Hello everyone!
I have a Crest Audio LA 601 that I recently purchased as 1 channel broken, I got it home, cleaned up the inside a bit and she worked fine, both channels sounded nice and powerful.
However I observed that the power lights on the amp would dim more than I thought they should on heavier bass notes.
Sure enough after about 3 sessions, about 2 hours each, one of those big Philips 10,000uf 67V filter caps went POP!!!
Now the first question, is how can I check if the other filter cap is still good, or if it is doomed to blow too. It doesn't have an obvious defect, and neither did the other filter cap. I know I should replace both, but this is my amp, and I'm cheap. I also noticed this cap has 3 legs, but it looks like one of them isn't connected to any traces, just a little pad to secure it so I assume a normal 2 leg radial cap will work.
Secondly, I see on ALL of the pcb's in this amplifier that the solder mask is bubbled up just like paint gets on a rusty car. If you just poke the solder mask a bit it chips right off the board, and there are some areas where quite a bit has chipped off.
Is this a serious issue, and if so can it be fixed? I'm almost tempted to coat all the boards in liquid electrical tape but I figured I'd ask first. I don't think it'd be much of a safety issue considering its got one heck of a thick metal case that's grounded and the outputs are dangerous as they are (pro amps can put out quite a few volts) so if it were to put the supply (I think about 60VDC) on the outputs, it'd be no more of an issue than just running it in general. I am however still a bit worried about corrosion occurring on the exposed traces on the PCB. Just let me know what you guys think.
One more question, how can I clean all the electrolyte off of the power supply pcb from that blown cap? I've never really had to deal with that sort of massive mess that that stupid cap spewed out.
I appreciate any and all help, thanks in advance! 😀
I have a Crest Audio LA 601 that I recently purchased as 1 channel broken, I got it home, cleaned up the inside a bit and she worked fine, both channels sounded nice and powerful.
However I observed that the power lights on the amp would dim more than I thought they should on heavier bass notes.
Sure enough after about 3 sessions, about 2 hours each, one of those big Philips 10,000uf 67V filter caps went POP!!!
Now the first question, is how can I check if the other filter cap is still good, or if it is doomed to blow too. It doesn't have an obvious defect, and neither did the other filter cap. I know I should replace both, but this is my amp, and I'm cheap. I also noticed this cap has 3 legs, but it looks like one of them isn't connected to any traces, just a little pad to secure it so I assume a normal 2 leg radial cap will work.
Secondly, I see on ALL of the pcb's in this amplifier that the solder mask is bubbled up just like paint gets on a rusty car. If you just poke the solder mask a bit it chips right off the board, and there are some areas where quite a bit has chipped off.
Is this a serious issue, and if so can it be fixed? I'm almost tempted to coat all the boards in liquid electrical tape but I figured I'd ask first. I don't think it'd be much of a safety issue considering its got one heck of a thick metal case that's grounded and the outputs are dangerous as they are (pro amps can put out quite a few volts) so if it were to put the supply (I think about 60VDC) on the outputs, it'd be no more of an issue than just running it in general. I am however still a bit worried about corrosion occurring on the exposed traces on the PCB. Just let me know what you guys think.
One more question, how can I clean all the electrolyte off of the power supply pcb from that blown cap? I've never really had to deal with that sort of massive mess that that stupid cap spewed out.
I appreciate any and all help, thanks in advance! 😀
I don't think I'm going to replace more than just the two filter caps. I don't want to put too much money into this amp.
well if you go on the cheap and replace just the main filters make sure you can test it for stability.
What exactly do you mean?
I'm thinking you mean don't sell it right away as it might not have fixed the issue. If that is what your trying to say, well, I'm not selling this amp ANY time soon.
Have any suggestion to how to clean up the electrolyte as well as if the solder mask issue is really an issue?
How exactly can I check that?
I've ran it for probably 4 hours full range with a bit of equalizer tuning before my crossovers came in and I ran it for that hour or so before it blew up.
I found something quite interesting just now. I've been wondering about the existing 67V caps, as 67 isn't a normal number like 63.
I tested from center tap to one end of the winding and measured exactly 50VAC on a true-rms multimeter. Now 50 * 1.41 = 70VDC, which is over the 67VDC caps used in the power supply in this amp.
I can't really tell if those caps are original or not, the solder joints look like they may or may not be original, I just can't tell...
Yep, I have a decent amount of the usual gear. Multimeters, Power supplies, Oscilloscope...
I tested from center tap to one end of the winding and measured exactly 50VAC on a true-rms multimeter. Now 50 * 1.41 = 70VDC, which is over the 67VDC caps used in the power supply in this amp.
I can't really tell if those caps are original or not, the solder joints look like they may or may not be original, I just can't tell...
Yep, I have a decent amount of the usual gear. Multimeters, Power supplies, Oscilloscope...
Last edited:
well monitoring B+ supply lines for noise and instability should be an easy thing after replacing the cap's that blew up.
what voltage did you measure on the other half?
what voltage did you measure on the other half?
Oh so all you want me to do is watch the supply on a scope, well no problemo.
Any abnormalities in particular that I should look for other than general waveform weirdness?
And do you agree I need a larger cap than 67V? Do you think a good manufacturer would put a 67V cap on a 70V rail? or is that rail a little less when connected to the other boards.....
I think when I buy new caps for this I'm going to get some 100V 10,000uf caps, simply because its my best bet, even for price.
EDIT: Both sides are 50.5VAC
Last edited:
increasing the voltage rating on the caps is not going to hurt just make sure your replacements will fit physically(a increase in voltage rating usually means a bigger cap size)
50.5 VAC loaded or unloaded?
50.5 VAC loaded or unloaded?
Yeah like I said, its about the same price for caps after 63v, the 80v and 100v are virtually the same. And actually the old caps are so old that they are actually going to be bigger than the new ones, even if the new ones are 100v instead of 67v!
Its 50.5VAC unloaded straight off the transformer as I don't want to reconnect it to the rest of the amp without having replaced those caps.
Go for 80V caps, just to be safe. I bet you 63V is too little or else Crest would have used a standard voltage part.
Well I'm surprised they can justify using even 67V, as I calculated the rectified dc should be 70V.
Either way, I'm going with 100V 10,000uf caps 😀 Because I can find them on eBay for almost half mouser's price.
Last edited:
it doesn't suprise me the Crest brand is not what it used to be since they where bought out.
if the new caps are smaller are you making sure temp ratings are the same most suppliers list the cheap and cheery caps first as a price grabber ignoring proper specs in a cost saving measure isn't prudent.
if the new caps are smaller are you making sure temp ratings are the same most suppliers list the cheap and cheery caps first as a price grabber ignoring proper specs in a cost saving measure isn't prudent.
I was going to buy these: Capacitor Rubycon 10000 10000uF 100V Electrolytic 105C Degree 70 35 1pc FL USA | eBay
Or possibly these (A bit cheaper but I need to confirm with the seller what manufacturer and temp rating): New Electrolytic Capacitor 10000uF 80V | eBay
In the meantime, I still need to figure out how to clean up the board that has capacitor electrolyte all over it.....
Last edited:
I'm very tempted to rip out the 2x Elna 8200uF 90V caps out of one of my Kenwood receivers just to fire up the crest audio.
I think I'll do that as soon as possible. But first I need to find out how to clean up the electrolyte from the blown cap....(any help???).
I think I'll do that as soon as possible. But first I need to find out how to clean up the electrolyte from the blown cap....(any help???).
- Status
- Not open for further replies.