colby sg 8000a signal generator 2 gear not working - Page 1
Forum section: electronics / repair

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 03, 2023, 03:25:35 am
content: Hi,the two position is "1950-5000", "5000-8000" of the SG 8000a signal generator, can not work, maybe lost one chip inside ?

author: MathWizard
author_rank: Super Contributor
timestamp: July 09, 2023, 06:38:10 pm
content: 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.

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 11, 2023, 02:17:46 am
content: 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.

author: MathWizard
author_rank: Super Contributor
timestamp: July 12, 2023, 10:20:43 pm
content: 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.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 14, 2023, 12:19:58 am
content: mm call me crazycould it be something else than a ic, seeing the traces could it be some dip relaysI would try to trace some layout around this dip socketflat cable dip / rotary switch switch ??

author: elecdonia
author_rank: Frequent Contributor
timestamp: July 14, 2023, 01:25:18 pm
content: 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?

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 17, 2023, 03:49:35 am
content: Quote from: MathWizard on July 12, 2023, 10:20:43 pmI will try to test if any voltage change for the empty IC pin.

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 17, 2023, 03:51:02 am
content: Quote from: coromonadalix on July 14, 2023, 12:19:58 ambut no service manual, how to find the problem.

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 17, 2023, 03:55:32 am
content: Quote from: elecdonia on July 14, 2023, 01:25:18 pmI 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.

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 27, 2023, 02:02:10 pm
content: Quote from: MathWizard on July 12, 2023, 10:20:43 pmI 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.

author: testpoint1
author_rank: Frequent Contributor
timestamp: July 27, 2023, 09:01:00 pm
content: list it in ebay now:https://www.ebay.com/itm/186009095447