Hi ZM, I have 18.22 mA and 18.24 mA on the board with the mosfets removed.
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that's good
now put one pair of (checked!) mosfets back (one in positive rail , one in negative rail ) and test
be sure that small bjts are good - put new ones if you can't be sure
now put one pair of (checked!) mosfets back (one in positive rail , one in negative rail ) and test
be sure that small bjts are good - put new ones if you can't be sure
Those measurements confirm that 0.02mA are exiting the circuit by another route.
That other route is probably the Power Ground to PSU Zero Volts.
Whereas post99 (left pic) shows 0.28mA exiting by another route. That big ground current probably indicates a fault.
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no,at least as I understood - in post #99 , he put Ammeter in parallel to existing PSU rails , which is obviously wrong way of current measurement
i have connected a pair of mosfets (Q5 and Q7 but in Peter Daniel's board, it is Q8) and the ampere reading is attached. The bjts are good as they are new ones.
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I can't see any difference between the two except the grounding which is different as I have changed this grounding according to Andrew's comment. i did both the amp at the same time together but somehow this channel gives a problem.
well , if mosfets are not having mixed pin wires , and if they're good ...... I can't see anything wrong
though - I'm not having capture of top and bottom copper of PD boards , so I can't say which mosfet position(s) are alive , meaning - of which mosfet position is source resistor monitored in Aleph CCS
if you're sure that all 4 mosfets are well and alive - connect them all
connect that pcb exactly in same manner as functional pcb , for now
though - I'm not having capture of top and bottom copper of PD boards , so I can't say which mosfet position(s) are alive , meaning - of which mosfet position is source resistor monitored in Aleph CCS
if you're sure that all 4 mosfets are well and alive - connect them all
connect that pcb exactly in same manner as functional pcb , for now
sorry - we are running in circles .......
- according to measurements in #106 - input LTP is functional ;
- recheck all resistor values in Aleph CCS area ( positive side of output stage)
-in fact - recheck all resistors (easier to say that , than to list them by function )
- while doing that , re-check all soldering joints
- if you're sure that mosfets are OK (consult mosfet testing article from FW site, how to properly test them ) , connect them all
- connect all wires in exactly same fashion as on functional channel
- fire it up ; check output offset and Iq ; best place to check Iq is measuring voltage across one of source resistors in negative output stage side (those connected to negative PSU rail)
- according to measurements in #106 - input LTP is functional ;
- recheck all resistor values in Aleph CCS area ( positive side of output stage)
-in fact - recheck all resistors (easier to say that , than to list them by function )
- while doing that , re-check all soldering joints
- if you're sure that mosfets are OK (consult mosfet testing article from FW site, how to properly test them ) , connect them all
- connect all wires in exactly same fashion as on functional channel
- fire it up ; check output offset and Iq ; best place to check Iq is measuring voltage across one of source resistors in negative output stage side (those connected to negative PSU rail)
Thanks ZM, I'll remove the board and check everything including PSU. I thought the positive rail is giving the problem.
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that difference of over 6mA must be exiting via another route, probably to the PSU Zero Volts.
Measure it and confirm you know where the current is going.
that measurement is completely illogical , so best to ignore ;
what counts , so far , is what's measured in #106
what counts , so far , is what's measured in #106
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