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Hello all, new to the group and happy to be here.

I just wrote a long intro about me and my new Tek 465 into the Yahoo groups
'new post' textbox, but it seems to have vanished ... so I'll briefly recap
(pardon the pun). I am a web and database programmer during the day but
have dabbled in electronics since I was 10. I'm in my 30s now and getting
back into modding my audio tube amps. I've always been building kits and
fixing through parts swapping in TV power supply boards, digital Arduino
projects, RC planes etc. But I've never really learned the math or
theory/design side of the analog world. As I'm looking to build some
personal audio gear (active crossovers, maybe some tube mono-blocks) I'm
teaching myself more theory. And I'm a very visual person and like learning
through gear so thought I'd get an analog o-scope.

Well I stumbed upon an as-is Tek 465 on Craiglist that I picked up Monday
near Chicago. I'm blown away by the detail in the service manual I found
online and the serviceability, and am starting with the power supply diag
in the manual to try to get things running. I don't have high expectations
for accuracy - I know a detailed calibration is a profession in itself. But
getting even rough readings would be a big help for me as I learn.

Current condition of the scope is a single dot in the center with no sweep.
Fan and lights work, knobs in good shape. Very complete scope but the sweep
IC gets super hot. I figured I'd have to swap a lot of caps and transistors
and maybe some regulators, but hoping I don't have to source the custom ICs
(but found a source so I guess there's hope).

So far I've confirmed a solid +55v rail, +15v rail and a drooping +5v and
no -8v with my DMM. The +5v droop goes away if I isolate the horizontal amp
board by pulling the connector. I posted on the EEVBlog forum and got a
response saying to check the ripple as well; seems I need another (working)
scope? Any hope that a cheap USB scope (opposite end of spectrum from this
beast!) would suffice?

Thanks in advance for your knowledge; I'll ask more detailed questions and
post pics as I get into things.

- Neil

On Wed, 30 Mar 2016 13:32:52 -0500, you wrote:

...

Fan and lights work, knobs in good shape. Very complete scope but the sweep
IC gets super hot.

...

So far I've confirmed a solid +55v rail, +15v rail and a drooping +5v and
no -8v with my DMM. The +5v droop goes away if I isolate the horizontal amp
board by pulling the connector. I posted on the EEVBlog forum and got a
response saying to check the ripple as well; seems I need another (working)
scope? Any hope that a cheap USB scope (opposite end of spectrum from this
beast!) would suffice?

A cheap USB oscilloscope will work to check ripple however so will a
voltmeter set to AC mode.

What sweep IC are you referring to?

A cheap USB oscilloscope will work to check ripple however so will a
voltmeter set to AC mode.

What sweep IC are you referring to?

Thanks for the tip on ripple and testing with a voltmeter. I found that as
an option after some digging later but didn't know if it would be accurate
enough to make diagnosis.

The scorching hot IC is part number 155-0049-01 and called a 'sweep
generator.' Here's one source
but it seems to be unavailable from there and out of stock on another site
here: I believe it's
U870 in the manual and someone with a similar issue mentioned it here:



I've confirmed a dead -8 volts at the regulator so my next steps are to
test and likely replace the rectifier.But it's hard to keep up my
enthusiasm on careful part swapping if that IC is unobtanium. I'd be fine
fixing the power supply and waiting out availability but disappointing when
the part cross reference sheet has only 4 components that don't have a
common replacement!

Thanks for your help! I can tell after a half a day the brainpower in this
group is great and even if I have to put this Tek project on hold I'm sure
I'll get a working one soon.

The scorching hot IC is part number 155-0049-01 and called a 'sweep generator.'

That part is used in several early 7000-series time bases.
7B50A and 7B53A are examples. A while ago, while still available, these plugins could be had for a few $$.

IYou may want to check the circuits around the IC before replacing because it could be the victim of a failure, not the source.

Raymond

That part is used in several early 7000-series time bases.
7B50A and 7B53A are examples. A while ago, while still available, these

plugins could be had for a few $$.

Thanks for the info - i may even buy a whole timebase to part out in the
worst case.

