Spectra using SIU & HHCH - no power up problem - - solut

[Jim202]

In support of the numerous Spectra radios out there using
the HHCH with a YLN-1120A SIU, there is a problem that WILL
show up. Sometime during the use of the radio system, it
will fail and you won't be able to power the radio back
on. This seems to be a random failure of an otherwise
fine working radio package.

The problem has been traced to a poor design by the
Motorola engineering people. There is a voltage sense
circuit that keeps tract of the incoming 12 volts DC.
If this voltage goes high or low, the circuit will prevent
the micro from allowing the radio to be powered up.
Problem is this circuit seems prove to failure itself.

The solution is simple. Cut one leg off of one of the
surface mount IC packages inside the SIU. I had a radio
on the bench the other day that was working fine. Went
back to it several hours later and it was dead. The power
was never removed or changed. It just died while running
on the bench.

It will take removing the cover from the SIU box. You
will need a small pair of side cutters to just snip the
# 40 pin off the U103 IC. If you hold the SIU box with
the key lock facing you, it is the large IC in the rear
left corner. The pin 40 you cut loose is the 1st pin on
the right side going to the rear. There is a surface
mount capacitor on this side of the IC. Pin 39 is the
last pin on the side facing toward the key lock on the right.

I have done this to about 6 SIU boxes so far. They have
lasted in normal mobile service for over a year since
this problem was first identified and resolved. I say
this for those that may be reluctant to take the voltage
sensing circuit out of play. The only other soulution
is to find another SIU and wait until that one also fails.

If someone needs more help, just email and I will try
to supply a photo of the pin location on the IC.

Jim

[mancow]

Excellent, thanks!

Now what about the other direction, radios that won't power down?

I was getting out of the car the other day after turning off the SIU and still heard traffic. I thought I left a portable on somewhere but realized it was coming from the VHF side. The HHCH was dark and it seemed to be off. I turned it back on then off again and it powered down fine and stayed off like normal. This has happened to me several times and it seems to be random.

[Jim202]

Never seen that problem. I would look at the power
switch in the HHCH or the power relay in the SIU.

Since I have moved, I still haven't found my Spectra
manuals. Kind of at a loss in being much help here on
this one.

Jim

Excellent, thanks!

Now what about the other direction, radios that won't power down?

I was getting out of the car the other day after turning off the SIU and still heard traffic. I thought I left a portable on somewhere but realized it was coming from the VHF side. The HHCH was dark and it seemed to be off. I turned it back on then off again and it powered down fine and stayed off like normal. This has happened to me several times and it seems to be random.

[mancow]

On another note... do you notice these things draw some serious power on RX? I have never measured it but if I leave it on all weekend the car battery will be dead by Monday morning.

I need to set it for ignition sense switched operation but I initially didn't do that because it's nice to be able to use it on surveillance when the car is completely off.

[Jim202]

Why don't you just add a switch with a double position.
This way in one position the radio can run off the ignition
feed. In the other position the radio can be fed off of a
hot feed to keep the receiver active with the engine off.
Wire the common to the radio.

Jim

On another note... do you notice these things draw some serious power on RX? I have never measured it but if I leave it on all weekend the car battery will be dead by Monday morning.

I need to set it for ignition sense switched operation but I initially didn't do that because it's nice to be able to use it on surveillance when the car is completely off.