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

[Lou Amadio]

Hi Dallas
Thanks for all the replies. Hope I am not inconveniencing you too much.

Q203, NPN, 2N1304: EB/BE=Hi/0.23, CB/BC=Hi/0.24, EC/CE=Hi/Hi
Q204, NPN, 2N1304: EB/BE=Hi/0.27, CB/BC=Hi/0.25, EC/CE=Hi/Hi

Checked all diodes on both PCBs - all OK.

Nothing getting hot anywhere.

C119 is now a link feeding the LEDs, which illuminate BTW. So, some output
from T202 at least

Still, I am beginning to suspect transformer T202, but how do I test it?

Next step is to disconnect the power supply PCB from the main board and see
if I can get +-15v with no other load.
Regards
Lou

On Wed, Jun 8, 2016 at 3:24 PM, Dallas Smith <dosmith at outlook.com> wrote:

> Hi Lou,
>
> I believe that the transistors are good. If they do not run to hot to hold
> on to.
> Yes CR105 feeds the negative supply. Did you check CR104 and CR105?
> Q203 and Q204 should also be check since they could shunt the transformer.
> Is transformer T202 and T203 hot. The high voltage windings on T202 could
> be leaky.
> Try taking out C119, did rails go to approximately 15 volts?
> Time to start isolating the supplies to various circuits to find the
> culprit by removing one leg of various resistors.
> You can deal with the carbon resistor accuracies later.
> I had all many issues with my meter, after all their very old.
>
> Dallas
>
> On 6/7/2016 11:09 PM, Lou Amadio wrote:
>
>> Hi Dallas
>> I set my DMM on Diode Check mode:
>> Q201, PNP, no part number: EB/BE=0.23/Hi, CB/BC=0.21/Hi, EC/CE=Hi/Hi
>> Q202, PNP, no part number: EB/BE=0.22/Hi, CB/BC=0.20/Hi, EC/CE=Hi/Hi
>> Q111, NPN, 2N1304: EB/BE=Hi/0.28, CB/BC=Hi/0.26, EC/CE=Hi/Hi
>> Q112, PNP, 2N1305: EB/BE=0.26/Hi, CB/BC=0.25/Hi, EC/CE=Hi/Hi
>>
>> The two 15v rails are down to about 5v each. The oscillator is working but
>> fluctuating badly on frequency.
>> Replaced all the electro caps. Have not replaced the resistors or diodes.
>> Will check these next.
>>
>> CR105 feeds the neg 15v supply cap??
>> Regards
>> Lou
>>
>>
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