开云体育

-------- Original message --------From: Bill Carns <wcarns@...> Date: 3/5/19 5:39 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Help with 7A18 problem By the way Jim, I think I forgot to send my location. Bill Carns661 Saddleridge DriveWimberley, TX 78676Many thanks again.-----Original Message-----From: [email protected] [mailto:[email protected]] On Behalf Of Jim FordSent: Saturday, March 02, 2019 8:02 PMTo: TekScopes@...: Re: [TekScopes] Help with 7A18 problemHi, Bill.I have a 7A18 that I don't need.? IIRC, it works just fine.? You can have it for shipping if you like.? I'm in Southern California.?? Where are you located?I will be back home in So Cal early next week, and I will confirm the condition of the 7A18. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone-------- Original message --------From: Bill Carns <wcarns@...> Date: 3/2/19? 2:26 PM? (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Help with 7A18 problem I'll have to go put the unit back in the mainframe and investigate but my memory says that most were bad.I have investigated more and remove the upper capacitor cover and, boy are those things hard to get at.? Gonna be real hard to get cleaning paper in there on all the switches.? Some are not bad, others really bad to get to.? One set has an additional little cover over them for some reason.Working on this thing is not for sissies.B-----Original Message-----From: [email protected] [mailto:[email protected]] On Behalf Of Albert OttenSent: Saturday, March 02, 2019 3:53 PMTo: TekScopes@...: Re: [TekScopes] Help with 7A18 problemOn Sat, Mar? 2, 2019 at 07:58 PM, Colin Herbert wrote:>> ---> On the subject of the input attenuators, they are the type which are > operated by cam-switches. They have springy gold-plated contacts that > get moved up-and-down by cams on the controls shaft. The circuit board > that they are on has gold-plating, too, and the board itself is made > of an easily-damaged material. You need to use thin strips of paper > moistened in IPA and trapped between the moving and stationary > contacts, they *gently* pulling the paper strip out. You may have to > do this a few times. Don't use any other solvents or contact-cleaner > as you will probably ruin the board. Of course it may only be one or > two of these contacts that is dirty, as has already been suggested; > there are only four attenuators there - they get switched in-and-out > to get the different VOLTS/DIV settings. In the most sensitive > VOLTS/DIV setting, they are all switched out, so if your 5mV/div > setting shows lousy bandwidth, then it is likely to be caused by some > other problem, not just the attenuators and their switching . Of course, there might be a problem there, too, but it won't be the only one.>Hi Colin, You probably were too quick in your statement about the 5 mV/div setting. In that setting all attenuators are bypassed by means of a series of closed contacts, so any dirty contacts there destroy the signal path.I'm not sure about the 7A18 construction. My impression is that? including AC/DC there are 10 contact pairs above the drum and 10 below the drum. (Each contact pair forming one switch).It would still be nice to hear from Bill which V/div settings are good and which are bad.Albert