Crest amplifier repair help

[kiermee]

Hey guys, I currently bought a crest audio PRO 10001 power amplifier and it started to give me some problems, I am kind of stuck with two problems:

1. When I turn on channel A on one the amplifier the green signal led and the DC/Temp led come on together and the amp does not go active. Has anyone ever repaired these amplifiers and encountered this problem? I have narrowed it down to the main output module but all the parts seem to be okay. Any assistance would be greatly appreciated.

2. The other side channel B the clip led and the DC/Temp led stays on and the amp does not go active.

[Zero Cool]

I have just finished rebuilding a 10001 and a 8002 and 8001 and ca12/9/6/4's and am now working on a 9001 I am however no expert but....

FIRST**** use massive amounts of caution when working on a 10001 that amp can and will kill you should you make a mistake. you have 320V across the upper rails at an ungodly amount of amps. these transformers are HUGE. remember this amp will do 5000 watts across 1 ohm!!! get your hand across those sinks and POOOF and they will vaporize a screwdriver and send lots of hot metal flying around! USE CAUTION! that warning on the top cover is not a joke! and remember those are ACTIVE LIVE heatsinks!!! and make sure you know how to SAFELY drain the power supply capacitor banks!

If you are not a SKILLED repair tech. stop right now! I have repaired many hundreds of amps and this thing still scared the bejezus outta me! (however it was also one of the tamest amps i have ever worked on!)



The problems i have seen most often in Crest amplifiers is bad capacitors. they look fine from the outside but pull one out of circuit and measure it and there bad. these are the small electrolytic types. there are 2 sets of solid white wires from each output module to the output relays. inject a a signal into the amp and take a look at the signal on those white wires. if the signal looks clean with minimal DC offset then you have bad caps causing it to stay in protect. a very common crest problem.

in the 10001 check in between the heatsink's. these amps have a tendency for those heatsinks to arc across the sinks. there are only 2 thin rails that hold the modules and rough tour duty service can cause those rails to bend and the sinks to touch and arc. even a bug getting between the sinks can cause them to arc if the amp is running hard!

Also look for open resistors. I have found many that after thermal cycling so many times they just go open.

check the shoulder washers on the TO-220 devices. many times they will get damaged during installation and the screws will make contact with the transistor case when warm.

Study the schematics and work your way through the problem. Ignore the front LED's these amps are pretty rock solid and when they fail...the go boom and there is lots of damage. otherwise the problems are pretty minor, bad caps, open resistors etc. so if you havent found exploded switch bank mosfets or output devices then most likely the problem is something small.

Other things i have found. the output devices are no longer available. Crest/Peavey replaces them with MJ21193/4 devices and i can report that works well. these amps also have an ODD ac line current draw at low power. they will idle around 1-2 amps and when the output reaches 1.8-2v RMS no load. the amp will draw 5-6 amps of current! I have spoken with crest about it and they say this is normal for that amp.

again i urge you to use caution. this is not an amp for beginners!!!



Zc

[wahab]

Originally Posted by Zero Cool

these amps also have an ODD ac line current draw at low power. they will idle around 1-2 amps and when the output reaches 1.8-2v RMS no load. the amp will draw 5-6 amps of current! I have spoken with crest about it and they say this is normal for that amp.

Zc

two amazing things...
both the amp and crest s behaviour...
seems that a famed brand can sell flawed products
and still get away with it the intellectually arrogant way...

you have a lot of merit dealing with these items...

[audiomachines]

Originally Posted by Zero Cool

I have just finished rebuilding a 10001 and a 8002 and 8001 and ca12/9/6/4's and am now working on a 9001 I am however no expert but....

FIRST**** use massive amounts of caution when working on a 10001 that amp can and will kill you should you make a mistake. you have 320V across the upper rails at an ungodly amount of amps. these transformers are HUGE. remember this amp will do 5000 watts across 1 ohm!!! get your hand across those sinks and POOOF and they will vaporize a screwdriver and send lots of hot metal flying around! USE CAUTION! that warning on the top cover is not a joke! and remember those are ACTIVE LIVE heatsinks!!! and make sure you know how to SAFELY drain the power supply capacitor banks!

If you are not a SKILLED repair tech. stop right now! I have repaired many hundreds of amps and this thing still scared the bejezus outta me! (however it was also one of the tamest amps i have ever worked on!)



The problems i have seen most often in Crest amplifiers is bad capacitors. they look fine from the outside but pull one out of circuit and measure it and there bad. these are the small electrolytic types. there are 2 sets of solid white wires from each output module to the output relays. inject a a signal into the amp and take a look at the signal on those white wires. if the signal looks clean with minimal DC offset then you have bad caps causing it to stay in protect. a very common crest problem.

in the 10001 check in between the heatsink's. these amps have a tendency for those heatsinks to arc across the sinks. there are only 2 thin rails that hold the modules and rough tour duty service can cause those rails to bend and the sinks to touch and arc. even a bug getting between the sinks can cause them to arc if the amp is running hard!

Also look for open resistors. I have found many that after thermal cycling so many times they just go open.

check the shoulder washers on the TO-220 devices. many times they will get damaged during installation and the screws will make contact with the transistor case when warm.

Study the schematics and work your way through the problem. Ignore the front LED's these amps are pretty rock solid and when they fail...the go boom and there is lots of damage. otherwise the problems are pretty minor, bad caps, open resistors etc. so if you havent found exploded switch bank mosfets or output devices then most likely the problem is something small.

Other things i have found. the output devices are no longer available. Crest/Peavey replaces them with MJ21193/4 devices and i can report that works well. these amps also have an ODD ac line current draw at low power. they will idle around 1-2 amps and when the output reaches 1.8-2v RMS no load. the amp will draw 5-6 amps of current! I have spoken with crest about it and they say this is normal for that amp.

again i urge you to use caution. this is not an amp for beginners!!!



Zc

I will keep this in mind thanks ZC

[kiermee]

Thanks guys for the assistance. Finally got the amp to run. Works fine.