SMR-4 Mk II Power Test Problems

Discontinued products Shruthi
#1

Hello Shruthi people…
I’ve got to the first testing stage on the filter board and hit some problems.
With 7.5v in, I get +2.27v at the red points and -2.11v at the green points.
With 9v in, I get +3.52v and -3.25v.
The 5v rail gives +2.27v at 7.5v in, and +3.52v at 9v in.

Pin 5 on the LT1054 chip gives +2.37v at 7.5v in, and +3.52v at 9v in.
I tried replacing the LT1054 with no result and I’ve checked the soldering, which is OK (I think…)
Also carefully rechecked component positions.

Power Supply Specs. : PRI: 100v-240v ~ 60/50Hz 550mA
SEC: 7.5/9/12v —2250mA
27vA

Please Help!

#2

What do you get straight out of the PSU? could be a dud.

#3

Hi 6581punk.
I’m getting 8v and 9.15v directly from the PSU.

#4

I seem to remember some earlier thread where a similar problem turned out to be that the 7805 and 7905 power regulators were mixed up…

#5

This is indeed what I’ve done. Off to practice my desoldering technique now… I’ll let you know soon. Many Thanks.