Hi There
I just did a recap job on the Amp a couple of days back. I put it back together last night.
The Amp is going into protect when I turn up either of the volumes. Seperately. The fans speed up aswell.
I'm only turning them up one or two notches.
They come out of protect when I turn them back down. The fans slow down too.
I'll try again tonight and see exactly what its doing. Lights etc.
I'm waiting on some BNC male plug to Banana plugs so I can use my scope leads with my multimeter.
A lot safer for testing. I can use the 10x aswell.
If anyone has the proper CA4 Schematic it might be of help. Ive got most of the other ones.
Cheers
BTW. The Amp was known to be going into protect before the recap. I just didn't test it beforehand.
I was under the impression it was in Protect full stop.
I just did a recap job on the Amp a couple of days back. I put it back together last night.
The Amp is going into protect when I turn up either of the volumes. Seperately. The fans speed up aswell.
I'm only turning them up one or two notches.
They come out of protect when I turn them back down. The fans slow down too.
I'll try again tonight and see exactly what its doing. Lights etc.
I'm waiting on some BNC male plug to Banana plugs so I can use my scope leads with my multimeter.
A lot safer for testing. I can use the 10x aswell.
If anyone has the proper CA4 Schematic it might be of help. Ive got most of the other ones.
Cheers
BTW. The Amp was known to be going into protect before the recap. I just didn't test it beforehand.
I was under the impression it was in Protect full stop.
Last edited:
I thought there might be one for the CA4 by itself. I think the CA2 might be closer. The PS and preamp are on the same board.
I've got the same as that but they don't seem to show the CA4 unless I'm missing it.
I'm going to try to do a video the Amp playing up.
I tried the Amp again earlier and it's popping through the speaker , it's looping ,the popping and going into protect over and over.
Let me go film it....
Cheers
I've got the same as that but they don't seem to show the CA4 unless I'm missing it.
I'm going to try to do a video the Amp playing up.
I tried the Amp again earlier and it's popping through the speaker , it's looping ,the popping and going into protect over and over.
Let me go film it....
Cheers
I measured the pins on the output power transistors and there's under 1 volt on all pins ,at idle with the volumes down.
With no load connected to the PA, is behavior the same as volume is advanced?
What is output voltage with volume at minimum? How does voltage change as volume is increased? Is there any DC across the volume control element with control at minimum?
Do any of your schematics have better clarity than my attachment? Readability is marginal….
What is output voltage with volume at minimum? How does voltage change as volume is increased? Is there any DC across the volume control element with control at minimum?
Do any of your schematics have better clarity than my attachment? Readability is marginal….
Hi
There's a few Service Manuals out there. I think I've got them all. Put Crest CA.. into web search and you'll get different ones. Not the CA4 though. They mixed them all up. There's different transistors in the CA4. Different Opamps. The Preamp part. None of the numbers matched up.
Let me get back to you on the tests.
There's a few Service Manuals out there. I think I've got them all. Put Crest CA.. into web search and you'll get different ones. Not the CA4 though. They mixed them all up. There's different transistors in the CA4. Different Opamps. The Preamp part. None of the numbers matched up.
Let me get back to you on the tests.
Your supplied video shows a serious mis-wiring error or possible 'Bridge Mode' error: i.e. when channel A is adjusted, channel B goes into 'PROTECT'. That can't happen (even though the video shows it happening).
You need to isolate/fix that issue first!
That is probably the only issue with the amp.
N.B. Fault-finding is impossible in 'Bridge Mode'.
Good Luck!
You need to isolate/fix that issue first!
That is probably the only issue with the amp.
N.B. Fault-finding is impossible in 'Bridge Mode'.
Good Luck!
Hi
I sorted the wiring fault. It was just the plugs on the board were the wrong way round. Send and return from the Volumes.
I sorted the wiring fault. It was just the plugs on the board were the wrong way round. Send and return from the Volumes.
I pulled the rectifier and tested it ,it checked out ,the same as a new one. So I put it back in.
New Video....
https://vimeo.com/1079049030?share=copy
New Video....
https://vimeo.com/1079049030?share=copy
BSST..
With no load connected to the PA, is behavior the same as volume is advanced?
Yes. Also ,Turning the Volume down registers on the signal LED. It can go into protect that way aswell. If/When turned down quickly.Not everytime. Seems to be intermittent in the way it behaves to go into protect.
What is output voltage with volume at minimum?
+86V -86V
How does voltage change as volume is increased?
Not tested Yet
Is there any DC across the volume control element with control at minimum?
Whats the best way of testing that.?
With no load connected to the PA, is behavior the same as volume is advanced?
