crest clicker

mechaboy1 · 26th October 2006, 01:05 AM

Do you guys know if these amps are tempremental? I just purchased a used Crest pro4801 amp. I brought the amp home and played some music on it for a couple of hours it sounded fantastic. It has lots of headroom and rarely ever clips. I took out the amp today and practiced again playing music. The amp acted a little funny when I moved my stand. I had the volume on the mixer all the way down and when I moved the stand it is mounted in it suddenly click on temp and channel one shut off. I could tell it shut off because it clicks very loud. Then a few seconds later it came back on again. I moved the stand agian and it click off again then clicked back on. I felt the amp and it wasn't even warm. I turned the volume on the mixer up and the vibration of the speaker next to it caused it to shut off again. I checked my connections and everything seemed ok. I moved the speaker further away from the amp and put the music up and the amp played fine no ckick offs. The amp isn't even warm it is cool to the touch. Could this amp have a blown channel? or are the sensor units in these amps touchy when you move the stands they are mounted in? How long should you run an amp to test it. I don't know if I should take it in to have it checked out, what do you guys think?

mechaboy1 · 26th October 2006, 02:09 AM

I tried a little test. The amp dials were turned all the way down. I tapped on the bottom of the amp with my hand and channel one clicked off again. The amp was sitting for an hour and was cold. I think a sensor or something is bad. If i were too us this amp as a head and sit it on top of a bass it would probably shut off.

clem_o · 26th October 2006, 10:46 AM

If the amplifier still plays, then the channels aren't blown, period.

What you probably have is a loose connection - this can be caused simply by a connector (inside the amp) that hasn't been seated properly, or it could be a cold solder joint, or a joint that doesn't have any (or too little) solder.

A good, experienced technician will probably be able to fix it even without a schematic, if it exhibits that kind of sensitivity to vibration...

Cheers

mechaboy1 · 26th October 2006, 08:16 PM

Thanks for the advice clem_o that sounds like exactly whats wrong with it. Last night I opened the amp and moved a few wires around and it didn't click off at all. I'll probably take it to my repair guy to have it checked out. Can these amps be cleaned or tuned in any way for better sound, I don't think this amp has been cleaned in years.

clem_o · 27th October 2006, 12:31 AM

It can be "tuned up" so to speak, to bring it back to factory-spec performance, if that's what you're asking - a check on the output offset voltage and output stage bias. But unless the person working on it is extremely experienced I'd stay away from trying to "improve" the amp.

Most pro-audio stuff are very well thought, and and any 'improvements' that one could possibly make (at reasonable cost) would either already have been put in, or if not, was probably due to some 'other' reason (i.e. stability, protection to either the amp or the speakers, etc etc)...

Of course there are exceptions - has a search turned up any comments on this particular model?

Cheers!

mechaboy1 · 27th October 2006, 01:15 AM

In a forum search I found one post on this model and it said to clean the molex board and board headers. I really don't want to modify the amp only to bring it back to factory spec as you indicated, this amp has alot of miles on it and I want to somewhat restore it. I've wanted an amp like this for years. I think it was used for a club installation in the past so it's been through war. is there a meter measuring tool to check the output offset voltage and the output stage bias? The last time I brought an amp to my local shop the tech said he couldn't check the amp without opening it up. I wanted him to check the wattage ouput. Thanks clem_o

clem_o · 27th October 2006, 01:41 AM

Hi mechaboy1,

If that amp's been in a club, it's probably got a lot of cigarette smoke residue etc, perhaps a nice cleaning will also do it some good - again this is something a tech should be able to handle, but yes, all of this does require opening up the amp and taking the board out, regreasing the transistor/heatsink interface, etc.

To check output offset and bias, all that is needed is a useable voltmeter (a general purpose analog or digital VOM). See if you can download a schematic specific to that amp, it would help the tech greatly if he knew which potentiometer sets what...

Cheers!

imix500 · 27th October 2006, 03:33 AM

Thats a great amp you've got there. The whole "professional series" was really well made.
You can practically weld with these amps.
As clem_o said, if that amp was in a club a good cleaning is in order, especially if it was run without the filters installed over the fan. The molex connectors are not sealed so a shot of D5 or the like is a really good idea, as well as the header on the input card. Be sure to replace the tie-wraps that hold the molex connectors together.

mechaboy1 · 28th October 2006, 04:49 AM

Thanks guys, I actually have an idea of what needs to be done. Here is a list of your suggestions.

D5 clean molex connectors
clean header on the input card
replace the tie-wraps that hold the molex connectors together
regreasing the transistor
heatsink interface ect.
amp filter

When I had opened the amp it was really dirty near the back of the amp and inside the 2 giant heat sinks. A filter is a great idea imix500. I cleaned what I could with a mini shop vac. When I saw the giant toroidal tranformer I rembered playing link the chain when I was a kid with my friends and the transformer, except this one would probably shock like hell. I'm going to have to take this amp to a qualified tech to have these things done to it.

imix500 · 28th October 2006, 05:01 PM

mecaboy1, they come with filters installed from the factory. You can get replacement filters and retainers from mouser. Crest (Mackie) will charge you a lot to buy from them.
I think those fans are 60mm? Double check before ordering.
Mouser Part # is 670-GRM6045 for a 60mm fan.

