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Search: Posts Made By: redwire
Forum: Troubleshooting Audio Equipment Yesterday, 11:44 PM
Replies: 31
Views: 403
Posted By redwire
Re: Reel to reel tube recorder Geloso G258, problem

Don't worry your english is good :)

I would say the schematic has errors. Usually, you lose bass when a coupling capacitor is low in value. But here, some factory capacitors are 10X higher in...
Forum: Troubleshooting Audio Equipment Yesterday, 12:55 PM
Replies: 31
Views: 403
Posted By redwire
Re: Reel to reel tube recorder Geloso G258, problem

I would say you have them mixed up. The voltages are also wrong. Check all pictures you have.

The 0.02uF and 0.05uF are switched with 0.002uF and 0.005uF.
Forum: Troubleshooting Audio Equipment 11-10-2019, 02:16 PM
Replies: 31
Views: 403
Posted By redwire
Re: Reel to reel tube recorder Geloso G258, problem

I would check the capacitors again, to make sure the values are good and soldering is done right.

What part did you use for "0.5 150V" ? Did you change the four "Commutatore" capacitors (for EQ on...
Forum: General Electronics Technical Discussion 11-10-2019, 01:33 PM
Replies: 19
Views: 446
Posted By redwire
Re: Connecting Neutral/Earth together

Why are you even running network/data cables in these? That's against Electrical Codes here. Where is the telephone wiring then?

A cheap chinese energy meter with the breaker/disconnect and skinny...
Forum: Troubleshooting Audio Equipment 11-06-2019, 09:31 PM
Replies: 31
Views: 403
Posted By redwire
Re: Reel to reel tube recorder Geloso G258, problem

I would say those differences do not matter, the capacitors are tiny bit bigger and would not make the bass go weak.
You must have mixed up a capacitor, or a new one is no good, or polarity...
Forum: General Electronics Technical Discussion 11-06-2019, 09:07 PM
Replies: 17
Views: 193
Posted By redwire
Re: High resistance measurement

No, the DMM is in series with the unknown resistor. This is the test circuit and the math formula, changed for a DMM with 10MEG input resistance on DCV.

I'd tried putting the DMM on current range...
Forum: General Capacitor Questions & Issues 11-06-2019, 02:53 PM
Replies: 5
Views: 104
Posted By redwire
Re: What are the best caps for AC coupling a video signal?

Polymer capacitors are used not for signal coupling because they have high dielectric absorption and non-linear behavior.
You will find your video is distorted because of the polymer capacitors....
Forum: General Electronics Technical Discussion 11-06-2019, 02:46 PM
Replies: 17
Views: 193
Posted By redwire
Re: High resistance measurement

I just use a multimeter with known input resistance, say 20MEG.
Set a bench power supply as high as I got, say 40VDC and measure the voltage. Then use the voltage divider equation to figure out the...
Forum: Troubleshooting Audio Equipment 11-05-2019, 02:38 PM
Replies: 3
Views: 64
Posted By redwire
Re: Yamaha RX-V3900 Powers On then Off (Protect)

You can see PS3 the MCU monitoring voltage divider at R75,R76,R77 for "PRVS". It adds the three rails together. The displayed number is raw 8-bit A/D count 0-255.
Forum: General Electronics Technical Discussion 11-05-2019, 11:38 AM
Replies: 6
Views: 102
Posted By redwire
Re: Plasma Height Voltage Divider board

I would check the +/-15V rails to the AD202KN, (https://www.analog.com/media/en/technical-documentation/data-sheets/AD202_204.pdf) in case the PSU brick is the problem. Does it work at low line...
Forum: Troubleshooting Audio Equipment 11-03-2019, 06:39 PM
Replies: 31
Views: 403
Posted By redwire
Re: Reel to reel tube recorder Geloso G258, problem

This is normal - when the tube is cold, high current surge for the heater and the fine wires will light up bright orange until the heater is warmed up.
Geloso put two 3.3R resistors for tube V1a...
Forum: General Capacitor Questions & Issues 11-03-2019, 06:34 PM
Replies: 10
Views: 148
Posted By redwire
Re: Different capacitors in the sassi and different values in the schematic !

Some capacitors can be higher or lower value, or voltage, they are not critical. If you need minimum 20K (0.02uF) but you have 25K (0.025uF) parts in stock, then you use them. Sometimes improvements...
Forum: General Electronics Technical Discussion 11-03-2019, 12:53 PM
Replies: 6
Views: 105
Posted By redwire
Re: CyberPower OR1000ELCDRM1U charger circuit problem

The PCB needs a good scrub with IPA and a toothbrush/q-tip.
I see flux water damage and corrosion. D35 looks like a cold solder joint.
Forum: General Electronics Technical Discussion 11-01-2019, 07:06 PM
Replies: 3
Views: 109
Posted By redwire
Re: Rechargable battery component -- datasheet needed.