Yes. Also ,Turning the Volume down registers on the signal LED. It can go into protect that way aswell. If/When turned down quickly.Not everytime. Seems to be intermittent in the way it behaves to go into protect.
What is output voltage with volume at minimum?
+86V -86V
How does voltage change as volume is increased?
Not tested Yet
Is there any DC across the volume control element with control at minimum?
Whats the best way of testing that.?
I did some testing and I've written the results down. I'll post them soon.
I tested all the Power transistor legs from what I can access and written the voltages down.
I tested all the Power transistor legs from what I can access and written the voltages down.
Here's the results of testing the Transistors going from the Left ,Front to Back ,then from Right ,Back to front ,as you see the amp above in Post #2.
You seemed to be having power supply issues earlier, posts 12 and 13. Are all supply voltages nominal now?
Are both channels now independent, stereo channels, i.e. no bridged configuration?
Be sure to test with no load applied until the amp is behaving.
I surmise you may be reporting supply rail(s) voltages? This is good to know, but my intent was the learn about the amps' output voltage. That is, there any DC present, measured before any speaker protection relays? Does it vary with volume control position? Hence the follow-up question about DC present on the volume control element. Ideally, there will bo no DC on any of the volume control terminals.
The voltages posted in #16 may be useful, but I don't have any way of knowing where they appear in the schematic. Can you locate the most appropriate of the schematics in the service manual and advise how the transistors you've labelled 1 though 4 in post 16 correspond to the SM schematic.
I notice that all voltages in the left channel seem to be negative, but those in the right channel are positive. Is this correct and can you offer any insights?
Are both channels now independent, stereo channels, i.e. no bridged configuration?
Be sure to test with no load applied until the amp is behaving.
I surmise you may be reporting supply rail(s) voltages? This is good to know, but my intent was the learn about the amps' output voltage. That is, there any DC present, measured before any speaker protection relays? Does it vary with volume control position? Hence the follow-up question about DC present on the volume control element. Ideally, there will bo no DC on any of the volume control terminals.
The voltages posted in #16 may be useful, but I don't have any way of knowing where they appear in the schematic. Can you locate the most appropriate of the schematics in the service manual and advise how the transistors you've labelled 1 though 4 in post 16 correspond to the SM schematic.
I notice that all voltages in the left channel seem to be negative, but those in the right channel are positive. Is this correct and can you offer any insights?
BSST..
The Voltages are OK. I was using the Heatsink as a GND. Ha.
The Amp wasn't bridged ,the plugs for the Send & Return were in the wrong way round L to R ,R to L.
Yea. I understand you man. The Spkr Relays are kicking in. We are trying to find out why. The Fans are reacting aswell. I could measure the send and return wires. Prongs on my leads are a little too big to go in the top of the plugs. I could put a bit of a clip and the prong in a terminal block. Let me do that and test the wires for DC.
Yea ,I'm just trying to find out other things at the same time.
I'll get the schematic numbers from the board.
Part Numbers for the tests I show in post #16
L 1. 2SA1302 PNP
2. 2SA1302
3. 2SC3281 NPN
4. 2SC3281
R 1. 2SC3281 NPN
2. 2SC3281
3. 2SA1302 PNP
4. 2SA1302
Also both drivers on each side (2) have high voltages on the Collectors only. 45 85 ,45 85. Small voltages on the Base and Emitters.
The Voltages are OK. I was using the Heatsink as a GND. Ha.
The Amp wasn't bridged ,the plugs for the Send & Return were in the wrong way round L to R ,R to L.
Yea. I understand you man. The Spkr Relays are kicking in. We are trying to find out why. The Fans are reacting aswell. I could measure the send and return wires. Prongs on my leads are a little too big to go in the top of the plugs. I could put a bit of a clip and the prong in a terminal block. Let me do that and test the wires for DC.
Yea ,I'm just trying to find out other things at the same time.
I'll get the schematic numbers from the board.
Part Numbers for the tests I show in post #16
L 1. 2SA1302 PNP
2. 2SA1302
3. 2SC3281 NPN
4. 2SC3281
R 1. 2SC3281 NPN
2. 2SC3281
3. 2SA1302 PNP
4. 2SA1302
Also both drivers on each side (2) have high voltages on the Collectors only. 45 85 ,45 85. Small voltages on the Base and Emitters.
BSST....
Theres +10v on both sides. When you turn the volumes up the voltage goes up on the other wire. Gets to 1v or so and Relay protection kicks in.
Theres +10v on both sides. When you turn the volumes up the voltage goes up on the other wire. Gets to 1v or so and Relay protection kicks in.