I just tried it and the bias adjusts no problem. With a 3k3 resistor and the bias dialed all the way down, (clockwise) I see 1V at PD. With the bias raised to 13mV across two a pair of emitter resistors I see 1.3V at PD. I didn't try hooking up an IPS but I'm pretty sure it will play.
I have 150R in R113 to cool down the drivers a little. All other values are per schematic.
Hope this helps
I have 150R in R113 to cool down the drivers a little. All other values are per schematic.
Hope this helps
Can you take a couple base voltage readings on the drivers? I had it powered up for 15 minutes on the bench. The drivers climbed to 90F. I don't seem to really have any current flow at all.
No joy with a Symasui input either. I can only maintain 8 volts on the positive rail with a 1.5k resistor for r11. It acts as if I have something shorted around the ND/PD connections but all looks good and no heat anywhere.
Base for Q107 is 1.52V and base for Q108 is 0.78V. Offset at the output is 308mV. This is with 13mV across a pair of output emitters. This is with +-30V rails and 3k3 jumpers.
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Thanks Terry. Mine are in the same ballpark but 1.5 mV across the emitter resistors. My circuit seems to be operating then. Just not able to supply enough current. I'm stuffing a 2 output board to compare now.
Post a decent picture of the OPS so we can have a quick look and maybe catch something amiss.
I'm using a toroid from an old Arcam amp. I think it's around 400 VA but it really drops off from open circuit voltage. Down to 32V with any kind of load. It's the 12 volt rail in the input section that drops off to 8 volts.
I see. I have been talking about the OPS. That front end is set by the zener. It shouldn't drop until the rail is below 12V. Something is wrong.
I think the Symasui is actually working correctly. I think it's just dragging itself down trying to feed the output board. It seems to operate fine standalone. I was stuffing a 2 pair board to test with until I realized I didn't have TO220 drivers. I'll be back at the office tomorrow. I'll stuff another 5 pair board and test. I'll post some pictures then too.
The IPS should work with the output shorted to the NFB. How can the OPS put any more load on it than a direct short? I would double check to see that you have the correct transistors in each location and that they are oriented correctly. I still think there is something wrong. The zeners set the front end of the IPS to 12V Unless the rail drops below that it should maintain 12V. It feed the bases of Q3, Q4, Q5 and the servo. Those are all P channel A992. My guess is one of those is wrong.
EDIT; It is also vital that the NFB is connected.
EDIT; It is also vital that the NFB is connected.
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The voltage doesn't drop off when the output is shorted to nfb. Only drops when connected to output board. I've only tested it idle. No input yet.
OK, sorry I didn't try this earlier. I just hooked my Symasui IPS to the OPS and fed it +-30V. It won't light D5 but it does light D6. Voltage at -ND is 305mv and +PD is 1.025. Keep in mind that I have 4k7 in R11 so I don't know what would happen if I put 1k5 in there. The Wolverine will play at 30V but maybe not the Symasui without some value changes. Someone more educated will have to help with that. I suppose I could temporarily parallel a resistor to R11 to see if that will help.
Yes I did. I connected them to the G2 point on the input board too. I assume they are supposed to connect to ground separately from the star ground?
Actually the star on the IPS doesn't get a connection outside its connection the the connector at the edge of the board, it forms a star-on-star arrangement. It shouldn't cause ant functional issue if a wire is connected there.
Does the +V and -V off the OPS stay within a couple of volts of the raw supply voltage? That is to ask are the capacitance multipliers working alright?
Does the +V and -V off the OPS stay within a couple of volts of the raw supply voltage? That is to ask are the capacitance multipliers working alright?