You may want to check the circuits around the IC before replacing because

it could be the victim of a failure, not the source.

Yes, i will be sure the surrounding circuits are perfect before plugging in
new. Thanks!

Hi,


I have one 155-0049-02 and will check my cabinets tomorrow to see if i have a -01. It would be $15 shiped to lower 48. respond off list to j_massengale@...


Jerry Massengale

That's awesome. I'm assuming the -02 is an updated compatible design so
would prefer that version. Ill reply off list with details. Thank you!
On Mar 30, 2016 9:28 PM, "jerry massengale j_massengale@...
[TekScopes]" <TekScopes@...> wrote:

Hi,

I have one 155-0049-02 and will check my cabinets tomorrow to see if i
have a -01. It would be $15 shiped to lower 48. respond off list to
j_massengale@...

Jerry Massengale

-----Original Message-----
From: Neil Elver neil.elver@... [TekScopes] <
TekScopes@...>
To: TekScopes <TekScopes@...>
Sent: Wed, Mar 30, 2016 7:47 pm
Subject: Re: [TekScopes] Introducing myself and my Tek 465 Project

A cheap USB oscilloscope will work to check ripple however so will a
voltmeter set to AC mode.

What sweep IC are you referring to?

Thanks for the tip on ripple and testing with a voltmeter. I found that as
an option after some digging later but didn't know if it would be accurate
enough to make diagnosis.

The scorching hot IC is part number 155-0049-01 and called a 'sweep
generator.' Here's one source
but it seems to be unavailable from there and out of stock on another site
here: I believe it's
U870 in the manual and someone with a similar issue mentioned it here:



I've confirmed a dead -8 volts at the regulator so my next steps are to
test and likely replace the rectifier.But it's hard to keep up my
enthusiasm on careful part swapping if that IC is unobtanium. I'd be fine
fixing the power supply and waiting out availability but disappointing when
the part cross reference sheet has only 4 components that don't have a
common replacement!

Thanks for your help! I can tell after a half a day the brainpower in this
group is great and even if I have to put this Tek project on hold I'm sure
I'll get a working one soon.

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Hi Neil,

I think you' d better follow Raymond's advice. In diagram <8> you can see that U870 needs the -8V supply to establish Vee. You (and I) probably have no idea what consequences an absent -8V (so 0V I suppose?) has for this IC. So first of all search the causes of the failing power supply lines!
It is not always true that a -02 version is immediately "better" than a -01 version. Sometimes surrounding components have to be changed as well. IIRC a terrible example are the many versions for a vertical amplifier IC in the 7904 scope, with a list of corresponding component changes and calibration instructions. The 067-0049-02 was introduced in the 465 at S/N B301600 and it was the only change at that S/N. So it seems that replacement of -01 by -02 is fine.
BTW please mention whether you have an "early" 465 (below B250000) or "late" 465 (B250000-up). There were several modifications and you preferably need a manual that covers your S/N.

Albert

Thank you Albert for lending your experience; these are great insights. I
had heard of the 'early vs late' but only in reference to transistor
soldering vs. through-board socketing and thought it was more in
construction than circuit design. But I don't know much ... new at all this
and a lot to absorb. I am at work now so can't lookup the serial but mine
is a through-board socketed model if that lends itself to be an earlier I
don't know. I think it was tested in '74 but the serial will tell for sure.

I'll do some research to see what changes may need to be made if using the
-02 version of this IC but will try sourcing the -01 if Jerry has it
available for sale. I had seen mention in a thread on a forum somewhere
that someone made that swap as a replacement but it wasn't very thorough
(and I don't know if it lasted 6 months in that position either).

I made a little progress last night toward getting the -8v up (which is
basically at zero) with dis-assembly to gain better access to the interface
board power section. Can't get a probe on the CR1561 rectifier from the
top. I'm starting with removal of the power supply filter caps to get some
access and to test them out-of circuit and may replace all depending on
sourcing options. I'm awaiting arrival of a standalone capacitor tester and
a transistor tester that'll do better than my DMM, and communicating with
Jerry who has that IC for sale.

