Is a schematic for amp9 available?
In an automobile, you have a significant differential between the ground at the head unit and the ground in the rear of the vehicle where the amp will be grounded. If you don't isolate the secondary side of the power supply from the primary, you'll have ground loop noise. If you break the ground connection in the amp (buss bar?), the secondary should float so you won't have two grounds for the audio circuit. The RCA shield ground will be the ground for the audio. The chassis ground connection in the rear of the vehicle will be the ground for the primary side of the transformer.
In an automobile, you have a significant differential between the ground at the head unit and the ground in the rear of the vehicle where the amp will be grounded. If you don't isolate the secondary side of the power supply from the primary, you'll have ground loop noise. If you break the ground connection in the amp (buss bar?), the secondary should float so you won't have two grounds for the audio circuit. The RCA shield ground will be the ground for the audio. The chassis ground connection in the rear of the vehicle will be the ground for the primary side of the transformer.
Ok, I'll be sure to keep the secondary ground separated and I'll also isolate my RCA plugs so my vehicles ground won't be connected to RCA ground. Now I'd better get toroid hunting....Perry Babin said:
Just a quick question, does the toroid rating have to exceed my amps power? I don't think I'll ever need more than 240W (24v @ 10A), so should I get a 250VA toroid? Or will I get away with less as it's high frequency (33kHz).
Service Manuals
Dear All
You can find voarious service manuals for Kenwood Car Audio on this web site, there is no requiremen of registration just download.
http://archive.espec.ws/section391/
Regards,
Risto
Dear All
You can find voarious service manuals for Kenwood Car Audio on this web site, there is no requiremen of registration just download.
http://archive.espec.ws/section391/
Regards,
Risto
I managed to find another more suitable amp to butcher 12v SPMS to power my amp9 in the end, so I didn't have to butcher this one after all.
Anyway, I thought I'd have a go at fixing this amp anyway, as more of a learning experience than anything. If I can get it working, it may come in useful as a backup amp...
I didn't have much to test it with apart from a 12v SLA and a computer fan, but with a few croc clips I managed to find out that it works...
It passes current from the outside two legs to the inside leg. and I tried putting reverse current on it, and it blocks the reverse current ok.
Would it be worth pulling D206 and testing it also?
Anyway, I thought I'd have a go at fixing this amp anyway, as more of a learning experience than anything.
If I can get it working, it may come in useful as a backup amp...Ok, I managed to get D207 out without too much drama.Perry Babin said:
I didn't have much to test it with apart from a 12v SLA and a computer fan, but with a few croc clips I managed to find out that it works...
It passes current from the outside two legs to the inside leg. and I tried putting reverse current on it, and it blocks the reverse current ok.
Would it be worth pulling D206 and testing it also?
If the square wave on the outer legs was swinging plus and minus 40v but the center leg had only -21v (using your scope to measure the voltage), the rectifier has to be defective. There should be no more than ~1v difference between the outer legs and the center leg.
I'm assuming that the -21v output was clean (no excessive ripple).
I'm assuming that the -21v output was clean (no excessive ripple).
I've just re soldered the recifier, and it's doing exactly the same as before... -21v.Perry Babin said:
Now, I double checked everything as I've got the PCB out of the chassis... I must admit I'm still getting to grips with my scope multimeter... I've only just found on VDC mode you get a more zoomed in view of the square wave going to the outside legs of the recifiers, and I've found that the wave looks offset vertically, the is far more of the wave above the x axis compared to below, around twice as much above compared to below... which explains why i was getting over +40V and only -21v.
I wish I noticed this before.
I was always using VAC mode where it's more zoomed out vertically for some reason, so I didn't spot the offset before... So it looks like the rectifier isn't causing the problem after all. I can grab a photo of the square wave if that's of any use at all?I'm guessing it's got to be one of the components in the oscillator part of the circuit, but I'm not really sure what part does what tbh. Where would be the best place to start?
I think there may be a bad connection somewhere. The windings that drive the positive rectifier also drive the negative rectifier so the voltage should swing to the same level both above and below ground.
Try resoldering all of the connections on the power transformer and all connections between the transformer and the rectifiers (jumper wires, etc).
