Recent Posts

1

Beginners / Re: Checking for noise in resistors

« Last post by TimFox on Today at 07:09:03 pm »

The T3 in noise mode is described in its manual, available online.
It applies something like +125 V through a current limiting resistor and amplifies the resulting audio through a high gain tube amp to allow listening for snap-crackle-pop noise.
The LM386 suggestion is a reasonable alternative for the 12SH7, but probably less bulletproof.

2

Test Equipment / Re: TinySA Ultra launched

« Last post by shapirus on Today at 07:07:28 pm »

Please explain why it should be fixed, except for cosmetic reasons when observing with a DSO?

It may be important in any practical application where a frequency sweep signal is used and it's expected that the signal won't contain any frequencies outside of those expected at any given time in the sweep range.

I'm not sure what those would be, I dont have any examples of my own.

3

Beginners / Re: Checking for noise in resistors

« Last post by floobydust on Today at 06:59:42 pm »

From the era of tube gear, many signal tracers have a "NOISE" mode switch built-in. Example Heathkit IT-12.
That applies high voltage bias to the probe about 115VDC/1.7mA and with the audio amplifier you can listen to the result.
A noisy resistor or capacitor with bad dielectric can be flushed out. It was a common problem in the day.

Yeah, that and the more capable T-3 are the Heathkit units I talked about in a previous post in this thread. It is unobtainium here in Europe at least at a reasonable price.
That was more or less the circuit I was trying to make, albeit somewhat modernized, i.e.: no tubes 

It's not hard- take an LM386 amplifier board $1.50 and run that with added blocking cap+protection diodes, and low noise HV power supply.

4

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by Karel on Today at 06:59:10 pm »

Still my question is unanswered:
Have you ever checked on the cross section?

No, because I order from Digikey/Mouser/Farnell.

5

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

« Last post by floobydust on Today at 06:58:23 pm »

If the LED string goes open-circuit, due to thermal expansion on the bonding wires/die attach, the PSU output voltage can rise up - and when the LED cools off and reconnects, the filter caps discharge hard into the string. So, I have seen blinking LED strings with many failed elements when I was thinking it would be just one LED failing.

The small capacitor by J3 is critical for the SMPS IC"s operation. Make sure its ESR is good as well as capacitance. These are 22-47uF 50V parts.

6

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

« Last post by xvr on Today at 06:58:18 pm »

Do you turn on power for amplifiers only for milliseconds? Or you will turn them on more o less permanently?

See Figure 9 in datasheet .

You should look on permanent Id, not pulsed

7

Repair / Re: Desoldering advice

« Last post by antenna on Today at 06:54:47 pm »

Thanks for the preheating and bigger soldering iron advice, the relay came right out.

It tested fine, all components under it tested good too.  I used some 63-37 and wicked it off to remove the low MP alloy, then put the relay back in with some Sn Cu Ag stuff that melts at 237°C instead of using the 60-40 188°C stuff I usually use.  I found no continuity at the motor, so their "low voltage" error code must have meant low current.  It seems that when it detects no current, the relay drops out.  Opening the motor and checking the brushes next. 

I appreciate all the help, thank you!

8

Test Equipment / Re: TinySA Ultra launched

« Last post by erikka on Today at 06:54:19 pm »

Please explain why it should be fixed, except for cosmetic reasons when observing with a DSO?

9

Beginners / Re: Is it safe to store CMOS devices in the AideTek ESD Boxes

« Last post by m k on Today at 06:53:58 pm »

Scalability is the key.

Your old word had limited parts from outside and sort of unlimited from inside, in this case inside is mostly out.
Now you have no limits for different kind of parts from outside, you think you have, but that's an illusion.

One pro system was a self of cardboard boxes where pink bags were stored.
Those boxes are still available.
Too heavy items can be a problem.

Original tubes are practical, until they are not.
I use cardboard tubes to stuff original tubes, long and short.
Short ones are not very practical and long ones are occasionally too short.
One part in one original tube can also be less than space friendly.

It's also sort of a norm that eventually something will break the current system.
So a junk box or two will be there, don't fight it.

You can also give away some of your earlier mechanical accuracy requirements.
This new lead free system will guide your way.

10

Beginners / Re: Fast PWM IC

« Last post by strawberry on Today at 06:53:40 pm »

custom circuit with digital logic gates or FPGA