Date   

Re: Very Inexpensive 7623A, but Problems

 

Bert,

I'm glad to hear that. This is my first toe dipped into the 7000-series, and I was hoping for a good experience.

I've got a 5000-series scope that has been a tale of woe, and nearly put me off the mainframes for good.

I also have a small stable of 400 and 2200-series scope that have been absolute joys, as well as a 2465 that was another surprising bargain. While this scope is only the slow end for me (the vertical plug-ins limit it to only 75 MHz) I was really interested in having an analog storage scope.

-- Jeff Dutky


Re: Shipped They Are

Ed Pavlovic
 

Larry,
Just to let you know my set of boards showed up here north of Chicago this morning. Thanks again for taking on the task of arranging the group order and all of the shipping!!!!

I did a quick inspection of the boards and was impressed with the quality of the boards.

Now I need to strip out one of my plug in frames and start assembling things!!!

Ed Pavlovic
KC9MMM


Re: Very Inexpensive 7623A, but Problems

Bert Haskins
 

On 2/13/2021 2:55 PM, Jeff Dutky wrote:
Other minutia:

The serial number is B183764.

The date codes on the ICs range between 77 and 78, so this scope looks like it's about 42 years old.
Hi Jeff.

I have two 7623As each in two different work areas.

They have been rock solid for over two decades.

Well worth your effort to restore.

 Bert



Re: Tektronix 7904 Repier

Kaveh
 

Hello everybody,
I wanted to let you know that I have now repaired the device. The fault was in the amplifier on the horizontal board. Three transistors were defective. I was not able to install the original parts from Tektronix, but I have installed comparison types that show quite a lot of values. I put the device into operation today and I'll be calibrating it soon. At this point I would like to thank you all for your advice and help. Have a nice evening to all of you and watch out for Covid 19. Thank you
Kaveh
PS: I took a few photos of the device, but I cannot attach them to this message. I'll try, maybe it'll work.


Re: Very Inexpensive 7623A, but Problems

Eric
 

The good news is you check pre trippler not post so you only need to measure -4Kv. If you have any image it is safe to assume the trippler is working.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Jeff Dutky
Sent: Saturday, February 13, 2021 2:22 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Very Inexpensive 7623A, but Problems

Eric,

Wow! It's a good thing I got myself a brand new HV probe for Christmas (rated to 40KV)! And here I was jumpy about the 2.5KV on the 475! Good times.

-- Jeff Dutky


Re: Very Inexpensive 7623A, but Problems

 

Other minutia:

The serial number is B183764.

The date codes on the ICs range between 77 and 78, so this scope looks like it's about 42 years old.


Re: Hey this isn't even on Tekwiki!

-
 

FYI Control F only searches the page that you're currently on. Type
"183 site:w140.com" without the quotes into Google and it will show you
every occurrence of 183 on the w140.com site. Note the colon between
"site" and the URL.

On Sat, Feb 13, 2021 at 12:50 PM snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

On Fri, Feb 12, 2021 at 11:50 AM, Kurt Rosenfeld wrote:

I just added a "183" link on the Main page in the "Other Instruments"
section.
OK, I thought someone was messing with my drugs. I never use search boxes
since either ctrl-F is faster, or googling is deeper ... so.. meh.






Re: Very Inexpensive 7623A, but Problems

 

Jean-Paul,

I also splashed out $18 for replacement knobs for the vertical plug-ins (they look the same as the trigger slope knobs on the 475/A, but their inner diameter is different), $50 for a replacement 7B53A, and a couple dollars for fuses and capacitors from Mouser. I'm sure that there will be another Mouser order, once I've figured out what's causing the display misbehavior, but I'm betting it won't total more than $30.

If I get a working 7623A out of this for less than $200 I'll call that a bargain.

-- Jeff Dutky


Re: Very Inexpensive 7623A, but Problems

 

Eric,

Wow! It's a good thing I got myself a brand new HV probe for Christmas (rated to 40KV)! And here I was jumpy about the 2.5KV on the 475! Good times.

-- Jeff Dutky


Re: Very Inexpensive 7623A, but Problems

Eric
 

Jeff

If yours is a storage scope the HV is really in the HV supply and on the storage board as far as I know. The main 7000 series goes up to a 130 V supply but there is a -4Kv supply for the tube which if I remember correctly is fed in to a voltage tippler which will give you an acceleration voltage of about 12Kv on the fat red wire. Not a tone of current there but it is still jumpy and nothing to mess with. My storage experience is limited to the 577 curve tacers but in there the storage flood guns get a 300 ish volt supply and the deflection plates are driven by 200 odd volts. I do recall that in one of my 7603's there was a bad driver transistor in the LV supply for the pass element. This caused my 130V rail to be off in the weeds at about 149V all because the pass transistor was not being told what to do. There are a couple of power supply design changes the very original 7603's were fan less and had a plastic cover. The metal ones I think have the fan.

Good luck with the restoration.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Jeff Dutky
Sent: Saturday, February 13, 2021 1:33 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Very Inexpensive 7623A, but Problems

Jean-Paul,

Thank you for the warning.

I paid $60+$35 shipping. It's not quite peanuts, but it's also not quite dinner out with the family.

Eric,

I will be taking lots of pictures.

