Can you post E,B,C voltages for TR4 and TR6 ?

Everything in that string is good. Retested T4 and T3 are good. Replaced T6. Made sure pinouts are all correct. Still showing voltage at the output.

When you plugged into the effects return with the guitar did it sound nice and clean ?
When you plug straight into the return jack you are bypassing the whole preamp and all the controls associated with the preamp.
A preamp boosts the guitar signal up a lot for the power amplifier, that's why a guitar straight in to the return is not very loud.
Do you have another amp you can use ?
Plug the send of another amp into the return  on the Fender and you will be using the preamp of the other amp and the power amp of the Fender.(guitar into other amp)
If that works then the Fender power amp is fine.
Try an overdrive pedal straight into the return and you are bypassing the preamp again.
You have to try to determine if the problem is the preamp or power amp.
Preamp is guitar input on front to the send jack on back.
Power amp is return jack to speaker out.

I'm looking for ideas. My friend's Fender Rumble 100 was working one day and the next day it wasn't. I told him that I would open up the amp and look for something obvious but I didn't see anything suspicious. On the normal channel, with the Gain and Master full up, it barely passes the sound of the guitar. On the Overdrive channel it is extremely noisy; so much so that it can't be used. And, as one starts to push that lower "vintage" tone button you can hear that loud beep tone. Plugging into the Effects Return jack yields a guitar sound that's fixed; a signal that isn't affected by adjusting the Gain, Volume or tone controls. I'll try to post links to the scheme and a short video.
Video
Schematic

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Quote from: RookieRecurve on March 31, 2024, 08:39:55 AMI see these pop up often around me, but not for that price!  There's one I saw for $100 with only one of the two channels working.  I thought about buying it to try and fix it, then flip it.  It would be too loud for me, but they are pretty amazing amps.  The ease of access to incredible schematics makes these a great buy.

I saw a guy on youtube that flips gear for a living and he nabbed one for $40! He said it was his very first amp so he made a video with it then sent it on it's way to someone who had bought it.

I am a shred and sweep player so it's a little harsh in the bass due to the very high, even order harmonics added by semiconductors, but in combining the dirty channel with my modeler and an overdrive pedal I actually designed around this amplifier's dirty channel used to overdrive the modeler, I get perfectly useable lead tones. I also have a Zoom G5 on the way to replace the one I have that some crazy b*t** smashed, and those with the 12AX7 in them turn damn near any amp into a thoroughbred.
That coupled with this and I have a brutal metal amp but really, an every genre amp. It's so friggin loud I could never actually use this much volume and in a live setting, I would definitely be using earplugs.

It's all about gain stage cascades and teaming the right devices. Solid-States have some universal problems shared by 99% of them, but Crate is highly underrated and players with really high standards would rather spend 3 grand on known gear combinations than experiment and get something built for $500 that is every bit as good as the 3 G's arrangement. The Zoom G5 is an example within itself because when you run the processor without the tube engaged, it's very digital and quite truly sounds cheap, but when you switch the tube in and crank it's gain, it makes every single patch you design for modeling whatever amp, pedal and speaker combination sound amazing. The harshness, "swooshing" etc. to your bass is completely filtered out of the signal by the tube's limited bandwidth. The 12AX7 is said to have a maximum of 20Khz for audio, but typical is actually 10 Khz. The semiconductors will add ridiculous harmonic bandwidth like 40 Khz to a 100 Hz bass note!
This trait is why solid-states continue to be the whipping boy of the industry and because digital circuits are still using solid-state semiconductors, 90% of those units aren't designed to compensate so the war wages on! I shutter at the sight of digital modelers and FX I see selling for $1500 and I can hear all those extremely high, even order harmonics still coming out of them and trashing the signal, but not every player is sweeping and shredding for it to matter.
The technology guarantees people will always spend big money on tube amps, and even I'm still guilty of that.

Quote from: Tassieviking on December 19, 2023, 12:06:40 PMIf you want to mess with the amp then you should leave the power amp section alone.
The pre-amp is where the tone shaping happens.
The closest you should go to the power amp is the 100nF cap going into the power amp, that 100nF cap with the 100k to earth is a HPF filter that drops any frequencies below 15.9Hz. Change to a 10nF cap and the frequency is 159Hz, experiment if you like.
I would concentrate on the tone stack, changes there will affect your tone more.

Are you sure it is not the speaker itself that is dark sounding ?

This is great advice here.  With the amount of variables in an entire setup, mucking with a SS can be difficult. Small electrical mods to your guitar, pedals, and adding an extension to play with cabinets and speakers will likely produce better results.

Old post, I know, but it's really solid information for anyone considering modding a SS.

I see these pop up often around me, but not for that price!  There's one I saw for $100 with only one of the two channels working.  I thought about buying it to try and fix it, then flip it.  It would be too loud for me, but they are pretty amazing amps.  The ease of access to incredible schematics makes these a great buy.

Thanks g1. I took a look at the resistors and transistors and R84, 85 and 86 seem to be out of spec. The transistors seem to read alright. I'm going to take a look at that site.

Quote from: saturated on March 29, 2024, 08:37:10 PMAlso it seems like the tube close to the doghouse (rectifier) looks kinda white ashen....idk.

 

If the Valve has a white haze then it has lost vacuum and it's DEAD.
Time for a new one, Phil