madan1
Badcaps Veteran
Last Activity: Yesterday, 08:18 AM
Joined: 11-27-2016
Location: Sofia
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Well, I changed the IC and still have the same issue - on power on it outputs ~3v and immediately shuts down. On power off I see another surge of ~3v, so I guess something else in that circuit is wrong. -
So I started taking apart the psu, the caps measured ~290uF for the 330uF, ~410uF for the 470 and 45 for the 47, which I think is OKish.. at least for now.
Traced the 3.3V rail to the 33063 regulator. It gets 12v on Vcc (between pin4 and pin6), so I guess it has failed.
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cisco poe switch PSU issue
Hello everyone.
I'm troubleshooting a cisco switch, which seems to have an issue with the PSU.
The psu has the following power rails - +12v, -53.5V and +3.3V
When connected to power, the +12 and -53.5 seem to work fine, but the +3.3 starts at ~3v and then goes down to ~0 (I guess this is the cap discharging). This happens both when the cable is connected and not to the switch board.
Any ideas what might be causing this behavior?
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Lenovo Ideapad S130 is the CPU dead?
Good day.
I'm trying to figure out what's wrong with a Lenovo Ideapad S130 motherboard. When I connect it to the bench PSU and limit the supply to ~2.2A (about the limit of the lenovo stock PSU), the board absorbs all the amperage and the voltage on the PSU drops down to about 4-5V.
The components on the board that get hot are the two mosfets ( 1 and 2 on the photo ) and the CPU. The resistance to ground measured on the power rail coils can be seen on the image (~17 and ~50 ohms). On the top of the CPU there are few caps which measure dead short. I checked all caps on the top side... -
Oh, well... I'm out of ideas.
I just probed MCU+5V hoping that a ripple would make the ICs behave bad, but "unfortunately" there was no ripple.Leave a comment:
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3 unites experiencing the same issue.. alright, now this looks like a common issue. The good thing is that corrupted firmware now seems to be less plausible. If someone has the unit still on the bench (mine is back in service as a 7channel power amp) I would suggest doing some tests while applying heat to c1 and c171 (both are on the main board, c171 is easily accessible, but c1 is next to the decode board and can not be accessed without removing the hdmi board).
In theory, increasing the capacitance of that two caps and/or increasing the resistance of r40 and r16 should delay the activation...Leave a comment:
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Have you tried other audio signal source? What about shorting the signal input to ground?
p.s. Download spectrum analyzer app and see what frequency is the hum - is it 50/60hz, 100/120hz.. ?Last edited by madan1; 11-23-2023, 09:08 AM.Leave a comment:
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Re: CA Azur 650R volume problem at start
Is it possible that the board and components surrounding the replaced caps were still warm when you tested the AVR?Leave a comment:
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Aaand that is why I have trust issues..
Finally managed to find some time (and will) to replace my "temporary" ghetto full bridge rectifier, removed the diodes, soldered the new one (of course according to its polarity), powered the unit and after few pops the magic smoke escaped. Right, must have done something wrong, install a new one, check for shorts and bad regulators.. power on.. and again the familiar popping sound, but this time managed to cut the power before the magic smoke had escaped. After several hours of wild goose chase I found that the polarity of some of the brand new rectifiers was reversed.. so just keep... -
Re: CA Azur 650R volume problem at start
I also had some time to play around with the avr. So replaced the eeprom IC16, but that did not fix the max volume on startup issue.
p.s. found a couple of bulging caps and a faulty bridge rectifier, but that had also no affect on the issue.Leave a comment:
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Re: Delco bluetooth mod help.
If you are tapping the BT signal in the CD signal you gonna need a "silent CD" which must play when you are listening to the BT.Leave a comment:
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Re: CA Azur 650R volume problem at start
Alright, I did not have time to get under the hood, but checked the service manual to try to find probable causes.
So I can think about two possible root causes - the speaker relays are activated prematurely or the CPU is is giving wrong instructions to the volume control IC.
In the past I've had a case with other model CA receiver, which had reached the end of life of the eeprom IC, thus (if I remember correctly) there was a problem with the volume control.. something like only vol MAX and vol MIN.. and this was...Leave a comment:
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Re: MARKBASS MINIMARK 802 - What is that relay ?
Seems to be on the amp side and I would guess it disconnects the speaker from the amp so that there is no pop sound when the amp is turned on.
PS
Here [url]https://cdn.badcaps-static.com/pdfs/aa9a0b5cb2a12fc5274664ceb5b3feac.pdf[/url] page 14, RL1 right next to the speaker connection. Just shunt it for troubleshooting and if it is the cause, then anything that fits the footprint and the control signal level (18v) should do the work.Re: MARKBASS MINIMARK 802 - What is ...s to be on theLast edited by madan1; 11-12-2023, 08:18 AM.Leave a comment:
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Re: best cheap/free scores 1.1
Probably my best cheap score of the year is a FBT J8A 8" active speaker. Got it from the usual scamplace ebay for about 20EU (~350-400eu current retail price). Described as "flooded, working but with distorted sound". After receiving it, I did not notice any water damage or signs of water neither on the amp board or the speakers. Just for in a case I removed the yellow glue of death from the pcb and after figuring out the input signal plugs I realized what a gem I've scored! I have always been skeptical about class D amps and small size...Leave a comment:
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Re: CA Azur 650R volume problem at start
Hi, I believe it was you who few days ago posted me a PM on the other forum (where previously have discussed the same problem with other ppl).
So no - I haven't found a fix for it, but to be honest, I haven't troubleshoot the issue any further. Might give it a try in the following days. I'll update if there is any progress.
By the way, what are your impressions of the receiver?Leave a comment:
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Re: Fbt Himaxx 60a schematics
Hi, did you find the schematics? In elektrotanya there are few FBT schematics, you might want to check them out.Leave a comment:
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Re: Receiver Onkyo HT-R570 no sound .
If you have an onkyo, denon, pioneer and probably more from that era ( 2005-2015 ) first check if your model uses the defective texas instruments DSP chips.Leave a comment:
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Re: What's wrong with my transformer?
Well, a total of 10 hours of unwinding/winding later I have sore fingers and a working transformer.
Not the prettiest one, but still - working with well balanced voltages. Indeed I was really surprised how balanced ended the voltages on the secondary side - both 35 and 14.5 have less than 0.05VAC difference even though I had to cut some wire on both.
I also found out what happens when the secondary side is shorted.. good thing all tests were done through a lamp.
Not applicable here - the carton tube...Last edited by madan1; 01-09-2023, 04:55 PM.Leave a comment:
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Re: BN44-00301A No signs of life
Start measuring this connector. There is a pinout right next to it....Leave a comment:
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Re: What's wrong with my transformer?
So after several hours of unwinding, finally reached the primary side... and voila - a short right on the black wires input. Unfortunately it had affected the windings beneath and of course - the affected spot is right at the other end of the coil and to reach it have to unwind the whole coil. After some cleaning found two significantly affected wires and after insolating them with some heatshrink, the short disappeared. The following days gonna test it with 220V and if it doesn't fail, I might try rewinding it.
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