White's PI3000 Voltage

[Tony]

Anyone care to comment on whether the extra (initial startup) 0.5V is risky or whether this old circuit has some safety margin built-in.?

I have 8x1.2v NiMH's which come off the charger at around 11.1v. I know they will soon settle down to nominal voltages after some run time.

The lower and upper Voltages are 6.5v to 10.5v as per the schematic.

I know I could use the 6 x AA alkalines but I'm trying to avoid these if possible.

I could also take the batteries off the charger before they are fully charged.

 

[Geotech]

There is a charge pump chip (ICL7660) that is rated for 10V, it is connected to the battery via a diode so it will see roughly Vbatt - 0.6V. That is where the odd 10.5V max comes from. However, the absmax rating of the chip is 10.5V so a battery voltage of 11.1V is right at the absmax rating. In the past I've abused the 7660 with voltages above the absmax rating but I won't guarantee you the same success. If you end up killing the chip, there is a 7660a version rated for 12V.

[Tony]

Thanks Carl for that great information.....so it's only the 7660 that's in the "firing line" ?

Is a "voltage converter" the same as a regulator? I'm reading some of the hand written notes on the top right hand side of the schematic.....some are tricky to read.

I pushed my luck with higher voltages when I had the TDIBH.......for marginal depth gains but plenty of heat.

From your recollection, is the PI3000 running a delay of around 30uS?

I found a good thread on the PI3000 modifications (Findmall) but would appear to be quite a bit of work for an extra inch or two.

I think the unit is from the mid 1990's....it has the 950 Zero Buoyancy coil which I believe was from the later models of the 3000.

Feel free to chime in with anything related to the PI3000. I have the schematic from Geotech and read through some information on the unit. I would like to replace most of the capacitors on the board for starters. Anything else that might be worthy of replacement (like for like parts or not).

Thanks,

Tony.

 

[Geotech]

The 7660 is used as a voltage inverter, to generate a negative voltage from a positive voltage. Not the same as a regulator. I know nothing about the PI-X000 series, never messed with one. If the delay is 30us, getting it down to 10-15us will help a lot. Someone on Geotech might have more ideas.