The amp is question is a MTX 6500D. I realize this sounds like a silly question, but I'm trying to figure out what is wrong with my amp. It works randomly and quits randomly, and I don't know why yet. The circuit board is among the cleanest I've seen, despite it being from 2001. When it decides to play, it sounds like it is putting out its rated power (at the will of volume/gain/crossover, et cetera).
On to the specific question: There are four large 4700 micro-farad capacitors on the board. Looking at the amp, oriented with the power-supply closest to me, the plastic top of the one on the far right is very squishy, in that I can push the plastic top in quite a bit; they decrease in softness until the capacitor on the far left is solid, in that I can't push the plastic top in whatsoever. I do not see evidence of any of them leaking on either side of the board.
I wouldn't think there should be this much physical variance among components that are supposed to be electrically "identical". Should I replace them all? How solid is a large(r) cap supposed to be?
I have a video that shows the difference in the caps. I can post the link if I'm allowed to post links to youtube.
The caps are made by ELNA, and they are marked with "2223T" and "L P 5". The rest of the information on them is 80 v, 4700µF(M), CE85°C, Thailand.
Is there a replacement part that works for this application?
Thanks in advance; I know I can get wordy...
- Joe
On to the specific question: There are four large 4700 micro-farad capacitors on the board. Looking at the amp, oriented with the power-supply closest to me, the plastic top of the one on the far right is very squishy, in that I can push the plastic top in quite a bit; they decrease in softness until the capacitor on the far left is solid, in that I can't push the plastic top in whatsoever. I do not see evidence of any of them leaking on either side of the board.
I wouldn't think there should be this much physical variance among components that are supposed to be electrically "identical". Should I replace them all? How solid is a large(r) cap supposed to be?
I have a video that shows the difference in the caps. I can post the link if I'm allowed to post links to youtube.
The caps are made by ELNA, and they are marked with "2223T" and "L P 5". The rest of the information on them is 80 v, 4700µF(M), CE85°C, Thailand.
Is there a replacement part that works for this application?
Thanks in advance; I know I can get wordy...
- Joe
Hi Joe
Welcome here.
i am not a cap specialist but i try to help you:
the caps are in aluminium case (negativ marked and it is the case - plus is the other leg). if a cap get old or is of a bad quality its top gets bloated on the top. the inner pressure gets higher ,electrolytic liquid gets partly out and the cap gets dry....the values gets worse...
2 things can worse the life of a cap = too long/hot temperature - so the temperature range for the usage of the caps has to be calculated! or the Voltage is too close on the rated voltage of the cap, e.g. 24V power supply and you use a 25V cap(better us a 35V cap)
if you want the "correct" cap all this factors make the caps stronger but more expensive - the size can be bigger too - so watch out.
so this plastic top is for prevent that if a old/damaged cap "runs out" and the liquid runs over the pcb. so my inteperetaion is that the cap where you cannot push easy is damaged because its aluminum hat is bloated. the others are normal. (if you cut out this platic top hat you should see
so to change all caps is your decision- it is a budget topic. its a car amp so the heat is a problem - it maybe good to look at 105° or 120°C rated caps. but after 18 years using its maybe ok to use the same rating (85°C)
chris
Welcome here.
i am not a cap specialist but i try to help you:
the caps are in aluminium case (negativ marked and it is the case - plus is the other leg). if a cap get old or is of a bad quality its top gets bloated on the top. the inner pressure gets higher ,electrolytic liquid gets partly out and the cap gets dry....the values gets worse...
2 things can worse the life of a cap = too long/hot temperature - so the temperature range for the usage of the caps has to be calculated! or the Voltage is too close on the rated voltage of the cap, e.g. 24V power supply and you use a 25V cap(better us a 35V cap)
if you want the "correct" cap all this factors make the caps stronger but more expensive - the size can be bigger too - so watch out.
so this plastic top is for prevent that if a old/damaged cap "runs out" and the liquid runs over the pcb. so my inteperetaion is that the cap where you cannot push easy is damaged because its aluminum hat is bloated. the others are normal. (if you cut out this platic top hat you should see
so to change all caps is your decision- it is a budget topic. its a car amp so the heat is a problem - it maybe good to look at 105° or 120°C rated caps. but after 18 years using its maybe ok to use the same rating (85°C)
chris
If it's just the plastic disk on top that happens to be "domed" a bit but it doesn't feel solid when pressing down on it, there's no reason to worry.
4700uF / 80V is a pretty sizeable cap, which i'm quite sure is available in snap-in versions only. It's not uncommon for those to have the top covered with an insulating disk held in place by the heatshrunk sleeving.
