Recent Posts

1

General Technical Chat / Re: ultra sonic transducers

« Last post by pete g on Today at 10:29:36 pm »

hi and thanks for your suggestion. i have found some circuits that i'am pursuing. i've tried several so far, to no avail. several more to go. the problem is to get the range i need.

2

Microcontrollers / Re: Routines to convert binary to BCD in C code

« Last post by cv007 on Today at 10:29:25 pm »

but with an 8-bit microcontroller you have to do the job differently.

Differently, but can still use the tools already in the toolbox.

uint64_t v = readCount();
uint32_t vH = v / 1000000000u;
uint32_t vL = v % 1000000000u;
//skip leading 0's, avr lu is uint32_t
if( vH ) print( "%lu%09lu\n", vH, vL ); else print ( "%lu\n", vL );

3

Repair / Re: Tektronix deprecated free trial options

« Last post by colorburst on Today at 10:27:15 pm »

The TDS family consists of dozens and dozens of models. What scope, specifically, are you talking about here?

4

Beginners / Re: The old "Replace blue LEDs with red LEDs" 7 segment question (74HC595)

« Last post by David Hess on Today at 10:25:01 pm »

When I dimmed LEDs driven by 74HC595s, I controlled the LED's supply voltage which was separate from the logic supply.

I doubt the 74HC595s are failing.  The limit for them is the GND and VCC pin current which should not exceed the datasheet value.

5

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by David Hess on Today at 10:17:56 pm »

1. Generate FM signal with 300-400MHz bandwidth between 500MHz and 6GHz carrier frequency.

Do you mean occupied bandwidth or modulation bandwidth?

6

Thermal Imaging / Re: Help with "80 series Thermal imager" by insight vision services

« Last post by Fraser on Today at 10:12:37 pm »

That’s is exactly what I need 

I will send you a personal message with my details 

Fraser

7

General Technical Chat / Re: Looking for reverse osmosis with less than 25% waste

« Last post by strawberry on Today at 10:10:43 pm »

to collect Mg and Ca much faster use two membranes and separate ore with compressed air at the same time cleaning memrane

8

Projects, Designs, and Technical Stuff / Re: Ebay 75mm Slide pots - Interesting Taper

« Last post by electr_peter on Today at 10:07:36 pm »

Linear pots are unusual in audio applications. Sliders intended to be used with motor control have two potentiometers inside - linear for position and non-linear for audio.

9

Beginners / Re: LC filtering for combined Vref/VDD of ADC

« Last post by strawberry on Today at 09:59:43 pm »

separate linear regulator may help to reduce ripple up to some ~1MHz
above 1MHz ferrite bead ,
 inductor saturation current and parasitic capacitance will limit filtering effect

10

Repair / Re: Tek FG502 fails at high frequency end of dial - help needed!

« Last post by BlownUpCapacitor on Today at 09:58:50 pm »

the collector voltage at Q292 which switches the ramp voltage on and off measured low (30-140mV depending on the multiplier settings)

That seems about right. Pulldown for Q175 changes with the multiplier setting, changing the flow of current through CR170.

to measuring -3V when the oscillator stopped.

Whoa, I think you got something!

Looks like the oscillator is locking itself in the negative cycle it seems.

But the problem is still evasive.

Maybe check the voltage across R155 during failure, and working? A negative voltage at the collector of Q292 indicates current flowing through it. Q292 is controlled through Q230A.

Check the circuit pictured below.

Also try removing CR204. Take it out of the circuit and see what happens. Earlier versions didn't have it.

Frankly I'm out of good ideas. Maybe someone else on the forum can help?