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Yamaha Amplifier

Thanks for the information.
In the absence of a variac, is there anything I can do better than switch on and hope the outcome is ok?
 
Hi, can anyone confirm whether I need to move this XLR switch to the left?
I don't think I do need to, but just wanted to double check.
I've plugged in a male XLR to RCA converter plug which has pin 3 labelled as Ground.
The audio signal source will be unbalanced from a preamp.
 

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Should the AC mains cable have a ground connection?
This one doesn't. It's a UK model. Photos attached.IMG_6845 copy.jpg
 

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Well, that IEC jack is not the standard power input. Judging by the terminal strip along side, it appears to me there was not a provision for equipment ground in the original wiring, considering only L and N identified.

I suggest consulting the service manual, freely available online, then match up the model and wiring as best possible and go with what it shows in the service manual.
 
Thanks!
Just looked at the service manual pdf.
Looks as though it's wired in accordance with the UK model, which is fine for me.Screenshot 2021-01-25 at 21.22.49.png
 
Just discovered that 7 out of 8 meter bulbs are blown.
I think Mouser are out of stock. Can anyone recommend a supplier of good quality replacements?
 
Played music through it on some tiny speakers and all sounds fine with no crackles or hums etc etc.
Great!

Have adjusted bias to 10.0 mV on each channel.
Great!

Measured DC Offset and
Right channel is 2.8 mV
Left channel is 32.8 mV

Anything to be concerned about the DC Offset?
Any obvious candidates to look at for improving this reading?
 
After 10 mins..

Left channel is rock steady at 2.8 mV
Right channel flickers up and down between 28 mV and 36 mV.

Any suggestions from anyone?
 
Amp now working very nicely over long periods of time with no overheating or audible issues through small speakers but would greatly appreciate any guidance on the following:

  • Channel A speaker terminals give a DC offset reading of 33mV that constantly bounces/flickers around 3mV above and below this figure.
  • Channel B’s meter needle is initially slow to start moving, but after a few minutes it works perfectly. Any suggestions for most likely culprit?
  • Which company makes or supplies the best replacement bulbs for the meter displays?

  • Do the 4 Amp glass fuses on the back of the amp have to be ‘T’? Is it a problem if ‘F’ fuses are used?
 
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