Hameg 605 Y-Out Oddity

[JoergR]

Hi all,

I'm in the process of repairing a Hameg 605 60MHz analog scope. I fixed the usual power supply issues and also some loose soldering pads on a connector and some broken solder joints and everything seems to work fine now - except the Y-Out on the back and I'm out of my wits here how this error can occur at all.

I've connected a sine wave to channel 2 and the calibrator square signal to channel 1. Y-out is connected to my second scope in the background.

Img 1) When triggering on channel 2 (the sine), it is passed through to the Y-out and displayed on the second scope as expected.
Img 2) When triggering on channel 1 (the square) - it is not passed trough to the Y-out and the second scope only sees a 1V DC signal.

But that should not be possible, since there is only a single buffer that routes the selected trigger signal to the Y-out and if this works for channel 2, I don't see what this would not work for channel 1. Img 3 shows the block diagram. Triggering works just fine for both channels - so why does the Y-out only work for the signal on channel 2?

Y-Out is on the bottom of the block diagram in the lower left corner of the TB Board.

Thanks a lot for any insight.
Joerg

[JoergR]

ok, figured it out - note to self: When fixing solder pads on a broken connector, fix all of them! And get new glasses!

The trigger signal is routed twice(!) from the Y-Board to the TB Board. Through pins 5 and 6 of the P2-3/1 connector. I'm not sure why this is done, but I suspect it enables the alternate triggering mode.

When fixing the broken connector P2-3/1, I had assumed the solder pad on pin 6 (on the right) was still ok, but on the photos you can see (in hindsight), that the connection to the trace is broken. Since I didn't want to remove the entire board again, I fixed it on the components' side. Not pretty, but I guess I'll get another chance to fix it for good at some later time.

Now everything is in working order and the Y-Out does output both channels 1 and 2.

As a side note, the pin numberings on the component layout schematic are wrong - 1 is 6 and 6 is 1 - in case anyone else runs into the same problem again.