harman kardon avr 3700

[yankys]

HI, I'm needing some help on a Harman / kardon avr 3700 it had a bad solder joint on one of the relays in the power board I fix the joint and there a jumper wire near this relay when the jumper is not connected the receiver will power on and function as it should but when I reconnect, it powers on get video and turns back off could this relay be bad?

[Chungalin]

Re: harman kardon avr 3700

A "relay"? That yellow box? Thats a film capacitor, man.

And that jumper wire, how did it get cut? Perhaps it has been always cut. And what's the point of that hole in the PCB exactly there?

[yankys]

Re: harman kardon avr 3700

The jumper was snap by myself accidentally when i was re soldering the yellow box but before that snap it would turn on and shut back off now with it apart it stay on. as for the whole it part of the board. i'm worried about causing more issue by leaving the jumper undone.

[Khron]

Re: harman kardon avr 3700

That hole might be there to increase the creepage distance between those high(ish) voltage traces - that IS the mains input side of things, by the look of it.

By what i can see on the bottom of the board, that jumper comes from one of the mains input pins, goes through what looks like an SMD diode (along with a "twin" from the other side of the mains input), then through a string of resistors, then into an optocoupler. The photos being barely 640x480 doesn't help much, though...

[yankys]

Re: harman kardon avr 3700

I think I've made the image larger.

[Khron]

Re: harman kardon avr 3700

That's a bit better. But still, that jumper doesn't seem to be entirely essential (although i'm sure it wouldn't hurt to reconnect it, as it was from the factory). Looks like some sort of AC-detection circuitry - the trace from said optocoupler snakes along the edge of the board, through some other resistors (likely some pull-up), and to the connector to (likely to the main processor or something).

At least for now, your best bet would be the first commandment of electronics troubleshooting:

Thou Shalt Measure Voltages

[Chungalin]

Re: harman kardon avr 3700

If that jumper wire was straight before cuting, it’s amazing how now both ends have a few millimeters of overlap!! It’s kind of a great force that has been applied to it so it has elongated and finally cut. I’d replace with a new jumper wire.

On the other hand, if you just have seen bad solders on that filter film cap, then you haven’t seen anything yet, because even if that cap is removed, the receiver should work fine in normal conditions. All components from AC input cable to the Rectifier Bridge are security and AC line filter components, not strictly required for working in normal power conditions.

You spend very few words to describe which was the problem the receiver had before you started to fiddle with it. This would be a good starting point.

[yankys]

Re: harman kardon avr 3700

when i first got this avr it would turn on and with in a second or so would turn off so i open the avr and look around i thought maybe some kind of relay was the fault. when i push on the yellow film cap it started working and continued for a couple of days and then went it back to the way it was when i got it. i thought a bad solder joint on the yellow film cap and it was bad so i re-solder it, i broke the jumper left the jumper undone it came on and stayed working. when i replaced the jumper it when back to turning off as soon as it turned on so i undone it again to see if it would stay on and it does all channel work as well as sources i am concern that this would cause other issues if leave it undone.

[yankys]

Re: harman kardon avr 3700

[QUOTE=Khron;623806]That's a bit better. But still, that jumper doesn't seem to be entirely essential (although i'm sure it wouldn't hurt to reconnect it, as it was from the factory). Looks like some sort of AC-detection circuitry - the trace from said optocoupler snakes along the edge of the board, through some other resistors (likely some pull-up), and to the connector to (likely to the main processor or something).

At least for now, your best bet would be the first commandment of electronics troubleshooting:

Thou Shalt Measure Voltages [/QUOTE ok ill check but it is working with the jumper undone.

[Jjosip]

Re: harman kardon avr 3700

Hi!
Thank you all. Badcaps forum is great. It helped me a lot.
I just wonder, does your AVR still works with that broken jumper? I'm trying to fix my AVR370. It has the same issues. Maybe breaking a jumper would help ? :-)
Thanks!

