Gerbing's Heat-troller Fix

[spinblue]

Quality solder iron tips are plated so that solder will 'wet' the tip, sanding or filing the tip takes off the plating. You are usually better off buying the correct tip if possible.

That may be, but I didn't go looking for that fine a tip.

I keep applying a little solder on the tip and use a wet rag to keep the tip plated.

 

[Zorlac]

Might wanna wear a grounding wrist strap when handling the new devices, they are static (ESD) sensitive.

I don't have any problems in this area as I have no potential.

 

[dcarver]

Well TreeDoc?

Did Zorlac's avatar finally get fully nekkid?

Did you finally strip the board of bad parts?

New parts installed?

well?

huh?

:lol:

 

[Tree Doc]

When Zorlac's avatar gets naked, I WANT TO KNOW IMMEDIATELY!

I ordered the MOSFETs yesterday and they're shipping from Texas. I'll maybe see them tomorrow but I want to ride rather than waiting for the Postman. I'd guess early next week will be judgement day.

I'll hit the Rat Shack tomorrow to get my wick, thought I had some in my kit but was denied.

 

[dcarver]

When Zorlac's avatar gets naked, I WANT TO KNOW IMMEDIATELY!

Next in line bud, next in line!

 

[mcatrophy]

When Zorlac's avatar gets naked, I WANT TO KNOW IMMEDIATELY!

I ordered the MOSFETs yesterday and they're shipping from Texas. I'll maybe see them tomorrow but I want to ride rather than waiting for the Postman. I'd guess early next week will be judgement day.

I'll hit the Rat Shack tomorrow to get my wick, thought I had some in my kit but was denied.

TD -

You've been inundated with good advice, but all in little snippets. Thought I'd spell out my complete take on your best approach, so here it is.

1 Make sure you're sat at a quiet, clean, alcohol-free (except for cleaning) bench/desk (with protection for its surface if you have a better half and it's on the living room table).

2. You've heard about earth straps. This is OK, but only if you have the appropriate workstation. If at home, my advice would be to understand that the problem of static electricity only arises when you can be at a different potential from what you're working on. So, whenever you start to work on it, make sure you touch the soldering iron metal barrel (a briefest light touch near the handle shouldn't burn you), touch the surface of the printed circuit board (where it says "RTN" would be good), and don't take the new FET out of its innermost packaging until you are ready (it will be in some sort of conductive plastic bag, foam or piece of plastic moulded tube). If you shuffle your feet or even your bottom, you can create large and potentially (pun intended) damaging voltages.

3. Cut the legs of the old device close to the body, try not to put strain on the legs soldered to the board (don't twist the cutters, go for repeated cuts if the first isn't successful).

4. Having lifted the old body out of the way, heat the top of a leg with the (freshly tinned) iron. When you think the solder has melted, quickly but gently grip the cut end of the leg with pliers or tweezers and lift; it should come away easily. If you have to use any force, the solder either hadn't melted or has re-frozen. Start again by tinning the top of the leg.

It may be that you can remove the leg simply by heating and "wiping it off" with the tip of the iron, I would consider this risky because you can smear molten solder across the copper tracks; this can be tricky to remove.

5. Having removed all the legs, clean the lands with the solder wick. Again, freshly tin the iron (helps conduct the heat into the wick), place the end of the wick over a land, hold the iron onto the top of the wick for a few seconds. You should see solder creeping into the wick both from the iron and from the board. Now carefully lift the wick off the board. IF IT SHOWS RESISTANCE TO LIFTING, STOP, it's soldered the wick to the board, you risk pulling a land off; re-tin the iron, hold it onto the wick, and melt the solder to get it off. Cut the contaminated end off the wick between each leg. Note that with practise, you can do several lands at once, but if this is your first go I don't recommend it.

You should be left with a board that has all the lands flat, probably not glossy.

Now the contentious bit, not everyone will agree with me here.

6. Touch the iron, the board and the packaging of the new FET, remove it from the packaging. Make sure none of the legs are bent, they should all be just off flat, the ends slightly lower than the bend nearer the body.

Turn the device on its back, now tin the underside (now uppermost) of each leg with as little solder as possible, clean the iron with your wet rag between each one. You may have trouble holding the device still, it will tend to stick to the iron with surface tension. It's a little dance, hold solder to leg, touch iron onto solder, as it sweats onto the leg, drop solder, use nail of finger to hold down body, slide iron off to pull excess solder off with the iron.

