Date   

7603 P.S. cans, slow warm-up and focus control

Mark Vincent
 

I have a 7603 I ordered new electrolytics today and will install them on
Fri. when they come in. The scope has always been slow to show a trace. The
crt is good. I tested it. It tested good after about 10-15 seconds as a
good tube would. The rest of the scope has been overhauled with new filters
and resistors as needed. Since the main filters are original, is the age of
these causing the slow warm-up, about 45 seconds? When it is warmed up, the
trace looks great. At this time, there is a slight intensity modulation on
the trace which I suspect are the filter cans going bad. I have heard that
at least one electrolytic in the supply is known to go bad first with the
others soon to follow. I have seen a picture of a 465 with bad caps with
the weird trace, not a 7603, yet. Mine still has a line as it should. I
ordered ones that are high temp, low ESRand long life. I know about the
ground lugs needing bridging. I do not know if the 76x3 series takes longer
to warm-up or not. The B+ voltages are right. I did set the fan voltage to
the high position which keeps it cooler than at the low position.

I am looking for a small pot to replace the focus pot in this scope. The
original is 50,000 ohms 1/2W. Mine burned up. There is 150V across that
pot. A 2W should have been used. I put in a smaller value pot with
resistors on each end. The shaft would be adjusted with the right side off.
I did keep the original to swap shafts so adjustment can be done from the
front if needed. A smaller value, e.g. 20,000 ohms, would be fine as I will
put resistors on each side of the pot to keep the centre position of the
pot at focus. It is the small diameter shaft, not the standard size.

Mark


Re: My 475

 

On Tue, Jul 6, 2021 at 10:53 PM, Rey wrote:


I was checking all the voltages and the only thats off, is the the 50v unreg
which reads 69,6 V
That's fine, it's just the unregulated voltage, straight from transformer secondary, rectifiers and buffer caps that the regulated 50V is derived from in the 'scope.

Raymond


FTAGH: Free to a good home: 465/475 scopes

Jeff Davis
 

Hi All,

I have roughly 25 Tek 465, 465B, 475, and 475A scopes, some with DMMs, available free for local pickup in the Orange County, California area.

These are in various stages of functionality from fully functional to won't turn on. Most have had some preliminary troubleshooting but I haven't attempted to repair any of these.

My intention was to fix them up and resell them on eBay as a retirement project. I found that the market prices for them didn't justify the time and effort to refurbish them (for someone else. For my own use is a different story!).

Unfortunately, any of these that aren't gone in a month or so will end up in the landfill, so I'd really like to see them find good homes. That said, I don't want to ship them - local pickup only.

73,

Jeff / N0DY


Re: My 475

Rey
 

Hi, by that I mean all the selection switch lights are on or off as I change the selection. I was checking all the voltages and the only thats off, is the the 50v unreg which reads 69,6 V


Re: My 475

Bill
 

You have received some great feedback. Be sure to follow the recommendations.
Bill


Re: Have a 2467B. Suggestions please on very poor focus

Siggi
 

On Tue, Jul 6, 2021 at 3:55 PM Raymond Domp Frank <hewpatek@gmail.com>
wrote:

This should:


https://groups.io/g/TekScopes2/files/Ronan_2476B_display_demo/20210706_090713.mp4

Thanks, that does work. I was looking for a video link in the thread and I
totally missed the file upload notification. The video is pretty grainy,
and recording the CRT tends to blow out the traces. Between the two, I'd
say this looks about the same as my 2467.

I'm also in agreement with you on the evils of cross-posting.


Re: Spectrum Analyzer Scope Adapter, KD1JV

EB4APL
 

The schematic corresponds to a Scalar Network Analyzer (In fact it is the Poor Ham Scalar Network Analyzer, PHSNA) not a Spectrum Analyzer. Two different kind of beasts.

Ignacio EB4APL

El 06/07/2021 a las 1:34, Roy Morgan escribió:
Thanks, I will get the board and parts to examine.

