How to measure voltage on 93 blues deluxe

[tbrogit]

Hey all,
Im trying to weed out a channel problem on my deluxe. I have read many posts on the deluxe involving replacing r71 and checking R86 and r85. I have replace r71 and that seems to be fine but I want to make sure Im getting the correct -16v and +16v on the rails. To be quite honest Im not quite sure how to measure this voltage.

If Im using the VOM and select DC votage.
I use the red lead to make contact with the left site of R86 and using the common lead connect that to the cathode side of c22. This reading is -21mv.

I use the red lead to make contact with the left site of R85 and using the common lead connect that to the anod side of c23. This reading os +21mv.

Any other readings for the right side of r86 and r85 to either side of the cr22 or cr23 are either 0 or ->150 .

Also the the positive 20 or -20 reading goes down as the amp is diispating voltage I assume.

Bottom line is im trying to check the -46 and -16 on r86 and +46 and +16 on r85.

Im taking these volatge reading with the amp unplugged. Im being very cautious so maybe im to take these reading plugged in.

So if someone can point me out to where the readings are taken I would appreciate it.

Thanks

[Enzo]

If the amp is unplugged, then none of the operating voltages inside it are present. Imagine you have a fan on your table to blow air at you, and you wondered how fast it was spinning. Hard to do when it is uplugged.

Safety first of course, but all voltage readings must be done with the amp operating.

Unless otherwise specified, all voltages are read with respect to ground. Meter red probe goes to whatever is being read, while black probe goes to chassis or other known ground.

[tbrogit]

Thanks Enzo. So if I was trying to check +40 and +16 dowstream I would need to check the lower reading at the end of the diode correct. In other words I should not measure there values by checking the two ends of the resistor correct? Sorry I know Im a newbie but Im actually learning quite alot and really appreciate the advice.

[Jazz P Bass]

It is perfectly acceptable to measure "across" a component.
It is a proper way to determine the voltage drop & current through the device.
What you want to do is hat Enzo recommended.
Black lead to chasis ground.
Red lead is your voltage probe.
As to "where" you measure, it depends what you want to measure.
In this case, yes, "downstream" is fine.

[Tom Phillips]

If you really have a DVM (Digital Volt Meter) then my comments don't apply here but...

...If Im using the VOM and select DC voltage. ...

What is the make and model of your meter? Is it really a VOM (Volt Ohm Meter)? That's old analog test instrument terminology. If it's really just a simple VOM then you may need to connect the read lead to chassis ground when you are measuring a negative DC voltage. The better VOMs had both DC+ and DC- function settings.
Cheers,
Tom

[tbrogit]

Thanks for everyones help. I was able to measure what I expected.
Take Care

[hrbay]

Never put both hands into a hot chassis....

An oldtimer, my dad, always said to keep one hand in my pocket when working live ... probably good advise.