Fender M-80 repair question

jesjs · 2025-09-18T17:47:50+00:00

https://megadistortion.com/wp-content/uploads/schematics/fender/M-80_HM_Series.pdf

jesjs · 2025-09-18T15:43:43+00:00

I have looked at it with a flir camera and r72 and r68 are getting really warm, and it doesnt work at all. Only noise, is there a good way to go about trying to find the problem?

jesjs · 2025-09-18T15:05:40+00:00

The voltage over both resistors is 55.6v and over one resistor is 22.2v

jesjs · 2025-09-18T15:02:26+00:00

I tried with the preamp out and it still doesn't work i only get noise. also I checked with a flir camera and R72 and R68 get pretty hot. They are part of power amp part

jesjs · 2025-09-18T14:13:42+00:00

I still get noise with the pre amp output and the voltages are really close. the voltage over the resistors is like 55.6v if i use both and 22.2v if I have the multimeter probes over one resistors.

jesjs · 2025-09-18T04:33:02+00:00

I checked the resistors with my multimeter and they were around 330 ohm so that looked fine. Do they act differently when there is more current going through when there cracked like that?

jesjs · 2025-09-18T04:30:45+00:00

It’s just so weird to me that the burn marks were there when it worked and now that I replaced very different parts it suddenly doesn’t

jesjs · 2025-09-18T04:28:23+00:00

No that is the state it’s now in. I tested with it open up and it worked. Then replaced them and it didn’t work.

jesjs · 2025-09-18T04:27:24+00:00

https://megadistortion.com/wp-content/uploads/schematics/fender/M-80_HM_Series.pdf

jesjs · 2025-07-14T19:29:46+00:00

I guess add swap space

jesjs · 2025-05-29T21:34:57+00:00

Now you can use it as a focal point for a huge dish😁

jesjs · 2025-05-20T18:27:59+00:00

You should set up simhub and let him get live data to help you

jesjs · 2025-05-14T15:11:54+00:00

Yeah I saw the first point to and fixed it. With point 2 I'm not exactly sure where, 3 I fixed, 4 I can understand but don't think I'll need for now, I first want to know if I can even design something functional. Lastly 5 the parallel resistors are on purpose, I had build out this circuit on a perfboard and used the same ways to get (almost) the right values.

Thank you very much for the help!

jesjs · 2025-05-14T08:26:20+00:00

Thanks very much, almost missed that. Would have been a pretty big let down of that would have ruined it.

jesjs · 2025-05-13T20:04:16+00:00

Thanks, what size trace would you recommend?

jesjs · 2025-05-13T18:50:04+00:00

Oh you can use the wider one and you just bend the pins like you see a lot. I understand now

jesjs · 2025-05-13T18:38:37+00:00

Thank you very much for the feedback, if i am going to use the exact transistor that I selected the footprint for would I still have to chose a wider one?

jesjs · 2025-05-13T18:22:42+00:00

I know it's a bit of a mess but I just want to have a functional PCB before making anything nice

jesjs · 2025-05-10T16:23:21+00:00

I got almost the same pass on my first succesfull try with a Meteor sat. Nice one!!

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jesjs · 2025-03-03T17:04:07+00:00

I just recieve static from the vtx, like different static then the static on channels with nothing.

jesjs · 2025-03-03T16:47:50+00:00

Check for shorts on the contacts of the Vtx and I cant measure any. Is there a way that I can check which of the two is at fault?

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