Re: 577 AC collector supply not reading zero on display


Hi DW,
It is unfortunate that you still have the two division long trace at the collector 6.5V range with the Horizontal set to 50mV/Div. I checked my 577 and it goes all the way to zero under the same conditions.
You should go to the Check and Adjustment Procedure in the Service Manual (section 5) and perform Performance Check / Adjustment Procedures 5, 6, 7, 8 on pages 5-6 through 5-8. Those adjustment / calibration steps will calibrate every aspect of the horizontal section of the 577. One of those steps will result in your adjusting the collector voltage to eliminate the 2 division long collector line you are seeing.

I do see a faint flickering pattern which shows up as a trace about 1 horizontal division long which happens 1 to 2 times per second. I never noticed it before because it is faint and infrequent. I don't think it is important enough to be concerned with. I'm not concerned with it on my 577.

Dennis Tillman W7PF

-----Original Message-----
From: DW
Sent: Sunday, December 01, 2019 11:28 AM
Subject: Re: [TekScopes] 577 AC collector supply not reading zero on display

I found the stop tab on the variac control for the collector. I carefully bent it slightly to get the wiper to come more on the edge without falling off.

I believe I notice improvement from this, now the collector in AC isn't quite as long as it was but it is still there. At 50mV horizontal volts at 6.5 collector volts with the variable collector all the way at 0 the line is 2 divisions long and has a strange flickering pattern.

Dennis Tillman W7PF
TekScopes Moderator

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