Michael,

There are lots of socketed ICs (and transistors) to be sure. I will check those after I've done my visual inspection and read the manual a bit (there's lots of warnings, printed on the frame it RED LETTERS, about high voltages. This is an entirely different beast than my 475s and 2200s).

-- Jeff Dutky


Re: Checking sampling diodes

Tom Lee
 

As others have said or implied, a 1GHz sampler is not demanding of the diodes. HP/Avago/Broadcom HSMS-281x (obsolete but still not hard to find) Schottkys are a close electrical match (a slight upgrade, actually). Your principal challenge will be mechanical if you do need to replace them.

The stock diodes are hardy enough to survive testing with a regular DMM's diode test function. But if you are a "belt and suspenders" guy, go ahead and add a 1k series resistor.

Cheers,
Tom

Sent from an iThing; please excuse the terseness and typos

On Feb 13, 2021, at 7:53, "Charles" <charlesmorris800@centurytel.net> wrote:

I acquired an S-1 sampling head for cheap, "Untested, for parts only" (Yeah, right, since it came from a surplus test equipment company!). We all know what that means.

Anyhow, as I expected, it doesn't work properly. From the bizarre trace I think that one of the two sampling diodes has failed, probably from input overload.

How would you recommend initial-checking them at DC? After looking at the specs for a replacement kit from Tek (https://groups.io/g/TekScopes/topic/7636255), it appears that 9 volts reverse, and at least 1 ma forward, should be ok. My Fluke 73 has a diode check function but I need to measure the max current available. I think it's 1 ma. Or I can just apply a little DC to the input connector and measure current to ground from the bridge outputs (pins H & I from the sampling board), which have 200 ohms in series with each diode.

If they're bad, it looks like there are plenty of Russian GaAs diodes available. The specs probably aren't quite as critical since this is a 350 ps head, not a 25 ps...

Thoughts?





Re: Very Inexpensive 7623A, but Problems

 

Jean-Paul,

Thank you for the warning.

I paid $60+$35 shipping. It's not quite peanuts, but it's also not quite dinner out with the family.

Eric,

I will be taking lots of pictures.

Michael,

There are lots of socketed ICs (and transistors) to be sure. I will check those after I've done my visual inspection and read the manual a bit (there's lots of warnings, printed on the frame it RED LETTERS, about high voltages. This is an entirely different beast than my 475s and 2200s).

-- Jeff Dutky


Re: Stan Griffiths estate sale

adesilva_1999@...
 

FYI. I sent a message to this person Paul, on Nextdoor but I am not sure if he will be interested in declaring his email address as it might become overwhelming. There are 28 interested parties in Nextdoor itself. Given the inventory there, I would think he has to explore all avenues. I don't see how one person can handle all that. I posted the link to this thread in the message to him. If he comes back to me, I will update here.


Re: Hey this isn't even on Tekwiki!

snapdiode
 

On Fri, Feb 12, 2021 at 11:50 AM, Kurt Rosenfeld wrote:

I just added a "183" link on the Main page in the "Other Instruments" section.

OK, I thought someone was messing with my drugs. I never use search boxes since either ctrl-F is faster, or googling is deeper ... so.. meh.


Re: Checking sampling diodes

snapdiode
 

You said " Russian GaAs diodes", I assume you refer to the mountains of Russian tunnel diodes, since Schottky diodes aren't GaAs.

Well, for the diode test, I'd stick a resistor in series just to be sure.


Re: Stan Griffiths estate sale

Greg Muir
 

If you go to the “Old Tek Scopes” page on Facebook:
https://www.facebook.com/groups/oldtekscopes/permalink/878380719616768
you will find the first posting made by Paul Roder, the person who posted the ad on NextDoor.

If you go to his page:
https://www.facebook.com/groups/153720895416091/user/1744278505/
you can message him directly.

Greg


Re: Checking sampling diodes

 

Yes, thank you, I already mentioned that :)
So, once again, how electrically fragile are they? Will I damage a good one with 1 ma of DC forward current?


Re: Help needed calculating trace impedance for SG503 Peak-to-Peak detector.

SCMenasian
 

Carefully check the table in John Bennet's paper. Adding a resistance to a reactance to yield an impedance should usually be done in quadrature, not arithmetically. i.e. Ztotal = sqrt(R^2+Xc^2).

Stephen Menasian


Re: Checking sampling diodes

snapdiode
 

Sampling diodes aren't tunnel diodes. The S-1 is pretty low bandwidth, any reasonable Schottky will work.


Re: Hey this isn't even on Tekwiki!

-
 

I've had to return several items and PP always refunded the full purchase
price AND shipping. One item (a BC-348) was destroyed by improper packing
and I returned it and I packed it properly so the return shipping was quite
a bit more than the initial shipping and PP refunded the shipping *both*
ways! What initially cost me about $120 including shipping, costs the
seller about $160 to get back.

On Sat, Feb 13, 2021 at 5:51 AM David C. Partridge <
david.partridge@perdrix.co.uk> wrote:

If goods not as described eBay rules say Seller pays return postage

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of John Williams
Sent: 12 February 2021 21:30
To: TekScopes@groups.io
Subject: Re: [TekScopes] Hey this isn't even on Tekwiki!

all the seller has to say to the buyer is “Return the item for a full
refund.” When the postage to return it is more than the refund, then the
seller wins.







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