June 2006

The buzzing is from the H-bridge that powers the IGBT’s. Half of the
fets are not getting a gate signal. The driver is not getting one of
it’s two gate signals. So I spent alot of time trying to buzz out the
board to find the pwm source for the H-bridge but could not. Anyone?

I’m glad I have a functional board now for reference. I can complete
my test fixture in minute detail. I’d like to duplicate the truck on
my bench so I can more completely test and characterize the board.
I’ve learned from rebuilding motor controls that just because
something spins a motor does not ensure that the various voltages and
pwm signals are at their nominal values. I’ve seen that a few times.
So I have a list of “test points” on my customers hardware that I go
thru and make sure are meeting spec. This took some time to figure
out. Our Dolphin boards need the same thing. I noticed that the pwm
firing the 300v supply chopper fet was 12v on one board and 10v on
another. Something is up. The board functions fine, but it strikes me
as trouble waiting to happen. A detailed test fixture makes looking at
these things much more thorough, accurate and repeatable, because
sometimes the tech gets tired šŸ˜‰

Now where’s my celebration beer?


This is the prototype bridgeboard pcb that isolates the bridge rectifier from the Dolphin main pcb.

Here is the bridge board that helped save my Dolphin tonight!!


My Dolphin Main board is now officially working!! I figured out how to
rework the bridge circuitry with minimum trauma to the Dolphin PCB.
Now the bridge is located on the new prototype fuse board as seen in
the above link.

Can there even be better news? So I turn on the ignition key and
everything boots up. Stable and fine. So I decide to try plugging into
120vac for some charging. Everything boots up again and then

What was that? So After the 3rd verification that something was wrong
I turned off all of the lights and fired her up in pitch darkness. Ya
know how polished the aluminum Dolphin case is on the inside? It was
acting like a mirror and reflecting back to me some high frequency,
low amperage intermittent arcing from under the charger!!

So I guess the charger needs to come out. I’m wondering if this was
the demon that trashed my main board! I’ll find out soon.

Feeling like I’ve conquered a small army of gremlins, I tried to fire
up another board that had the same sort of damage. The board is
buzzing back at me when power is applied on the bench. All 4 of the
regulators and the chopper fet are working fine. The pwm to the
chopper fet is clean and pretty. Not sure where the buzzing is coming
from but it’s keeping the board from talking to the laptop.

I’m not much of a drinker and it’s time for a beer!

1 down, 3 to go.


This is the wiring diagram of the board that I built to help protect the Dolphin when the bridge rectifier blows or when the charger's fets blow. It has DC out for damaged pcb's. This very damaged Dolphin main board was reworked by Andy. With some more debugging, I got the board running on the bench. When I put in the truck for testing, this board blew up my charger. The fet driver was replaced and the charger worked fine after that

Since the rectifier is now removed, why would I get 58 ohms across (-)
and (~) on empty holes? That sounds alot like a board issue. Have you
ever checked for this in your repairs?

I found the exact same bridge today. Same brand and country. It’s date
code is just 1991 instead of 1992. However, I also bought a bridge
that is 4 amps instead of 2 amps. It has larger diameter leads. But
the good news is that the holes in the pcb are perfect for the larger
bridge. It makes no sense to me to keep using the same bridge with the
failures being so common. I got some just in case the board owners
want a direct replacement. I think the original rectifier is just
wearing out. It could be a manufacturing process issue from 14 years
ago. So I’m looking for a higher rated replacement.

As for fuses, I’ll buy the correct ones soon. For now I found some 1
amp and smaller for debugging.

Since this is a common problem we need to tell everyone to get those 2
120vac wires fused asap. The structure of the circuit board gets
damaged, not just the parts. We cannot get any more boards, ever! Is
there anything else I should modify to better protect this board?

The bridge rectifier was shorted. It took me longer than usual to
remove it. Maybe 15 seconds. I’m slipping in my old age.

So what else do I look for before powering this baby up? I’ll probe
around so see if anything else is shorted.

We seriously need to make schematics of this stuff. I know I will when
I get this baby done.

So I need to look at the bridge rectifier labeled D1003. There is also
a large diode nearby.

So why did my 1 amp main board fuse blow? What circuit does it fuse?

I can get those resistors at an awesome surplus place when I get the

No other wires were damaged thanks to teflon insulation. Alcohol just
wiped off the residue. Although one of the resistors solder joints
became a weld šŸ™‚ So they didn’t use these as fuses. They used them to
limit current. Or maybe inrush current. In the end they acted like
fuses. I’ll put a fuse holder in there for the 2a fuse. You sure it
needs 2amp and not a 1/2 amp fuse?

The dead truck checklist is now updated with pics of each fuse and the
fet pins.

The pic shows that two power resistors in series with the two 120vac
wires going from J3 on the main board to P3 on the charger pcb, pins 1
and 4. They are the ones that smoked. I can only guess their value. 5
stripes. Starting with brown and black. The next 3 stripes were
vaporized. 5w or 3w rating Iā€™m guessing. Any idea what value they are?
Inductor perhaps? They appear to be carbon comp.

The fets on the charger are reading in the megohms range. The ohm
meter read fairly high values across the 4 regulators pins. But that
only shows no shorts, not failures.

I have enough pics to update the dead truck checklist as Iā€™m using it
now šŸ™‚


I will post the pics in the files section once I get the documentation
of this issue and the issue itself finished. For now I’ll leave links
to the pics on my own site.

1) Blown fuse on main board. No other fuses blown.

2) Here is the other problem….

What were those two power resistors value and purpose?

I plug the truck in Friday night. Let it charge. It does shut off, I
think. I was asleep so I am guessing because when I checked it in the
morning, the fans and relays were still drawing from the acc battery.
It was down to 6 volts. But the emeter showed zero volts. So I put the
charger on the 12v battery, and it was done when I got home Saturday
night. I plugged the truck into 120vac and it would not charge, or
even fault. So I turned the key on. The faults that came up in Dolcom
were 0001 0110 0000 0000.

Battery Voltage is too low. (lower than 270 volts)
12v bias supply is too low. ( Lower than 10 volts)
Power down sequence has been activated in the Dolphin unit.

The packs are at 305v. The pack’s relays are operating fine. The
trucks relays are not throwing closed at all.

When I turn the key on it’s not starting the truck. Only the fault
lite comes on.

So, I gotta dead truck.