I only use the light bulb for initial turn on to see if any mayor error happen all was good I mention that I removed after so I can then do bias adj I was playing music for a while all normal no distortion at all good music definition but why when I check bias it doesn't show any number? is really weird I will try tomorrow again to see if I can adjusted correctly I'm gonna fallow your advice to see what is going on this is the first time that I have this weird behavior on bias adjustment
BTW - does Volverine use a servo? I just don't remember.
I was thinking about possible reasons for the bias going to zero. Here is one of the possible options - if you measure the voltage over a single emitter resistor and DC offset goes away from zero, you end up with DC current flowing through the speaker and one side of the OPS, and no current and zero bias on the other side.
I was thinking about possible reasons for the bias going to zero. Here is one of the possible options - if you measure the voltage over a single emitter resistor and DC offset goes away from zero, you end up with DC current flowing through the speaker and one side of the OPS, and no current and zero bias on the other side.
The Wolverine I have does not have a servo but I can try with the Greenamp V1.2 the last IPS that OS made the schematic I'll if I have DC on the output but is weird because I was playing music for a while and I didn't see any signs of distortion the audio was great
VAS current? oh ok maybe I will check with my Greenamp swith the board to see if that helps
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Here are the testing tips that I followed (posted sometime back by one of the veterans).
Test the input separate from the output first. Put a 1k resistor from PD to the feedback connector and another 1k resistor from ND to the feedback connector. You should have around 11 volts between PD and ND and your DC offset measured at the feedback connector should be only a few mV. You can put a signal to input and read it at the feedback connector like this. Get your input board operating properly first before connecting to the output board. You should be getting 7.7mA across R22 if everything is working right too.
The output board can be tested by putting a 15k resistor from PD to V+ and another 15k resistor from ND to V-. Install 1 output pair and you should be able to set up your bias. I'm sure OS's feedback resistor scheme should work but I'm not familiar with it.
L1 - 1.5uH - 18 turns of 1.25mm wire, 12mm Diameter
You should use a bulb limiter when you are testing. It's a lot easier to see a 50 watt bulb out of the corner of your eye than to watch an ammeter on a limited supply. As you turn up your bias you should be able to see the bulb starting to glow.
After both halves are operating properly on their own, put them together and start testing again.
I fire mine up in sections. Fire up the outputs first with a bulb limiter in series with the mains and 15k resistors on the inputs. One from V+ to VD+ and one from V- to ND-. It's safest to do this with 1 output pair installed. The bias pot should be wound to the highest resistance setting. If the output board powers up without the bulb staying lit, try winding up the bias and see if you have control of the adjustment. Also measure DC on the speaker output. There shouldn't be much if everything is operating correctly. Bias should be 65 - 75mA, or around 30mV across a pair of emitter resistors. The bulb will light up as you increase the setting. If all is good turn down the bias and install all the output pairs, and check again. If all is good wind down the bias adjustment.
Fire up the input stages with their outputs disconnected from the output board and 1k resistors jumpered from PD+ to the NFB connection and from ND- to the NFB connection. Measure the voltage drop across R12. Adjust R19 so this is 3.8mA (3.8V). do the same with R13 and R10. After that's set, measure the voltage between PD+ and ND-. You should read around 11V if everything is working right. Also measure the DC offset at the NFB connection. I do this with the servo pulled out first just to see how good the input is matched, then with the servo in place. With the servo installed, there shouldn't be more than around 25mV present. If everything is well matched, it will be drifting around 2 or 3 mV.
The above is for the Spooky IPS.
If the input seems to be good, connect it to the output board and fire it up with the bulb still in place. Check for DC offset on the output and wind your bias up again. If you seem to have control of the bias, play some sine waves through the amp just to make sure everything is stable. The bulb will glow dimly as you slowly turn up the amplitude of the sine wave. If it goes from off to bright instantly, you probably have some oscillation. If all seems good, remove the bulb and start it up again. Set up your bias again and warm the amp up for a bit. You can just let it idle for a while, or cheat and hook up a load and play some sine waves. Keep checking the bias as it warms up. Also keep checking the temperature of the R137. If it's getting hot you likely have oscillation happening.
Once it's warmed up and if everything seems stable, it's time to listen to it and see what you think.
