[volt-nuts] Replace neons with LEDs in Fluke 845AB

[Dallas Smith]

Hi  Lou,

What voltage are on the 15 volt rails? They are not regulated ±1 volt 
seems reasonable. Check/Replace C117, C118, Q111, Q112; these are the 
only components that can significantly draw the supplies down. If your 
unit is like mine the carbon resistors have changed 30 % by now in the 
positive direction. Also check for the regulated +10 volt supply at 
CR105. What is the reading on your meter semi range of your digital ohm 
meter across the emitter/collector? When using digital ohm meter to 
check semi's, the reading is actually the voltage across the junctions. 
What is the six junction readings you get on the EBC on the transistors? 
(forward and reverse readings).

Dallas


On 6/7/2016 2:05 AM, Lou Amadio wrote:
> Hi Dallas, no, I do not have a curve tracer but I have an oscilloscope and
> function generator. What do you suggest?
>
> The +/-15v is really low so I need to do something.
>
> If I change to Si, are R207_8 likely to be lower or higher?
>
> Regards
>
> Lou
>
> ..............................................................................................................
> On 7 Jun 2016 2:26 am, "Dallas Smith" <dosmith at outlook.com> wrote:
>
>> Hi Lou,
>>
>> It's normal for some leakage in germanium transistors. Do you have a curve
>> tracer?
>> If you change them to Si you will have to re-bias them (i.e. R207_8).
>> The 84 Hz may change also, might have to adjust C203.
>> But should be possible.
>>
>> Dallas
>>