Have you had luck resoldering your Cruise Control Amplifier???
 

Hey there,

I have tried twice now to resolder my cruise control amplifier...and I am RETARDED!!!!! :furious2: :confused:

Can someone who has had luck doing this help me out? I will pay for your time, and of course shipping back to me.

Thanks

Saint

sometimes its not a cold solder joint...but failed components...

Exactly my point. I figure that resoldering the board is the logical first step. It is cheap to do, especially if you do it yourself, and this has fixed the problem many times.

I have a rough idea about how to solder...but I think I may be running into a problem with the protectant on the board. Maybe that is what is causing my resolder failure.

There was guy here or at the mbworld who offered to resolder for $10 I think. I cant find his post anywhere.

I do hope you are using rosin core solder and not acid core solder. But you do understand a good point..knowing how to solder...you can overheat components or tracks and ruin them lingering too long or using too high a wattage iron..

I don't know who that was that did it for $10......shipping would be twice that....

Typically, you do not want to add solder when you fix "cold solder" joints. You just want to reheat the existing solder, and make sure it melts properly. Another option, is to use a desoldering braid or pump, to remove solder than replace. Just adding additional solder is going to make a mess, and possibly bridge or short something.

I'll go over the whole thing for free if you want to pay for shipping back and forth both ways. Is there a typical joint that goes bad, or do you just reflow everything in hopes of it coming back to life?

Any known component that goes bad? I'm an EE and I spent 5 yrs as a bench tech, so I know what im doing as far as protecting components etc, but i've never played with one of these before.

Take care,

George

I was too..but have been away from it for 11 years....I have never seen schematics on the CC unit...my guess is capacitors that have dried with age and totally screwed the RC constant killing the circuit...but without schematics its like navigating NYC blindfolded

I've fixed 3 clock mechanisms by replacing the caps. The caps were absolutely bone dry inside. I found the board fairly well made and easy to desolder. If the caps in the CC are like the ones in the clock, they aren't house marked and clearly state uF, working voltage, and polarity. It would probably be worth getting a list together of all the electrolytic caps and ordering them from Mouser or Digi-Key. Modern caps are almost always smaller given WV and capcaitance,so space shouldn't be a problem.

Don't get them from Radio Shack, they are doggie dirt and you will go into debt at their prices (if you can actually find them anymore, given their fine selection).

Mouser and Digi-Key also sell "hi-temp" caps, which are probably worth the premium in this application.

10% on an RC is a HUGE variable....from personal experience and good caps that is about as close as you get. Unless you have a LC meter and hand pick.

That makes sense....

If they arent house marked, it should be a piece of cake.

As far as parts sources, both of the ones you mention are good, but shipping may kill you on a smaller order. I happen to have an entire electronics research lab at my disposal at work, so unless they use some exotic values, We should have anything I could possibly need.

The other beauty of older electronics is the lack of SMD devices. Do you know how much of a pain it is to solder those damn little things?

Take care,

George

OH I know....I've done it a few times....

You pay the shipping both ways and I'll give it a shot.
What are you out $10.00 total in shipping.
I've never added solider to the 2 that I have repaired
just reheat the old stuff until I got the ripple effect in the soldier.
What car does it go in?

It can be done, even by an old fart (47) with eyesight not what it was. A temp-controlled iron with small tips, flux pens, good (but not expensive) tweezers, and $5.00 of cheap jewelers' loupes! Because it was getting impossible to hack without being able to to do surface mount, I designed and built a microprocessor controlled nixie-tube watch as my first try at it. In some ways, it's actually easier than through-hole (except when you get down to super-fine-pitch or ball-grid array chips, then the equipment gets astronomically expensive).

On the concern about RC constants in the cruise circuit, I'd find it hard to beleive that MB would design a circuit where 10% would be critical, particularly on a cap. These things aren't really even that close (for long!) in reality, and it is possible to design analog circuitry where the effects of conponent tolerance are minimal. Just the extreme temp variations in a car would cause problems in an overly-sensitive circuit. If there are actually any timing-critical caps, they are probably polystyrene or specially made disk caps. Using an electrolytic in a timing circuit is generally not a good idea (but IANAEE).

For example, I'll bet that many electrolytic caps in my (working, for now) cruise control module are probably +0/-40% or more right now, given their age.

Just because i live breathe and eat this stuff, I try to stay with DIP devices for my hobby stuff, but you are right, its becoming increasingly harder.

I really don't see first of all if you would need an RC timing circuit in a cruise control amp. After all what does the cruise control amp do? The only thing you need an RC timing circuit for, is either to create a pulse of some sort, or to create an osscilator. Secondly, I really cant see using an Electrolytic cap, considering poly or film caps, are readily available, and cheap, in any useable value for an RC timing circuit with a time constant suitable for one of the above uses.

My bet is that they are probably used as blocking caps, to remove DC from a mixed signal, pre and post " amp". Problem being if they break down, they no longer pass the AC either. Thats why it doesn't really matter if they are -40% , as long as they still pass the AC, the device still works.

So its probably one of two issues, one, a cold solder joint. Or two, a failed electrolytic, no longer passing AC.

I've actually seen both cases.

Take care,

George

Wow, thank you guys so much.

This is for a 1990 300TE...sorry about not mentioning that...pretty stupid for not.

Sending pm's.....

Here are a couple of pics I took. The board is 4in x 5in

Ok.. I have the board now.....
 

What to replace trying to repair it on the blind. I.e. No schematic, and NO way to test it.

Went through all the solder joints and traces. Touched up a few joints. All traces now have continutity.

Circuit has a total of 6 electrolytic caps. I'm going to take it to work and check them on an LCR Meter we have.

Now. There are 3 unmarked BJT transistors on the board.

There is a 40 pin DIP IC Marked ITT V8001-501, haven't been able to find any info about it online. but the top edge looks a but suspect - swolen.

There is an LM2091 Quad comparator on board. and a bunch of xener and regular diodes, as well as two pairs of heat shielded FET's that are setup in a Darlington Array.

I can post a high res version of the circuit, if anyone would like to see.

If anyone has an older reference or catalog, I would appreciate any info on the big 40 pin IC.

Take care,

George