Assistance with voltage doubler cct please

[bicter]

Hi,
Building the Silverdog kit @revD.
Initially, I connected power the incorrect way at step 3 due to being ham fisted and not paying attention to what I was doing.
I've replaced all components and now have an isue with the +5V supply. -5V is OK.
I measure 4-10mV at the input to the 78L05 and obviously no output from the regulator.
When I measure the voltage at the junction of D2 and D3 with respect to TP10, I measure -6V.
Not being familiar with the way this portion of the cct works, is anyone able to suggest/guess what the issue may be?
I forgot to add that I don't have ready access to a CRO as I have to travel 60K to use one.
Any and all suggestions welcome
Regards
Terry

[Chet]

Hi,
Building the Silverdog kit @revD.
Initially, I connected power the incorrect way at step 3 due to being ham fisted and not paying attention to what I was doing.
I've replaced all components and now have an isue with the +5V supply. -5V is OK.
I measure 4-10mV at the input to the 78L05 and obviously no output from the regulator.
When I measure the voltage at the junction of D2 and D3 with respect to TP10, I measure -6V.
Not being familiar with the way this portion of the cct works, is anyone able to suggest/guess what the issue may be?
I forgot to add that I don't have ready access to a CRO as I have to travel 60K to use one.
Any and all suggestions welcome
Regards
Terry

Hi Bicter

Check the voltages on the 555 chip to be similar to the voltages at this location;
http://www.geotech1.com/forums/showt...908#post200908
Did you replace the 555 chip? It is quickly destroyed with reverse voltage applied.

Have a good day,
Chet

[bicter]

Chet,
Thanks for replying.
I made an error in my previous post. I'm only at step 2 (FIG3) and consequently the 555 isn't in cct yet.
I'll follow up on the link you posted and confirm the voltages on each pin. Those figures give me a good help.

Regards
Terry

[Qiaozhi]

Hi,
Building the Silverdog kit @revD.
Initially, I connected power the incorrect way at step 3 due to being ham fisted and not paying attention to what I was doing.
I've replaced all components and now have an isue with the +5V supply. -5V is OK.
I measure 4-10mV at the input to the 78L05 and obviously no output from the regulator.
When I measure the voltage at the junction of D2 and D3 with respect to TP10, I measure -6V.
Not being familiar with the way this portion of the cct works, is anyone able to suggest/guess what the issue may be?
I forgot to add that I don't have ready access to a CRO as I have to travel 60K to use one.
Any and all suggestions welcome
Regards
Terry

As it says in the Build Document (Step 2):
The LT1054 is configured as a positive voltage doubler
(referenced to the -VB supply), which boosts the battery voltage to twice its normal value, and is
then regulated by U3 (78L05) to +5V. Measure the voltage at TP2, and confirm it is +5V.

In this case, there should be a positive voltage at pin 8 of U2 (LT1054) - measured with reference to TP10 (0V) - equivalent to (or just below) the battery voltage. If not, then U2 is quite likely to be faulty.

[bicter]

Thanks Qiaozhi
It looks like the LT1054 is dead. Will order a new one and keep my fingers crossed

Regards
Terry