Roy Morgan
K1LKY Western Mass

On Jul 5, 2021, at 3:25 PM, DaveH52 <ac2gl.dave@gmail.com> wrote:

On Sun, Jul 4, 2021 at 11:58 AM, Roy Morgan wrote:

KD1JV Spectrum Analyzer
Is this the one?
https://www.qsl.net/kx4om/images/ScalarNetworkAnalyzer/SNA_Schema.jpg




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Re: Have a 2467B. Suggestions please on very poor focus

Mark Vincent
 

Raymond,

Thanks for letting me know the status of is scope. I did not know he had a video. I also am not on either of the other two groups. I only went by what was posted here. I do not know his level of experience or ones around him to help in person. Checking parts to confirm one way or another is one thing provided you know how and what to do. Changing is another.

Mark


Re: Have a 2467B. Suggestions please on very poor focus

 

On Tue, Jul 6, 2021 at 09:52 PM, Raymond Domp Frank wrote:


Siggi,
I already complained about Ronan's cross-posting. His main thread is on
TekScopes-2.
Here's the link to the video:
That quote doesn't work, of course.
This should:

https://groups.io/g/TekScopes2/files/Ronan_2476B_display_demo/20210706_090713.mp4

Raymond


Re: Have a 2467B. Suggestions please on very poor focus

 

On Tue, Jul 6, 2021 at 09:41 PM, Siggi wrote:


On Tue, Jul 6, 2021 at 3:25 PM Raymond Domp Frank <hewpatek@gmail.com>
wrote:


Ronan's 'scope works fine, generally, as can be seen in his video. Except
for the Rifa caps, replacement of components isn't "compulsory" and even
risky if one doesn't have the experience and tools needed to do quality
work.
I'd love to see that video, if only for reference to my 2467.
Siggi,
I already complained about Ronan's cross-posting. His main thread is on TekScopes-2.
Here's the link to the video:

**** QUOTE ****
The following files have been uploaded to the Files area of the TekScopes2@groups.io group.

/Ronan_2476B_display_demo/20210706_090713.mp4

By: Ronan <bass.woofer@gmail.com>

Description:
Demo of issue Ronan / 2476B with the finest focus I can get, while increasing the Readout Intensity from min to Max, the indicator LEDs flash as they do when I press "A/B Trig"
*** UNQUOTE ***

Raymond


Re: Have a 2467B. Suggestions please on very poor focus

Siggi
 

On Tue, Jul 6, 2021 at 3:25 PM Raymond Domp Frank <hewpatek@gmail.com>
wrote:

Ronan's 'scope works fine, generally, as can be seen in his video. Except
for the Rifa caps, replacement of components isn't "compulsory" and even
risky if one doesn't have the experience and tools needed to do quality
work.
I'd love to see that video, if only for reference to my 2467.


Re: Have a 2467B. Suggestions please on very poor focus

 

Ronan,
We're seeing the principal reason for my dislike of cross-posting.
You're getting responses from people who are unaware of what has been achieved and established already.
I fell into the same trap by responding on TekScopes after my responses on TekScopes-2.

Raymond


Re: Have a 2467B. Suggestions please on very poor focus

 

On Tue, Jul 6, 2021 at 09:17 PM, Mark Vincent wrote:


Ronan,

Check the power supply voltages for d-c and ripple. The electrolytics, some
resistors and several tantalums are known to give problems. Mr. Yachad of
Condor Audio has a parts kit for the 2465/7 series with instructions. He will
be glad to help you if you have questions. He is on this group. He is
excellent with these series of scopes.

