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Search: Posts Made By: electricboyo
Forum: Troubleshooting Audio Equipment 10-21-2018, 01:18 PM
Replies: 7
Views: 296
Posted By electricboyo
Re: Onkyo A-8250 50V on DC Offset transistor

This model and some other Onkyo amplifiers have an unusual architecture for the output stage.

There are 3 low value emitter resistors connected to the output transistors. One or more of these...
Forum: Troubleshooting Audio Equipment 10-20-2018, 11:55 PM
Replies: 77
Views: 2,095
Posted By electricboyo
Re: Electron Kinetics Eagle 2C amplifier problem

After looking at your photos of the PC board again up-close I am thinking perhaps some of the power transistors for the bad channel aren't actually soldered to the PC board. Or rather, their solder...
Forum: Troubleshooting Audio Equipment 10-20-2018, 05:32 PM
Replies: 7
Views: 296
Posted By electricboyo
Re: Onkyo A-8250 50V on DC Offset transistor

When an output transistor has failed I temporarily remove all of the main output transistors from the faulty channel. By this I am referring to the large output transistors bolted to the heat sink....
Forum: Troubleshooting Audio Equipment 10-20-2018, 05:19 PM
Replies: 184
Views: 48,687
Posted By electricboyo
Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Always use a “dim bulb tester” to apply mains power to these types of amplifiers. 60W or 100W conventional incandescent light bulb is about the right size. You need to get the amplifier to the point...
Forum: Troubleshooting Audio Equipment 10-20-2018, 05:13 PM
Replies: 28
Views: 1,086
Posted By electricboyo
Re: Pioneer QX-949 in protect mode / no audio

There are some batches of the small TO-92 case transistors in 1970’s era audio gear that develop intermittent and sometimes persistent failures after 40 years. Intermittent crackling, popping, and...
Forum: Troubleshooting Audio Equipment 10-18-2018, 10:26 AM
Replies: 77
Views: 2,095
Posted By electricboyo
Re: Electron Kinetics Eagle 2C amplifier problem

Based on your previous voltage measurements I suggest checking all 4 of the large power resistors connected between the emitters of the channel B output transistors. One or more of these resistors is...
Forum: Troubleshooting Audio Equipment 10-15-2018, 03:52 PM
Replies: 77
Views: 2,095
Posted By electricboyo
Re: Electron Kinetics Eagle 2C amplifier problem

I suggest checking the value of all resistors on the PC board. Do this with power off and with an ohmmeter. Resistors can fail in the "open circuit" state without looking burnt or damaged.
...
Forum: Troubleshooting Audio Equipment 10-14-2018, 06:08 PM
Replies: 77
Views: 2,095
Posted By electricboyo
Re: Electron Kinetics Eagle 2C amplifier problem

What we need are very sharp clear photos of both side of the PC board. If you remove the mounting screws from all the power transistors and the input and output jacks then you should be able to lift...
Forum: Troubleshooting TVs and Video Sources 11-12-2014, 04:47 PM
Replies: 20
Views: 2,231
Posted By electricboyo
Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Yes, I solved the exploding L5973D issue:

Re: magnavox 32mf231d/37 no power backlights flicker

My solution:

Often the 16V to 12V regulator IC at location 7003 on main (scaler) PC board will...
Forum: Troubleshooting TVs and Video Sources 11-11-2014, 05:50 PM
Replies: 20
Views: 2,231
Posted By electricboyo
Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

LCD tv sets contain multiple regulated power supplies: These certainly DO interact with each other. For example, your faulty 2200uf/25V caps could interact with the PFC controller in such a way...
Forum: Troubleshooting TVs and Video Sources 11-11-2014, 10:43 AM
Replies: 20
Views: 2,231
Posted By electricboyo
Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Large high-voltage electrolytic capacitors (such as 150uF 450V) normally have a much longer life than the lower voltage capacitors located in power supply secondary circuits.

Therefore, whenever a...
Forum: Troubleshooting TVs and Video Sources 11-10-2014, 09:41 PM
Replies: 15
Views: 1,381
Posted By electricboyo
Re: Help identifying part on samsung lcd main board

I have personally seen a faulty LM1117 LDO chip. Not burned, no physical damage, but still it had no output. There wasn't a short circuit on the output. In my case, replacing the faulty LM1117...
Forum: Troubleshooting TVs and Video Sources 11-07-2014, 02:05 PM
Replies: 37
Views: 2,946
Posted By electricboyo
Re: magnavox 32mf231d/37 no power backlights flicker

Update:

Replacing capacitor 2002 (100uf/25V) IS the solution to the fried voltage regulator IC 7003 (L5973D).

