• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

JVC AX-R97: Fuses Blowing after changing burned resistors

kasbah512

kasbah512

Member
I changed out the resistors on the spreadsheet, and now im blowing fuses. I know I used the ones to spec from the service manual, so now I'm not sure what to do. I believe R803 may be the culprit for some reason, but I'm not sure how to proceed. Any advice would be appreciated.
 

Attachments

  • Screenshot from 2023-09-26 14-59-13.png
    Screenshot from 2023-09-26 14-59-13.png
    21.5 KB · Views: 5
  • Screenshot from 2023-09-26 14-59-53.png
    Screenshot from 2023-09-26 14-59-53.png
    294.4 KB · Views: 5
Register to hide this ad
Burned resistors are just the symptom of something else being shorted. The burned resistors were probably open because of them being burned. When you replaced them, you reconnected the circuit and whatever was causing them to burn, is now showing it's ugly head.

You most likely have a shorted transistor that is associated with those burnt resistors.

Got any pics of the area where these resistors are?

Just by reading your post, you probably didn't know this but it is common knowledge amongst experienced repair techs. You should probably have someone else take a look at it for you before it becomes a door stop.
 
I already tested all transistors and replaced the shorted ones awhile back. I cracked it open again because the level meter would show some signal at zero volume, but only when speakers were disconnected. A minor issue, but im stubborn. It wasnt worth the time but i have less of a backlog to work on so im trying to get this one to 100%. Ill send pics when i get home. R803 is the only one not matched Left/Right channel so im assuming its this one. Best case, I'm wrong and i can reference the left channel for whats already in circuit.
 
I suppose ill start with disconnecting the outputs and tracing again like before. I dont think it's oscillating in the output stage at least. The level meter only displays incorrectly on the right channel, but nothing shows up on my 150 mhz scope
 
Last edited:
redk9258 said:
Oscillation?
Maybe transistors are shorted again if it's blowing fuses.
Click to expand...
Definitely something is blown. Im catching full rail voltage at the base of all the output transistors on both left and right channels for both npn and pnp. -65 dc and +65 dc. Theres a start i suppose. Ill report back when i get a chance to dive deeper.

It was putting out a clean 125 watts prior to swapping out the resistors however.
 
I guess check the values of the replaced resistors and for solder bridges or a lead touching something.
 
Make a Dim Bulb tester and don't go on the mains until you no longer have a short, else you will just burn up perfectly good electronics parts.

Rail voltage everywhere is very likely no ground on the amp board.
 
You must log in or register to reply here.
Back
Top Bottom