[Jjosip]

Re: harman kardon avr 3700

Just to describe my problem...
My AVR370 just turns OFF randomly. Only orange standby led stays on. Sometimes it happens ten times in a row and sometimes once in a two days. It seems like it was ok when I resoldered joints on a power supply board, but after a few days it happened again. Then I resoldered joints on an amp board, but no use...
It happens even with no speakers ar any other cable except power cable connected.
Now I'm thinking about removing a jumper :-)
Any advice? Sorry about my English...

[jiroy]

Re: harman kardon avr 3700

I think this jumper is an Error detection , so you have definitely an error . Although it is intermittent , It could be fatal to over ride its role as detector . The error can be a heating IC as it can be a much smaller threat . It's up to you if you want to take the risk .
If i was in your place , i will check for stressed components , weakened capacitors , take measures here and there searching for abnormalities ..

[Jjosip]

Re: harman kardon avr 3700

Ok. It's really frustrating. I will take measures as much as I can. I allready checked some capacitors and it seems they're ok. If someone have some suggestions about What and how to measure, it would be great.

[Pjstone]

Re: harman kardon avr 3700

Hi I have a avr3700 doing the same thing. It must be a known issue but I can't find any info on it and harman was no help at all. Any luck with yours yet? Harman was about as helpful as this.

[budm]

Re: harman kardon avr 3700

Hi I have a avr3700 doing the same thing. It must be a known issue but I can't find any info on it and harman was no help at all. Any luck with yours yet? Harman was about as helpful as this.

Exact same problem and pushing on the board with wooden stick will not make the unit to come on temporary.
Those diodes, resistors and opto looks to be for AC detection, it may be for if the AC voltage is too high, the OPTO will turn on and not allow the whole unit to come on except the standby power supply section, so when the jumper is cut (OPTO is completely OFF), there is no more Over Voltage AC protection. If you have VARIAC then you can verify that theory by lower down the AC Voltage and also monitor the receiving side of the OPTO to see what is going on.

[Jjosip]

Re: harman kardon avr 3700

Ok. After all measurements i made... All power supply board voltages seems to be ok. +/-5V is about 5.1, +/-12V is 11.84, 50V that leads to AMP board is 51.3V.
After all, it seems like a problem with AMP board because, if I disconnect 3pin 50V power connectot to the AMP board, AVR works fine and I can not force it to Shut Down. I disconnected output transistors and measured some resistances and Hfe with some cheap multimeter. 2sd transistors are mostly about 150Hfe, but three of them are about 100Hfe. 2sb transistors are about 55Hfe, but two of them are about 40Hfe. Could this be a clue, I don't know.
There's a 25pin connector at AMP board. It has OC_DET pin and I measure 0,47V constant. While I was checking GND pin voltage, it was 0V and jumped to 0,45V and then AVR turned OFF. Could this be a transistors problem?

[Jjosip]

Re: harman kardon avr 3700

Sorry.. 2sd transistors are about 55Hfe and 2sb are about 150Hfe

[eugene_u]

Re: harman kardon avr 3700

Hello, wondering if I could ask Yankys a huge favor - check part number on chip marked as IC91 on power supply pcb. Mine exploded and I could not find any schematics for this version of power supply.
Thanks in advance.

[Jjosip]

Re: harman kardon avr 3700

Hello, wondering if I could ask Yankys a huge favor - check part number on chip marked as IC91 on power supply pcb. Mine exploded and I could not find any schematics for this version of power supply.
Thanks in advance.

You think IC91 is different between AVR370/AVR3700?
As much as I know, some jumpers are, or not used depending on 100V/240V and some main capacitors may be different.
IC91 in my AVR370 has marks:

D22203
OB2358AP
L

[eugene_u]

You think IC91 is different between AVR370/AVR3700?
As much as I know, some jumpers are, or not used depending on 100V/240V and some main capacitors may be different.
IC91 in my AVR370 has marks:

D22203
OB2358AP
L

Thanks for info. Greatly appreciate you quick response. if the only difference btw 370 and 3700 is the input voltage - PWM controller should be the same.
So, will look up for 370 schematics, at least it will give me some clues what could cause the explosion and what kind consequences could be.
Wondering, if any reliable source of OB2358 known to this forum? Looks like Ebay only the option. But, knowing quality of "old new stock" from China, I am quite hesitant to go that route.