I've been using the repaired TV set for a full week. It is continuing to work...
Forum: Troubleshooting TVs and Video Sources 10-30-2014, 12:32 PM
Replies: 37
Views: 2,946
Posted By electricboyo
Re: magnavox 32mf231d/37 no power backlights flicker

Good news!

I have 2 main boards that are working perfectly after replacing the L5973D (PC board location 7003) AND capacitor 2002 (100uF/25V).

This confirms L5973D fails because capacitor 2002...
Forum: Troubleshooting TVs and Video Sources 10-26-2014, 08:56 PM
Replies: 37
Views: 2,946
Posted By electricboyo
Re: magnavox 32mf231d/37 no power backlights flicker

I'm on the trail of finding out why so many of the main PC boards on these TV sets fail.

Quite often the 24V to 12V regulator IC at location 7003 will be burned, cracked, or have a small hole near...
Forum: Troubleshooting TVs and Video Sources 10-26-2014, 08:40 PM
Replies: 22
Views: 6,558
Posted By electricboyo
Re: Magnavox 32mf231d no picture or sound

Please check the thread below for additional info about replacing the L5973D voltage regulator.

http://www.badcaps.net/forum/showthread.php?t=28636&highlight=l5973%2A

It is 100% necessary to...
Forum: Troubleshooting TVs and Video Sources 10-26-2014, 08:27 PM
Replies: 25
Views: 3,917
Posted By electricboyo
Re: L5973D IC info for Magnavox 32MD231D

UPDATE:

The non-working main PC board (p/n 313815866881) I bought on ebay is now working.

I replaced the L5973D (item 7003 on PC board). I also replaced capacitors 2002 (100uF 25V) and 2007...
Forum: General Capacitor Questions & Issues 10-16-2014, 02:10 PM
Replies: 22
Views: 2,543
Posted By electricboyo
Re: Old caps...

Even more important than the electrolytics, electronic gear from the 1950's and 1960's contains many "paper" capacitors. These are sometimes referred to as "wax paper," "bumblebee," or "black...
Forum: Troubleshooting TVs and Video Sources 10-04-2014, 06:46 PM
Replies: 8
Views: 1,016
Posted By electricboyo
Re: Saw a cap vent today

Black Beauty caps. :poof:

Guitar players will pay an arm and a leg for these things. They use them inside the guitar body as a tone control cap. I guess that's OK since there's no DC voltage and...
Forum: Troubleshooting TVs and Video Sources 10-03-2014, 01:44 PM
Replies: 25
Views: 3,917
Posted By electricboyo
Re: L5973D IC info for Magnavox 32MD231D

I purchased a 32MF231D scaler board on eBay. It was advertised as "needs repair." Because of that it cost me only $22.

It's L5973D IC is burned, same as my TV.

In fact, the eBay scaler board...
Forum: Troubleshooting Power Supplies and Power Supply Design 09-30-2014, 03:49 PM
Replies: 4
Views: 1,760
Posted By electricboyo
Re: QJE PS3010 - bad EMI/RFI bypass ceramic cap on secondary side

It would be quite useful if you could post a picture of the board and of the capacitor.

I have recently seen several ceramic capacitors that became leaky. Not necessarily a dead short, but a low...
Forum: Troubleshooting TVs and Video Sources 09-30-2014, 01:47 PM
Replies: 8
Views: 1,016
Posted By electricboyo
Re: Saw a cap vent today

Electrolytics aren't the only type that can pop.

I restore antique radios. Old radios contain axial "paper and foil" capacitors. Typically these are in molded black plastic tubes with colored...
Forum: Troubleshooting TVs and Video Sources 09-30-2014, 01:35 PM
Replies: 26
Views: 1,884
Posted By electricboyo
Re: LG42PX4RV-2A no 5v stb

Check the following 2 resistors on the power supply:

R130 (red-red-gold) should be 2.2 ohms
R203 (red-red-silver) should be 0.22 ohms

These are flameproof resistors. When overloaded by a...
Forum: Troubleshooting TVs and Video Sources 09-30-2014, 01:22 PM
Replies: 8
Views: 1,016
Posted By electricboyo
Re: Saw a cap vent today

After 40+ years of electronics work, I still must confess to occasionally mounting an electrolytic capacitor with reversed polarity! Doing this certainly does cause them to vent!

-EB
Forum: Troubleshooting TVs and Video Sources 09-29-2014, 05:24 PM
Replies: 25
Views: 3,917
Posted By electricboyo
Angry Re: L5973D IC info for Magnavox 32MD231D

Bumping this thread because I'm attempting repair of a Magnavox 32MF231D.

Initially my TV would not power up. It had several bulged/high ESR capacitors on the main power supply board. In fact...
Showing results 1 to 25 of 26

 
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