Fender 100w twin amp no sound

Yes, though you'll have to wire them directly to the new head, not running itno the Frontman amp itself.

no filament power then, filament fuse open..blown winding on transformer, regulator bad..You an ET with shop full of tools...then we can get to work...

Do some quick tests to locate the fault area....
i) With all gain controls at minimum & amp warmed up, turn on the standby switch & observe the large output valves for sparking or flashing (could be breakdown in one of them).
ii) Remove V6 (12AT7). Is the crackling still there? If so, the fault is in the final output stage (four 6L6GT's).
iii) To test the output stage, keep V6 removed & remove V7 & V9. If the fault clears then one of those 6L6's is likely to be faulty.
iv) If the fault persists, reinsert V7,V9 & remove V8,V10. If fault clears, then V8 or V10 is the culprit.
v) If the fault still doesn't clear, then desolder coupling capacitors C22,C23 - which may be leaky.

I suspect the fault is the output stage valves, in which case it's best to buy a matched set of 4 & re-bias.

No valve tester is needed here!

... do you, by any chance, have non humbucking pick ups on your guitar? Just curious...

Not sure of how it is feeding back. Two possibilities... the reverb tank in the cabinet is no longer shock mounted. The other is your guitar can "hear" the speaker... make sure you are away from the amp. With the reverb on, the feedback stability is less than with it off so make sure your guitar is away from the amp. Acoustic guitars are more sensitive to this than solid body ones.

Do you have the speakers connected properly?? If so, maybe speaker wiring needs checked.

When i turn on my 212R it turns on in drive channel. if footswith is plugged in, then it turns on in the clean channel, but after switching in drive it is impossible to switch it back in clean channel. What could be wrong? Swith position doesnt change anything and it seems like switch is OK.

No, when you plug into the power amp in that disconnects the feed-through of the preamp.

if this a tube amp then your tubes might be going bad. but if it is a solid state amp then im not to sure whats going on.

First make sure you have the TRIM knob positioned correctly. When playing loud the Red Led should just blink a bit so you know you're not overloading the preamp and Digital sections. The Twin Reverb Patch is a clean place to start so select that first. On this amp it's a good idea to set the MASTER to 5 and use the VOLUME control at as low a setting as you can. The GAIN control should be set under 4. You better sound crystal clear on this setting. Try turning up the volume to see how loud you can get without breaking up. It's a guitar amp so there will be some grainy distortion but it should be very light. I bet you get through this test without much trouble. After that you need to be very careful about what settings you're using since many of the presets may not mesh with your guitar pickups. You should concentrate on tweaking one highgain setting and learn about how the controls interact. The amp is so much more complicated than a 10 knob standard guitar amp. Most people need to put in some time to get a handle on it.

As far as the tubes go, typically they can get microphonic which was a problem with versions 1.1 and 1.0 of this amp so check that. Fender had a Cyber twin upgrade kit way back to fix this but if you have version 1.2 or 1.3 that's not it. Problems with this amp are typically caused by control setting more often than an electronic problem but this reponse should get you started figuring it out.
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