Thanks,

Neil

Albert, just wanted to point out that I found a spec document describing
the 155-0049-02 with an internal circuit description of the sweep control
IC found here:

(page 5-27)

Looking deeper to see if there's such thing as a 155-0049-01 spec
description to compare to. There was mention in one forum that the '02 is
an improved version of the 01 as there were problems with the initial
version' but no more detail.

I've confirmed a dead -8 volts at the regulator so my next steps are to

> test and likely replace the rectifier

The absence of -8 V is caused more often than not by a short. You should be able to check what's going into the regulator, thereby possibly avoiding a lot of disassembly of the circuits upstream.
Usually, a dipped tantalum capacitor causes these shorts. Specifically, I've seen C1569 being shorted. It's located on the A9 Interface Board, rear side, near the middle and easy to reach and replace without removing the board.
With the power off, measure the resistance across C1569. If shorted, you'll measure anything up to about 30 Ohm.
You may temporarily replace it with any >= 20 uF cap with Working Voltage (WV) spec. of at least 15 V.

An obvious difference between early and late >=B250000 versions is the replacement of the vertical output amplifier, from an "integrated" version, to a discrete version.

Raymond

Thank you so much Raymond. I'l make sure to check those and had read about
those tantalum caps going to short failure mode but didn't know where to
start testing. I am getting no voltage going into the regulator which is
why I'm focused on the CR1561 rectifier at the moment. I happen to have a
new NTE5318 rectifier on my bench that is rated to 200v and 4A, and will be
checking further for compatibility but think I can swap that in if the
other is faulty. If not I have a link to a parts cross reference to source
one from.

On Thu, Mar 31, 2016 at 10:49 AM, hewpatek@... [TekScopes] <
TekScopes@...> wrote:

I've confirmed a dead -8 volts at the regulator so my next steps are to
test and likely replace the rectifier

The absence of -8 V is caused more often than not by a short. You should
be able to check what's going into the regulator, thereby possibly avoiding
a lot of disassembly of the circuits upstream.
Usually, a dipped tantalum capacitor causes these shorts. Specifically,
I've seen C1569 being shorted. It's located on the A9 Interface Board, rear
side, near the middle and easy to reach and replace without removing the
board.
With the power off, measure the resistance across C1569. If shorted,
you'll measure anything up to about 30 Ohm.
You may temporarily replace it with any >= 20 uF cap with Working Voltage
(WV) spec. of at least 15 V.

An obvious difference between early and late >=B250000 versions is the
replacement of the vertical output amplifier, from an "integrated" version,
to a discrete version.

Raymond

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

On 31 March 2016 at 16:49, hewpatek@... [TekScopes] <
TekScopes@...> wrote:

I've confirmed a dead -8 volts at the regulator so my next steps are to
test and likely replace the rectifier

The absence of -8 V is caused more often than not by a short. You should
be able to check what's going into the regulator, thereby possibly avoiding
a lot of disassembly of the circuits upstream.
Usually, a dipped tantalum capacitor causes these shorts. Specifically,
I've seen C1569 being shorted. It's located on the A9 Interface Board, rear
side, near the middle and easy to reach and replace without removing the
board.
With the power off, measure the resistance across C1569. If shorted,
you'll measure anything up to about 30 Ohm.
You may temporarily replace it with any >= 20 uF cap with Working Voltage
(WV) spec. of at least 15 V.

?For reference, I measured approx. 50 ohms across the -8V with it powered
off. Mine was an open-circuit bridge rectifier. You can chop it up to
remove it, if you don't want to completely dismantle the scope to get to
the back of the PCB. I used heavy duty cutters and my room was littered
with the shrapnel. When soldering the new one in, leave about 1/4 inch of
exposed leads and lean the body of the BR at an angle.

Malcolm?


[Non-text portions of this message have been removed]

I am getting no voltage going into the regulator which is
why I'm focused on the CR1561 rectifier at the moment.

That seems a valid conclusion. It definitely looks like you have a situation like Malcolm's. Follow his good advice.
I'd just like to add that it's a good idea to try and avoid excessive stress on the PCB while removing the bridge rectifier to avoid damaging the traces and through-holes. And avoid getting shrapnel into your eyes...

