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  1. sureshot

    Solder issue.

    Doing a bit of soldering today, usually I use lead free 4% silver 95.5 % tin 0.5 % copper. All's going well. Then to reinforce some traces I used some 60 /40 lead tin solder I had spare, as the high grade silver solder is expensive. Anyway I went back to components soldering, and was getting...
  2. sureshot

    thyristor vs triac

    I thought a triac was two thyristors back to back in a single package ?
  3. sureshot

    Transformer question

    An indication on what it was powering should narrow down its power value, a look at the PCB if that's possible to interpret the secondary taped voltages on the input.
  4. sureshot

    Over voltage protection.

    Thanks ! Its built for fun really, and to power radio gear, typically all of it. Yet its the amplifier that draws all the power at 100 watts. For future proof and the option to use 250 watts, I don't actually get the RF output rated by the manufacturer, so the 100 watt unit gives me around 80...
  5. sureshot

    Good Soldering Station

    I know this isn't a solder station, recently I invested in an Antex Gascat 120 its cordless flexibility is amazing. The tempreture range is adjustable but limited, so not as much tempreture differential as a solder station. But I've built a few circuits with it now, and the cordless freedom is...
  6. sureshot

    Over voltage protection.

    Thank you for this in depth description, I think I will read up a bit more on the operational elements, and what's going on in the crow bar circuit under different circumstances. My knowledge is limited, so a good read up first before finding a suitable circuit to build. With a series resistor...
  7. sureshot

    Over voltage protection.

    Ah ok might not be such a good idea then, thanks for the info, quick blow fuse and crow bar circuit it is then.
  8. sureshot

    Over voltage protection.

    Thanks, yes I will, I'll have to look at resettable verses sacrificial fuse, resettable sounds interesting out of the two.
  9. sureshot

    Over voltage protection.

    Think I will add a crow bar, rather than just a zener and fuse combination.
  10. sureshot

    Over voltage protection.

    Ok yes the MOV across the mains input, and some filtering, and yes suppression diode on the secondary output. Thanks !
  11. sureshot

    Over voltage protection.

    Thanks for your reply, think I've got it, on the input (mains) I was going to use an adiqate fuse, and MOV and NTC for soft start. This question was for over voltage on the output. So 12 Volts DC powering radio equipment, in the event of a fault situation not to exceed, or over OVP kick in...
  12. sureshot

    Over voltage protection.

    A quick question here.. How affective in terms of speed, and function is a fuse and zener diode protection against over voltage. This compared to adding an SCR and it then being a crow bar circuit. So my question is, will a fuse and zener be suitable for psu circuit over voltage protection ...
  13. sureshot

    Newbie Soldering Station

    I've used this company for over 10 years now, very good to order from, prices reasonable as well. They do a few good quality soldering stations. I use the Antex 18 and 15 watt electric irons, also purchased the Gascat 120 from them. Have a look ! There very prompt service...
  14. sureshot

    Relay operations

    All electronics part relays are known as solid state types. Depending on load (very important on life) relays contact make and break can top 80'000 switchings. But its very dependent on a few factors, including contact material, and current loads.
  15. sureshot

    Transistor hfe

    I'm glad you thinks so AK ! As I say I am certainly fascinated by its simplicity and how it can ramp up and amplify such low currents.
  16. sureshot

    Transistor hfe

    I know your post Steve is in reply to AK. But the l7812 using the original schematic, so far with 2 x TIP2955's and powering my loads up to 8.2 Amps, stability is fairly good. I know these aren't super high loads.. And the voltage drop is 0.3 volts at that said 8.2 Amps. Having said that this...
  17. sureshot

    DC Curent and Voltage regulation.

    Atx power supplys make very handy units ! I've converted a few now and also server power supplys. Have a look at this link ! By the way your posted lab PSU links.. PSU 3 looks good to me for that price. http://jumperone.com/2011/06/atx-power-supply-tutorial/
  18. sureshot

    Transistor hfe

    No I took note of some if you want to call it sarcasm, personally I didn't see as that. The few times it croped up it did leave me amused, "resistor are like a sewer in a circuit" Lol. The above comments conflict a little ( less Steve's comment) "Its good for the l7812 to be running at a minimum...
  19. sureshot

    Transistor hfe

    Thank you Steve ! So it looks like I've been going in completely the wrong direction... I thought the resistance from previous comments needed to be reduced. I still don't know on paper what the circuit numbers will be using 100 ohms 0.5W for this higher power MJ11033 transistor will be. I know...
  20. sureshot

    Transistor hfe

    Ok time to make a decision, as I don't think I'm going to able to pin down an exact value for R7. I'm going to start out with a 25 ohm 0.5 watts. As to this calculation being correct I'm unsure. A value of 25 ohms for R7 contributes 160mW through R7 and a current of 80mA. And I think this...
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