Updates and Corrections

[Qiaozhi]

Polymer has spotted a small error in the Build Document. The parts lists was showing C20 as 100pF, and it should have been 100nF.
The Build Document has been updated

Please check you have the latest version, which is now [Doc. Ref. 20160920]. This is displayed in the footer of each page.

[Qiaozhi]

Forgot to update the number of 100nF capacitors from 8 to 9.
Build Document reference is now [Doc. Ref. 20160920-A].

[eclipse]

Looking at the schematic - small improvement can be made if pin 8 of LT1054 (V+) be attached to output of 78L05.
This will eliminate the low voltage battery requirement of LT1054 (15V) / 7660 (which is even lower) 10 to 12V.
Also 79L05 can be removed in this case.

[Qiaozhi]

Looking at the schematic - small improvement can be made if pin 8 of LT1054 (V+) be attached to output of 78L05.
This will eliminate the low voltage battery requirement of LT1054 (15V) / 7660 (which is even lower) 10 to 12V.
Also 79L05 can be removed in this case.

I don't really understand what you're suggesting here. Have you actually tried this in practice?

Pin 8 of the LT1054 is an output that drives the input of the 78L05. So I'm not sure why connecting the output of the 78L05 to the output of the LT1054 is going to achieve anything. Note that the battery positive (+VB) is treated as 0V in this design, but the LT1054 is referenced to the -VB line.and is configured as a voltage doubler. The 78L05 is referenced to the 0V line and is driven from the voltage doubler.

The difficulty is getting your head around the idea that +VB is being treated as 0V.

[eclipse]

I haven't tried it, I have bunch of these 7660 chips which are unsafe to operate over 12V (quite low really).

So my suggestion is to use them directly connected to +5V for generating the -5V thus eliminating the max input voltage requirement of these chips and 79L05 can also be omitted.





Here how it may look like after the change.

[eclipse]

You're probably right on this... I may need to find other solution to get proper voltages without the max input voltage restriction of 7660.
I had just one LT1054 but it was damaged by reverse battery connection

[kt315]

from +5V you get only -3V under loading. that you see on schematics values is abstraction.

[Qiaozhi]

from +5V you get only -3V under loading. that you see on schematics values is abstraction.

I was about to say that, but KT315 beat me to it.

[Xtrem]

You're probably right on this... I may need to find other solution to get proper voltages without the max input voltage restriction of 7660.
I had just one LT1054 but it was damaged by reverse battery connection

You have right that there is a problem, i have also LT1054 burned.
You have 3 SOLUTIONS , 7912, or better LM337 . Remove the PL1 connector and cut the copper line of the -BAT,exact at the point of the PL1,
so you have separated the -BAT , from the supply voltage of the LT1054.
You have only to solder a 7912 or LM337 to the point of the PL1 , give importance at the connections of these stabilisator ICs, INPUT have to be soldered
to -BAT ,GROUND to +BAT(downside the PCB the whole copper are GND), OUTPUT is now supplying no more then -12 VDC.
I prefer LM337 trimming the output to about -10 VDC.
3 Solution is , after cutting the -BAT ,connect 2 diodes in series, (1n4007) , so your supply voltage to the LT1054, is everytime lower at about 1,4V from the
-BAT
I hope i helped,and you have understanding me, sorry about my English.


Same problem exist on the BARACUDA, on the contrary SURF , has a safer Supply.

[Qiaozhi]

The 7660 wants to let out the magic smoke at any opportunity, whereas I have never managed to blow up an LT1054. Your supply voltage needs to get above the absolute maximum rating of 16V to damage the LT1054. Be careful though, because there is also an LT1054L, which is only rated at 7V.

[Qiaozhi]

Same problem exist on the BARACUDA, on the contrary SURF , has a safer Supply.

There are some more basic issues with the Surf-PI; such as using a PMOS in the TX circuit (Vds is only -200V) and the audio tone depends on the TX pulse rate.

There is no problem with using an LT1054 in the supply circuit, unless you are careless enough to connect a battery pack (or power supply) above 16V.
The original Baracuda Legend has more deep-seated problems associated with the way the smoothing capacitors are connected that can destroy certain components at start-up. These problems have been resolved in the Geotech Baracuda REV-A design.

[Xtrem]

My answers above are for the Minipulse, (using 7912, lm337, 2xdiodes)
after i have seen that im posting ...on Baracuda thread.
Surf and Baracuda ,are very similar projects, i preffer Surf , its far better for 2 reasons, you can use the cheap 7660, with no problem,
(only +5VDC input)
and Surf has a 4066 for switching the signals on the integrator , that is better then the JFETs on Baracuda.

[kt315]

My answers above are for the Minipulse, (using 7912, lm337, 2xdiodes)
after i have seen that im posting ...on Baracuda thread.
Surf and Baracuda ,are very similar projects, i preffer Surf , its far better for 2 reasons, you can use the cheap 7660, with no problem,
(only +5VDC input)
and Surf has a 4066 for switching the signals on the integrator , that is better then the JFETs on Baracuda.

[Qiaozhi]

My answers above are for the Minipulse, (using 7912, lm337, 2xdiodes)

There is no problem with the MPP power supply circuit. If you're worried that the LT1054 can be destroyed if the supply voltage goes above 16V, then don't let it get that high. It's like saying there's a fault with the Surf-PI design because you connected it to a 35V battery, when the maximum input voltage of the 78L05 is 30V.

The 7660 is a different issue, because it's maximum voltage rating is lower than a typical fully charged 12V (nominal) battery pack.

[Xtrem]

There is no problem with the MPP power supply circuit. If you're worried that the LT1054 can be destroyed if the supply voltage goes above 16V, then don't let it get that high. It's like saying there's a fault with the Surf-PI design because you connected it to a 35V battery, when the maximum input voltage of the 78L05 is 30V.

The 7660 is a different issue, because it's maximum voltage rating is lower than a typical fully charged 12V (nominal) battery pack.

You have absolutely right Qiaozhi, but the problem is that i dont trust anymore the Chinese suppliers, i have buy from these
7660A and LT1054, the 7660 dont burn because i have hold the voltage lower then 12, the 1054 burn at ....14vdc.
Because of the pins compatibility, im never shure what of kind the LT1054 are, maybe they are 7660a.