Exact Model 566 Sweep Function Generator - Page 1
Forum section: electronics / repair

author: HMPMMP
author_rank: Newbie
timestamp: April 03, 2023, 01:50:47 am
content: Hello All,This is my first post and a request for some help. A while ago I acquired an Exact Electronics Model 566 Sweep Function Generator. Unfortunately it did not come with a manual or schematics. I've done some basic testing - power supply checks fine and the caps are all good. I'm able to get a very noisy signal out of some functions but others don't work at all. I've not tried the sweep yet.For the past month or so I've searched on-line and at local swaps for information / manuals / schematics on the device and have checked most of the manuals links posted here. Other than a few pictures, the only thing I've been able to come up with is an old video posted by Alan on his W2AEW Youtube channel. Does anyone here have a manual / schematics they wish to part with or can you point me to where I can find one on line? I think a thorough calibration may solve most of the problems I'm encountering.Thanks,Harry

author: jonpaul
author_rank: Super Contributor
timestamp: April 03, 2023, 03:00:34 am
content: Usually scratchy pots and switches.Open, use co,trol cleaner/ lube on every control and switch.Exercise after spraying.Should solve most "noisey" problems,Jon

author: lowimpedance
author_rank: Super Contributor
timestamp: April 03, 2023, 03:05:08 am
content: Finding information for this manufacturer is like trying to find hens teeth in a hay stack!. I have a few models andallneeded some TLC of the switches as bad contacts will cause many odd behaviors from noise to completely dead ! That's next thing after power supply checks to look at. Another is carbon comp. resistors drifting high causing DC bias conditions to change, not good for DC coupled stages.Of course beware of tantalum caps if used.Some pictures of the front and PCB/internal construction would be helpful too.

author: HMPMMP
author_rank: Newbie
timestamp: April 03, 2023, 03:28:50 am
content: Thanks for the quick replies. I hope my pic of the front of the 566 actually attaches to this post - not very good at attachments yet. I'll get a few pics of the board tomorrow. It's a single layer PCB with mostly discreet components.I have cleaned all of the pots and switches with Deoxit but that didn't seem to help. None of the components appear discolored although someone before me replaced a couple of diodes and a filter cap. There are a bunch of test points on the board and that's where a service manual will come in handy. - And I know what you mean about trying to find info about Exact and their products. Just not much out there.Thanks again.

author: HMPMMP
author_rank: Newbie
timestamp: April 04, 2023, 12:52:53 am
content: Hello All,Attached is a pic of the 566 PCB. There are a bunch of test points and adjustment pots. I fear that when the new diodes and cap were installed (upper right corner), whoever did it made some additional adjustments. I'm OK with following a circuit / PCB trace but, not this OK. I'm getting lost in this one pretty fast. A service manual and schematic will really help.Thanks.

author: lowimpedance
author_rank: Super Contributor
timestamp: April 04, 2023, 03:27:40 am
content: I suspect your best bet would be to get whatever 'exact' generator model manual you can find and look at the adjustment instructions for the various 'trimmer names', as the function and name on the silk screen are very similar across the generator models I have seen.Also try to get the deoxit into the switches and pots where ever you can see an opening and then exercise that control to work the fluid in. Old switches/pots like these really do cause all sorts of issues.It does look to be fairly clean inside, cant see any tantalum bead caps which is good however it does contain quite a few of the old carbon comp. resistors which do drift.

author: Jetecnet
author_rank: Contributor
timestamp: April 04, 2023, 12:55:41 pm
content: Manual for 566 is available herehttp://www.jetecnet.com/others.html

author: HMPMMP
author_rank: Newbie
timestamp: April 04, 2023, 08:12:49 pm
content: Thanks for the suggestions. I really appreciate it.

author: HMPMMP
author_rank: Newbie
timestamp: April 04, 2023, 08:14:05 pm
content: Thank you for the link to the service manual. I've sent my order email. Thanks again.