Help with new to me ST-120 Stereo Amplifier - Scratchy noise in right channel
- Thread starter Jeepnmon
- Start date
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- vta st-120
It's the small "transistor-like devices mounted on the top side.
nj pheonix
Lunatic Member
Sorry to hear that Bob was always great to work with. Roy was hit and miss.
check the connections on the grey resistor that sitting more or less vertical, and measure it directly at the resistor to see what it has to say for itself. If its not 10 ohms and/or the solder isn't good, swap the resistor or fix the solder as appropriate. Looks like a 1 watt metal oxide resistor.
and again to be contrary, the LM334 will have nothing to do with the funny bias measurements on this tube. Whether its the cause of the noise or not I don't know, but my usual method for fixing things is to take care of things I know are not working and go from there.
trainbuftony
Electron Herder
I've unfortunately got to be that jerk this morning.
In the close up photo of the tube socket you posted, the original builders soldering technique leaves a lot to be desired.
The correct way to attach wires and component leads is via a mechanical connection prior to soldering. That means they must go through the hole, and wrap tightly around the terminals before soldering.
The builder of your unit put the lead in the hole and filled the remaining space with a glob of solder as if it was hot melt glue.
No wrap, no mechanical connection...
Personally I'd go through every single socket and correct that first. Order what you need to order to put that right. Solder is a lousy adhesive and will crack and you won't see the crack and it will crackle and pop and annihilate any device down stream...
Go ahead, ask me how I know.
Start by desoldering all the pins and wires from The problem socket. Make every wire wrap tightly around the terminal and once its mechanically secure melt lead into the joint.
Someone once said that your amp should work without solder....
Point of that remark, is that there should be no connections that are intermittent, every one of them should be crimped to the terminals with enough force that no motion occurs between parts.
Has to be that way, not because I said so, but because those are the best practices.
In the close up photo of the tube socket you posted, the original builders soldering technique leaves a lot to be desired.
The correct way to attach wires and component leads is via a mechanical connection prior to soldering. That means they must go through the hole, and wrap tightly around the terminals before soldering.
The builder of your unit put the lead in the hole and filled the remaining space with a glob of solder as if it was hot melt glue.
No wrap, no mechanical connection...
Personally I'd go through every single socket and correct that first. Order what you need to order to put that right. Solder is a lousy adhesive and will crack and you won't see the crack and it will crackle and pop and annihilate any device down stream...
Go ahead, ask me how I know.
Start by desoldering all the pins and wires from The problem socket. Make every wire wrap tightly around the terminal and once its mechanically secure melt lead into the joint.
Someone once said that your amp should work without solder....
Point of that remark, is that there should be no connections that are intermittent, every one of them should be crimped to the terminals with enough force that no motion occurs between parts.
Has to be that way, not because I said so, but because those are the best practices.
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@trainbuftony hits it on the head. I saw that too but didn't want to be the jerk but he is right. Solder isn't glue. Do as he suggests on the noisy socket. If that fixes it, you know what you have to do. You could try reflowing the solder on the pins of that socket as a first troubleshooting test.
Happy hunting,
John
Happy hunting,
John
I still have my assembly manual and all documentation that came with my kit. If there's anything you would like me to post just ask. I expect all of it is available on the internet (almost everything is of course) but if not I can post it
Lavane
Lunatic Member
Good to know.
I agree. A noisy resistor in one of the early stages would be my guess.
I doubt the soldering is the problem. Wrapping wires round the sockets before soldering may be considered "correct" but it makes it a pain to unsolder anything and I doubt the joints are so bad that they're causing a problem.