Hi Jason, i found out today that the ebay OPS BJT were dud ie Qnjw 0302 was NPN and hfe was 18, Qnjw 0281 was NPN ,hfe only measured 20 as well. So all this time the driver Qnjw 0320 was NPN all along. I took out all drivers and pre-drivers and measured again . Those mje340 and 350 all ok, my originals Qnjw were blown so had to be replaced. Lesson learnt from ebay fakes!!!. I have messaged them, interesting to hear their response. Anyway fired up again with all new drivers/predrivers/OPS-one pair only for now with bulb limiter. I was able to adjust current output through the 0.22R resistor. The current measured through 0.22RE was 50mA.The flash sink is hardly warm, good sign but the main problem i find is DC offset measured at 140mV. The bulb is only dim so i hope so far so good.
Quan
Quan
The offset could be a slight difference in the resistors used to simulate the IPS and 140mV is fine. Remember the testing phase for the OPS had no correction from feedback. Once an IPS in installed the feedback will drive the offset lower.
And semis off ebay... It costs more but I suggest using a reputable vendor known to buy direct from the manufacturer.
Bill of Materials, Schematic, etc. for each PCB
Is there a final Bill of Materials, Schematics, and other documentation for
each of the PCB's? Or point me to each thread and thread number for this information. Maybe I could help compile all the possible BOM's for each PCB's. Example PCB's are: (1) IPS (CFA-XH), IPS (Symasui), 2P OPS, 5P OPS, etc.
Take care.😕
Is there a final Bill of Materials, Schematics, and other documentation for
each of the PCB's? Or point me to each thread and thread number for this information. Maybe I could help compile all the possible BOM's for each PCB's. Example PCB's are: (1) IPS (CFA-XH), IPS (Symasui), 2P OPS, 5P OPS, etc.
Take care.😕
No one has yet done any 'official' BOMs to the best of my knowledge. I do keep intending to sit down with the Mouser site and put something down but somehow it hasn't happened yet. I should at least do up a spreadsheet for the versions I have re-spun.
The main SlewMaster thread has all the schematics in their various iterations and lots of banter about parts and implementation. I would like to see OS rejoin us sooner rather than later for his input if possible.
Hi Jason, what are your thoughts about 2SC3263/2SA1294 as OPS BJT?.I am thinking of using them for 2OPS.
Quan
Quan
They are a nice looking device in TO-3P (MT-100) package. These are LAPT devices (60MHz) with lower Cob than most. Should work quite well.
Hi Jason,
Are there directions somewhere for setting the pots on the Symasui IPS? I have searched and can't find it.
Thanks, Terry
Are there directions somewhere for setting the pots on the Symasui IPS? I have searched and can't find it.
Thanks, Terry
There is only one adjustment on the board. It directly controls the input CCS which then indirectly controls the VAS current. Use the PD-ND-NFB connection using resistors to measure the setting.
OS seems to have targeted the 4.5-5mA range for all of them so there are no issues swapping IPS onto the OPS (idea being you would likely not even have to rebias the OPS). I would target the 4.5mA mark +/-0.5mA for ideal compatability.
Hi Jason, i have test iPS/OPS. One chanel DC offset is 1mV but the other channel DC offset is 195mV. I am able to adjust bias through 0.22R and measure 16.5mV(about 75mA). I did match the input pair of IPS pretty closely. Where should i be looking at?. TIA.
Quan
Quan
Remind me which IPS we are talking about. Are you using the CFA-XH or the Symasui? Does the problem follow the IPS if you swap them?
Hi Jason, i am using CFA-XH atthe moment. The OPS boards seem to be ok as DC offset is good when i swapped the other board in. I suspect one of IPS is not functioning as expected.When i adjusted the bias current i find it is difficult to match the current flow through the vas resistors.
Quan
Hi Jason,
This has probably been asked but I can't find it. Is there a schematic specifically for the baby slew? I guess what I want to know is if there any other changes other than using the TO-220 drivers? are caps all the same value? Did you use cas/csb?
Thanks, Terry
This has probably been asked but I can't find it. Is there a schematic specifically for the baby slew? I guess what I want to know is if there any other changes other than using the TO-220 drivers? are caps all the same value? Did you use cas/csb?
Thanks, Terry
Terry,
Just one schematic, everything is the same except for the drivers and fewer output sections.
Just one schematic, everything is the same except for the drivers and fewer output sections.
Generally I just start off with the adjusters centred and the OPS bias set low, use the adjusters to get the offset as close to 0 as possible, set up the bias in the OPS and test it. The current range is limited on the IPS adjusters and it will be close to correct anyway. You may use each adjuster a smaller amount rather than one adjuster on its own.
Thanks Jason, so should i set the OPS bias lower say at 11mV ie 50mA across the 0.22 R first?. Currently i set IPS by measuring 2V across each 470R connecting across FB/ND/PD, OPS- connect 8K resistor across V/PD, -V/ND then adjust across 0.22R for 16.5mV.
Quan
Bring the OPS to 10mA or the minimum you can get if it doesn't go that low when connecting the IPS for the first time. On the CFA-XH, centre the adjusters as a preset. Use the adjusters to get minimal offset and then adjust the OPS bias. The actual VAS current has a limited range and will be in the ballpark with the adjusters centred. Try that and see how it goes.
The testing procedures for checking the sections individually is just for verification, when joined together they should be setup together.
The testing procedures for checking the sections individually is just for verification, when joined together they should be setup together.