Low Cost PCB's Low Cost Components

Recent Posts

Pages: [1] 2 3 4 5 6 ... 10 Next
1
Hi CJay,

You have a good point.  However, there are 2 big elephants in the room you neglect to address.

Problem 1:

There should be some minimum standards before one present something as a good solution to others

In general lose components don't have a large charge, exceptions not withstanding.  In this case, the little PCB in front of the test pin adds minimal value.  Both of my testers were destroyed while I was doing in circuit testing.  The machine was power off but I forgot to discharge all the caps.  This is the most common situation.  In this scenario, to use that little PCB to discharge the DUT in circuit is cumbersome indeed!   Just use a test lead to discharge the DUT in circuit.

The PCB does provide a reminder that the DUT should be discharged.  However, isn't this task much more simply accomplished with a label tape to the tester?  Frankly, wouldn't you agree the PCB approach is actually worse than a label because it is too complex for it does in comparision? 


Problem 2:

Routinely, we cobble together quick and dirty solutions because we have competing priorities (CJay, this is your more interesting things argument).  This absolutely fine!  But to argue a quick and dirty effort as a good solution you are just fooling yourself and others.  Bad CJay :--  We have commercial solutions and community base solution all pursuing the goal of solving the one component that fails the most: the human operator!  The low rent PCB approach is not a solution; never mind good!   



2
Test Equipment / Re: DER EE DE-5000 LCR Meter
« Last post by macboy on Today at 01:04:28 AM »
DCR is intended to measure resistors, and it works at DC like any multimeter or ohmmeter.
Rs and Rp are part of an AC impedance measurement. The meter measures the impedance by measuring the magnitude and phase of the response of the DUT to a sine wave excitation at the selected frequency. It then fits this response to either a series or parallel model:
- In series mode, the meter models the impedance of the DUT as a resistance (real component) in series with a reactance (imaginary component). That reactance may be inductive or capacitive. When set to Rs display mode, the meter displays only the value of the resistance component and ignores the reactive. This can be used to display the ESR of very large capacitors at high frequencies (e.g. for SMPS work) which is not possible in Cs mode.
- Likewise, in parallel mode, the meter models the impedance of the DUT as a resistance (real component) in parallel with a reactance (imaginary component). Rp is only the real component of the impedance.
- other sub-displays are mathematically calculated from the reactance, resistance (Rs or Rp), and frequency.

This is explained, more or less, in the first couple pages of the manual.
3
I'm very interested in the full schematics, even if a faulty one doesn't turn out to be viable as I've got a couple of *massive* toroids that could be pressed into service if necessary.

 I had a read of that thread too, there's half a sort of schematic in there and I'm nurturing a mad scientist thought that it *may* be possible to parallel those series windings and get even higher current out of what is already a monster of a supply but as yet I don't know what the secondaries are.

Definitely needs better diodes and more capacitor though :)
The Mastech schematic from the old thread is basically it - don't think there are too many differences but I will see if I can dig out the paper copy and scan it.

I think that the secondaries are all different voltages.

The diodes seem OK in practice - I did think about using an ideal bridge driver but it would just push heat to the pass transistors, and they don't need the extra strain.
4
Repair / Re: two humming audio amps mystery
« Last post by Armadillo on Today at 12:59:40 AM »
Grrr. Renamed jpeg to jpg...

This looks like a good low frequency hum pickup antenna booster.... LOL
5
Big Clive has done a video on these showers

6
However, I am wondering whether the fix for the Siglent version (SPD-3303S) is the same as the Instek (GPD-3303S)?
My understanding is that Instek did fix the problem on the current systems but I could not find a more recent schematic for the Instek (GPD-3303S) to compare against my Instek unit.
I don't know anything about the Siglent side of things, but for GW-Instek I think the opposite of your statement is true.  I believe that old Instek GPD-3303S units are OK, and newer ones built after the release of the GPD-4303S will have the CH3 overshoot problems.  If you read through the second page of this thread there is some discussion on the different versions out there.

I haven't looked into this since all the activity back in February so I suppose it is possible that GW-Instek have cleaned things up in the meantime, but for some reason I highly doubt it.
7
Do you mean you are using .STEP?

If so, right click on the graph, View, Select Step and you'll see an entry for every step. There's no legend, you just have to select them in turn to work out the colour scheme in use. Yes, not particularly satisfactory, but that's how it is.

Does what I need it to. Thanks!
8
You can have one of these in unknown condition for £60 shipped....

http://uk.farnell.com/digimess/hy3020/power-supply-1ch-30v-20a-adjustable/dp/4283235

Be good for parts if it doesn't work, shame it tops out at 25A though.

That'll certainly give me enough current to run the legal limit for my licence class right now so yes please, I'll send funds and details over when I get home tonight.
I would have bought it for repair had you not done so - but then I already have two under the bench awaiting attention.

If failed then go straight for the output transistors before anything else - these PSUs really like to blow up one or more of the pass transistors.

Teardown & some notes here http://www.eevblog.com/forum/testgear/digimess-hy3020-teardownreview/. I have the schematics somewhere if you need.

The 2N3055 output transistors are almost certainly outside their thermal envelope at high currents and peak voltage drop (not sure what the drop across the output transistors will be at 13.8V out). I change for 2N3773, MJ15015 is another possibility. I also put a meaty reverse biased diode across the pass transistors as they don't have any protection for voltage applied to the outputs (eg if there is a hefty capacitor somewhere).

I'm very interested in the full schematics, even if a faulty one doesn't turn out to be viable as I've got a couple of *massive* toroids that could be pressed into service if necessary.

 I had a read of that thread too, there's half a sort of schematic in there and I'm nurturing a mad scientist thought that it *may* be possible to parallel those series windings and get even higher current out of what is already a monster of a supply but as yet I don't know what the secondaries are.

Definitely needs better diodes and more capacitor though :)
9
Portugal £20 for a big 12Kg package.

Great, thank you  :-+
10
I've also got some PSP603 versions, 0-60V 0-3A for the same price.
I think I want one... Do these have the binding posts or the (awful) recessed banana sockets?

Binding posts for the 60V ones as well
Pages: [1] 2 3 4 5 6 ... 10 Next