Harman Kardon AVR 146 Won't stay powered

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

There is thermal protection fuse on the primary winding of the transformer which mounted under the MYLAR tape on the transformer, that fuse may have blown.
For example:
http://www.electronicrepairguide.com...r-speaker.html

[stj]

Re: Harmon Karden AVR 146 Won't stay powered

if it is the thermal fuse,
make sure nothing on the outputs is shorted before you replace it - or it will blow again.

and there is a way of soldering thermal fuses - you solder at minimum temperature to the end of the wires while holding the fuse wires near the fuse body with pliers or similar to block the heat.

otherwise the iron will blow your new fuse!!

[Agent24]

Re: Harmon Karden AVR 146 Won't stay powered

Assuming CN91 connects to the primary of the transformer directly and does not pass through anything else, then it may well mean the transformer is bad.

However you may want to try testing directly at the primary pins of the transformer in case the PCB has a break or something.

Also look at the pins and check the transformer winding is soldered into them and not broken

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

The two wires of the primary winding are connected to the CN91, the CN91 PIN 1 which is the Neutral on the PCB is connected to one of the transformer primary winding wire, the second wire of the primary winding is connected to pin 2 of CN91 on the PCB which is connected to the fuse F901, the other end of the fuse is connected to one of the relay RY94 N.O. Contact, the C contact of the relay is connected to the 120VAC LINE of the power cord.

[Agent24]

Re: Harmon Karden AVR 146 Won't stay powered

The two wires of the primary winding are connected to the CN91, the CN91 PIN 1 which is the Neutral on the PCB is connected to one of the transformer primary winding wire, the second wire of the primary winding is connected to pin 2 of CN91 on the PCB which is connected to the fuse F901, the other end of the fuse is connected to one of the relay RY94 N.O. Contact, the C contact of the relay is connected to the 120VAC LINE of the power cord.

I was thinking of the board that the transformer sits on, not the main board. I assume the other half of CN91 doesn't connect directly to the windings and has to pass through at least a connector, some PCB traces, and the mounting pins on the transformer, any of which could also be a problem.

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

Agree, I think to be sure how the primary winding wires are routed, he needS to show us the two PCBs where the pins of the transformer are soldered to and the wire connected to CN91.

[Agent24]

Re: Harmon Karden AVR 146 Won't stay powered

I don't know if you saw it, but the main transformer and associated circuitry on its boards are shown on Page 7 of the schematic in the bottom left of the page.

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

Yes, that is the simplified SCH.
I look at the PCB layout page 45 for those two boards (CUP11916-3, CUP11916-4) mounted to the transformer pins, the primary winding is not connected to the those board but it actual has two wires coming out of the transformer. It is the same setup as the other model I worked on. s

[Bslodk]

Re: Harmon Karden AVR 146 Won't stay powered

Ok, thank you for the clarification on the the thermal fuse. I will start peeling back the insulation and look for a thermal fuse and check the connectivity points on the transformer. will post what I find.

Understood about the output posts, too, if I find a thermal fuse blown.

[Bslodk]

Re: Harmon Karden AVR 146 Won't stay powered

Ok guys, I have torn into the transformer as best I can peeling away the tape and I find NO thermal fuse, believe me, I wanted to find one. So, I have checked for voltage at CN91 and I have 120 VAC when the relay kicks in. Additionally, I probed the wires to ensure there was not a break in the leads to transformer, but find nothing. No voltage at any of the posts.

The next question, where do I find a transformer for this beast considering there is no rating or schematic drawings on the output voltage for the transformer? I could hardwire the two circuit boards to another transformer, but not when I do not know the specs. Help!!!

[rievax_60]

Re: Harmon Karden AVR 146 Won't stay powered

Ok guys, I have torn into the transformer as best I can peeling away the tape and I find NO thermal fuse, believe me, I wanted to find one. So, I have checked for voltage at CN91 and I have 120 VAC when the relay kicks in. Additionally, I probed the wires to ensure there was not a break in the leads to transformer, but find nothing. No voltage at any of the posts.

The next question, where do I find a transformer for this beast considering there is no rating or schematic drawings on the output voltage for the transformer? I could hardwire the two circuit boards to another transformer, but not when I do not know the specs. Help!!!

There is no need to do all of that. The thermal fuse usually wired to 2 pins on the transformer's primary side where it can be easily checked for continuity.
It can also be easily pulled out from between the layers after a small piece of the bobbin is broken away.

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

Show us the pictures of what you have done to the tansformer, may be you are not at the right winding.

[Bslodk]

Re: Harmon Karden AVR 146 Won't stay powered

Ok, guys. Here are the pics. I pulled off all the tape that I could without wanting to cause damage to the windings. Are you possible saying that I need to break off part of the plastic to gain access to the thermal fuse?

Sorry for the confusion, I am just trying to follow the steps I am told. Once again, I appreciate the help in advance.

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

I cannot see much in the pictures where the RED/BLACK wires of the primary go too, I expect to see something like this:
http://therepairblog.blogspot.com/20...ower-pump.html
If it does not have the fuse, then you are out of luck.

[rievax_60]

Re: Harmon Karden AVR 146 Won't stay powered

I had hoped that it looked something like this,
https://www.badcaps.net/forum/showth...al+fuse&page=2

[R_J]

Re: Harmon Karden AVR 146 Won't stay powered

The part number I have for the transformer is clt5u026zu Cost was around $120.00
If it does have a thermal fuse, just jumper it out. Here is where it could be located (this is not the same transformer) usually under the tape where the primary wires go in (red and black wires)

Amazon has 3 used amps complete $148.00 http://www.amazon.com/Harman-Kardon-.../dp/B000MWPD0I

[Bslodk]

Re: Harmon Karden AVR 146 Won't stay powered

Wow, you guys are fantastic!! I was about to give up until you provided another thread of a similar transformer. I started chipping away at the plastic this morning. After doing some probing, digging, etc., there it was and it is definately OPEN.

I was concerned I might have damaged the wiring, but when bypassing the thermal fuse I am getting 1.6k of resistance so I feel confident I will be ok. The next question is do I need to rewrap the windings in any kind of tape to protect them after replacing the thermal fuse?

[stj]

Re: Harmon Karden AVR 146 Won't stay powered

the body of the fuse should be pressed against the side of the windings somwhow to read the temperature.

[budm]

Re: Harmon Karden AVR 146 Won't stay powered

"but when bypassing the thermal fuse I am getting 1.6k of resistance" Please verify that reading again, the DCR should be less than 5 Ohms for primary winding DCR. Once it all connected back up, make sure to check the power supply sections, output section for shorts, I would use light bulb in line with the power feeding the unit.

[Bslodk]

Re: Harmon Karden AVR 146 Won't stay powered

I was incorrect on the resistance, it was 160000. Anyway, thainks to everyone, especially BUDM. Indeed, it was the thermal fuse that was buried inside the transformer. I checked all the diodes, resistance on the boards connected to the transformer to verify there was no short. I took the suggestion about how to solder a thermal fuse without overheating it, plugged it in and BAMM. It is now workig!!

I could not have done this without all of the support so I thaink each and everyone of you!!!