GM digtial dash round #1

[BOB URZ]

Well, i just got the toronado dash in from my brother in law.
So far, its about what i expected. There is a caged power supply module
screwed on to the back of the gauge cluster. It appears to
be a switcher. It has a single large plastic power transistor driving
a transformer. There appears to be 4 DC outputs. each outputs appears
to be a 1/2 wave type DC supply. Three of the outputs have 33@100v
caps on them. I assume these are the power supplies for the display
tubes. The fourth has a 470 @10 volts. I assume this is for logic
in the display. From the cap values, i can assume 3 high voltage DC
supplies and 1 low voltage.

There are three wires (some doubled) on the input side. So, I assume
there is 12 volts, ground, and one switching wire. One would assume
the switch wire switches on 12 volts, but i am doing some further
checking before i put power on to it.

The unit has a soldered on fuse on the PC board. The fuse is fine.
Solder joints look OK. The semi's seem OK with fluke check in
circuit. Nothing looks burnt.

So that's what's there. We will see what we find after further sleuthing
and a bench power up. But from what i have seen, it looks fixable.

Bob

 

[BOB URZ]

Well, i just got the toronado dash in from my brother in law.
So far, its about what i expected. There is a caged power supply module
screwed on to the back of the gauge cluster. It appears to
be a switcher. It has a single large plastic power transistor driving
a transformer. There appears to be 4 DC outputs. each outputs appears
to be a 1/2 wave type DC supply. Three of the outputs have 33@100v
caps on them. I assume these are the power supplies for the display
tubes. The fourth has a 470 @10 volts. I assume this is for logic
in the display. From the cap values, i can assume 3 high voltage DC
supplies and 1 low voltage.

There are three wires (some doubled) on the input side. So, I assume
there is 12 volts, ground, and one switching wire. One would assume
the switch wire switches on 12 volts, but i am doing some further
checking before i put power on to it.

The unit has a soldered on fuse on the PC board. The fuse is fine.
Solder joints look OK. The semi's seem OK with fluke check in
circuit. Nothing looks burnt.

So that's what's there. We will see what we find after further sleuthing
and a bench power up. But from what i have seen, it looks fixable.

Bob

Well, it looks like MY bro is going to sell the car as is.
But it was educational. Transistor Q5, a 2sa1215 was open
on the PS board. This seems to be the switching transistor
to turn the supply on. I tried to swap in another PNP. The
switch wire appears to work by grounding it. With the
switch wire grounded and the sub transistor in, the sub
would immediately heat up and the circuit would not
oscillate. All other semis seemed to be ok.
Nothing looked burnt.

If this were mine, i would get the car shop manual and trace down the
wiring further as to function and take the cluster itself apart.
I am pretty sure it needs 3 HV DC supplies and and low Volt
logic supply. My guess is some of the people fixing these are
using building block brick DC/DC supplies and creating a replacement out of PS Block
modules if its not fixable.
I smell a bad transformer in this one, but cannot be sure at
this point. Thought i would pass along what i found so far
incase some other brave soul tries to
do this in the future.

With more resources and a lot more time, i still think its fixable.



Bob

 

[Art]

Giving up on the thing eh?? Selling as is??