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Search: Posts Made By: redwire
Forum: General Electronics Technical Discussion Today, 03:38 PM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

OK the pots are Alpha (http://www.alphapotentiometers.net/html/16mm_rot_pot.html) so a "B500k"
"A" is audio (logarithmic) taper.
"B" is linear taper.
"C" is reverse audio (antilog) taper.

It's...
Forum: General Electronics Technical Discussion Today, 10:48 AM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

Those potentiometers are weird chinese stuff because it is a dual-potentiometer housing, right angle, PCB mount, but only the one top wafer is used. The WH148 family is a pretty generic chinese...
Forum: General Electronics Technical Discussion Yesterday, 01:59 PM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

If it's low or full-blast only, then I think most likely the pot has failed, or its soldering connections. It could be a low quality lazy BT137 triac, I did see that once.

I would check the (hot...
Forum: General Electronics Technical Discussion 03-23-2019, 01:50 PM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

I think this YH852D+V2 pump is mains AC powered, with other 852D+ variants instead using the 24VDC wand blower fan. Here I see three triacs, two opto-couplers, one DIAC.

The AC triac controls are...
Forum: General Electronics Technical Discussion 03-22-2019, 09:27 PM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

A stalled pump rotor would draw more current and give lower voltage for a given control setting. Once it's spinning, the voltage reading would go up. It's just an AC light dimmer/TRIAC doing the...
Forum: General Electronics Technical Discussion 03-22-2019, 06:21 PM
Replies: 51
Views: 949
Posted By redwire
Re: Hot Air Station - Air Pump Failing

I think it's mechanical stiction in the pump, high friction that needs it set high to get it moving, rotating.
Forum: General Electronics Technical Discussion 03-22-2019, 06:19 PM
Replies: 7
Views: 82
Posted By redwire
Re: Help finding resistor for Craftsman 82357 R41

It takes well past 100V to roast a 20k 1/2W resistor.
pcb pics will help. It's probably not 20k.

It's a nice DMM, I did not know Sears offered such full featured multimeters.
Forum: Troubleshooting Power Supplies and Power Supply Design 03-20-2019, 02:12 PM
Replies: 27
Views: 208
Posted By redwire
Re: Voltage Regulators and Heat Issues

OK from your picture it's an Ali/fleabay piezo buzzer/beeper, which is a piezo-disc with built-in oscillator. It already has an inductor and 2SC1623-L6 transistor, two resistors inside. Attached pic...
Forum: Troubleshooting Power Supplies and Power Supply Design 03-20-2019, 12:32 PM
Replies: 27
Views: 208
Posted By redwire
Re: Voltage Regulators and Heat Issues

Your piezo drive circuit sucks, you need a resistor across it to discharge its capacitance and bring the crystal back. AC drive is best.

With an added inductor, you can get over 5-10X the voltage...
Forum: Troubleshooting Power Supplies and Power Supply Design 03-20-2019, 11:16 AM
Replies: 27
Views: 208
Posted By redwire
Re: Voltage Regulators and Heat Issues

It is common to add an inductor to make a boost converter just for the piezo buzzer. This can make is very loud. It is used in some smoke alarms and battery powered things where you want more than 3V...
Forum: General Electronics Technical Discussion 03-18-2019, 07:17 PM
Replies: 9
Views: 165
Posted By redwire
Re: Failed RF power transistors...DC testing (i.e. with multimeter)?

Depending on the frequency, hams are converting some transmitters from BJT to mosfet. It's also a popular mod for CB radios.

For your TX, the problem might be upstream at the driver stage, or bias...
Forum: General Electronics Technical Discussion 03-16-2019, 01:17 PM
Replies: 9
Views: 165
Posted By redwire
Re: Failed RF power transistors...DC testing (i.e. with multimeter)?

In-circuit testing rarely works because there are shunt inductors or transformers in tuned circuits, so you get low ohms across the diode-junctions.

Newer RF PA parts are mosfets, BJT's with Si-Ge...
Forum: Troubleshooting Power Supplies and Power Supply Design 03-14-2019, 09:29 PM
Replies: 14
Views: 894
Posted By redwire
Re: Recapping Tektronix 2235 PSU

For C956:
2235A has a pi-filter with C956 10uF and Tek added C957 270uF, for the +30V rail. So there are two capacitors.
2235 has no pi-filter or C957, so only C956 270uF.

