we are also adding new BIGGER heat sinks to them.

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

What is the possibility of photos of this? I may be venturing into the cruise control amp due to intermittent operation.

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Sam

84 300SD 350K+ miles ( Blue Belle )

if it works there so will be photos

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

While I've replaced a number of transistors in a few cruise control amplifiers, those were symptoms of the problem, not the root cause. I believe the amplifiers toasted because the servo is not working correctly.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

well the transistors were bad, but it still doesnt work. we tested most everything on the board and didnt find anything else bad. so im thinking it might be the actuater. but, on the plus side i fixed the clock,odometer,and bypassed the rehostat so now i dont have flakey dash lighting. if i figure out the cruise i will post pics.

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

i was wrong. i didnt get it all the way plugged in like i thought. IT WORKS!!!!!!!

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

Guess we need a schematic posted of the circuit layouit for a mercedes cruise control. Perhaps there is already one out there and I just have not seen it. Unless there is some form of cascade design wonder why all four transistors were bad? Or perhaps as somone mentioned the transistors were just damaged by actuator itself. Wonder if also just a substandard quality of transistor was used in manufacture. I have about three controls I would like to dig into but preffer a schematic. On the otherhand if board is single side foiled perhaps I can draw up one myself. I wonder if the company that manufactured these for mercedes would release a schematic. The manufacturer that comes to mind is phillips as some of their products of that vintage were so unreliable. Phillips had the poorest assembly soldering I ever saw for a large company as well. There are probably other manufactures with as poor a track record I just cannot think of any. Cruise controls are a long way from rocket science. Perhaps it's time we started a dedicated thread about rebuilding these babys ourselves and checking out the actuator. What do you fellows think? There are a lot of us out here with at least a smattering of electronic knowledge. We have a start as availability of transistors and cost is mentioned.

anxiously awaiting those pics. I resoldered a few points on mine but it didn't help. looking forward to seeing where you replaced those transistors, I'll definitely give that a try.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Wonder what the proffesional cruise control amplified builders are doing to increase reliability? There are design problems inherent I think. The additional heat sinking sounds like a good move in tandem whith the more modern and perhaps far more reliable transistors. I also suspect the bias arrangements will have been reworked on the pro rebuilds. Just find it strange that our amps have been a large problem for so long without a lot of information accumulated and posted on site other than basically re-solder the board.

Hmmmm..........bigger heat sinks. I will need to look at that when I take mine apart. This points toward a failure symptom on mine. While it is cold, the amp works usually. However, if the cabin temps are very warm, I can't get it to engage.

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Sam

84 300SD 350K+ miles ( Blue Belle )

i will try to post pics tonight. i also plan on drilling a few small vent holes and possibly a little cpu fan to cool it.

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

How about tie-wrapping the aluminum case to your expansion valve nearby?

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

eh i dont think it would cool as effectivly. i figure a few small holes and a fan for like a pentium 1 should do the job

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

ok even with resizing it wont let me post them. if someone will send me their email address and could resize them for me it would be greatly appreciated

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

heres an original picture (thanks to wolf walker) notice the wimpy heat sinks on the transistors at the top of the board

Attached Thumbnails

 

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it