Peavey Max 115 Blown L1 & L2 Coils

[EndToEndAudio]

Blown L1 and L2 coils in power output section. Initial issue, powers on, plays for about 20 mins then emits super shitty digital noise. I swapped for equivalent coils and replaced resistors in area. Also replaced U5, TDA8954 chip. Now have no output at all. Power and preamp is fine as I have headphone out. Any ideas? Thanks.

[Jon Snell]

Schematic?
Check your work if it now doesn't run anymore.

[glebert]

There are a few different versions of the MAX 115. This is one of them and has TDA8954. When you say power is fine does that mean the voltage rails?

[Jazz P Bass]

"Check your work"
Check the soldering of the TDA output ic pins.

[Jon Snell]

Failure of L1 & L2 is caused by the tuning capacitors leaking; C21 & C26. They are rated at 63volts, very close to the rail voltages.
Another cause is square wave overload distortion, producing large amounts of HF that see C21 & C26 as a short circuit.
The TDA very rarely fails!

[EndToEndAudio]

My work of the chip is really good aside from the massive error of removing the pcb pad 12 when removing old chip. Schematic says 12-NC so I thought I should be good? Output of chip +/- should be 16 and 21.

https://www.nxp.com/docs/en/data-sheet/TDA8954.pdf

Definitely going to check my work again today. Break out the microscope.
I'm impressed with the thorough responses on this site. I appreciate it.

[EndToEndAudio]

Is it strange that I don't have continuity between coils and corresponding chip pins?

Also, please check my choice of coil replacement? I replaced coils with this part:

https://www.mouser.com/ProductDetail...3v2JgzdQ%3D%3D

[EndToEndAudio]

Tuning caps measured good for farads with my fluke. HOWEVER, I do not have an ESR meter. Is an ESR meter necessary? I haven't been able to spend the $150 on a Peak but if I want to do this level of repair I might have to.

Thanks

[g1]

My work of the chip is really good aside from the massive error of removing the pcb pad 12 when removing old chip.

Is it double sided board? If so you may have lost a connection between top and bottom at pad 12.

[velobob1@gmail.com]

Same issue…wondering who to take/ship it to to fix. Local amp guy won’t work on stuff that’s not tube

[Enzo]

Find a different amp tech. "I only work on tubes" guys scare me. He may be great at tubes, but It suggests they have limited electronic skills. Any competent tech can handle this work.

Welcome to the forum. As a new guy, may I suggest adding your location to your profile. When we try to assist it matters if you are in the USA or the UK or VietNam. If you don't want to be specific, even just East coast, midwest, or west coast would help

And I might also suggest putting your email addy online can result in unwanted spam, if one of the many netbots finds it.

Go to the Peavey support web page and see if there are authorized shops near you:
Peavey Electronics Corporation

And sometimes it can be useful to check other brands for service centers. Anyone rated for Fender or Roland or any of a number of others, is likely to be well able to handle this.