JTM 45 Input Section Issues..
Posted: Mon Aug 07, 2017 7:48 pm
Hello everyone, this is my first post on the Metropoulos Amp Forum. Thank you to whoever is taking the time out to read this, I appreciate this forum and everyone's willingness to help. Without out further delay, I'm just gonna jump right in.
I recently just finished building my very own JTM45 amplifier. It's working great, but the only thing I am having trouble with is the 4 jack input section. All of the tone controls work as intended, as well as both volume controls. However, I am only getting signal when I plug into the low level inputs of each channel. In other words, The bottom right and bottom left inputs work flawlessly, but I am getting zero signal from either the upper left or upper right inputs. This is my first every amp build, so I know there are going to be some issues, which is why I'm coming here. Here is what I've tried so far:
The top inputs have never worked, even when the amp was first plugged in. I was so excited to get such a killer tone out of the bottom right input that I didn't care and kept playing. After a while the bass and mid controls cut out completely. I opened the amp up again and discovered that the second grouping of 68k resistors came unsoldered and there was also a bad ground on the pot bus. I re soldered those joints but the mid and bass controls still did not come back. I had all the circuitboard wiring underneath, so I couldn't see what was going on. After not getting results, I decided to undo all the wiring and re solder all of the wires around the top of the board, where the components are. It looks much cleaner, and to my relief, the bass and mid controls were back to functioning capacity (I'm assuming it was a bad ground solder underneath the board). The top inputs still do not work, even though I rewired and double/triple checked that I had everything right according to my MetroAmp instructions, schematics, and pictures online.
It's safe to say that I am stumped. I checked the resistors on the input jacks for corrosion or breaking/cracking, I've checked for cold solder joints, and I'm confident that the Cliff Jacks themselves are in good shape. I'm convinced that I am missing something both completely silly and right in front of my face, and I'm hoping someone here will be able to point it out for me. The wiring is on top of the board and it's clear enough to see what's going where, just in case I made a silly wiring error. Tubes are in good shape, and the wires themselves are good(no slicing or break in the wires). Very thankful for this forum so that I could ask for your help!! Thanks so much in advance. For some reason I'm having a hard time attaching pictures. It says the board attachment quota has been reached.
I recently just finished building my very own JTM45 amplifier. It's working great, but the only thing I am having trouble with is the 4 jack input section. All of the tone controls work as intended, as well as both volume controls. However, I am only getting signal when I plug into the low level inputs of each channel. In other words, The bottom right and bottom left inputs work flawlessly, but I am getting zero signal from either the upper left or upper right inputs. This is my first every amp build, so I know there are going to be some issues, which is why I'm coming here. Here is what I've tried so far:
The top inputs have never worked, even when the amp was first plugged in. I was so excited to get such a killer tone out of the bottom right input that I didn't care and kept playing. After a while the bass and mid controls cut out completely. I opened the amp up again and discovered that the second grouping of 68k resistors came unsoldered and there was also a bad ground on the pot bus. I re soldered those joints but the mid and bass controls still did not come back. I had all the circuitboard wiring underneath, so I couldn't see what was going on. After not getting results, I decided to undo all the wiring and re solder all of the wires around the top of the board, where the components are. It looks much cleaner, and to my relief, the bass and mid controls were back to functioning capacity (I'm assuming it was a bad ground solder underneath the board). The top inputs still do not work, even though I rewired and double/triple checked that I had everything right according to my MetroAmp instructions, schematics, and pictures online.
It's safe to say that I am stumped. I checked the resistors on the input jacks for corrosion or breaking/cracking, I've checked for cold solder joints, and I'm confident that the Cliff Jacks themselves are in good shape. I'm convinced that I am missing something both completely silly and right in front of my face, and I'm hoping someone here will be able to point it out for me. The wiring is on top of the board and it's clear enough to see what's going where, just in case I made a silly wiring error. Tubes are in good shape, and the wires themselves are good(no slicing or break in the wires). Very thankful for this forum so that I could ask for your help!! Thanks so much in advance. For some reason I'm having a hard time attaching pictures. It says the board attachment quota has been reached.