26th October 2006, 01:05 AM	#1
mechaboy1 diyAudio Member Join Date: Sep 2006	crest clicker Do you guys know if these amps are tempremental? I just purchased a used Crest pro4801 amp. I brought the amp home and played some music on it for a couple of hours it sounded fantastic. It has lots of headroom and rarely ever clips. I took out the amp today and practiced again playing music. The amp acted a little funny when I moved my stand. I had the volume on the mixer all the way down and when I moved the stand it is mounted in it suddenly click on temp and channel one shut off. I could tell it shut off because it clicks very loud. Then a few seconds later it came back on again. I moved the stand agian and it click off again then clicked back on. I felt the amp and it wasn't even warm. I turned the volume on the mixer up and the vibration of the speaker next to it caused it to shut off again. I checked my connections and everything seemed ok. I moved the speaker further away from the amp and put the music up and the amp played fine no ckick offs. The amp isn't even warm it is cool to the touch. Could this amp have a blown channel? or are the sensor units in these amps touchy when you move the stands they are mounted in? How long should you run an amp to test it. I don't know if I should take it in to have it checked out, what do you guys think?

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26th October 2006, 02:09 AM	#2
mechaboy1 diyAudio Member Join Date: Sep 2006	I tried a little test. The amp dials were turned all the way down. I tapped on the bottom of the amp with my hand and channel one clicked off again. The amp was sitting for an hour and was cold. I think a sensor or something is bad. If i were too us this amp as a head and sit it on top of a bass it would probably shut off.

26th October 2006, 10:46 AM	#3
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	If the amplifier still plays, then the channels aren't blown, period. What you probably have is a loose connection - this can be caused simply by a connector (inside the amp) that hasn't been seated properly, or it could be a cold solder joint, or a joint that doesn't have any (or too little) solder. A good, experienced technician will probably be able to fix it even without a schematic, if it exhibits that kind of sensitivity to vibration... Cheers

26th October 2006, 08:16 PM	#4
mechaboy1 diyAudio Member Join Date: Sep 2006	Thanks for the advice clem_o that sounds like exactly whats wrong with it. Last night I opened the amp and moved a few wires around and it didn't click off at all. I'll probably take it to my repair guy to have it checked out. Can these amps be cleaned or tuned in any way for better sound, I don't think this amp has been cleaned in years.

27th October 2006, 12:31 AM	#5
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	It can be "tuned up" so to speak, to bring it back to factory-spec performance, if that's what you're asking - a check on the output offset voltage and output stage bias. But unless the person working on it is extremely experienced I'd stay away from trying to "improve" the amp. Most pro-audio stuff are very well thought, and and any 'improvements' that one could possibly make (at reasonable cost) would either already have been put in, or if not, was probably due to some 'other' reason (i.e. stability, protection to either the amp or the speakers, etc etc)... Of course there are exceptions - has a search turned up any comments on this particular model? Cheers!

27th October 2006, 01:15 AM	#6
mechaboy1 diyAudio Member Join Date: Sep 2006	In a forum search I found one post on this model and it said to clean the molex board and board headers. I really don't want to modify the amp only to bring it back to factory spec as you indicated, this amp has alot of miles on it and I want to somewhat restore it. I've wanted an amp like this for years. I think it was used for a club installation in the past so it's been through war. is there a meter measuring tool to check the output offset voltage and the output stage bias? The last time I brought an amp to my local shop the tech said he couldn't check the amp without opening it up. I wanted him to check the wattage ouput. Thanks clem_o

27th October 2006, 01:41 AM	#7
clem_o diyAudio Member Join Date: Jun 2005 Location: Manila	Hi mechaboy1, If that amp's been in a club, it's probably got a lot of cigarette smoke residue etc, perhaps a nice cleaning will also do it some good - again this is something a tech should be able to handle, but yes, all of this does require opening up the amp and taking the board out, regreasing the transistor/heatsink interface, etc. To check output offset and bias, all that is needed is a useable voltmeter (a general purpose analog or digital VOM). See if you can download a schematic specific to that amp, it would help the tech greatly if he knew which potentiometer sets what... Cheers!

27th October 2006, 03:33 AM	#8
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Nashville, TN	Thats a great amp you've got there. The whole "professional series" was really well made. You can practically weld with these amps. As clem_o said, if that amp was in a club a good cleaning is in order, especially if it was run without the filters installed over the fan. The molex connectors are not sealed so a shot of D5 or the like is a really good idea, as well as the header on the input card. Be sure to replace the tie-wraps that hold the molex connectors together.

28th October 2006, 04:49 AM	#9
mechaboy1 diyAudio Member Join Date: Sep 2006	Thanks guys, I actually have an idea of what needs to be done. Here is a list of your suggestions. D5 clean molex connectors clean header on the input card replace the tie-wraps that hold the molex connectors together regreasing the transistor heatsink interface ect. amp filter When I had opened the amp it was really dirty near the back of the amp and inside the 2 giant heat sinks. A filter is a great idea imix500. I cleaned what I could with a mini shop vac. When I saw the giant toroidal tranformer I rembered playing link the chain when I was a kid with my friends and the transformer, except this one would probably shock like hell. I'm going to have to take this amp to a qualified tech to have these things done to it.

28th October 2006, 05:01 PM	#10
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Nashville, TN	mecaboy1, they come with filters installed from the factory. You can get replacement filters and retainers from mouser. Crest (Mackie) will charge you a lot to buy from them. I think those fans are 60mm? Double check before ordering. Mouser Part # is 670-GRM6045 for a 60mm fan.

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