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Search: Posts Made By: Per Hansson
Forum: Troubleshooting Audio Equipment 08-10-2022, 11:29 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Great! :)


No this capacitor is not as important, based on its location in the schematic it is there to provide an initial change in the base voltage to transistor Q7, changing the feedback...
Forum: Troubleshooting Audio Equipment 08-09-2022, 12:23 PM
Replies: 3
Views: 72
Posted By Per Hansson
Re: JBL PB12 Won't Turn On

It's brown-red-red-gold, it has just been heated up so much that the color bands got burned up... You can make a sanity check with a multimeter: it may still measure ok.

The reason I know this is...
Forum: Troubleshooting Audio Equipment 08-09-2022, 02:38 AM
Replies: 3
Views: 72
Posted By Per Hansson
Re: JBL PB12 Won't Turn On

I don't think the board is cracked, it looks like the PCB has carbonized, the voltage found a new path to travel...
Usually when you have this type of damage there will be more parts destroyed.
So...
Forum: Troubleshooting Audio Equipment 08-09-2022, 02:22 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Famous words:

In the voice of Homer Simpson: Doh!


Do you mean it measures correctly in the other unit?
I would expect that Q7, RT2, R17 and C35 skews the results.
You can try to reverse the...
Forum: Troubleshooting Audio Equipment 08-08-2022, 02:46 PM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Pretty much enough time has passed now that there should not be any charge in your gate left since your last test, so just check it with the ohm meter now like you did before.
But leaving the gate...
Forum: Troubleshooting Audio Equipment 08-08-2022, 12:47 PM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Wow, I must say everything seems to work really well!
Just one thing: with the MOSFETs now out of circuit redoing the test do you have infinite resistance if you ground the gate?

You could do the...
Forum: Troubleshooting Audio Equipment 08-08-2022, 10:36 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Not really, you could take some measurements, for example ohm out VCC pin 7 to GND pin 5 and then compare to your working unit.
In fact you could ohm out all pins in relation to ground and compare...
Forum: Troubleshooting Audio Equipment 08-08-2022, 08:31 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

This could be pointing in the direction that the UC3844N is what is bad, I'm really not sure though...


Q5 is not NPN but a PNP transistor, can you please just double-check this, as with the info...
Forum: Troubleshooting & Designing Networks 08-08-2022, 06:24 AM
Replies: 3
Views: 149
Posted By Per Hansson
Re: Windows 2016 server L2TP/IPsec VPN - two subnets

Thanks for coming back, just out of curiosity did you figure out exactly why it happens?
It does on my workstation laptop, occasionally it will get a wrong IPv6 DNS server entry.
But I'm not sure...
Forum: Troubleshooting Audio Equipment 08-08-2022, 12:08 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Q3/Q4 results: Their bases are connected together, so equal results are expected.
Q6 results: This transistor has a 100ohm resistor (RT2) between base and emitter so this result could be normal....
Forum: Troubleshooting Audio Equipment 08-07-2022, 04:40 PM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Ok, lets try to test Q3, Q4 & Q5 in circuit starting with Q3 an NPN transistor:
With everything off and allowed time to discharge connect your meter in ohms mode, positive lead to the base of the...
Forum: Troubleshooting Audio Equipment 08-07-2022, 08:30 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Ok, it sounds like your analog meter sources enough voltage to actually turn on the diode then from those readings, so it can be assumed to be correct.
Good that you tested the diodes with the light...
Forum: Troubleshooting Audio Equipment 08-06-2022, 08:44 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Sounds fine!


