Infamous CE1000

[Tabmo]

Hello. I have a CE1000 that is making a low volume hum on both channels. The volume level of the hum does not change with adjust of the input pot. Both channels are producing audio but at a much lower volume than they should. Any ideas on where I can look would be greatly appreciated. I have downloaded the documentation from Crown and have begun to wade through it. Thanks..

[trevorus]

Does it sound like 60 or 120Hz? Sounds like it could need a cap job. Also check for DC at the outputs. (just my semi experientially educated guess. The smarter guys will be in to correct me most likely.)

[Tabmo]

It sounds like 60hz and there is not DC on the outputs..

[Jazz P Bass]

#1. Check each & every power rail.
If both channels are humming, the common item is the power supply.
Also, the main board screw pads must be clean & the screws tight.
Three of the screws are a common for grounds on the amp.
I just repaired a C-1000 with a blown channel.
Whooee.
Surface mount city.
Which main board number does the amp have?

[Tabmo]

Thanks trevorus and Jazz P Bass for the replies. I have attached an image showing two numbers on the main board?? Also I am assuming I will have to remove the board to check the power rails. -Tabmo

[Tabmo]

I did a search in the CE1000 service manual and was not able to find either number in my photo. 127452-1 and 127451-2. Any idea why? Or am I looking at the wrong numbers? Thanks again.

[trevorus]

Oh, man. I HATE (working on) SMT stuff. I'm glad I sold my CE1000 I used to have.

[Jazz P Bass]

The board schematic is for the 127452-4.
Link: http://www.crownaudio.com/media/pdf/..._serv_revd.pdf
It starts at Page# 576.
Make sure that you do the 'Bootstrap Resistor Mod".
That is covered on Page# 548.
You add a 1K/ 5W resistor on the white wire.
The 127452-4 has the circuit change.
If you do remove the board for powering up, you must connect the three mounting holes that are shiny to the common ground.
Also you will need to make 3 jumpers to extend the bridge rectifier wires.

[Tabmo]

Thanks Jazz P Bass!

[Jazz P Bass]

Oh, if you do remove the board, mark down were the wires go.
You do not want to reconnect it wrong.
The white wire that goes to the middle of the main board will have to be unsoldered to remove the board.
(This is the wire that will get the 1K/ 5W resistor)
Resolder it when testing (or the led's will not light)
And don't forget to remove the fan header.
The screws are Torqx by the way.

[Tabmo]

Jazz P Bass, Just to let you know it may be a few days before I get to what you suggested. Just letting you know. Thanks for the advice.

[Tabmo]

I had a chance to a take a deeper look at the CE1000. The voltages all appeared to be normal. I measured the +/- 98VCC and the +/- 15 VDC. Both appeared to be normal. What tolerance should I be looking for on the voltages. The + 15 was just under 15 and the -15 was just above. Also Should I look at the voltage divider voltages that right above the +/- 15 VDC circuit on the schematic? Did I miss any other voltages that I should check? Thanks.. -Tabmo

[Jazz P Bass]

So the DC voltages check.
Flip your volt meter to read Volts ac & test them again.
You will be looking for any voltage rails that have any Vac ripple on them.
The main rails expect a little.
What the + has, the - should have.
The + & - 15 Vdc rails should have zero ripple.
What you are doing is testing the supply capacitors ability to filter the rectified voltages.

Oh, do the blinking led's turn off at power up.? (they should)
And does the 'Protect LED' go out (it should)

[Tabmo]

Jazz P Bass. Thanks for the response. I was thinking that maybe one the caps was not acting like a cap. I was also thinking I was going to have to find an o-scope to look at them. I did not think of using my meter. Good idea.. I believe the LED's are acting normal. Thanks.

[Tabmo]

I measured ~ 26 VAC on C1. What do you think about that?