It's a Klixon 6MM series battery protector. Datasheet http://ps-2.kev009.com/ohlandl/misc/klixon_mm.pdf
I don't know where to buy them, they are supposed be self-resetting, that one at 70C.
Forum: General Electronics Technical Discussion 10-31-2019, 03:00 PM
Replies: 30
Views: 400
Posted By redwire
Re: Improving a slow/fast digital clock

Tuning fork crystals are delicate. Maximum drive level of 1μW for 32.768kHz parts so they need a big series resistor ~300k is usually missing.
So most circuits overdrive them, and they age rapidly...
Forum: General Electronics Technical Discussion 10-30-2019, 01:11 AM
Replies: 3
Views: 88
Posted By redwire
Re: 7 segment LED displays: Common cathode vs. common anode

Digit common is the highest current, up to 8 LED's worth if you include the decimal point, muxed. So a 20mA/segment display could use 40-160mA.

IC's and logic gates will source less current than...
Forum: General Electronics Technical Discussion 10-28-2019, 07:50 PM
Replies: 71
Views: 4,437
Posted By redwire
Re: Need help to ID this transistor

All the TO-3 diodes are dual except for power zeners. Are you sure?
Microsemi has 50W zener in TO-3 package with the two pins shorted, and either polarity available. Example Microsemi 1N2816A 18V...
Forum: General Electronics Technical Discussion 10-28-2019, 01:01 PM
Replies: 14
Views: 221
Posted By redwire
Re: LED modifications that have a warning...why?

The warning is a mandatory (user manual) requirement by the FCC. It appears on everything, from wireless headphones, radios, led light bulbs...
It seems to be saying if you change cabling on your...
Forum: General Electronics Technical Discussion 10-27-2019, 02:09 PM
Replies: 30
Views: 400
Posted By redwire
Re: Improving a slow/fast digital clock

It would need to use a crystal for timekeeping from the battery. This unit looks like good quality.
I think there is no voltage regulator (maybe just zener Z2) and they wear out the NiMh battery...
Forum: General Electronics Technical Discussion 10-26-2019, 04:37 PM
Replies: 30
Views: 400
Posted By redwire
Re: Improving a slow/fast digital clock

I worked in power generation, multiple 400MW coal-fired plants and they did have few hour shifts to correct (long term) frequency. If you throttle down the turbine (lower steam pressure), power...
Forum: Troubleshooting Power Supplies and Power Supply Design 10-26-2019, 04:27 PM
Replies: 5
Views: 148
Posted By redwire
Re: Globalscale Sheeva Plug

It looks pretty cheap in there, the first generation was a cheaper PSU. It looks like Sheevaplugs die due to capacitor fails.

Does it even have a mains fuse?
Forum: General Electronics Technical Discussion 10-26-2019, 04:11 PM
Replies: 30
Views: 400
Posted By redwire
Re: Improving a slow/fast digital clock

I can't afford the heating bill, lol. It has to be hotter than the highest ambient temp, say 35C and only HAM gear has it.

I tried to calibrate a Casio watch, but it's cold sitting on the dresser...
Forum: General Electronics Technical Discussion 10-26-2019, 02:44 PM
Replies: 22
Views: 3,348
Posted By redwire
Re: Dollar store window / door alarm - Hacking question

Pretty sure the alarm is only a reed switch input and a blob chip that generates a simple siren. It has no delay. I think the input cap is for noise immunity given the large 1MEG resistors.

There...
Forum: General Electronics Technical Discussion 10-26-2019, 02:43 PM
Replies: 30
Views: 400
Posted By redwire
Re: Improving a slow/fast digital clock

Mains frequency moves up and down but is still pretty accurate over the long term. It's better for timekeeping than a cheap quartz crystal oscillator- because they change frequency based on...
Forum: General Electronics Technical Discussion 10-25-2019, 11:38 AM
Replies: 26
Views: 331
Posted By redwire
Re: CCTV cameras: single PSU or individual PSUs ?

Many cameras have fake pixel counts - under the fine print they are "5MP interpolated" but only 1MP raw.
The white speckles can be a noisy CMOS sensor or sometimes the result of using too small...
Showing results 1 to 25 of 500

 
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