Test the input separate from the output first. Put a 1k resistor from PD to the feedback connector and another 1k resistor from ND to the feedback connector. You should have around 11 volts between PD and ND and your DC offset measured at the feedback connector should be only a few mV. You can put a signal to input and read it at the feedback connector like this. Get your input board operating properly first before connecting to the output board. You should be getting 7.7mA across R22 if everything is working right too.
The output board can be tested by putting a 15k resistor from PD to V+ and another 15k resistor from ND to V-. Install 1 output pair and you should be able to set up your bias. I'm sure OS's feedback resistor scheme should work but I'm not familiar with it.
L1 - 1.5uH - 18 turns of 1.25mm wire, 12mm Diameter
You should use a bulb limiter when you are testing. It's a lot easier to see a 50 watt bulb out of the corner of your eye than to watch an ammeter on a limited supply. As you turn up your bias you should be able to see the bulb starting to glow.
After both halves are operating properly on their own, put them together and start testing again.
I fire mine up in sections. Fire up the outputs first with a bulb limiter in series with the mains and 15k resistors on the inputs. One from V+ to VD+ and one from V- to ND-. It's safest to do this with 1 output pair installed. The bias pot should be wound to the highest resistance setting. If the output board powers up without the bulb staying lit, try winding up the bias and see if you have control of the adjustment. Also measure DC on the speaker output. There shouldn't be much if everything is operating correctly. Bias should be 65 - 75mA, or around 30mV across a pair of emitter resistors. The bulb will light up as you increase the setting. If all is good turn down the bias and install all the output pairs, and check again. If all is good wind down the bias adjustment.
Fire up the input stages with their outputs disconnected from the output board and 1k resistors jumpered from PD+ to the NFB connection and from ND- to the NFB connection. Measure the voltage drop across R12. Adjust R19 so this is 3.8mA (3.8V). do the same with R13 and R10. After that's set, measure the voltage between PD+ and ND-. You should read around 11V if everything is working right. Also measure the DC offset at the NFB connection. I do this with the servo pulled out first just to see how good the input is matched, then with the servo in place. With the servo installed, there shouldn't be more than around 25mV present. If everything is well matched, it will be drifting around 2 or 3 mV.
The above is for the Spooky IPS.
If the input seems to be good, connect it to the output board and fire it up with the bulb still in place. Check for DC offset on the output and wind your bias up again. If you seem to have control of the bias, play some sine waves through the amp just to make sure everything is stable. The bulb will glow dimly as you slowly turn up the amplitude of the sine wave. If it goes from off to bright instantly, you probably have some oscillation. If all seems good, remove the bulb and start it up again. Set up your bias again and warm the amp up for a bit. You can just let it idle for a while, or cheat and hook up a load and play some sine waves. Keep checking the bias as it warms up. Also keep checking the temperature of the R137. If it's getting hot you likely have oscillation happening.
Once it's warmed up and if everything seems stable, it's time to listen to it and see what you think.
Yes, from the write-up above;
The output board can be tested by putting a 15k resistor from PD to V+ and another 15k resistor from ND to V-. Install 1 output pair and you should be able to set up your bias.
The 15k resistors simulate the output of the IPS so you can adjust the bias. If this works them the problem is likely in the IPS.
oh man sadly I already installed all power transistors
you think is I install those 15k with all pairs installed and try again?oh yes with out the load got it, this is my first board picture look awful but I will clean better
ok I will wait for the replay if I can do this " The output board can be tested by putting a 15k resistor from PD to V+ and another 15k resistor from ND to V-. Install 1 output pair and you should be able to set up your bias."
with all pair installed
Attachments
You can test with all transistors in place. Potential drawback - if something goes terribly wrong, with 1 pair you lose fewer transistors than having all of them in place
Set the bias pot to the position of minimal bias, before you power on the thing.
I will minimal bias
last question with those 15k installed I can then adjust bias even I have all those 5 pairs?
I will minimal bias
Yes, but you measure just one pair (any of them).
Note - this is just for the purpose of testing. As soon as you remove 15K resistors and connect the OPS to IPS board, you need to set the bias pot to the minimum bias position again ard re-adjust the bias from scratch.
thank guys yes I made a light bulb dim tester a few days ago before first turn on got it, to be sure then IPS and re-adjusted
If I remember correctly, those drivers run pretty warm. That plate should be of good size.
oh yes that most be the problem! I run them without the small heat sink for the drivers and the tracking small bias transistor the other ones is correct is under the PCB with thermal grease and insulated Q104 so Q103a most be on heat sink with driver together oh ok