Hi Jim,
The Museum of Radio and Technology is located in Huntington, WV about 15 minutes away from the Ohio, Kentucky boarder. We get visitors from all over the country and the world, for that matter but many folks that live in state don¡¯t know that we exist.
If you are a Amateur Radio operator and have never been to Hamvention you could tie a trip to both places together. Many do.
Ripley
The words are mine but this iPad does what it will with them.
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On Mar 5, 2019, at 2:55 PM, Jim Olson <v_12eng@...> wrote:
I'm curious where the Museum is located it sounds interesting to me too I'm in the SF bay area.
Jim O
On March 5, 2019 at 4:55 AM SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:
Hi Reed,
Yes sir working at the Radio Museum is a lot of fun and hard work at the same time but now that I am retired it is a great place to volunteer a few days a week.
Between the NTE539 and NTE538 which one would you recommend for the Tektronix 475?
Ripley
The words are mine but this iPad does what it will with them.
On Mar 5, 2019, at 12:08 AM, Reed Dickinson <reed714@... mailto:reed714@... > wrote:
Hi Ripley:
Wiring in a NTE538 is a little different than wiring in an NTE539. When you get your 3Xer write ma back and I will detail how to do it.
Your antique radio setup sounds most interesting. I would probably be helping you out at that facility if it were on the left coast.
Reed
On Monday, March 4, 2019, 4:43:02 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:
Hello Reed,
You just have been reading my mind. I was wondering how to handle the HV lead out to the CRT. What about the Focus Tap on the module. I am guessing that is left unterminated and highly insulated from anything around it.
Our plan is to repair the scope so that we can sell it. The Museum of Radio and Technology is a nonprofit all volunteer organization. We don¡¯t charge for admission so our revenue sources are from cash donations, sales from our gift shop , small grants, and the three swap meet/auctions that we host every year.
I will keep everyone posted as I bring this repair to completion.
Ripley
Sent from Mail for Windows 10
From: Reed Dickinson
Sent: Monday, March 4, 2019 4:59 PM
To: [email protected] mailto:[email protected]
Subject: Re: [TekScopes] 475 with no Display and no HV
Hi Ripley:
Good show, a new 3X voltage multiplier will get your 475 back on the air. If you elect to get an ECG or NTS 538 or 539 you will have to splice the HV lead leaving the new tripler. I very carefully slip a piece of thick wall plastic tubing over where the splice will be, carefully solder the joint leaving NO sharp points, coat the entire joint with silicone and slip the tubing over the joint. I put a small tie wrap over each end to keep moisture out. The 538 or 539 will fit in the space the present tripler is in, you will need to drill two mounting holes for the retainer screws.
Reed Dickinson
On Monday, March 4, 2019, 1:40:15 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:
Hi Reed,
Per your suggestion I disconnected the wire from the secondary of T1320 to the voltage tripler and powered up the scope. The waveform at TP1318 immediately snapped to 32 volts p-p at about 70Khz without any persuasion via the 1K resistor trick. I also checked the oscillator over at the junction of CR1329 an C1326. It measures 320 volts p-p so it looks like I need to order a voltage tripler module.
Thank you so much for your help. Obviously, you know your way around these scopes.
Ripley
Sent from Mail for Windows 10
From: SuddenLink
Sent: Sunday, March 3, 2019 8:27 PM
To: [email protected] mailto:[email protected]
Subject: Re: [TekScopes] 475 with no Display and no HV
Hello Again,
I went back to the circuit around Q1306 and Q1308 this evening. The resistors are all within specs. C1305 was pulled and checked. It is also fine. C1304 is good and so is C1302.
By the way I am checking the capacitors with a DE-5000 LCR meter. It was never let me down yet.
The only component that I have not replaced or substituted is Q1306. It checks fine on my little Chinse component tester. For whatever that is worth.
Enough for today.
Ripley
Sent from Mail for Windows 10
From: Steph L
Sent: Sunday, March 3, 2019 7:05 PM
To: [email protected] mailto:[email protected]
Subject: Re: [TekScopes] 475 with no Display and no HV
Hi Ripley,
How about C1305 0.1uF.
If open, gain of Q1306 (and whole oscillator loop) will be lower and perhaps not enough to maintain oscillation? (Great suggestion from Don re 1K pull up touch on Q1318 base.)
Steph
PS. Still nubie here and unsure which "Reply" button to click on. I clicked on Ripley's "what the heck?" message "reply" button and see it has been inserted a few messages prior! That is really confusing. I'm in Melbourne Oz GMT +10 hrs. Is this the reason (i mean time difference guys and not quirky)
