AU517 with a random resistor size on protection board R05

[JoshHendi]

So recapping my protection board on the AU517. Did the caps, diode, and fusistors. Literally on my LAST component to replace, which is R05. The service manual says this should be 100ohm, along with R06 07 and 08, but the R05 I pulled from my unit (which was working, and original) isn't 100ohm but instead 1400ohm?! (and it doesn't look stressed, and has a different color code than the other 3 100ohm resistors)

I'd assume I should replace it with the same value, since my amp was working perfectly before, but 100hm vs 1400ohm is a big difference, and I only have 1.2k and 1.5k

So what should I do?!

 

[petehall347]

what is the board id number ? f-????

 

[JoshHendi]

F-2675... Beginning to think the original owner who sold this to me wasn't telling the truth about it never being serviced

 

[JoshHendi]

So it seems the set of four diodes that R05 connects to (D9, D11, D13, D15) were replaced. I'd like to keep everything even on both channels, would I be okay with replacing those diodes (and the other side) with 1N4004 and then go back to a 100ohm resistor on R05?

From looking at the solder joints, it seems the four diodes above were replaced and maybe the value of R05 was put in to compensate for the diode replacements?

 

[JoshHendi]

So after doing some research, I can just replace the eight diodes with 4004's install a 100ohm resistor in R05, and call it a day.

Any objections or observations?

 

[Hipocrates]

Any objections or observations?

10D2 is a 1.5A rectifier
1N5394 is a better option, but I guess the 4004 will do just fine.

 

[petehall347]

r05 100 ohm 1/2 watt

 

[Hyperion]

From looking at the solder joints, it seems the four diodes above were replaced and maybe the value of R05 was put in to compensate for the diode replacements?

It is possible that the positive regulator (TR01 / ZD01) isn't working properly and the 1400Ω resistor was the 'fix' - best check the output voltage at pin 15 after changing that resistor.

 

[Overundr1]

Absolutely (what John said)

-Lee

 

[petehall347]

i agree entirely . .. half a job again ..seeing to much of this lately

 

[slimecity]

You need to distinguish between a factory change in component spec (which may differ from some component values that are specified in the SM) and subsequent work that someone may have done on this amp.

Usually the latter can look a bit sloppier, and the solder on the trace side of the PCB may look newer or "shinier" than the factory soldered joints.

 

[JoshHendi]

You need to distinguish between a factory change in component spec (which may differ from some component values that are specified in the SM) and subsequent work that someone may have done on this amp.

Usually the latter can look a bit sloppier, and the solder on the trace side of the PCB may look newer or "shinier" than the factory soldered joints.

Yea I see the shiner solder joints on just the 4 diodes (didn't notice if the R05 solder joints were shiner, but I'd have to imagine so) so I am gonna get the board back to the service manual layout. Matched diode replacements and an 100ohm resistor. Thoroughly inspected the rest of the board and everything else is original

 

[JoshHendi]

It is possible that the positive regulator (TR01 / ZD01) isn't working properly and the 1400Ω resistor was the 'fix' - best check the output voltage at pin 15 after changing that resistor.

so i check TR01 and ZD01 and they both checked out working (and original)

Should I be good to go on just replacing the 4 diodes, changing R05 to 100hm?

 

[petehall347]

best check the output voltage at pin 15 after changing that resistor

 

[JoshHendi]

15 and 16 at 31v

Thanks for all the help guys!