Orange OB1-300 Amp Repair HELP

[Splatterpunx]

Hey there! I need some help figuring out and identifying some resistors in my amp. Long story short, years ago was playing a gig and liquid (definitely beer I play punks shows and people fling beer around sometimes) got into my amp and it blew up. Years later I hung onto it and have been taking some amp repair classes. Now I'm currently trying to repair this head. I already know what needs to be replaced. Orange was kind enough to label the parts they used on the board itself. My problem is a group of 4 resistors. The resistors themselves are too scorched to identify and the spot where the part is labeled (right underneath them) is also scorched so I can't read it either. Im hoping one of you kind folk who also owns an OB1-300 or 500 and can take a nice clear picture of this section and tell me what is labeled underneath. Orange will not provide schematics and pictures online of the inside of the amp are not good enough.

The resistors are as followed- R64, R65, R70, and R82. The pictures I provided is the best pic online that I can find and the second pic is my amp both have the sections I'm referring to circled in red. Any help will be greatly appreciated!!!!!

 

[MARVIN MECKLER]

This'll be a good one!

 

[agedhorse]

You will find a whole lot more parts than those resistors that have failed. Do you have a meter, current limited variac supply, the schematic, scope and signal generator so that you can confirm your newly acquired amp repair education?

Since you posted that the manufacturer would not provide the schematics, you will have your work cut out for you (based on my experience). I can not share anything that I have, sorry. You might look at the complementary side to see if that yields a clue, but some topologies use a current source on one side which can be very misleading.

 

[Splatterpunx]

You will find a whole lot more parts than those resistors that have failed. Do you have a meter, current limited variac supply, the schematic, scope and signal generator so that you can confirm your newly acquired amp repair education?

Since you posted that the manufacturer would not provide the schematics, you will have your work cut out for you (based on my experience). I can not share anything that I have, sorry. You might look at the complementary side to see if that yields a clue, but some topologies use a current source on one side which can be very misleading.

The instructor and I went through the whole thing and found out what needs to be replaced. He seems to believe it's repairable if I can find the right parts and dudes been doing amp repairs for 40+ years so I trust his opinion. If it doesn't work and blow up again oh well. Atleast I got some solder practice. But if it does work hell yeah! I just think it's worth a shot cuz it's such a cool amp. Thanks for the input.

 

[agedhorse]

Well good luck then.

 

[tadawson]

See if you can read the color codes off the undamaged picture . . .

 

[Splatterpunx]

See if you can read the color codes off the undamaged picture . . .

I've been trying lol. The pics online aren't very good quality and my phone screen is very good quality either so it very hard to distinguish the colored stripes.

 

[lowdownbp5]

For me it would be a trip to the recycle center

 

[S-Bigbottom]

This will be a good Final Project for your class, making new traces and all.
Good luck.

That photo you are using in the first post is from @NickRich who has not been here since 2021 so he will not be able to get a tighter shot than his post in the Amp Guts thread.
https://www.talkbass.com/threads/am...s-see-those-pics.513929/page-82#post-25071783

See if someone with a big screen can blow it up cleaner for ya.
I meant the image, not the amp.

 

[S-Bigbottom]

This should be readable for your Teacher.

 

[agedhorse]

This should be readable for your Teacher.


View attachment 5475410

I would never rely on color codes on 1% metal film resistors from a photo, there are way too many colors that are not clearly discernible. Very different than 5% carbon film due to the body color difference.

 

[S-Bigbottom]

Darn right, I was not going to try to pic colors from that image.

 

[radrusspdx]

I realize that I am a few months late on this reply, but I was searching for an OB1 schematic and stumbled on this thread. Here is a picture of that area taken with my microscope. From left to right it looks like 560Ω, 560Ω, 100kΩ, and 4.7Ω.

 

[rickdiculous]

I've been trying lol. The pics online aren't very good quality and my phone screen is very good quality either so it very hard to distinguish the colored stripes.

I realize that I am a few months late on this reply, but I was searching for an OB1 schematic and stumbled on this thread. Here is a picture of that area taken with my microscope. From left to right it looks like 560Ω, 560Ω, 100kΩ, and 4.7Ω.

View attachment 7028010

Did you ever find that schematic?