You can check pin 2 of U4310 to see if you have the -2kv. The heater supply
can be checked at pins 1 and 14 of U4310 using a battery operated meter or
VOM, e.g. Simpson 260, across the two pins to see if you have the 6,3VAC for
the heater. Do NOT measure the heater voltage from ground to either pin 1 or
14! Pin 3 of U4310 should be about -2100V, Check TP4302 for -1100V, If these
voltages are low, the power supply is suspect as it is common to both
oscillator circuits. Replacing the parts in the power supply and elsewhere can
make things work right that look bad before replacing. Your focus and dim
trace likely will be right with the new parts. U4310 can be bad. The focus
adjust should be from 0 to 15V on one side of R4435. Check the zeners, diodes
and transistors in the focus circuit to confirm if any are bad. R4333 I will
say is way out of tolerance. Mouser has radial types in 100meg. The 1/2W or 1W
will work fine. The original carbon one could be 50, 60, etc. percent high or
even open. The carbon one in my 2465B was 170meg. It was replaced with a new
one. Here is the link for 1W types in stock:
https://www.mouser.com/Passive-Components/Resistors/Film-Resistors/Thick-Film-Resistors-Through-Hole/_/N-7gz43Z1yzvvqx?P=1z0vkovZ1z0wsz3Z1z0wljo&Keyword=100+meg+resistor&FS=True.
The 1/2W part number is: 588-MOX-300001006FE. The 1/2W is more expensive than
the 1W.

The 2 100mfd decoupling electrolytics for the two oscillator circuits should
be replaced with something like Nichicon ULD or UHE type. The kit mentioned
above likely has these two in it. Mr. Y. can confirm this.

The RIFA caps are to be pulled out and replaced! Those I know are in the kit.
Anyone on this group will attest to replacing these automatically/on-sight.

I hope you get this nice scope working right. It is a great scope.

Mark
Hi Mark,
Ronan's 'scope works fine, generally, as can be seen in his video. Except for the Rifa caps, replacement of components isn't "compulsory" and even risky if one doesn't have the experience and tools needed to do quality work.

Raymond


Re: Have a 2467B. Suggestions please on very poor focus

Mark Vincent
 

Ronan,

Check the power supply voltages for d-c and ripple. The electrolytics, some resistors and several tantalums are known to give problems. Mr. Yachad of Condor Audio has a parts kit for the 2465/7 series with instructions. He will be glad to help you if you have questions. He is on this group. He is excellent with these series of scopes.

You can check pin 2 of U4310 to see if you have the -2kv. The heater supply can be checked at pins 1 and 14 of U4310 using a battery operated meter or VOM, e.g. Simpson 260, across the two pins to see if you have the 6,3VAC for the heater. Do NOT measure the heater voltage from ground to either pin 1 or 14! Pin 3 of U4310 should be about -2100V, Check TP4302 for -1100V, If these voltages are low, the power supply is suspect as it is common to both oscillator circuits. Replacing the parts in the power supply and elsewhere can make things work right that look bad before replacing. Your focus and dim trace likely will be right with the new parts. U4310 can be bad. The focus adjust should be from 0 to 15V on one side of R4435. Check the zeners, diodes and transistors in the focus circuit to confirm if any are bad. R4333 I will say is way out of tolerance. Mouser has radial types in 100meg. The 1/2W or 1W will work fine. The original carbon one could be 50, 60, etc. percent high or even open. The carbon one in my 2465B was 170meg. It was replaced with a new one. Here is the link for 1W types in stock: https://www.mouser.com/Passive-Components/Resistors/Film-Resistors/Thick-Film-Resistors-Through-Hole/_/N-7gz43Z1yzvvqx?P=1z0vkovZ1z0wsz3Z1z0wljo&Keyword=100+meg+resistor&FS=True. The 1/2W part number is: 588-MOX-300001006FE. The 1/2W is more expensive than the 1W.

The 2 100mfd decoupling electrolytics for the two oscillator circuits should be replaced with something like Nichicon ULD or UHE type. The kit mentioned above likely has these two in it. Mr. Y. can confirm this.

The RIFA caps are to be pulled out and replaced! Those I know are in the kit. Anyone on this group will attest to replacing these automatically/on-sight.

I hope you get this nice scope working right. It is a great scope.

Mark


Re: My 475

 

Rey,

When you say that "the screen lites up" what do you mean by that? Are you saying that you have two straight lines, but when you apply a signal to either input channel you don't get any vertical deflection of either trace?

As other's have said, the first step in any diagnosis like this is to check the power supply voltages. This is easy to do on the 475 as there are labeled test points on the main interface board for each power supply rail.

I will hold my own speculation about what the fault might be until after we find out what the power supply voltages are.

