[Boatanchors] need to replace?

[Richard Knoppow]

     To clarify, you do not need to remove the tubes to make resistance 
measurements. Disconnect the power. Many maybe most, resistors can be 
checked in place. Note that if a resistor reads much higher than its 
marked value its bad, if it reads lower see what is in parallel with it.
    Carbon composition resistors almost always go up in value with age. 
The higher the marked value the more its likely to have drifted.
    Capacitors in the circuit can cause resistance values to read wrong 
when there is no problem. Reverse the leads to the ohm meter to see if 
it reads the same both ways.
     Resistance measurements are done with no power applied so no damage 
can be done. It is a fairly powerful method of trouble shooting. If the 
resistance measurements are reasonably close one can then make voltage 
measurements. In all cases be sure of what you are measuring. Voltage 
measurements in the handbooks were made with voltmeters having certain 
characteristics. Make sure the input resistance of the meter you use 
matches the meter used for the handbook measurements. For most fairly 
modern equipment the meter will be either a VOM with 20,000 ohms/volt 
input or a VTVM, typically with 10 or 11 megohm input. Some very old 
equipment will have been measured with a 1000 0hm/volt meter, so 
readings will be high with a higher resistance meter. In general a VTVM 
or DVM is necessary to measure grid bias circuits because they are very 
high impedance. Most DVM's also have 10Meg or 11Meg input impedance. 
Higher impedance will generally not cause significant errors.
    Again, general rules for trouble shooting is 1, know your tools. 2, 
know what you are measuring . 3, Check power supply first. 4, Follow the 
signal path.

On 9/23/2024 5:16 PM, Mark K3MSB wrote:
> As Al said, replace the electrolytic capacitors.
> 
> Remove the tubes.   Look at the schematics.   You can test a lot of
> resistors in circuit as capacitors will isolate resistors for DC
> measurements.   Use tube pins as one node for measurements.
> 
> Then try the signal generator.
> 
> 73 Mark K3MSB
-- 
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998