gentoo-tpt20/

The chips have the following written on them and my assumptions

220 (uf or mf assuming uf)
0207 (date code)
e (2.5 volts)

I cant seem to find a 2.5 volt 200uf so im assuming i have the voltage wrong if anyone can help me out it would really be appreciated.

[PCBONEZ]

Re: ibm thinkpad t20 capacitor identification

Well first off it's very unlikely they are Tantalum caps.
Tantalum caps have next to no tolerance for ripple and because of that very few [if any] uses in a PC.

Not likely Aluminum electrolytic either. I don't think they come in that package type.

Pretty sure you are looking for Solid Polymer caps and 2.5v is common in Polymers.

.

[PCBONEZ]

Re: ibm thinkpad t20 capacitor identification

MAX1632 has no on-board memory so it's not 'remembering' one of the outputs was bad, it not getting a reset signal on pin 11.
.

[sluggy]

Re: ibm thinkpad t20 capacitor identification

Hi there thats not actually my web page its just the same problem I have. I will try put in some Solid Polymer caps in and see how i go. Do you know any decent supplier for capacitors and such in the uk apart from rswww.com and tahnks for the quick reply.

[PCBONEZ]

Re: ibm thinkpad t20 capacitor identification

No I don't but I'm in the US.
Other members can guide you on UK sources better than I can.
If RS doesn't have it then Digikey does ship overseas.

My point about the missing reset was that the problem may be entirely somewhere else in the circuit and those caps are fine. Solid Polymer rarely go bad. I suspect there is another IC [or possibly just a voltage divider circuit] that is responsible to reset the MAX1632 and THAT may be where the actual problem is.
.

[sluggy]

Re: ibm thinkpad t20 capacitor identification

Well my plan is to change the MAX1632 and ADP3421 chips for voltage regulation im thinking its more so the adp3421 than the max1632. Ill need to find somewhere that is selling the ADP3421 as well just getting the capacitors incase its not the voltage regulators. If the above dont work im stumpedwhat do do next ill let you guys know howi get on.

[PCBONEZ]

Re: ibm thinkpad t20 capacitor identification

You really need to trace that out and draw up the schematic.

I can't offer much more help. I haven't been inside a Thinkpad since like 2002? and I've never worked on one of their motherboards.

Hopefully a Thinkpad guru will wander in.

.

[Wizard]

Re: ibm thinkpad t20 capacitor identification

If the mosfet totem blows one side every time replaced, it is the MAX1632 railing. I had to do this repair to my D600 by replacing the IC and mosfet IC (each IC have two mosfet totem pole).

Cheers, Wizard

[sluggy]

Re: ibm thinkpad t20 capacitor identification

Thanks guys ill replace them parts and hope for the best I just use the computer to listen to the radio and play a snes game now and then the machine has been going for years. Hopefully i can bring some life back into it. I just need to find a source for the chips and im good to go been a while since I had the ole soldering station out. Usually im lucky and its just caps or a simple 3 pin power mosfet to replace godbless esr meters heheb

[Agent24]

Re: ibm thinkpad t20 capacitor identification

I have seen this type referred to as "Hi-C" Capacitors in motherboard marketing.

I think it stands for 'Highly Conductive'

I don't know what they're made of though

[Harvey]

Re: ibm thinkpad t20 capacitor identification

You might want to have a read of this http://forum.thinkpads.com/viewtopic.php?f=28&t=48835 and you'll see that the "blink of death" symptom is an ongoing issue that nobody has yet narrowed down.

Good luck finding the issue - you might need it

MAX1632 has no on-board memory so it's not 'remembering' one of the outputs was bad, it not getting a reset signal on pin 11.
.

From what I've read, the MAX1632 is powered continually, even when the laptop is off. An over/under voltage latch would need removal of PSU an battery to clear. However, on the one that I saw with this symptom, it was almost random as to if the machine would power up or not, which to me suggests an fault condition further down the line that is just causing the MAX1632 to shut off.

Either way, its a strange issue.

[Wizard]

Re: ibm thinkpad t20 capacitor identification

I had to replace MAX1632 PWM buck regulator IC in my D600. It blew a hole in the totem pole power MOSFET 8 pin SMD IC.

Try and replace it and carefully check (inspect visually/measure/ohm) the MOSFET that is connected to this IC.

Cheers, Wizard

[precision001]

Re: ibm thinkpad t20 capacitor identification

I also have a D600. How would you test that power mosfet? I bought a logic probe, have a 100mhz scope and a DMM. What can I do with that to test an IC mosfet?

[Wizard]

Re: ibm thinkpad t20 capacitor identification

Cannot very easily as it is very interconnected in one IC due to 2 MOSFETs in one package. But if it has no crater and reads any ohms except zero or extra low ohms like 1 or so, probably good.

MAXxxx does have current sensing design, if the regulator output is SHORTED as like less than 40 ohms even lower (typical lowest ohms I can get for a D600). Then there is a overload somewhere.

What's the problem?

Cheers, Wizard

[precision001]

Re: ibm thinkpad t20 capacitor identification

Cannot very easily as it is very interconnected in one IC due to 2 MOSFETs in one package. But if it has no crater and reads any ohms except zero or extra low ohms like 1 or so, probably good.

MAXxxx does have current sensing design, if the regulator output is SHORTED as like less than 40 ohms even lower (typical lowest ohms I can get for a D600). Then there is a overload somewhere.

What's the problem?

Cheers, Wizard

Well I have one D610 that will turn on for 3 seconds, then shuts off. I tried reflowing the maxim chips and the BGA chipsets - no effect, so I'll toss that one to the side for now. The other D610 turns on and stays on, but displays no video. The output on that one to a diag card is 3E (video timers?). I'm going to check the crystals in action with my scope, but I'm sure they'll be fine. I suspect problem to be in the CMOS circuitry, rather than in TTL but at this point I don't know where to zoom in on. No chips appear to overheat while it stays on. No physical damage or any visible trace damage. I have a logic probe but I don't really know how to use it yet, however, I'm sure my problem is not a VCC to Ground short since I get a signal when I connect the negative probe to 0 and the positive probe to +5 from USB. As you can see, I'm just kind of "feeling things out" right now. I'm interested in the Dell D600/D610/D620 systems, they seem to break down often.