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Im still troubleshooting my 468. My schematic is blurry and I was wondering if anyone could tell me the proper voltage at the base of Q958 and Q987A on the A15 board. I have 15V on one side of R971 but he other side is wildly fluctuating between 9V and 12V I don't think thats right. Thanks guys.

+13volts

You need to get a better manual copy ...I know just the place
Dave
manuals@...

--
Dave
Manuals@...
www.ArtekManuals.com

On Mon, Dec 17, 2018 at 07:21 PM, Artekmedia wrote:

+13volts

You need to get a better manual copy ...I know just the place
Dave
manuals@...

On 12/17/2018 9:14 PM, lop pol via Groups.Io wrote:

Im still troubleshooting my 468. My schematic is blurry and I was wondering

if anyone could tell me the proper voltage at the base of Q958 and Q987A on
the A15 board. I have 15V on one side of R971 but he other side is wildly
fluctuating between 9V and 12V I don't think thats right. Thanks guys.

--
Dave
Manuals@...
www.ArtekManuals.com

Thank you very much.
"You need to get a better manual copy ...I know just the place"
I get the hint :)

I have a pretty clear jpg of the A15 schematic but I have not been able to log on to the site. PM me your address and I will send it to you.
Michael

I have a mediocre PDF file of the 468 manual, Artek's manuals are highly recommended and Dave is extremely helpful, to the point of finding and scanning a missing page from an obscure manual that I purchased from him.

My mediocre copy seems to say +13.0V on the base of Q958. Have you noticed that C869 which has nearly 15V across it is rated only at 15V?

Roger

lop pol
Dec 17 #153208

Im still troubleshooting my 468. My schematic is blurry and I was wondering if anyone could tell me the proper voltage at the base of Q958 and Q987A on the A15 board. I have 15V on one side of R971 but he other side is wildly >fluctuating between 9V and 12V I don't think thats right. Thanks guys.

Artekmedia
Dec 17 #153209

+13volts

You need to get a better manual copy ...I know just the place
Dave
manuals@...

On Tue, Dec 18, 2018 at 12:38 PM, Roger Evans wrote:

I have a mediocre PDF file of the 468 manual, Artek's manuals are highly
recommended and Dave is extremely helpful, to the point of finding and
scanning a missing page from an obscure manual that I purchased from him.

My mediocre copy seems to say +13.0V on the base of Q958. Have you noticed
that C869 which has nearly 15V across it is rated only at 15V?

Roger

Yes I did notice that and replaced it with a 25V tantalum. This thing has me totally stumped. Thanks for the reply.

I have both Tektronix Service manuals for the 486. Volume 2 is P/N 070-3516-00 and the latest revision is December 1982. On schematic #8 it shows +13.0V at the bases of Q958 and Q987A. Bear in mind that R971 connects to the +15V bus at one end, but then goes to chassis via R970 (the B sweep start pot) and R972. So, the voltage on the slider will vary according to the position of the slider of R970. If my arithmetic is correct this variation will be 12-13V, so your maximum 12V is low and your minimum 9V is also low. Maybe R970 has a dirty track?
Colin.

On Wed, Dec 19, 2018 at 05:24 AM, Colin Herbert wrote:

I have both Tektronix Service manuals for the 486. Volume 2 is P/N 070-3516-00
and the latest revision is December 1982. On schematic #8 it shows +13.0V at
the bases of Q958 and Q987A. Bear in mind that R971 connects to the +15V bus
at one end, but then goes to chassis via R970 (the B sweep start pot) and
R972. So, the voltage on the slider will vary according to the position of the
slider of R970. If my arithmetic is correct this variation will be 12-13V, so
your maximum 12V is low and your minimum 9V is also low. Maybe R970 has a
dirty track?
Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of lop pol
via Groups.Io
Sent: 18 December 2018 02:14
To: [email protected]
Subject: [TekScopes] 468 still

Im still troubleshooting my 468. My schematic is blurry and I was wondering if
anyone could tell me the proper voltage at the base of Q958 and Q987A on the
A15 board. I have 15V on one side of R971 but he other side is wildly
fluctuating between 9V and 12V I don't think thats right. Thanks guys.

I replaced R970 with a used variable resistor which ohmed out correctly. I guess I should get a new one just to make sure. We are all on the same page, so at least that is good.

The one here:



Seems to be good enough. Not color but looks pretty good. It is about 40% of the way down the page. Two parts, looks like 1 is theory of operation and all that, didn't see the tunnel diode tutorial but you know how they are. All the schematics seem to be in 2. You could just about skip a year of engineering school reading those things. So if nothing else you need part 2. The whole thing is about 300MB.

Couldn't find R970 on the print, where is it ?

On Wed, Dec 19, 2018 at 03:56 PM, Jeff Urban wrote:

The one here:



Seems to be good enough. Not color but looks pretty good. It is about 40% of
the way down the page. Two parts, looks like 1 is theory of operation and all
that, didn't see the tunnel diode tutorial but you know how they are. All the
schematics seem to be in 2. You could just about skip a year of engineering
school reading those things. So if nothing else you need part 2. The whole
thing is about 300MB.

Couldn't find R970 on the print, where is it ?

lop pol
Dec 17 #153208

Im still troubleshooting my 468. My schematic is blurry and I was wondering if anyone could tell me the proper voltage at the base of Q958 and Q987A on the A15 board. I have 15V on one side of R971 but he other side is wildly fluctuating between 9V and 12V I don't think thats right. Thanks guys.

Colin Herbert
5:24am #153239

I have both Tektronix Service manuals for the 486. Volume 2 is P/N 070-3516-00 and the latest revision is December 1982. On schematic #8 it shows +13.0V at the bases of Q958 and Q987A. Bear in mind that R971 connects to the +15V bus at one end, but then goes to chassis via R970 (the B sweep start pot) and R972. So, the voltage on the slider will vary according to the position of the slider of R970. If my arithmetic is correct this variation will be 12-13V, so your maximum 12V is low and your minimum 9V is also low. Maybe R970 has a dirty track?
Colin.






Here is R970 on the A15 board. /g/TekScopes/photo/80501/0?p=Name,,,20,1,0,0

This is where I'm at.

I have a trace that is too short horizontally the beginning of the trace lengthens and contracts intermittently. The 15V side of r971 is dead on 15V the other side bounces anywhere from 9V to 12V. C869,C874,C848,C776 and R970 have been changed. Along with 90% of tantalums on the A12 board and Both power supplies recapped. I'm just in so deep I can't give up. Too stubborn to quit too dumb to fix it.

I was finally able to log in today. I posted the pics of the A15 board here:

/g/TekScopes/photo/78665/0?p=Name,,,20,1,0,0

Hope this helps.
Michael

lop pol
Dec 17 #153208

Im still troubleshooting my 468. My schematic is blurry and I was wondering if anyone could tell me the proper voltage at the base of Q958 and Q987A on the A15 board. I have 15V on one side of R971 but he other side is wildly fluctuating between 9V and 12V I don't think thats right. Thanks guys.


On Wed, Dec 19, 2018 at 07:25 PM, Michael Wyatt wrote:

I was finally able to log in today. I posted the pics of the A15 board here:

/g/TekScopes/photo/78665/0?p=Name,,,20,1,0,0

Hope this helps.
Michael

Thank you so much Michael. I can finally read the A15 voltages!! Also thank you Jeff for the awesome site. I love this group. Thanks again guys.