-- Jeff Dutky


Re: My 475

Tom Lee
 

Dagnabit -- you're right, Dave.  I'm apparently thinking of a chart in some manual for another model.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 7/6/2021 10:52, Dave Peterson via groups.io wrote:
Just scanned the 475 SM online doc. I didn't find a diagnosis chart - is that not in the online 475 manual?

Wanted to throw this in the suggestion box - after checking and verifying the LV supplies: check F1318 at the rear of the main board - near the transformer. This drives the HV oscillator and the tantalum 47uF cap on the other side of the fuse is a somewhat common short. It's a relatively easy fix. Don't bypass the fuse if it's out, check for a shorted C1318. That'll take down the CRT without affecting the LV supplies and other indicators.

Dave



On Tuesday, July 6, 2021, 9:47:36 AM PDT, Rey via groups.io <cis181ellin=yahoo.com@groups.io> wrote:
Hi guys, my first post here looking for answer I found this place. I'm looking for a bit of guidance, my 475 just quit it was working fine. Both channels are gone, no beam find. Every switch light works, the screen lites up. But no trace out of either channel.  I'm a hobbiest and I understand that electrical things do weird things.  But any ideas and/or pointers would be appreciated. I already downloaded the schematic.
Thanks









Re: My 475

Dave Peterson
 

Just scanned the 475 SM online doc. I didn't find a diagnosis chart - is that not in the online 475 manual?

Wanted to throw this in the suggestion box - after checking and verifying the LV supplies: check F1318 at the rear of the main board - near the transformer. This drives the HV oscillator and the tantalum 47uF cap on the other side of the fuse is a somewhat common short. It's a relatively easy fix. Don't bypass the fuse if it's out, check for a shorted C1318. That'll take down the CRT without affecting the LV supplies and other indicators.

Dave

On Tuesday, July 6, 2021, 9:47:36 AM PDT, Rey via groups.io <cis181ellin=yahoo.com@groups.io> wrote:

Hi guys, my first post here looking for answer I found this place. I'm looking for a bit of guidance, my 475 just quit it was working fine. Both channels are gone, no beam find. Every switch light works, the screen lites up. But no trace out of either channel.  I'm a hobbiest and I understand that electrical things do weird things.  But any ideas and/or pointers would be appreciated. I already downloaded the schematic.
Thanks


Re: My 475

Tom Lee
 

Welcome!

Standard procedure is to check the supplies (there are several in that scope). A quite common problem is a shorted "teardrop" tantalum capacitor, but a few quick measurements will tell you a lot.

If you've downloaded the manual, you should also take a look at the troubleshooting chart. The manual is incredibly well written.

Good luck!

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 7/5/2021 18:48, Rey via groups.io wrote:
Hi guys, my first post here looking for answer I found this place. I'm looking for a bit of guidance, my 475 just quit it was working fine. Both channels are gone, no beam find. Every switch light works, the screen lites up. But no trace out of either channel. I'm a hobbiest and I understand that electrical things do weird things. But any ideas and/or pointers would be appreciated. I already downloaded the schematic.
Thanks




Re: My 475

Paul Amaranth
 

Check all of the LV power supplies. That's always the first stop. Get the
service manual and make sure all of the supplies are within spec for voltage
AND ripple. Nothing works if the power supplies aren't right.

Paul

On Mon, Jul 05, 2021 at 06:48:42PM -0700, Rey via groups.io wrote:
Hi guys, my first post here looking for answer I found this place. I'm looking for a bit of guidance, my 475 just quit it was working fine. Both channels are gone, no beam find. Every switch light works, the screen lites up. But no trace out of either channel. I'm a hobbiest and I understand that electrical things do weird things. But any ideas and/or pointers would be appreciated. I already downloaded the schematic.
Thanks







!DSPAM:60e48921145828472026532!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: My 475

 

My inbuilt autoresponder says: "Check the low voltages" and report back. The voltages are interdependent.
Highly likely you'll find a defective/shorted (Tantalum) capacitor.
Use dwg11 in the service manual as a reference.

Raymond

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