Try resoldering all of the connections on the power transformer and all connections between the transformer and the rectifiers (jumper wires, etc).
Another screw up by me...
I was measuring everything with respect to the battery ground. I totally forgot that the trafo has a different ground on the secondaries...
Anyway, I remeasured the outputs of the rectifiers with the ground on the secondary this time, and I'm getting a +33v and -33v... I assume this is ok, even tho the schematic states +48v and -48v (I think). The secondary ground is 12v away from the battery ground if that makes any sense....
So by the looks of it the SPMS part of the circuit is fine. I guess some other part of the circuit must be the problem. I'll see if I can check the output stage somehow... bit I've got a pizza that's about to burn to I'm gonna have some food first then come back to it in a bit....
I was measuring everything with respect to the battery ground. I totally forgot that the trafo has a different ground on the secondaries...
Anyway, I remeasured the outputs of the rectifiers with the ground on the secondary this time, and I'm getting a +33v and -33v... I assume this is ok, even tho the schematic states +48v and -48v (I think). The secondary ground is 12v away from the battery ground if that makes any sense....
So by the looks of it the SPMS part of the circuit is fine.
I guess some other part of the circuit must be the problem. I'll see if I can check the output stage somehow... bit I've got a pizza that's about to burn to I'm gonna have some food first then come back to it in a bit.... The schematic has ±40v as the rail voltage with 14.4v in.
According to the schematic, the secondary is directly connected to the chassis ground. If you don't have continuity (~0 ohms) between the chassis ground and the secondary ground, there is a broken connection. W70 (very near the point where the B+ terminal goes into the board) and the large metal buss bar are part of the circuit that connects the chassis ground and the secondary ground.
According to the schematic, the secondary is directly connected to the chassis ground. If you don't have continuity (~0 ohms) between the chassis ground and the secondary ground, there is a broken connection. W70 (very near the point where the B+ terminal goes into the board) and the large metal buss bar are part of the circuit that connects the chassis ground and the secondary ground.
I checked it with a multimeter, and the resistance readings were all over the place... Certainly more than 1Kohm.Perry Babin said:
After a little searching, it looks like W70 has a bad solder joint:
An externally hosted image should be here but it was not working when we last tested it.
I'll fix that, then put it back in the chassis and give it a whirl.
Ok, I've put it all back together, and it's doing the same thing, no output on the speakers...
Now, I can hear the relay (K1) clicking almost instantly after I connect the remote wire, and after seeing it on the schematic, it looks like it's some sort of speaker protection system...
It does this with or without a speaker connected, so I'm guessing something somewhere is making the relay switch when it shouldn't..
Now, I can hear the relay (K1) clicking almost instantly after I connect the remote wire, and after seeing it on the schematic, it looks like it's some sort of speaker protection system...
It does this with or without a speaker connected, so I'm guessing something somewhere is making the relay switch when it shouldn't..
Since you have the schematic diagram and a scope, you can trace the signal through the amp.
Before you begin, confirm that you have both + and - 15v (approximately) on the op-amps. {pin 4 of the op-amp is -15. Pin 8 is +15. If those are present, begin tracing the signal.
Begin at the RCA jacks and follow the signal through the op-amps. The signal line is a bold black line. Where does the signal stop?
Before you begin, confirm that you have both + and - 15v (approximately) on the op-amps. {pin 4 of the op-amp is -15. Pin 8 is +15. If those are present, begin tracing the signal.
Begin at the RCA jacks and follow the signal through the op-amps. The signal line is a bold black line. Where does the signal stop?
My signal is around 150mV (rms), just a 70Hz sine wave. The signal actually makes it all the way to the speaker terminal, but is now 200mV when the amp is on, and 150mV when the remote wire is disconnected (but still 30V or so in the rail caps). All these readings were taken with my black probe going to signal ground.
I tried measuring the voltage across the + and - speaker terminals, and there is nothing. 0v, not even the 150mV from the signal...
Could the "input muting" part of the amp just be muting all the time?
I tried measuring the voltage across the + and - speaker terminals, and there is nothing. 0v, not even the 150mV from the signal...
Could the "input muting" part of the amp just be muting all the time?
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