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Search: Posts Made By: redwire
Forum: General Electronics Technical Discussion Yesterday, 09:36 PM
Replies: 2
Views: 18
Posted By redwire
Re: I am looking for a transformer secondary of 60 volts @ 30 amp

Are you sure about your specs? 60VAC 30A output is 1,800VA and about a 45lb beast. That small transformer is probably overloaded and why it is stinking.

1,500VA control transformers are common but...
Forum: Troubleshooting Audio Equipment 06-28-2020, 12:53 AM
Replies: 5
Views: 80
Posted By redwire
Re: Altec Lancing ACS41

I know the LM324 has a gritty sound/mid-range blare to it due to the cross-over distortion so I change them out. Quad op-amp alternates:
LM837 (https://www.ti.com/lit/ds/symlink/lm837.pdf) is older...
Forum: Troubleshooting Audio Equipment 06-27-2020, 08:34 PM
Replies: 5
Views: 80
Posted By redwire
Re: Altec Lancing ACS41

These are good systems and worth repair/recap. I have an ACS48 coming in for repair and it looks really well built.
You can change out the LM324 for a better op-amp with less cross-over distortion,...
Forum: General Electronics Technical Discussion 06-24-2020, 03:36 PM
Replies: 55
Views: 1,351
Posted By redwire
Re: TO-220 exploded...estimated overload?

yes TO-220 fullpacks ran really hot, I tried them(MOSFETs) in mains SMPS instead of all the insulator/hardware to keep it simple. Thermal imaging cam showed over double the operating temp.
MOSFET's...
Forum: General Electronics Technical Discussion 06-24-2020, 12:32 PM
Replies: 55
Views: 1,351
Posted By redwire
Re: TO-220 exploded...estimated overload?

TO-220F has quite poor heat transfer to a heatink, around half that of the TO-220.
I was going to build an audio power amp using them but they can't get rid of heat:
FJPF5200 (TO-220F) 2.5C/W...
Forum: General Electronics Technical Discussion 06-22-2020, 11:33 AM
Replies: 14
Views: 289
Posted By redwire
Re: Can someone confirm these resistor values?

A first-order 6dB/oct crossover like OP's, the resistors are only to pad the tweeter which might have say 100uH inductance so a few uH is not an issue.

My Amrel LCR meter will also give negative...
Forum: General Electronics Technical Discussion 06-21-2020, 11:30 PM
Replies: 14
Views: 289
Posted By redwire
Re: Can someone confirm these resistor values?

I've never seen non-inductive resistors used in a passive cross-over network.
The inductance of ordinary wirewound resistors is very low, at most a few uH which is so small compared to the inductors...
Forum: General Electronics Technical Discussion 06-21-2020, 03:49 PM
Replies: 55
Views: 1,351
Posted By redwire
Re: TO-220 exploded...estimated overload?

You might be over-torturing things using light bulbs as load? Their resistance is non-linear and much lower when cold.
A 100W 120VAC bulb is 144 ohms lit but at 1/2 voltage drops to 124 ohms, and...
Forum: Troubleshooting Game Consoles & Other Weird Devices 06-15-2020, 08:09 PM
Replies: 24
Views: 910
Posted By redwire
Re: HDD Spins up and down again at power on

Older WD Green drives had problems with Intellipark, it was auto parking heads so frequently (after every 8 seconds) the drives wear out. I changed that setting to 500 seconds using WDIDLE3.exe and...
Forum: General Electronics Technical Discussion 06-12-2020, 04:15 PM
Replies: 55
Views: 1,351
Posted By redwire
Re: TO-220 exploded...estimated overload?

Silicon rectifier diodes will dissipate roughly a watt per amp. This is with a center-tapped transformer, dual diodes, so one on 1/2 the time. A bridge dissipates twice as much with two diodes on at...
Forum: Troubleshooting Audio Equipment 06-09-2020, 08:34 PM
Replies: 2
Views: 214
Posted By redwire
Re: Yamaha RX-V483 - dead

OP why did you cross-post pics here (https://www.electronicspoint.com/forums/threads/yamaha-rx-v483-dead.293030/) and leave us nothing? :frown:
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-08-2020, 04:39 PM
Replies: 3
Views: 186
Posted By redwire
Re: HP Power Supply 6632A: Fast Mode vs Normal Mode?

Almost all cheapola bench power supplies have a large output capacitor to keep them stable, which makes CC mode lousy.

