| Electronics > Projects, Designs, and Technical Stuff |
| Trasistor Cruve tracer + Hameg 1004-3 XY weirdness |
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| duak:
I would check the following: One of the solder joints of the output connector may be bad. Does the oscilloscope have a bandwidth limit control that reduces the bandwidth of the input channels? I couldn't see one on the sales sheet from Hameg. If there is one, does it make a difference when activated? The current sense signal (CH2) will be of small amplitude. I suggest getting a proper shielded cable with the correct connectors. A 10:1 probe will definitely add noise. There are some design features in the schematic from the other link that I don't understand. However, I don't want to comment until the above things have been tried. |
| TERRA Operative:
--- Quote from: duak on October 15, 2019, 07:15:41 pm ---The current sense signal (CH2) will be of small amplitude. I suggest getting a proper shielded cable with the correct connectors. A 10:1 probe will definitely add noise. --- End quote --- This could be a thing. For my unit, I have shielded cables from the X and Y outputs on the PCB to the front panel BNC jacks, then standard BNC cables directly to the scope inputs, so it's shielded and 1:1 all the way on both channels. |
| AngraMelo:
--- Quote from: duak on October 15, 2019, 07:15:41 pm ---I would check the following: One of the solder joints of the output connector may be bad. Does the oscilloscope have a bandwidth limit control that reduces the bandwidth of the input channels? I couldn't see one on the sales sheet from Hameg. If there is one, does it make a difference when activated? The current sense signal (CH2) will be of small amplitude. I suggest getting a proper shielded cable with the correct connectors. A 10:1 probe will definitely add noise. There are some design features in the schematic from the other link that I don't understand. However, I don't want to comment until the above things have been tried. --- End quote --- Until now, all my tests were done either with a BNC>banana cable or the scope probes that are all 10:1. Im just finishing the enclosure (actually it is finished, it's the transformer that is taking some time to arrive) and during the assembly process I made sure to use coax from the board to the bnc connectors and Im making provisions to make a very small BNC>BNC cable. The Hameg has no bandwidth limit but that is an interesting thought. Maybe the 2 Channels dont have the same bandwidth? so when I invert inputs (YX instead of XY) I get a clear picture? Or somehow the XY mode limits the bandwidth of one channel but not the other? What do you guys suggest about the transistor connections? Should I run a small wire with a croc tip to hook the transistors up? would that be horrible? Also, just ordered some more beads for the cables, Im going to load those suckers up with ferrite. |
| AngraMelo:
--- Quote from: TERRA Operative on October 15, 2019, 10:38:35 pm --- --- Quote from: duak on October 15, 2019, 07:15:41 pm ---The current sense signal (CH2) will be of small amplitude. I suggest getting a proper shielded cable with the correct connectors. A 10:1 probe will definitely add noise. --- End quote --- This could be a thing. For my unit, I have shielded cables from the X and Y outputs on the PCB to the front panel BNC jacks, then standard BNC cables directly to the scope inputs, so it's shielded and 1:1 all the way on both channels. --- End quote --- My order will probably be here the beginning of next week. I order some BNC connectors to make a very small cable. Also ordered some more ferrite beads for the cables. |
| TERRA Operative:
I have 10cm leads from the PCB to binding posts on the front panel, then I use 10cm banana to test hook leads to attach the transistor etc. As long as I keep the test leads spaced apart, I get no issues at all. |
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