Recent Posts

1

Test Equipment / Re: Tek 2465 Horizontal Sweep Issue

« Last post by factory on Today at 05:55:58 pm »

If it's never had a PSU service, check the condition of the capacitors, they leak conductive electrolyte and short circuits of the PSU circuitry can cause damage, to lots of parts all over the scope, the caps in the picture are from a 2465 of similar age to your scope.

Does connecting a signal to the inputs change the trace at all?

David

2

Beginners / Re: Amplifier type

« Last post by MarkT on Today at 05:51:25 pm »

Thank you for your replies. I am actually using this circuit connecting it to a photodiode and sourcing its current from anode as input. That’s why I thought this amplifier can be considered as a trans impedance amplifier, since it converts current to voltage, but I guess I am wrong.

The input is ac-coupled so it can't be the only thing connected to the photodiode...  Photodiode amps usually have the diode direct on the inverting input and the frequency response set by the feedback network.

3

Test Equipment / Re: Looking for a replacement general purpose oscilloscope for home use

« Last post by joeqsmith on Today at 05:49:45 pm »

No problem.  Thanks for checking.

I first posted about this scope in 2015.  There was some conversation about the SSD.  The Transend has been in there 9 years and counting without a single problem.  That's with a fair amount of use. 

I thought this is where they had recommended the CPU upgrade.
https://www.eevblog.com/forum/testgear/teledyne-lecroy-waverunner-64xi/

Found it. 
https://www.eevblog.com/forum/testgear/what-oscilloscope-buy/msg765218/#msg765218

4

Repair / Re: Rhode Schwarz CMU200

« Last post by minolta on Today at 05:49:45 pm »

I have repaired CMU200 several times with different faults. The worst of them was overvoltage. It was because of wrong multiturn poti on PCB of PSU (wrong contact inside). This is terrible design of PSU- - with bad contact in poti there is maximum voltage near double! Designed by some school?
These DELTA PSU are crazy. In all are very bad capacitors. Changing of them - almost dead approx 25 capacitors - are very very bad work, impossible to desolder etc... primary side is heavy coated, so measuring or change something is terrible. Realy, I am afraid next CMU for repair bacause next PSU will be necessary to refurbish.

5

Beginners / Re: hFE of a NPN transistor

« Last post by MarkT on Today at 05:45:41 pm »

i want to use the transistor to turn an LED on and off, the transistor will be connected to a 9v 200mah battery and i think that LED can have maximum input of 5v and 25ma.

atteched you can find the a screenshot of the datasheet of the LED, i have a green one.

Then hFE is irrelevant, it doesn't apply to a transistor used as a switch.  You need the Vsat entries in the datasheet.  Typically this will be quoted at Ib = 0.1 * Ic, which is what's usually needed to saturate a transistor on.  So 2.5mA or so for base current to turn it on.

If the LED is 5V and 25mA you will need a current-limiting resistor of (9-5)/0.025 = 160 ohms in series with the LED.

6

Repair / Re: Which USB3-SATA dock/cradle/adapter for 3.5+2.5" hdds without 4K/sec emulation?

« Last post by fzabkar on Today at 05:44:22 pm »

I've opened the case of my Sharkoon SATA QuickPort XT USB 3.0 dock and confirmed the Bridge IC:

There is also an "E" version of the IC which I believe supports AES hardware encryption.

https://upload.wikimedia.org/wikipedia/commons/6/6c/ASMedia_ASM1051E_ABA91140A2_T6A_1143.jpg

Some of these bridge ICs have internal code which enables them to run as a generic bridge when the external memory (8-pin SPI flash?) is disabled. If yours is one of these, then perhaps the default sector size in generic mode is 512 bytes?

Edit:

WD's My Books use the same Asmedia bridge.

https://goughlui.com/2015/10/25/how-to-remove-wd-hard-drive-from-mybook-enclosure/

P/N: WDBFJK0060HBK-04
Default WD My Book 1230 VID 0158 PID 1230 REV 1065

I cut the Vcc lead (pin #8) from the EEPROM, and the device detects as USB Mass Storage Device VID 04D9 PID 2013 REV 0103 and disables the goofy 4k sector translation mode as well, so regularly written 512e drives >2Tb actually read correctly.

Hope this is useful.

– Gough

You may need to cut the *WE pin as well, as sometimes the IC can still be powered up via this pin (because it is tied to Vcc) when Vcc is cut.

7

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by iMo on Today at 05:43:35 pm »

Using the second PIO is feasible, sure. We need to have the final design of the rundown ready and we may try to place that into the second PIO.
The small HW issue will be with the handling of the PWMA and PWMB signals, as those have to be manipulated from both PIOs then.

PS: Kleinstein likes to have the end of the runup at the negative side . Years back I made tons of simulations here with the runup, but cannot remember how the runups ended up. My feeling is the runup may end up at both sides. Perhaps there is a trick..

8

Metrology / Re: WinGPIB - Windows GPIB App (multi-purpose)

« Last post by IanJ on Today at 05:42:48 pm »

Rax,

In WinGPIB press the NOTEPAD GPIBchannels button and it will open a text document with lots of hints, tips & examples of using WinGPIB.
The idea is you can edit that text document with your own stuff......but for a kick-off it's all mine.

R&S is using VISA which is a generic standard adopted by many manufacturers, so you can use it.
You can of course also use RS232 if you want instead of VISA, there are examples in the text document for that.

Ian.

9

Beginners / Re: Dimming signal 0-12V from microcontroller (logic level to 12V PWM)

« Last post by MarkT on Today at 05:41:38 pm »

The MOSFET driver is a perfectly capable level shifter, probably too capable as it will have hard edges and generate a fair bit of EMI as a result if driving a long cable.  So I'd say use it if its close to the PSU, otherwise find a lower EMI solution like smoothed PWM.

10

Metrology / HP 5071A cesium standard CBT hot wire ionizer heating system short circuit

« Last post by testpoint1 on Today at 05:40:19 pm »

Hi all,

I got an old HP 5071A, the CBT hot wire ionizer heating system shorted, the two terminal only 150 Mill Ohm,  anyone has the suggestion to resolve it ?