JTM 45 Input Section Issues..

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tonehunt1679
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JTM 45 Input Section Issues..

Post by tonehunt1679 » 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.

Tazin
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Re: JTM 45 Input Section Issues..

Post by Tazin » Tue Aug 08, 2017 4:39 pm

Did you use the correct type of Cliff jack? They should be the "shorting" type not the "open" type. Could also be the 'link' wires between the High and Low jacks are incorrectly placed. Are the 1meg resistors correctly intstalled?
You can also use a multimeter set to continuity check what is going on when you plug a cable into the High input.

tonehunt1679
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Re: JTM 45 Input Section Issues..

Post by tonehunt1679 » Tue Aug 08, 2017 6:06 pm

Thank you for the reply. I ordered the kit from Valvestorm, so I'm assuming the Cliff Jacks are correct, when I get home I will look into that and make sure they are the correct ones. I still can't post pictures.. when I try to upload a picture of the Input Jack wiring it says, "Sorry, but the board attachment quota has been reached". If you gave me an email perhaps I could send them to you that way, I'm not sure how else to show you what's going on inside the amp. With the amp opened up and flipped over so you're looking at the inside of the chassis, the resistor is installed across the bottom to prongs of the bottom input jack, again matching the Metroamp instructions I have. I'm not sure if any of this is helping, because I may very well be looking at this THINKING I'm right and have something wired wrong, just like you said. if there is any other way to upload pictures, please let me know. I'm doing what I can to not be difficult to work with. Again, thanks for taking the time out to try to help me.

tonehunt1679
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Re: JTM 45 Input Section Issues..

Post by tonehunt1679 » Tue Aug 08, 2017 7:58 pm

I think I may have found the issue. Again.. I think it's something stupid that is staring me directly in the face. Would a resistor of the wrong value stop the input jacks from working? I seem to have put in a 100k resistor instead of a 1M resistor. (Brown Black Yellow instead of Brown Black Green). I am hooking up the soldering iron now to fix this issue and hopefully I'll have all four inputs working. I'll keep you updated.

Tazin
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Re: JTM 45 Input Section Issues..

Post by Tazin » Tue Aug 08, 2017 8:00 pm

The Metro board no longer allows photo uploads so you have to use a photo hosting site (there are a few free sites out there).

Tazin
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Re: JTM 45 Input Section Issues..

Post by Tazin » Tue Aug 08, 2017 8:01 pm

tonehunt1679 wrote:I think I may have found the issue. Again.. I think it's something stupid that is staring me directly in the face. Would a resistor of the wrong value stop the input jacks from working? I seem to have put in a 100k resistor instead of a 1M resistor. (Brown Black Yellow instead of Brown Black Green). I am hooking up the soldering iron now to fix this issue and hopefully I'll have all four inputs working. I'll keep you updated.
Possibly....

tonehunt1679
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Re: JTM 45 Input Section Issues..

Post by tonehunt1679 » Tue Aug 08, 2017 10:38 pm

That was it!! Thanks for helping me talk this out, lol. I appreciate it. The right resistor is in and everything is working flawlessly. Again, many thanks. Cheers, and happy playing! -Tonehunt1679

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neikeel
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Re: JTM 45 Input Section Issues..

Post by neikeel » Wed Aug 09, 2017 6:42 am

Just saw this thread
Well done for troubleshooting - very satisfying isn't it? Almost better than a perfect build out if the blocks.
That is ho you get into modding and experimentation when your builds are perfect straight away!
Neil

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