Re: 577 D1 function won't turn off

Dave Voorhis

I have a 577 D1 that came with the original but weak CRT installed and a replacement CRT in a box. Storage mode on the original weak CRT worked well, but the primary trace was almost too dim to see.

I installed the replacement CRT. It's bright and sharp, but storage mode now doesn’t work at all. Thinking that I might have inadvertently nuked something in the storage circuitry during the CRT replacement, I temporarily jury-rigged the old CRT to verify that the storage mode still worked. It did.

I haven’t yet done the adjustment procedure, as the storage mode isn’t that important to me at the moment, but I will.

Question: is it typical for the storage settings to be critical enough and/or vary enough from CRT to CRT, for storage mode to work well on one CRT and not at all on another?

On 7 Dec 2019, at 05:50, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:

Hi DW,
I have a 577 D1 which has similar behavior but not as bad as you described. There is an adjustment procedure in the service manual that will, in theory, bring the storage back into proper operation. I found the procedure difficult to follow and several of the adjustments seemed to have little effect. I wasn't satisfied with the results from following the step by step procedure in the service manual.

After going through the procedure in the service manual several times I felt like nothing I might do could make things any worse so I took matters into my own hands and fiddled with the adjustments now that I knew more about what they were supposed to do and what effect they were supposed to have.

In the end I did improve the storage to where it worked well enough that I was satisfied with it. There were two things I was unable to adjust properly. The first occurs when I turn the 577 on. As the CRT warms up the storage gun partially floods the screen and I have to press the erase buttons to clear this. After I do that the storage seems to behave itself. The other one is the storage Brightness knob doesn't seem to do anything.

I still don't know if I wasn't following the procedure in the manual properly or if I have a problem in the storage circuitry of the 577 that I need to troubleshoot.

Dennis Tillman W7PF

-----Original Message-----
From: DW
Sent: Friday, December 06, 2019 8:38 PM
Subject: [TekScopes] 577 D1 function won't turn off

This 577 is a D1 version, the ability to temporary hold display information in a analog format which is actually quite neat.

This feature appears to be fully function when I want to use it, the problem is when I don't want to use it I can't seem to get it to turn off!

What I am experiencing is a ghosting effect (seems partially on), it is most noticeable with the intensity turned up but minimal when down. The retention seems short, ghosting disappears although some might stay retained on the screen. Using the clear button with the upper or lower pressed appears to temporarily fix this. I also find when I power on the instrument two big round circles appear on the display and then gradually fade but doesn't disappear entirely until cleared.

Dennis Tillman W7PF
TekScopes Moderator

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