Recent Posts

1

Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by Joel_l on Today at 01:45:43 pm »

I put things back together enough to turn it on. what I found this morning was slight different that what I found ( thought I found ) last night.

Frequency is OK. I checked several points  and all were good ( Agilent E4432B )

Amplitude seems OK, worst I saw was .6 dBm low. TG trace was not horrible but I don't know what it looked like before. ( pic attached )

Input impedance is still off, the only way I have to gauge this is using one of my transmitters and TX'ing into the SA. Before the over power, I was getting a near perfect SWR, now I get high SWR on all 3 TXs I tried.

When I measure the switches, U1 is different than the others.

I went back and rechecked all the diodes in the path at each stage, all were OK.

I will replace U1 ( maybe all just cause )

Thanks

2

Test Equipment / Re: Hacking the Rigol MSO5000 series oscilloscopes

« Last post by BTO on Today at 01:45:35 pm »

I've updated the other post and there is a DETAILED PDF there............ GO FOR IT !!!
i still haven't made the video but the pdf should take care of everyone i think

3

Beginners / Re: LiPo battery charging problem

« Last post by Gyro on Today at 01:45:34 pm »

No. In fact you should use the manufacturer's utility of some other s/w to terminate the charge at around 80%. Your battery will last far longer then.

4

Test Equipment / Re: Hacking the Rigol MSO5000 - Dr Mefisto Licensing Method

« Last post by BTO on Today at 01:42:28 pm »

UPDATE : The Step by Step Instructional PDF is now available (it's detailed)

Also if possible (Because i'm interested to know) could you please leave comments if this worked for you or if it didn't , i think this will start working for everyone.

5

Repair / Re: LED Strip lights flashing like a bad 90s rave

« Last post by Grytpype on Today at 01:41:49 pm »

Thank you both for the advice. I'll check the LEDs first and carefully pick through the high-voltage side if I'm feeling brave enough.

6

Other Equipment & Products / Re: NO DIY repair for you (festool rotex)

« Last post by kripton2035 on Today at 01:39:47 pm »

so, to finally close this topic ...
I ordered a replacement board from festool, for some 140€ with shipping... and it was not the culprit !!!!!!
the small jst connector at the top of the board goes to a ntc inside the motor cage, that is inside the cage and not removable
(for the record the jst is NOT at a standard pin spaces, at least I did not have the same in stock)
so I cutted the ntc cable, soldered another 100Ω ntc, and voilà... now it's working
it was only some 10cts component that was faulty.

hope this may help someone else.

7

Beginners / LiPo battery charging problem

« Last post by hap2001 on Today at 01:34:07 pm »

Hello.
My laptop only charges to 98% and not higher, but the voltage tops at about 13.18v, which means almost 4.4v for single cell.
Is this something I should worry?
Thanks.

8

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by john23 on Today at 01:31:38 pm »

Hello I am trying to solve this riddle :-)
As shown in the diagram The output of DB02S2415A difference is 15V , this floating voltage supply goes into UCC5304DWVR which creates again a floating voltage for NDT3055L NMOS.
This floating voltage opens the NMOS and current goes threw from drain to source.
The problem starts with the parts that is not present in the schematics.
I need to connect TGA2590 power amplifier to J4 node. It needs 20V on the drain.
How do i make sure i have the desired 20V on that node and get the current of the NDT3055L(which was opened by the floating voltage of UCC5304DWVR)?
If there is some method i could use? because this floating voltage is confusing. i am used to this of voltage where each node has exact voltage with respect to some reference.
From the LTSPICE model I need some how to make 24V into 20V and make it pulsating open and close like the V2 because currently forsing steady 20V which is not good. is athere something that could be done?
Thanks.
 

9

PCB/EDA/CAD / Re: High current traces meeting small component legs

« Last post by mag_therm on Today at 01:26:46 pm »

After also pondering about this subject on (already built)  RF linear amp using T0267, last night I added the drain lead and pcb track to the 2D heatsink model.
Quickfield 2D model was adjusted as follows:
The 100mm long original heatsink model was shortened to a slice exactly 3mm long (into page) to match the drain leg width .
The  addedd pcb substrate is  1.6mm thick. Track is  1 Ounce ( 0.35mm thick)

The DC conduction model was coupled to provide track heating. Due to dimensions of the pcb track and the MosFet drain leadout, this should be accurate enough up to about 3 MHz.
It became apparent the the DC current flowing in the 3mm wide pcb track would need to be increased above the actual drain current, in order to visualize  track heating contribution.  So DC current along track into drain is 11 Amp. Also the track was lengthened to enable visualization of the temperature along the track, away from the TO267.
All surfaces in the model are cooled by Convection: 20 W/m^2.K, Radiation E=0.5, to 30C

Not knowing the thermal resistance from Silicon to the drain lead, I solidly joined them.
The silicon heat generated in the TO267 is sufficient to cause the heatsink temperature to be 47C. That is heatsink operating temp in the cabinet which has ambient of about 30C. The case temperature is then 60C which is near to thermocouple measurement.

Here is a section of the transient thermal results at T=2400 second:
https://app.box.com/s/wvhkshkswyijiiy7v3h8c4ra6fn59m70
Here is a close-up of the power loss in the track and the soldered drain leadout due to the 10Amp DC only
https://app.box.com/s/6f6bb2d5fdzjs8bwipz8gxpxotgqvr3c

Conclusion for this model: The junction heat generated in the TO267 is swamping the heating of 10 Amp flowing in the 3 by 0.035 mm pcb track.
Note the direction of the heat flux arrows.

If there is any data for the typical thermal resistance between drain pin and junction, I could re-run model using that.

10

PCB/EDA/CAD / Re: JLCPCB alters soldermask without any notice

« Last post by KL27x on Today at 01:25:38 pm »

I'm still waiting on confirmation that my replacement order is even started. When this first began, I wasn't in a hurry. But weeks have passed for nothing.

While popping back onto my account to check, I noticed something I missed before. They didn't even alter my soldermask. They just decided it would better to use my paste layer as the top soldermask layer.   

Now I see how this could happen with no query. They don't have strict rules for layer extension ".xxx" at JCL. I suppose engineer that doesn't speak english might just pick the one he likes, even though my layers are clearly titled in english. And it should not have made sense, because I sent top and bottom soldermask layer (matching extension) and only top paste layer. That's just my default gerber, containing everything I might usually need.

In the future, I'll be sure to remove any unnecessary layers.