Hi
we replaced a couple of capacitors in a BMW 325is stereo. One was bad. The sound is good now but the heat sink at the back of the unit gets really hot after about 15 minutes of playing. It's made by Alpine I understand. I didn't put any new heat dissipating paste on when we reassembled the deck. Could that be the reason or can there be anything else? Thanks for any advice
Peter
we replaced a couple of capacitors in a BMW 325is stereo. One was bad. The sound is good now but the heat sink at the back of the unit gets really hot after about 15 minutes of playing. It's made by Alpine I understand. I didn't put any new heat dissipating paste on when we reassembled the deck. Could that be the reason or can there be anything else? Thanks for any advice
Peter
It's normal for a heatsink on an amplifier to heat up.
Regarding the heatsink compound, it's good that the heatsink is hot. It means that the heat is getting transferred.
Do you know how hot it was getting before you worked on it, listening to it at approximately the same level and length of time as you did today?
Was anything other than the work on the head unit done to the stereo system?
How much does the heatsink heat up if the system is at just above 0 volume for 10 minutes (tested from a cold start)?
Regarding the heatsink compound, it's good that the heatsink is hot. It means that the heat is getting transferred.
Do you know how hot it was getting before you worked on it, listening to it at approximately the same level and length of time as you did today?
Was anything other than the work on the head unit done to the stereo system?
How much does the heatsink heat up if the system is at just above 0 volume for 10 minutes (tested from a cold start)?
Thank you for the responses. The caps we replaced are of good quality though not the original Nichicon ones. Except for two I could not get hold of those. They are all the same value though, two of them are a little higher voltage. The deck was opened up because for a couple of months it had been acting strange. Crackling sound and a lot of noise on start up which eventually went away and it played normal after about 15 minutes. Then finally it began to smell and the sound stopped all together. One cap was totally burned up. Even the board was black under it. Fortunately all connections were undamaged. Replaced 6 caps on that side of the amp but did not replace all 18 of them. Perhaps I should have but it's a lot of work. Cleaned everything up and checked all wiring and connections. The sound is good now although when it's cold there is still some crackling on start up. It goes away after about a minute or two. I checked the heat sink again this morning early when it was still cool and it took about 45 minutes to get hot but it was okay to touch. Perhaps the other day the temperatures were too high. I could not keep my finger on it longer than a couple of seconds. I checked it daytime. Unfortunately I have no way of knowing how hot it used to get as it was never removed from the dash until now. Always worked well until about two months ago. It's old but it was one of those premium decks Alpine made for the BMW 325is and other models so it's supposed to be of high quality. Thanks again
Peter
Peter
Does the board have traces on both sides of the board or only on one side? If both, did you clean both sides of the board?
For the OP of for those with similar problems who may read this.
When ordering parts, order heatsink compound if you will need to separate the heatsink from the audio amplifier or the regulators.
Acetone and cotton swabs generally gets the board clean enough but the electrolyte can leach well away from the caps so it's sometimes difficult to get it all unless you're thorough.
Sometimes, the electrolyte will cause the board to become conductive. When that happens, you may need to cut the conductive parts away. If that breaks a trace, it may require hardwiring the connections.
Other information.
The heat that's applied to the heatsink is related to the output level and the length of time it's played.
Some amplifier ICs run cool at idle and some slightly warm. If an IC causes excessive heating at idle, it's likely defective.
For the OP of for those with similar problems who may read this.
When ordering parts, order heatsink compound if you will need to separate the heatsink from the audio amplifier or the regulators.
Acetone and cotton swabs generally gets the board clean enough but the electrolyte can leach well away from the caps so it's sometimes difficult to get it all unless you're thorough.
Sometimes, the electrolyte will cause the board to become conductive. When that happens, you may need to cut the conductive parts away. If that breaks a trace, it may require hardwiring the connections.
Other information.
The heat that's applied to the heatsink is related to the output level and the length of time it's played.
Some amplifier ICs run cool at idle and some slightly warm. If an IC causes excessive heating at idle, it's likely defective.
Good point, thanks. The board has traces on both sides and I cleaned only the one where the bad cap left black marks. Also, I did not use acetone. Alcohol with cotton swabs instead. I sprayed it with an electrical contact cleaner too but not with the Deoxit which seems to leave a trace. Should I take it out and re-clean both sides? The model number, by the way, is Alpine CM 5908 18 caps.
Don't take it apart unless you have to... but you will likely have to if all of the caps are from the same series. If more than one leaked, they (same series caps) likely have all started to leak.
Acetone seems to do better but alcohol is better than nothing.
I'd recommend cleaning both sides. If nothing else, it removes the solder flux from the solder side so you can better check for contamination/saturation of the board by the electrolyte.
For double-sided boards and through-hole caps, the vias that connect traces from one side of the board to the other can be damaged or completely eaten away.
When cleaning, it's important that you remove any board material that's darkened. Scraping it away with a razor knife is often the easiest way for areas that are mostly barely damaged.
Acetone seems to do better but alcohol is better than nothing.
I'd recommend cleaning both sides. If nothing else, it removes the solder flux from the solder side so you can better check for contamination/saturation of the board by the electrolyte.
For double-sided boards and through-hole caps, the vias that connect traces from one side of the board to the other can be damaged or completely eaten away.
When cleaning, it's important that you remove any board material that's darkened. Scraping it away with a razor knife is often the easiest way for areas that are mostly barely damaged.
Not sure if they are the same series. The caps are different values. Two's and three's mostly. Right now it seems okay but if it gets hot again and the crackling doesn't stop or gets worse I'll take it out again. I am not very good at de-soldering. Find it a real pain that's why I didn't change all 18 caps but I will do a new clean up if necessary.
If the leads are bent over, apply additional solder and straighten the legs with the soldering iron tip. With the added solder, the tip of the soldering iron will easily bridge between the solder pads. Heat both and pull the cap while the solder is molten.
Using good solder with a flux core helps.
Desolder with desoldering braid. Use fresh braid (bright in color, not brown). Braid with flux in it is better than braid without. If you don't have good braid, liquid flux (saturate the braid before use) helps. Do an ebay search (or the French equivalent) for:
Kester 186 951 reflow flux needle bottle xbox
Clean the area well with acetone or alcohol. and examine carefully with a lighted magnifying glass.
Using good solder with a flux core helps.
Desolder with desoldering braid. Use fresh braid (bright in color, not brown). Braid with flux in it is better than braid without. If you don't have good braid, liquid flux (saturate the braid before use) helps. Do an ebay search (or the French equivalent) for:
Kester 186 951 reflow flux needle bottle xbox
Clean the area well with acetone or alcohol. and examine carefully with a lighted magnifying glass.
Good advice, thanks. Almost all the leads are bent. Don't have any flux or desoldering braid but I see if I can get hold of some. Your first approach would have been very helpful on my Nakamichi home stereo decks. They all needed partial recapping periodically and often ended up with hard wire reconnections. It's even more difficult on this small board.