North Hills CS-152 Current calibrator

[Vgkid]

Pigrew, how do you get such good images of the traces on the boards?

[pigrew]

Pigrew, how do you get such good images of the traces on the boards?

I photographed the board, and then traced lines (on the computer) over the actual traces, using Paint.net. It takes about fifteen minutes or maybe half an hour per board. Drawing the schematic takes much much longer.

I've already drawn up the layout of the next board, but it's schematic is still in progress.

[Vgkid]

Started tracing out the circuit, it is not how I expected it it be.

[pigrew]

I got some of my replacement diodes (1N5240, 10V zeners) for the card I've been working on.

I soldered them in, replaced the unknown NPN transistors (in the burnt area of the board, though they might still be OK) with 2N2222 (hopefully a reasonable choice.... not sure what model the old ones were), and realized that the huge 1N2163 9.4V zener diode had failed open.

I can't believe how many problems this supply has... as if someone kept running it and using it without verifying that it was still working. Or maybe it was some sort of parts unit where modules were the ones that had failed in other units.

I'm having trouble finding a direct replacement of the diode and don't really understand the circuit.

The 1N2163 has a very very low temperature coefficient, and very low zener impedance. (9.0-9.8V@10mA, <15ohm, <0.005%/C,500mW). I'm having trouble finding a substitute. Seems someone on eBay is selling one for $10. I might have to go that route....

I wish that I understood the circuit, how it's used, and if it really needs that low of a tempco.

If it only sets a voltage limit, then I could probably use a 1N5240 (10V Zener), and accept a bit of voltage compliance drift, but I'm not sure that that is its purpose.

[Vgkid]

What is the module you are working on? not like I can compare mine to yours...
For the zener, if the circuitry is not pulling much current look into the 1N93(5/6/7/8) series on ebay, though you might need to change the biasing zener to limit the current.  Or go overkill and make a basic voltage regulator.

[pigrew]

What is the module you are working on? not like I can compare mine to yours...
For the zener, if the circuitry is not pulling much current look into the 1N93(5/6/7/8) series on ebay, though you might need to change the biasing zener to limit the current.  Or go overkill and make a basic voltage regulator.

It's TR1, card D. It's the board a posted schematics of recently.

That module has four boards (one of which is a small rectifier and voltage follower board).

I'll try with the 1N5240, and see what happens.

I also wonder if the diode really should be there. The board has two channels which are otherwise symmetrical. The other channel has a resistor in place of the weird Zener.



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[Vgkid]

Looks like you could use a 9v zener, or a variable resistor+series resistor.

[Vgkid]

It looks like there are now 5, CS-152's floating around. 2 units have sold on ebay, within the last month.

[mcguire]

I'm one of the guys with a CS-152.  I just spotted a CS-140, which seems to be an earlier implementation, on eBay.  Item number 152558667333.  It's cheap but the shipping is not.  I thought about it, but am not going to grab it.

  EDIT: It's *currently* cheap, as it's marked down.  The regular price is, IMO, rather high.  Right now it's listed at $38.51.

                             -Dave