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Hello all.
I try my best to stick with tubes.. but I also try to help the local solid state guys out when I can (this is not one of those times so far! Haha)
Apparently these amps are highly sought after these days and can go for a good amount of money. So figured it was worth looking at.
Do the usual basic checks..
It appears to have an issue with the preamp.
(very low output, no overdrive. Sounds clean n both channels, and very low volume. )
And plugging directly into the return isn’t as loud as it should be either. But one thing at a time!
I swapped the 4558 IC’s as they’re socketed and was a quick swap to see if one had failed. No change.
I changed the two 3.3 uf caps as they had very high ESR. No change. The rest are what appear to be factory Nichicon. And all testing ok thus far.
I reflowed any suspect solder joints.
I’ve tried tracing the signal with my scope. Can’t seem to make much headway.
The signal comes in from the input jack. And then it is immediately pulled down… which seems odd. Unless it’s designed to be lowered for an amplifying stage.
And then we get back to my lack of understanding solid state devices still. And why I try to steer clear. But even newer tube amps use solid state devices.. so I’m always trying to learn more. At least to be able to diag basics when I run into them.
Is there a way of explaining transistors and the IC’s
like gain stages of tubes? Like grid to plate?
stuff I could easily look for on any transistor or IC?
Certain common voltages to look for etc?
I have trouble with understanding how they turn on and off with certain voltages still. And what certain things they need, to look for, for them to work properly.
Always appreciate any and all help! I’ve learned so much from the very experienced techs on this forum.
This one.. which looks seemingly very simple.. has me lost in the weeds currently. I don’t even know what to look for or test next at this point.
Here’s a couple pics and a schematic. I need to work on something else for a bit to clear my head of this one! Haha
Thanks in advance!
I try my best to stick with tubes.. but I also try to help the local solid state guys out when I can (this is not one of those times so far! Haha)
Apparently these amps are highly sought after these days and can go for a good amount of money. So figured it was worth looking at.
Do the usual basic checks..
It appears to have an issue with the preamp.
(very low output, no overdrive. Sounds clean n both channels, and very low volume. )
And plugging directly into the return isn’t as loud as it should be either. But one thing at a time!
I swapped the 4558 IC’s as they’re socketed and was a quick swap to see if one had failed. No change.
I changed the two 3.3 uf caps as they had very high ESR. No change. The rest are what appear to be factory Nichicon. And all testing ok thus far.
I reflowed any suspect solder joints.
I’ve tried tracing the signal with my scope. Can’t seem to make much headway.
The signal comes in from the input jack. And then it is immediately pulled down… which seems odd. Unless it’s designed to be lowered for an amplifying stage.
And then we get back to my lack of understanding solid state devices still. And why I try to steer clear. But even newer tube amps use solid state devices.. so I’m always trying to learn more. At least to be able to diag basics when I run into them.
Is there a way of explaining transistors and the IC’s
like gain stages of tubes? Like grid to plate?
stuff I could easily look for on any transistor or IC?
Certain common voltages to look for etc?
I have trouble with understanding how they turn on and off with certain voltages still. And what certain things they need, to look for, for them to work properly.
Always appreciate any and all help! I’ve learned so much from the very experienced techs on this forum.
This one.. which looks seemingly very simple.. has me lost in the weeds currently. I don’t even know what to look for or test next at this point.
Here’s a couple pics and a schematic. I need to work on something else for a bit to clear my head of this one! Haha
Thanks in advance!
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