Graetz Bridge is just a really bad Google translation from Polish (https://pl.wikipedia.org/wiki/Mostek_Graetza), it should say "diode bridge...
Forum: Troubleshooting Power Supplies and Power Supply Design 08-06-2022, 05:08 AM
Replies: 17
Views: 480
Posted By Per Hansson
Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Ok, in these readings you no longer are close to a dead short on the primary winding so something in your testing must have changed?
For another example here is a new transformer I bought by mistake...
Forum: General Computer & Tech Discussion 08-06-2022, 12:19 AM
Replies: 17
Views: 322
Posted By Per Hansson
Re: laptop vs desktop rust spinner longevity

Not a study per se, more of anecdotal evidence:
But in industrial machines I service the Siemens PCU50 HMI PC is very popular.
It does feature a 2.5" HDD in a nice "free hanging" HDD cage.
I...
Forum: Troubleshooting Audio Equipment 08-05-2022, 02:21 PM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

Yes, most likely your R3 & R4 resistors where rated at 38K when new (orange, grey, orange, gold)
looking back through the thread I found many others report the same value.
I'll refer back to what I...
Forum: Troubleshooting Audio Equipment 08-05-2022, 09:49 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

c6 & c7 findings:
I have an analog multimeter (i know...so old school, but i have had it for many years, and electronics for me is limited!), so my measurements are approximate.
C6 measures...
Forum: Troubleshooting Computer Displays 08-05-2022, 03:59 AM
Replies: 2
Views: 101
Posted By Per Hansson
Re: Acer X223HQ (Version Bbd) on/off-power-cycling

The "unknown power IC" is the IC802 on the back of the PCB, an NCP1337 PWM Controller or the Power FET it is driving: Q804 an AP2761i N-Channel power MOSFET.
Your missing components are for an...
Forum: Troubleshooting Audio Equipment 08-04-2022, 11:30 PM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

No, don't mix up C6/C7 with C8.
When I asked you to measure across C6 & C7 this is because this is the mains input, your mains voltage is 115VAC between live and neutral.
Note how there is a jumper...
Forum: Troubleshooting & Designing Networks 08-04-2022, 01:38 PM
Replies: 22
Views: 418
Posted By Per Hansson
Re: Netgear = By far the most horrible support ever!

I would too, this kind of bullshit should not be tolerated!
Forum: Troubleshooting Power Supplies and Power Supply Design 08-04-2022, 01:31 PM
Replies: 35
Views: 8,053
Posted By Per Hansson
Re: Corsair CX400W 5vsb goes into safety loop

The layers are so thin and close together that they aren't very visible in a picture like that. I've seen the small value high voltage caps cracked open (huge case sizes like 4040 just for the...
Forum: Troubleshooting Audio Equipment 08-04-2022, 05:22 AM
Replies: 430
Views: 142,148
Posted By Per Hansson
Re: Repairing Alesis M1 Active mk2 Monitor Speakers

The blue LED has a direct connection to the power board and has nothing to do with the actual board the connector is on.
So if it is flashing it probably means the UC3844N is shutting down because...
Forum: Troubleshooting Power Supplies and Power Supply Design 08-03-2022, 02:04 PM
Replies: 35
Views: 8,053
Posted By Per Hansson
Re: Corsair CX400W 5vsb goes into safety loop

The Corsair CX400 lives again!
I did a cursory Google search and found this post on eevblog:
https://www.eevblog.com/forum/repair/atx-psu-troubleshooting-what-should-i-do-next/

In it user JeanF...
Forum: Troubleshooting Power Supplies and Power Supply Design 08-03-2022, 01:24 PM
Replies: 17
Views: 480
Posted By Per Hansson
Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Here is an example from a Seasonic SS-250FS with a VEE19FRC3 5VSB Transformer:
Primary:
3.44ohm
1.85mH
444kHz
Q=9.2

Aux:
0.24ohm
0.06mH
Forum: Troubleshooting Computer Displays 08-03-2022, 01:17 PM
Replies: 64
Views: 24,727
Posted By Per Hansson
Re: Dell P1110 21" CRT repair thread

On PDF page 7 you have the mains input on the left.
Just measure between live and neutral with your multimeter with a new fuse in the monitor.
Since it blows as you plug it in I expect a really low...
Showing results 1 to 25 of 500

 
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