Lex Computech CV860A recapping

[TheSolarShed]

After recently acquiring 12 scrap computers, most of which require recapping, interest has been renewed in this board that I acquired in late 2009. A friend of mine got two of them from his place of work. Neither of them boot at all. The only thing that happens is a single 'click' from the onboard speaker and that's it. I remember back then that I heard a very faint 'whistling' noise coming from the board. The row of Teapo capacitors next to the CPU are bulging, a dead giveaway. I've decided to replace all the larger sized caps as they are a collection of Teapo and Evercon. The smaller 10uF, 22uF, and 100uF Teapos will stay (SS series), or replace them too?



I found another reason today why these board don't work. A few of the large caps in the power supply area are loose. One pin of a few caps physically move in the hole! Hope the board hasn't been damaged.

The original specifications of the major caps are:
Teapo SC
1000uF
6.3v
670mA ripple
85mΩ ESR
8x15mm

Teapo SZ
1500uF
16v
2318mA ripple
16mΩ ESR
10x20mm

Evercon ME
1500uF
16v
?? ripple
?? mΩ ESR
10x20mm

I don't know what the ripple current and ESR are for the Evercons. I haven't been able to find the datasheet for the ME series.

I've been looking for suitable replacements. As I see it, the ripple current is more of a capability whereas the ESR is more of a characteristic. Therefore, I surmise that a ripple current greater than or equal to the original is recommended, but the ESR should be as closely matched as possible. Thus, a brief search yields the following results:

1000uF replacement:
Rubycon YXG 1000uF 87mΩ 840mA 6.3v 8x16mm
SamXon GT 1000uF 87mΩ 840mA 6.3v 8x16mm

1500uF replacement:
Rubycon MBZ 1500uF 13mΩ 2550mA 16v 10x20mm
Nichicon HM 1500uF 13mΩ 2550mA 16v 10x20mm
SamXon GD 1500uF 13mΩ 2550mA 16v 10x20mm

However, I've read that the MBZ series has been discontinued.

Also, while desoldering a few caps on one of the boards, I noticed this a few days later. What could it be? It seems to be spreading from the holes. I had been using flux, would that have caused this? Will it affect the board in the long run? It's not like the copper is lifting or anything. It's also on the top side.


Regards,
TheSolarShed

[Th3_uN1Qu3]

Re: Lex Computech CV860A recapping

That stuff near the holes is just flux, you can wipe it off with acetone. You are correct about the Rubycon MBZ being discontinued, but Nichicon HM will do just as good. The replacements you picked are suitable, so go ahead and order them.

[ray pinkerton]

Re: Lex Computech CV860A recapping

How did you get on with the re-capping? Did it fix the board?

I have a Lex Neo and the board in it has blown caps. It is being used as a Procyon Classic and I'd like to get it running if possible so any feedback you can give me would be welcome.

Thanks

Ray

[TheSolarShed]

Re: Lex Computech CV860A recapping

Hi, Ray,

Thank you for your interest. Unfortunately, I haven't gotten round to ordering any caps as of yet. I have some 20+ computers that need recapping and am thus building up my complete list before ordering. But I am putting this board at the top of my list and am going to get it repaired as soon as possible. I hope to order the caps before the weekend and get back to you as soon as possible.

Also, what should I do about the Evercons, anyone? I'm going to use the Teapo replacements in their place as I guess they used the Evercons with the intention of them being the same as the Teapos.

Regards,
TheSolarShed

[TheSolarShed]

Re: Lex Computech CV860A recapping

How did you get on with the re-capping? Did it fix the board?

I have a Lex Neo and the board in it has blown caps. It is being used as a Procyon Classic and I'd like to get it running if possible so any feedback you can give me would be welcome.

Thanks

Ray

After many months, I have been able to order replacement caps and today I recapped both of my CV860A's.

The first one worked for a bit without any RAM. It beeped at me which is more than it has ever done. So I stuck in some RAM but thereafter it stopped doing anything. Now it doesn't even turn on. I may have damaged the board from desoldering.

The second board beeped at me without any RAM as well. So once again the real test... Stuck in some RAM and powered it on. Lo and behold... It booted up without any issues! The desoldering and resoldering process went a lot smoother on this board.

Cheers,
TheSolarShed

[Per Hansson]

Re: Lex Computech CV860A recapping

If the boards are identical you could try moving the BIOS chip from the working board to the non-working one
Sometimes they get corrupted due to the instability caused by the bad caps...
(Around 2% of the boards I see have this problem)

[TheSolarShed]

Re: Lex Computech CV860A recapping

Ok, so upon further testing the board isn't quite as it should be. It will only boot up if it's being turned on from a completely off state. If it's turned on from a soft power off state then it won't boot. After a few power cycles it just won't boot at all, no matter what.

Another issue is that an inductor in the power supply region gets hot... Up to 50C. And that's just standby usage. Pretty sure that's not supposed to happen.

The caps right next to the CPU get warmer than surrounding temperatures. Not worringly warm, but it can be felt on the back of the finger. Is that normal?

There are still some smaller caps I haven't replaced. Those smaller 10uF/22uF caps.

I may need to re-recap this board with caps from a reputable supplier, but it's a promising start. Anyone with any input?

Regards,
TheSolarShed

[Per Hansson]

Re: Lex Computech CV860A recapping

Problems related to the startup are commonly caused by the small (below 100uF caps) being out of spec...

[TheSolarShed]

Re: Lex Computech CV860A recapping

Thanks, Per Hansson. I'll replace those caps too and see if there is an improvement.

Regards,
TheSolarShed

[tmiha71]

Re: Lex Computech CV860A recapping

What's consumption of this board (VIA - very low consumption), PSU is to blame for this damage, and very likely, for not POST-ing/booting after recap...

Please post pictures of PSU (opened, of course)... Try to shorten wires from PSU (if external) to board, and - if needed, lenghten the wires from PSU to wall-socket...