You need FAST mode when doing CC stuff. It's important.
Example is set to...
Forum: General Electronics Technical Discussion 06-08-2020, 04:33 PM
Replies: 4
Views: 196
Posted By redwire
Re: Phase Loss Monitor having false triggering ( bad capacitors issues)

Nichicon (https://www.nichicon.co.jp/english/products/solid/index.html) also has some new solid polymer capacitors to 125C/257F or 135C/275F or 150C/300F. But that is where plastics melt and...
Forum: General Electronics Technical Discussion 06-08-2020, 01:32 PM
Replies: 4
Views: 196
Posted By redwire
Re: Phase Loss Monitor having false triggering ( bad capacitors issues)

It would nice to see pictures of the inside of the module. It must use a small mains power transformer?
I repaired a simpler phase loss detector and I think it was damaged from spikes 480VAC monitor...
Forum: Troubleshooting Power Supplies and Power Supply Design 06-03-2020, 02:41 PM
Replies: 18
Views: 2,072
Posted By redwire
Re: Recapping Tektronix 2235 PSU

Glad it helped :) some capacitors in the Tek 2235 and 2235a are before EIA standard values became popular and measuring the size of everything drove me nuts.
When recapping equipment, I've also...
Forum: General Electronics Technical Discussion 06-02-2020, 10:41 PM
Replies: 11
Views: 734
Posted By redwire
Re: High side Mosfet swich design

OP's circuit, R2 is silly as it is limiting to 5mA and R1 is too low and a P-ch mosfet? not sure how the circuit even starts, it's prob. the substrate diode always on :lolsign:
I always put in a...
Forum: Troubleshooting Power Supplies and Power Supply Design 06-02-2020, 10:28 PM
Replies: 25
Views: 852
Posted By redwire
Re: QW-MS3010D 30V 10A Variable PSU Blown MOSFET

The power supply is a half-bridge configuration with transformer drive to the power mosfets. So shorted mosfets cannot damage the KA7500 (TL494). But the gate-drive resistors, R2 50R? looks be blown...
Forum: General Electronics Technical Discussion 06-01-2020, 09:11 PM
Replies: 17
Views: 468
Posted By redwire
Re: KORG Tuner GT-2 not working

I don't know what the meter should read with no signal. You can use a signal generator at 430, 440, 450Hz and check if the panel meter is accurate. Or play a youtube tuning video to it and see if it...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-01-2020, 02:23 PM
Replies: 2
Views: 162
Posted By redwire
Re: Oscilloscope Opinion

THS720/730 have been out since 1996, kinda old like Fluke Scopemeters. Portable scopes are not very good, lots of compromise. Little memory, low sampling rate and LCD display and most are optimized...
Forum: General Electronics Technical Discussion 06-01-2020, 12:55 PM
Replies: 156
Views: 4,385
Posted By redwire
Re: Running a microcontroller in car - power supply aspects

Are you are using this mode:
set_sleep_mode(SLEEP_MODE_PWR_DOWN);

Make sure you turn off the A/D, brown out detection, maybe watchdog timer to get really low current draw under 0.5mA when you go...
Forum: Troubleshooting Power Supplies and Power Supply Design 05-31-2020, 09:53 PM
Replies: 9
Views: 303
Posted By redwire
Re: Samlex SEC-14 linear power supply 13.8VDC 10A repair

chinese 2N3055's at their limit? :chair: If the pass transistors short, 22VDC will kill radio/battery etc.
At 10A, that is around 70W of heat... no way 8 fins 7/8" deep can pull off under 1C/W...
Forum: Troubleshooting Power Supplies and Power Supply Design 05-31-2020, 03:26 PM
Replies: 9
Views: 303
Posted By redwire
Re: Samlex SEC-14 linear power supply 13.8VDC 10A repair

Yes it's the same weird protection circuit, sometimes you have to pull power and reboot. The protection transistor and error amp make a LATCH. It can throw you a curveball when troubleshooting.
...
Forum: General Electronics Technical Discussion 05-30-2020, 10:08 PM
Replies: 25
Views: 599
Posted By redwire
Re: Decorative Solar Lamp Question

It looks fixable. I use q-tips with alcohol IPA to clean the corrosion and flux. I only resolder dull looking connections.

It's strange the long trace is black, not sure where the water got in (at...
Forum: General Electronics Technical Discussion 05-27-2020, 01:30 PM
Replies: 17
Views: 468
Posted By redwire
Re: KORG Tuner GT-2 not working

To protect against reverse-polarity battery, I put a 1N4004 diode right across the battery input, so that shorts the battery but you can't really keep it on the snap for a long time. Or a series...
Forum: Troubleshooting Game Consoles & Other Weird Devices 05-26-2020, 04:36 PM
Replies: 14
Views: 315
Posted By redwire
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