Strange SG503 Leveled Signal Generator behavior


I have a very nice late style SG503 that has strange operating behavior. rotting the band switch to various frequencies, it typically shows 000, and adjusting the frequency control does not fix this. if I drop down to a lower band, then back up again, it usually springs to life. go up, back to all zeroes, drop down, it can work on a band that previously did not work. I can make any band work, just not when going up in frequency.

it acts like an oscillator adjustment is wrong, preventing it from running, maybe an ALC mis-set? when working, everything is perfect, and output is great. I went though doing a visual, and re-tightened all screws, no issues seen, and no difference.

I have another one (older), and it does not have this quirk, so I thought a quick query here was in order. Is this something known, or a unique problem?

any help appreciated.
all th ebest,
walter (walter2 -at-
sphere research corp.


Hi Walter...
I mentioned a similar experience a couple months back after tolerating it for a while.
The solution I found was related to the variable capacitor shaft contact and the range selector rotary switch contacts. Lubricating the capacitor's brass bearing with medium viscosity 'paint on' Deoxit lubricant seemed to help solve the issue. But the rotary range switch contacts need to be cleaned and lubricated primarily.

A matter of 10 minutes or so.


Ok....just checked my Unit again and it shows a bit of the odd behaviour when adjusting the variable capacitor...applied low viscosity (yellow) deoxit this time to both of the capacitor's brass shaft bearings...and exercised the variable capacitor range of motion...problem evaporated. Looks like its a bit of oxidation that takes place that causes the issue.



I tried the variable cap de-oxit plan,
works slightly better, but not a solid fix.
I will have to try and get down to the rotary switch contacts.

all the best,

Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:-
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