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7070 - Relay not clicking

blueapple

blueapple

New Member
Hi Folks!

My 7070 stopped emitting sound this past week. I pretty sure I've narrowed it down to the F-2624 board, but I need some help finding the issues.

Here's what I've done so far:
  • Removed the 2624 and 2626 boards, relay clicks instantly.
  • Added the 2626 board, relay clicks 5-6 seconds after.
  • Added the 2624, no clicks.
  • It doesn't blow any fuses.
  • Check the DC balance, I get 4.4v on both sides and the trim pots doesn't change the value.
  • Check the Bias current, I get 45.2v(!) and the trim pots doesn't change the value.
I read about the possibility of faulty fused resistors, but I'm not sure where they are located, and more importantly, how to test them.

Any help would be much appreciated!
 
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It's most likely the fuse resistors on F2426. There is a lot of posts and threads on that board and the fuse resistors. The most likely suspects are the 180 ohm resistors R33 and R34. Next likely are the 150 ohm resistors R41,42,43,44. Replace them with 1/2W metal film resistors. Don't use carbon resistors.

After you replace them, adjust the DC offset and Bias current.

- Pete
 
Many thanks Pete... I just placed an order for the resistors. Hopefully this takes care of it!

I'll update this post as soon as I've swapped them.

Cheers!
 
Alright, I got a little antsy, and replaced R33 and R24 with carbon resistors I had. It did the trick! I'll swap them with metal film as soon as they come in.

That being said, I'm having a had time getting a reading on F05 and F06/F07 for the bias current. With the multimeter set to mA, I get a 0 reading. Any trick?

I should also mention that I'm now getting a hum when the source is set to AUX. Could it be due to bias current being way off?

Thanks again!
 
only trick I know is to check the meter fuse and connections. On most meters there's a separate hot connection for the current ranges...
 
Last update...

I was able to get a reading for the bias current... I stupidly forgot to change the positive lead on my DMM to read the mA. :/

The hum was coming from a cheap RCA cable I used to test the receiver. All is well.

I have to say that I'm enjoying the sound of 7070 more then my SX-880 and 2245. It's a keeper.

Thanks a bunch for the help!
 
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