Also, R204 (1K) is cracked but reads ok
Also, R204 (1K) is cracked but reads ok.
I shoulda checked the rails before installing outputs, I was in a hurry. (Worst time to do work). But with the neg 40 volts still present on pos speaker terminal, I suspect that the problems is elsewhere, right?
The rails come up ok, but drop and swing back up repeatedly. I disconnected the (-In) to the driver card earlier (to verify whether the neg voltage was present in preamp; it wasn't, but the -IN on the card still had the neg voltage.), didn't make a difference in symptoms.
PS.. before readings in above posts I replaced R173..
Also, R204 (1K) is cracked but reads ok.
I shoulda checked the rails before installing outputs, I was in a hurry. (Worst time to do work). But with the neg 40 volts still present on pos speaker terminal, I suspect that the problems is elsewhere, right?
The rails come up ok, but drop and swing back up repeatedly. I disconnected the (-In) to the driver card earlier (to verify whether the neg voltage was present in preamp; it wasn't, but the -IN on the card still had the neg voltage.), didn't make a difference in symptoms.
PS.. before readings in above posts I replaced R173..
Anyone have a schematic for a Planet Audio vx2200 or a Kole QX1-3000D?
So, anybody got a schematic on this one?
Is it something dumb I'm missing?
So is it safe for me to disconnect the output gates temporarily to make sure that the neg voltage isnt coming from an output - that it to narrow it to the driver board?
So, anybody got a schematic on this one?
Is it something dumb I'm missing?
So is it safe for me to disconnect the output gates temporarily to make sure that the neg voltage isnt coming from an output - that it to narrow it to the driver board?
Hey folks, on the driver cards for these amps there are twelve connections - the functions of some are obvious, but some are not - in the below list, what do 6 and 9 do?
1 IN+ (balanced input pos)
2 IN- (balanced input neg)
3 SG (signal ground)
4 +15 (pos op-amp supply voltage)
5 -15 (neg op-amp supply voltage)
6 SW ????
7 Vpp (pos rail?)
8 DRV (drives pos bank of outputs)
9 Out ????
10 PG (power ground?)
11 DRV (drives neg bank of outputs)
12 Vnn (neg rail?)
The silk screen marks 6 as SW and 9 as OUT, so what are there functions?
1 IN+ (balanced input pos)
2 IN- (balanced input neg)
3 SG (signal ground)
4 +15 (pos op-amp supply voltage)
5 -15 (neg op-amp supply voltage)
6 SW ????
7 Vpp (pos rail?)
8 DRV (drives pos bank of outputs)
9 Out ????
10 PG (power ground?)
11 DRV (drives neg bank of outputs)
12 Vnn (neg rail?)
The silk screen marks 6 as SW and 9 as OUT, so what are there functions?
SW is the control terminal for the class D circuit. When near the positive rail, the driver board is disabled. When the voltage on the SW pin is near ground, the driver board is enables.
The OUT pin connects to the source of the high-side FETs and the drain of the low-side FETs. This is where you will see rail-rail oscillation on the output transistors.
The OUT pin connects to the source of the high-side FETs and the drain of the low-side FETs. This is where you will see rail-rail oscillation on the output transistors.
Ah, ok, thanks Perry. So is the OUT used for feedback or sensing purposes to prevent oscillation?
Had to keep the work queue flowing; came back to this amp this morning.
Pulled outputs.
Checked rails.
Pos rail approx 68 volts.
Neg rail approx -200 and offscale peaks.
LOL..
I think this might be related...
Had to keep the work queue flowing; came back to this amp this morning.
Pulled outputs.
Checked rails.
Pos rail approx 68 volts.
Neg rail approx -200 and offscale peaks.
LOL..
I think this might be related...
The out terminal is used as the reference for the drivers. The high-side drivers basically ride on that point and drive the high-side outputs on and off from that point.
Rail voltage of approximately ±70v would be about right. It's difficult to get negative 200 and only positive 68. They should be about even since they're taken from the same windings. Measure the voltage again on the center legs of the rectifiers. Do you read the same positive and negative voltages there?
Rail voltage of approximately ±70v would be about right. It's difficult to get negative 200 and only positive 68. They should be about even since they're taken from the same windings. Measure the voltage again on the center legs of the rectifiers. Do you read the same positive and negative voltages there?
Ok, regarding the OUT terminal, excellent explanation - I was asking myself what should the gate voltage be, and then considered the example of an N type fet with pos rail on the drain and load at the source - if gate-source has to be ~ 2volts to turn it on, then as output changes the voltage at the source change, so you're trying to hit a moving target... And you don't need the reference for the low-side because with load at drain and neg rail at source you have a static target, right?
On this board there are 4 rectifiers and two transformers - I checked all 4 from each transformer's center tap. That was the result I got.
The KA3525 chip is the same as the SG3525 right?
I'll measure the voltages on the 3525 when I get a chance. R173 smoked again, then R190 after I removed all of the outputs.
On this board there are 4 rectifiers and two transformers - I checked all 4 from each transformer's center tap. That was the result I got.
The KA3525 chip is the same as the SG3525 right?
I'll measure the voltages on the 3525 when I get a chance. R173 smoked again, then R190 after I removed all of the outputs.
The KA and SG ICs are the same.
Right. It's charging the filter caps.
If you shine a bright light from the back of the driver board and look at it from the other side (around Q124 and Q125), do you see any dark shadows that are not related to anything on either side of the board? Clean both sides of the board with acetone before doing this if the board is dirty.
Right. It's charging the filter caps.
If you shine a bright light from the back of the driver board and look at it from the other side (around Q124 and Q125), do you see any dark shadows that are not related to anything on either side of the board? Clean both sides of the board with acetone before doing this if the board is dirty.
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