"Top-less" - https://ae01.alicdn.com/kf/HTB11SAX...0V180uF-Snap-in-PSU-Capacitor.jpg_640x640.jpg
Insulating top (like yours sound) - https://www.goldmine-elec-products.com/images/G24013B.jpg
That being said, Elna is among the handful of trustable brands - i'd trust older Elnas more than brand-new CapXon and other crappy ones 🙄
What are the circumstances when the amp starts acting up?
4700uF / 80V is a pretty sizeable cap, which i'm quite sure is available in snap-in versions only. It's not uncommon for those to have the top covered with an insulating disk held in place by the heatshrunk sleeving.
"Top-less" - https://ae01.alicdn.com/kf/HTB11SAX...0V180uF-Snap-in-PSU-Capacitor.jpg_640x640.jpg
Insulating top (like yours sound) - https://www.goldmine-elec-products.com/images/G24013B.jpg
That being said, Elna is among the handful of trustable brands - i'd trust older Elnas more than brand-new CapXon and other crappy ones 🙄
What are the circumstances when the amp starts acting up?
Thank you the information. Will it hurt anything to remove the plastic tops on the capacitors to see if they look damaged?
I can't find any of the exact same caps other than on ebay; is it acceptable to replace with a different part of the same specs?
I can't find any rhyme or reason why the amp comes on and off. It doesn't matter if it's the first time I start the vehicle in the morning or after the work day of sitting in the sun. I have good voltage on my RCA's. Measuring between the ground terminal and the negative batter post, I only got a few millivolts. I have very near battery voltage at the amp terminals. Every component in the amp looks really good, in my opinion. I've already ordered a replacement amp, so I'm really trying to repair this for fun and to say I did it!
- Joe
I can't find any of the exact same caps other than on ebay; is it acceptable to replace with a different part of the same specs?
I can't find any rhyme or reason why the amp comes on and off. It doesn't matter if it's the first time I start the vehicle in the morning or after the work day of sitting in the sun. I have good voltage on my RCA's. Measuring between the ground terminal and the negative batter post, I only got a few millivolts. I have very near battery voltage at the amp terminals. Every component in the amp looks really good, in my opinion. I've already ordered a replacement amp, so I'm really trying to repair this for fun and to say I did it!
- Joe
Definitely I would not buy these from ebay, too much crooks selling fakes there. The brand is not important, look for a similar type with same specs and dimensions. And buy from a reputable supplier like Mouser or other.
If the caps were bloated / burst, trust me, you'd know (even without removing the tops). If the aluminium casing under those tops is still flat, you've got nothing to worry about.
https://upload.wikimedia.org/wikipedia/commons/b/b9/Vp6_blown_capacitor.jpg
If you insist on replacing them, though, sure, similar specs are fine. That being said, i'd rather stick with the handful of Japanese brands (Panasonic/Matsushita, United ChemiCon, Rubycon, Nichicon, Elna), from a reputable source (Mouser, Digikey, Farnell / element14). The earlier tip about going for a 105C rated part (up from the stock 85C) is worthwhile.
Not quite sure what "good voltage on your RCAs" might mean. Measuring DC voltage between the negative (ie. ground/shield of the input RCAs?) and the negative battery terminal / DC input is perfectly normal - desired, even.
"Very near battery voltage on the amp terminals" = i hope you mean the DC input, not the speaker outputs.
Temperamental behaviour could point towards thermal causes, but i'd much rather suspect the input / primary side of the built-in power supply. Those 80V caps are quite definitely on the secondary side, smoothing the boosted voltage coming out of the switchmode power supply (12V in -> +/-60V-ish or so?) that then feeds the amplifier section.
https://upload.wikimedia.org/wikipedia/commons/b/b9/Vp6_blown_capacitor.jpg
If you insist on replacing them, though, sure, similar specs are fine. That being said, i'd rather stick with the handful of Japanese brands (Panasonic/Matsushita, United ChemiCon, Rubycon, Nichicon, Elna), from a reputable source (Mouser, Digikey, Farnell / element14). The earlier tip about going for a 105C rated part (up from the stock 85C) is worthwhile.
Not quite sure what "good voltage on your RCAs" might mean. Measuring DC voltage between the negative (ie. ground/shield of the input RCAs?) and the negative battery terminal / DC input is perfectly normal - desired, even.
"Very near battery voltage on the amp terminals" = i hope you mean the DC input, not the speaker outputs.
Temperamental behaviour could point towards thermal causes, but i'd much rather suspect the input / primary side of the built-in power supply. Those 80V caps are quite definitely on the secondary side, smoothing the boosted voltage coming out of the switchmode power supply (12V in -> +/-60V-ish or so?) that then feeds the amplifier section.
I will start a new thread, as this is becoming very specific to my amp. I really appreciate the help.
- Joe
- Joe
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