To replace C906, put...
Forum: Troubleshooting Power Supplies and Power Supply Design 03-14-2019, 08:51 PM
Replies: 25
Views: 376
Posted By redwire
Re: Apple ][+ Astec power supply

Apple II power supply Astec AA11040 or AA11040-B schematic etc. https://ia801002.us.archive.org/1/items/Astec_Power_Supplies_Aug82/Astec_Power_Supplies_Aug82.pdf
Have to look inside to see what part...
Forum: General Capacitor Questions & Issues 03-13-2019, 01:47 PM
Replies: 5
Views: 2,831
Posted By redwire
Re: Wurth capacitors

Wurth trying to bust into the capacitor business, they have great pricing and the film caps are good.
Wurth electrolytics are made in china and seem like a cheap build (low hrs lifetime) despite the...
Forum: General Electronics Technical Discussion 03-10-2019, 03:07 PM
Replies: 15
Views: 220
Posted By redwire
Re: Dead car battery and alternator strain?

Older (car) generators and dynamos needed output current limiting so they would not burn up under heavy load. This was done by a current-sense winding on the relay coil in the mechanical regulator,...
Forum: General Electronics Technical Discussion 03-08-2019, 02:34 PM
Replies: 15
Views: 220
Posted By redwire
Re: Dead car battery and alternator strain?

I see temperature has a big effect on lifetime.

Johnson Controls revenues $6 billion for car batteries, 135 million made per year. They are pretty much the big dog making almost all car batteries,...
Forum: General Electronics Technical Discussion 03-07-2019, 07:53 PM
Replies: 15
Views: 220
Posted By redwire
Re: Dead car battery and alternator strain?

Modern cars have high drain with the key off. 50-100mA so battery life is short, it's always discharging.

Car battery main failure is usually corrosion of the plates. What do you expect to happen...
Forum: General Electronics Technical Discussion 03-07-2019, 11:39 AM
Replies: 4
Views: 120
Posted By redwire
Re: Help identify component?

The Toshiba U5ZA27 zener is in a Toshiba-exclusive package, slightly different size than the Vishay part and rated 1/2 the max. current. I'd stuff the Vishay part in lol.

It's neary impossible to...
Forum: General Electronics Technical Discussion 03-07-2019, 11:28 AM
Replies: 15
Views: 220
Posted By redwire
Re: Dead car battery and alternator strain?

You can't charge a block of ice - so if the battery went dead and froze, you'll probably have to bring it inside and thaw it out to charge it.
It depends on how cold and how low the battery is....
Forum: General Electronics Technical Discussion 03-06-2019, 12:52 PM
Replies: 4
Views: 120
Posted By redwire
Re: Help identify component?

That looks like a massive 6,600W TVS DO-218 used in automotive electronics. It can withstand load dump and surges.
I know it as Vishay SM8A27 (https://www.vishay.com/docs/88386/sm8a27.pdf) used on...
Forum: General Electronics Technical Discussion 02-27-2019, 12:29 PM
Replies: 22
Views: 311
Posted By redwire
Re: The extrasensory perception solder iron.

I hate (Hakko) brass wool, I find it's hard on tips scratches the plating. Damp sponges have always worked fine. Not making a steam bath like some dumb people seem to enjoy.
If there is black slag...
Forum: Troubleshooting Power Supplies and Power Supply Design 02-27-2019, 12:23 PM
Replies: 62
Views: 9,775
Posted By redwire
Re: Muskoka 35" curved fireplace power supply.

Yes the AC Line "L INPUT" comes into the board through the big relay top spade terminal. Then you need Neutral to pin 1 of the other connector, to give the board power.

I would check the "fuse"...
Forum: General Electronics Technical Discussion 02-20-2019, 08:33 PM
Replies: 20
Views: 360
Posted By redwire
Re: Microwave Issue

I would say that's not right because the circuit is a half-wave voltage doubler and it does not output pure DC.

If you use a scope and HV probe, you will see 1/2 wave pulsating DC from +11V to...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 02-19-2019, 03:06 PM
Replies: 22
Views: 325
Posted By redwire
Re: Is this really LMP silver solder?

I've used it to solder to stainless steel
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