colby sg 8000a signal generator 2 gear not working

[testpoint1]

Hi,

the two position is "1950-5000", "5000-8000" of the SG 8000a signal generator, can not work, maybe lost one chip inside ?

[MathWizard]

So are you saying the rest of it works, but not the last 2 ranges ? I'd start checking that switch I guess, then trace back from the output to see if the signal is there anywhere.

[testpoint1]

yes, rest is working, when using the 2 positions, even the LED also off. the switching is no problem, I guess maybe one chip is lost.

[MathWizard]

IDK those machines, but it looks like a nice size to work on. Is there a bunch of voltages on that empty chip holder ? Does the voltage to any of the pin sockets change when you set that switch ? It could be just empty, I'm sure you can find pictures of PCBs with empty sockets, made and sold that way for some reason.

After a quick search I can't find any manual or schematics. I wish I had something like that to work on, I'd start mapping the output circuit, see what turn's on or off when you go from the working settings, to the last 2 settings.

I'm guessing there's hardly any digital stuff or chips, so it should be easier to find the part that's not doing what it's supposed to do.

Or maybe it is just missing that chip, maybe there was a problem and it burned out. If it had a 2nd chip just like it, I'd still be cautious of just swapping them, in case there's a problem that burned out the previous 1.

[coromonadalix]

mm call  me crazy 

could it be something else than a ic, seeing the traces   could it be some dip relays    

I would try to trace some layout around this dip socket

flat cable dip / rotary switch switch ??

[elecdonia]

Could that IC socket be empty on purpose?
I’ve seen test gear where a similar empty IC socket is used for test points, presumably with a factory test system.

Another possibility is these 2 frequency ranges at the high end of the scale (1.9GHz to 8GHz) are an option which this particular unit wasn’t equipped with. There are several large unpopulated areas on the PC board shown in your photo. So perhaps there were different versions/options, some of which were not installed in your unit?

It’s likely that generating frequencies above 1.9GHz would require additional hardware.

Do you have a service manual or schematic for this beast?

[testpoint1]

IDK those machines, but it looks like a nice size to work on. Is there a bunch of voltages on that empty chip holder ? Does the voltage to any of the pin sockets change when you set that switch ? It could be just empty, I'm sure you can find pictures of PCBs with empty sockets, made and sold that way for some reason.

After a quick search I can't find any manual or schematics. I wish I had something like that to work on, I'd start mapping the output circuit, see what turn's on or off when you go from the working settings, to the last 2 settings.

I'm guessing there's hardly any digital stuff or chips, so it should be easier to find the part that's not doing what it's supposed to do.

Or maybe it is just missing that chip, maybe there was a problem and it burned out. If it had a 2nd chip just like it, I'd still be cautious of just swapping them, in case there's a problem that burned out the previous 1.

I will try to test if any voltage change for the empty IC pin.

[testpoint1]

mm call  me crazy 

could it be something else than a ic, seeing the traces   could it be some dip relays    

I would try to trace some layout around this dip socket

flat cable dip / rotary switch switch ??

but no service manual, how to find the problem.

[testpoint1]

Could that IC socket be empty on purpose?
I’ve seen test gear where a similar empty IC socket is used for test points, presumably with a factory test system.

Another possibility is these 2 frequency ranges at the high end of the scale (1.9GHz to 8GHz) are an option which this particular unit wasn’t equipped with. There are several large unpopulated areas on the PC board shown in your photo. So perhaps there were different versions/options, some of which were not installed in your unit?

It’s likely that generating frequencies above 1.9GHz would require additional hardware.

Do you have a service manual or schematic for this beast?

I also hesitate if the option not enabled, I have the operating manual, but not said the option; and I found a strange problem, in other postion, the LED is ON, when in the particular position (1.9GHz above), the LED is off, seems like lack some parts. maybe is a option ? if that is RF problem, I think the LED should be still on.

[testpoint1]

IDK those machines, but it looks like a nice size to work on. Is there a bunch of voltages on that empty chip holder ? Does the voltage to any of the pin sockets change when you set that switch ? It could be just empty, I'm sure you can find pictures of PCBs with empty sockets, made and sold that way for some reason.

After a quick search I can't find any manual or schematics. I wish I had something like that to work on, I'd start mapping the output circuit, see what turn's on or off when you go from the working settings, to the last 2 settings.

I'm guessing there's hardly any digital stuff or chips, so it should be easier to find the part that's not doing what it's supposed to do.

Or maybe it is just missing that chip, maybe there was a problem and it burned out. If it had a 2nd chip just like it, I'd still be cautious of just swapping them, in case there's a problem that burned out the previous 1.

I tested it, seems the voltage of each pin for the missed chip no change between different gear, that means nothing about the chip, I have no way to continue, will list in eaby as part soon.

[testpoint1]

list it in ebay now:
https://www.ebay.com/itm/186009095447