7. Place device onto the board, note the orientation. Try to align it as accurately as possible. Now simply touch the iron onto the top of a leg, push down gently. You should feel it move down as the residual solder melts. Lift the iron, wait for the solder to freeze, then repeat for the next leg.

8. When all legs are done, inspect closely for any whiskers of solder between any lands (that aren't joined by the board copper). If you see any, use the solder wick to remove them.

9. I'd suggest using a meter to check for any connections that shouldn't be there. Any tracks that aren't obviously joined should have a resistance greater than a few hundred ohms (it might be worth measuring between lands before fitting the new devices in case the circuit does have lowish resistance). It might also be that diodes on the board or within the FET device could give you a false reading. If you get a reading of around 600 ohms, try reversing the meter leads, if it now reads much higher, it's probably OK.

10. Measure the resistance fron the +12 to the RTN lands, this should be more than a few hundred ohms (positive lead of your meter to the +12).

11. Test it! (You're on your own here, can't help you.)

 

[Zorlac]

"Turn the device on its back, now tin the underside (now uppermost) of each leg with as little solder as possible, clean the iron with your wet rag between each one. You may have trouble holding the device still, it will tend to stick to the iron with surface tension. It's a little dance, hold solder to leg, touch iron onto solder, as it sweats onto the leg, drop solder, use nail of finger to hold down body, slide iron off to pull excess solder off with the iron."

Nah, I'd NEVER do that, just orient that lil' sucker and heat the four corner pins to slightly tack it in place & hit all 8 pins with a itty bitty smidge of .010" solder. I'll mail you some if you can successfully desolder the dead fets.

Eveything else mca says is good stuff, thanks for your input on this mca!

Mark.

 

[mcatrophy]

"Turn the device on its back, now tin the underside (now uppermost) of each leg with as little solder as possible, clean the iron with your wet rag between each one. You may have trouble holding the device still, it will tend to stick to the iron with surface tension. It's a little dance, hold solder to leg, touch iron onto solder, as it sweats onto the leg, drop solder, use nail of finger to hold down body, slide iron off to pull excess solder off with the iron."

Nah, I'd NEVER do that, just orient that lil' sucker and heat the four corner pins to slightly tack it in place & hit all 8 pins with a itty bitty smidge of .010" solder. I'll mail you some if you can successfully desolder the dead fets.

Eveything else mca says is good stuff, thanks for your input on this mca!

Mark.

I did say

...

Now the contentious bit, not everyone will agree with me here.

...

 

[Zorlac]

I dunno, when you're wrong,... you're just wrong. :lol:

 

[mcatrophy]

I dunno, when you're wrong,... you're just wrong. :lol:

On that I agree with you.

 

[Tree Doc]

mcatrophy, thanks so much for the pointers. They are extremely helpful.

I do have a grounding strap but I'll be careful how I handle these components.

I'll post up my results when I get finished!

 

[Tree Doc]

Update:

Zorlac asked how this repair endeavor ended up. I had replaced the FET's twice. The second time because the system still did not function after my first attempt and I thought maybe I damaged the FET's by improper handling so I used the second pair I had on standby. After what I thought was very cautious handling, the second attempt yielded a non-functioning controller still. Bummer! <_< I just set it all aside and figured it was worth the try and I only had about $10 wrapped up in my attempt.

After today's contact with Zorlac, I was motivated to take another look at the deal. After probing on the backside of the circuit board, I noticed that when I jumped what I thought was a resistor of some sort, the damned thing started working! Zorlac again helped me I.D. the offending component. A .99 cent Microwave Oven Thermal Protective Fuse! SHIT!

Of course, none available at Rat-Shit Shack so off to Santa Maria again to this old, old school electronic supply shop. They had EXACTLY what I needed. I took TWO just in case!

An hour and a half later, I was BACK at the shop to buy 4 more. Guess how hard it is to solder a thermal fuse that blows at 200* F? :blink: :lol:

I devised a better heat-sink (frozen cold pack) and nailed the install on the first attempt (or #3 depending on how you look at it!)

IT WORKS!!!

Now, the wife has heat when she needs it.

Thanks for all the help and advice!

 

[Bounce]

so is this a real HeatTroller from the HeatTroller company or one of the knock-off ones that were made by Gerbing after they sent a licensed HT off to China?