Raymond

Thanks guys - i was debating that but kept telling myself 'that's not what
a seasoned pro would do! take it apart and do it right' - good to know
brutal tactics are accepted as long as there's some caution. I may try a
dremel cutoff tool with a running shopvac nearby... I don't know I'd trust
myself to not slip and break something nearby once I got on a roll :) And
being a few feet from my welding table and its giant pliers and grinders
could give me bad ideas.

On Thu, Mar 31, 2016 at 11:10 AM, hewpatek@... [TekScopes] <
TekScopes@...> wrote:

I am getting no voltage going into the regulator which is
why I'm focused on the CR1561 rectifier at the moment.

That seems a valid conclusion. It definitely looks like you have a
situation like Malcolm's. Follow his good advice.
I'd just like to add that it's a good idea to try and avoid excessive
stress on the PCB while removing the bridge rectifier to avoid damaging the
traces and through-holes. And avoid getting shrapnel into your eyes...

Raymond

[Non-text portions of this message have been removed]

i was debating that but kept telling myself 'that's not what

> a seasoned pro would do! take it apart and do it right'

You are absolutely right. OTOH, it's wise to move and change as little as necessary and there's no law that forbids soldering at the component side. Just make sure that the PCB remains in as good a state as you can (hence my earlier advice). Bend the wires of the new rectifier so they fit the PCB holes without stress and you can easily reach them while soldering. As Malcolm suggests, you may leave a sensible length of the rectifier's legs visible and bend its body.

Raymond

On 31/03/16 17:24, hewpatek@... [TekScopes] wrote:

i was debating that but kept telling myself 'that's not what
a seasoned pro would do! take it apart and do it right'

You are absolutely right. OTOH, it's wise to move and change as little as necessary and there's no law that forbids soldering at the component side. Just make sure that the PCB remains in as good a state as you can (hence my earlier advice). Bend the wires of the new rectifier so they fit the PCB holes without stress and you can easily reach them while soldering. As Malcolm suggests, you may leave a sensible length of the rectifier's legs visible and bend its body.

I have been known to replace an axial electrolytic by nipping its wires right next to its body (hence leaving its leads still soldered to the board), and soldering the replacement to the original leads. I did use forceps as a heat shunt, so there was less danger the original lead would become detached.

That felt preferable to the relative horrors of removing a 465's board. Desoldering the delay line isn't my idea of fun!

Hi,


The tek ref I have does not list the -01. I replaced the -02 in my 7B80 with a -01 and both served well past 250Mhz. I sent Neil a -01 per his request. I have more -02s but do have another -01. I would very much like to know what the -01 issue was.


Jerry Massengale

Thanks Jerry - I'd be buying a 7000 series time base off feabay for
that one IC if not for you! I'd be very curious as to the version
difference too.

With all the mention of 'touch as little as possible' it's changed my
thinking and I'm thankful to hear it after realizing what's involved
with just moving one board out of the way yesterday. A lot different
than the servers I manage that are meant to have parts swapped - no
soldering irons there.

What has people's experience been with the giant power filter caps?

Do they tend to be bad after this many decades from age? Or is it
really dependent on chance and hours on the unit?

Can these be tested 'in-circuit'? I'm guessing that excessive ripple
would point to needing to focus on these but saw on a rehab thread it
seemed someone had swapped a few and was curious why or if it's a
matter of course.

On 31 Mar 2016 09:10:46 -0700, you wrote:

I am getting no voltage going into the regulator which is
why I'm focused on the CR1561 rectifier at the moment.

That seems a valid conclusion. It definitely looks like you have a situation like Malcolm's. Follow his good advice.
I'd just like to add that it's a good idea to try and avoid excessive stress on the PCB while removing the bridge rectifier to avoid damaging the traces and through-holes. And avoid getting shrapnel into your eyes...

Raymond

In the past I have overloaded a few plastic packaged power transistors
resulting in shrapnel in the ceiling, the wall, me, etc.