Fender Red Knob Twin (1987-1994) aka THE TWIN upgrades

[jalexquijano]

Can anyone recommend any real upgrades for a Fender Red Knob Twin? Is it worth swapping the original speakers and Output Transformer? My amp sounds perfect at the moment. However sometimes once the amp warms up you can hear some frying bacon or frying eggs noises in the background. Then after some minutes it dissapears.

[Enzo]

If it sounds perfect, what is there to upgrade? The occasional noise sounds like a problem to solve, not something needing upgrades.

You have to decide what you want an upgrade to DO. Is it worth replacing speakers and transformers (on an amp that sounds perfect)? I don't know, what do the present parts not do as well as you'd like? CHanges to an amp ought to have a purpose.

[jalexquijano]

Frying bacon / Egg background noises elimination

Where should i look then to eliminate those occassional frying bacon or egg background sound??? I have already changed all the filter caps, most of the potentiometers, power resistors.

I have not yet changed the orange drop caps that are found on the pcb where the control pots are mounted.

[Enzo]

Noises: first thing to look at is tubes, they are the most common source of noise. Resistors get noisy, particularly those in the plate leads. Carbon composition ones in particular. Oxidized tube socket pins can cause noise. I don't think of caps as a source for that noise. You could even have some contamination on the circuit board.

The approach is to isolate the problem. When it makes noise, does turning all the controls to zero make it stop, or does it continue anyway? If zeroing all the knobs kills the noise, then turn them back up and find out which one do or do not affect the noise in ANY way. In other words, if a volume control affects how loud the noise is, or if a tone control affects the tone of the noise, then the noise is coming from before those controls in the circuit. If they have no effect, then the noise is coming from after them.

[jalexquijano]

Noises: first thing to look at is tubes, they are the most common source of noise. Resistors get noisy, particularly those in the plate leads. Carbon composition ones in particular. Oxidized tube socket pins can cause noise. I don't think of caps as a source for that noise. You could even have some contamination on the circuit board.

The approach is to isolate the problem. When it makes noise, does turning all the controls to zero make it stop, or does it continue anyway? If zeroing all the knobs kills the noise, then turn them back up and find out which one do or do not affect the noise in ANY way. In other words, if a volume control affects how loud the noise is, or if a tone control affects the tone of the noise, then the noise is coming from before those controls in the circuit. If they have no effect, then the noise is coming from after them.

Just a short list of what i have replaced in the amp:

1- All power tubes

2- All preamp tubes

3- All preamp tube and power tube sockets

4- Front input jacks (Stereo PCB 9 pin jacks)

5- Power resistors

6- volume 1 and Treble 1 pot on channel 1

7-Gain pot on channel 2

8- Carbon composite resistors across power tube sockets were replaced with Metal Oxide resistors

9-All Filter caps including bias caps

10- New reverb tank

The ocassional frying bacon noise appears every once in a while even with the amp in zero (shows in the background) You can barely notice it when playing. Based on your theory the noise is coming after the control pots as moving them do not affect.

[JoeM]

I've had the frying bacon sound occur due to dirty tube pins/sockets. Now I routinely clean all the tube pins with De-oxit Gold.

[Gtr_tech]

Noise caused by tube socket connections can usually be chased down by moving the tube(s) around in the socket. I've gotten in the habit of polishing the tube pins (mainly preamp tubes) with a dremel and a wire wheel. They can get weird....I dunno what they were plated with but it can cause problems over time. Deoxit on a toothpick works well to clean the socket.

Reading the laundry list above, I'd say look to plate load resistors ('specially in the phase inverter if the master vol doesn't affect the noise), and reflow any suspect solder joints.

[jalexquijano]

Noise caused by tube socket connections can usually be chased down by moving the tube(s) around in the socket. I've gotten in the habit of polishing the tube pins (mainly preamp tubes) with a dremel and a wire wheel. They can get weird....I dunno what they were plated with but it can cause problems over time. Deoxit on a toothpick works well to clean the socket.

Reading the laundry list above, I'd say look to plate load resistors ('specially in the phase inverter if the master vol doesn't affect the noise), and reflow any suspect solder joints.

Please read my list. I have already changed all preamp and power tube sockets. They are all Brand new. I dont think i will need to use DEOXIT or contact cleaner. Something else must be causing the frying bacon noises. Please bear in mind this is not always present it is intermittent.

[Leo_Gnardo]

I have already changed all preamp and power tube sockets. They are all Brand new. I dont think i will need to use DEOXIT or contact cleaner. Something else must be causing the frying bacon noises. Please bear in mind this is not always present it is intermittent.

A new tube does not guarantee a good tube. Possibly one of your new preamp tubes is causing this problem. You may be able to track it down by replacing one at a time. And yes, tracking "intermittent" problems like this is time consuming & frustrating.

If you have a "The Twin" that is this well-behaved, count yourself lucky. They have a reputation for being problematic amps. There's a reason some call them "The 'Evil' Twin". I have one that intermittently loses volume. Haven't been able to fix that problem & it's been months. Lucky the owner is very patient.

Now I gotta go fry some bacon for real, breakfast calls!

[gbono]

So do you hear the noise at the pre amp output? What about injecting a know good signal into the power amp when the problem occurs? Tricky.

Assume that these jacks have been inspected and cleaned?

[g1]

Reading the laundry list above, I'd say look to plate load resistors ('specially in the phase inverter if the master vol doesn't affect the noise), and reflow any suspect solder joints.

Plate load resistors are a somewhat common cause of intermittent "bacon frying" noises. Sometimes freeze spray or a heat gun will help find which one is causing the problem.