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Help hooking up replacment transformer

gadget73 said:
parallel 300B meaning 2 per channel. That could be push-pull or single ended parallel but some pics of the guts would answer that. If one per channel, its just straight up single ended.


drag and drop the pics into the reply window. If you have several, drop them all, then click the "all thumbnail" option
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I'm pretty sure it's just straight-up singled ended. The 300B is hard to see from the photo of the full underside, but it's in the upper right hand side between the choke and the white caps, green resistor, under the purple electrolytic.
 

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That 220uF/250V cap is close enough to get a lot of heat from the green power resistor. That heat will reduce the life of that capacitor significantly. May want to move it away if at all possible. Just FYI.
 
fmjunkie said:
They also sound a little "thin".
Click to expand...
It would be worthwhile to determine the low frequency output power capability of the James JS-6123HS transformers at the DC current you're running.

Here's a page that compares a few of the popular SE OPTs, including this one. It's not enough to determine full-power output, but it does provide a few clues. I've read posts here and there from owners claiming bass response isn't great.

http://www.sacthailand.com/Transformer_TestOutput.html

Jack
 
Last edited:
Thanks Jack, and good point THD+N. I'm leaving town for the weekend, but will check those caps out when I have some time next week. I don't know how much time was put on these amps, but that section may be problematic.
 
The power transformer is fairly close to the input circuitry. Maybe try removing the fasteners for the power transformer that hold it to the chassis and slowly rotate the power transformer to see if the hum changes in amplitude.

Also the the primary of the output transformer wiring runs right next to the choke, looks like it even touches the choke. This could be inducing EMF into the signal there.

How did you determine it was 60Hz hum? Did you use a scope or just by ear?
 
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