Orange OR80 Combo Repaired!

[HNB]

My vintage Orange combo has been making a weird distorted noise off and on. I wanted to see if you guys might know the cause. I am hoping it is something simple like tubes going bad or something. You can hear it in this demo of a guitar I just sold.

https://youtu.be/CMnVgxJsnrQ?t=13

[JSett]

My vintage Orange combo has been making a weird distorted noise off and on. I wanted to see if you guys might know the cause. I am hoping it is something simple like tubes going bad or something. You can hear it in this demo of a guitar I just sold.

https://youtu.be/CMnVgxJsnrQ?t=13

Yeah, swap some new power tubes in to check. My old '74 OR120 would do that sometimes when a tube was going bad. It burnt out a screen resistor in the process so worth opening it quickly and checking one or both isn't cooked a little.

[HNB]

I checked the tubes and the power tubes are so bulky they don't want to sit right. I am going to order a new set. I checked the resistors and they look ok.

20230425_121744 by Christopher Louck, on Flickr

20230425_121713 by Christopher Louck, on Flickr

[HNB]

I ordered a set of JJ EL34-6CA7 power tubes that are matched. Hopefully that does the trick. The shape of them will definitely sit better.

[Dr Tony Balls]

UF, yeah those KT88s (or 66s?) should not be in there. That noise might even be caused by one tube making intermittent connection because the glass envelope is keeping it from seating correctly.

[andy_tchp]

Wowsers, that's a new one.

[HNB]

They are Groove Tubes 2af? There is no labeling on the glass to say what they are.

2023-04-26_10-54-56 by Christopher Louck, on Flickr

[JSett]

Yeah, I concur, those aren't the right tubes at all

Fuck those off and put in some proper ones. It'll be much happier for it. FWIW I used to just run standard issue JJs in my one and ran them hard every single week at rehearsal and at all our gigs. Never skipped a beat. I did use to change them every year regardless though, as I don't want any unexpected failures...I figured £40/year or whatever it was was a small outlay considering I did all the tech work myself.

[OffYourFace]

They are Groove Tubes 2af? There is no labeling on the glass to say what they are.

2AF is not the model number. It's most likely something to do with matching. Those are most likely KT66s but could also be KT77 or KT88.

But someone could've changed a resistor to make those tubes work. You might want to take it to a tech and have it biased. Otherwise, it'll either sound cold or too hot and burn out the tubes. Tubes are expensive now!

[HNB]

Here is a gut shot. If I am understanding what I read correctly, the bias pot should be the one closest to the power tubes. The other is a noise adjustment pot? Here is a picture.

2023-04-26_12-55-33 by Christopher Louck, on Flickr

[JSett]

Here is a gut shot. If I am understanding what I read correctly, the bias pot should be the one closest to the power tubes. The other is a noise adjustment pot? Here is a picture.

2023-04-26_12-55-33 by Christopher Louck, on Flickr

Yep, the one in the middle-ish is the bias, the other one on the far left is the hum balance. I used to bias mine at 34-38 on my BiasRite.

[OffYourFace]

See that resistor in the middle with the sloppy solder joints? That could be the bias range resistor. You need to determine if that's the right size for EL34s

[JSett]

See that resistor in the middle with the sloppy solder joints? That could be the bias range resistor. You need to determine if that's the right size for EL34s

Yeah, check the one on the right. Also, now I've zoomed-in, there looks to be a jumper installed on another resistor (left circle)

[HNB]

I am not anywhere near knowledgeable about schematics, but this seems to be one for this amp?

http://www.orangefieldguide.com/OFG_SCH ... hem_74.gif

[HNB]

If I am reading the color bands right it is 1.5k Ohms? Brown Green Red Gold?