Topics

465 No Go

Dm Armstrong
 

I bought a very used 465 for not much money. When I got it home I found the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I replaced two Tantalim Caps under the high voltage cover , replaced the fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the brightness , but nothing else. I can't move it up or down or side to side.
All my low voltages are right on except the -8 . I have replaced the big 3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut. The IC is the same as another , swap places with no change. The Transistors are Transistoring , and the Resistors are Resisting . All that's left is The Bridge Rectifier, it is soldered so tight to the board I don't know how to check it. What the chance it is bad? Any help will be greatly appreciated.
Thank You
Dave

Craig Sawyers <c.sawyers@...>
 

The bridge rectifier is certainly a possibility. Tek changed the specs on the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there excessive ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I replaced two Tantalim Caps under the high voltage cover , replaced the fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the brightness , but nothing else. I can't move it up or down or side to side.
All my low voltages are right on except the -8 . I have replaced the big 3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut. The IC is the same as another , swap places with no change. The Transistors are Transistoring , and the Resistors are Resisting . All that's left is The Bridge Rectifier, it is soldered so tight to the board I don't know how to check it. What the chance it is bad? Any help will be greatly appreciated.
Thank You
Dave

Dm Armstrong
 

The voltage is .79 positive. When I had the Big 3000 uf Electrolytic out I
think I measured +5 on the positive post were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ? Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to side.
All my low voltages are right on except the -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave





Dm Armstrong
 

I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .




On Tue, Jan 8, 2019, 9:08 AM Dm Armstrong via Groups.Io <dm.armstrong1=
gmail.com@groups.io wrote:

The voltage is .79 positive. When I had the Big 3000 uf Electrolytic out I
think I measured +5 on the positive post were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ? Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <
c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there
excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to
side.
All my low voltages are right on except the -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The
Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know
how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave







tom jobe <tomjobe@...>
 

If you look in the Tekscopes message archive, there should be lots of discussion about how to change the 4XX bridge rectifiers.
The two methods I've used were... either crush the rectifier piece by piece by nibbling it away a little piece at a time, or wiggle the complete rectifier gently side to side to fatigue the four leads until they break and then pull each lead out of the PCB separately.
In either case, put in the highest rated rectifiers you can find and squeeze in there, with the leads bent over at an angle so you can easily reach under and solder the new rectifier to the board.
Rectifiers are common failures in the these kinds of 4XX oscilloscopes.
tom jobe...

On 1/8/2019 7:14 AM, Dm Armstrong wrote:
I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .




On Tue, Jan 8, 2019, 9:08 AM Dm Armstrong via Groups.Io <dm.armstrong1=
gmail.com@groups.io wrote:

The voltage is .79 positive. When I had the Big 3000 uf Electrolytic out I
think I measured +5 on the positive post were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ? Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <
c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there
excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to
side.
All my low voltages are right on except the -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The
Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know
how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave






george edmonds
 

Hi
Just check that it looks like four diodes with a DMM set on diode test.
73 George G6HIG

On Tuesday, January 8, 2019 3:14 PM, Dm Armstrong <dm.armstrong1@...> wrote:


I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .




On Tue, Jan 8, 2019, 9:08 AM Dm Armstrong via Groups.Io <dm.armstrong1=
gmail.com@groups.io wrote:

The voltage is .79 positive. When I had the Big 3000 uf  Electrolytic out I
think I measured +5 on the positive post  were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ?  Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <
c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there
excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to
side.
All my low voltages are right on except the  -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The
Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know
how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave







Chuck Harris
 

The bridge rectifier's diodes can be either: good, shorted, or open.

If they are good, no problems, the voltage on its filter capacitor
will be 1.4 x the Vrms it is being fed. There will be significant
ripple under load, but it will be at 2x the line frequency.

If any are shorted, the capacitor will be taking on the AC power line
in a fight for its life. It will get very hot very quickly. As you
might imagine, the scope will be drawing unusually high current from
the power line.... given time, fuses will blow, capacitor guts and
smoke will get released.

If any are open, the capacitor will either be fed 1/2 wave
rectified AC, or nothing. If it is fed 1/2 wave rectified AC,
the voltage on the capacitor will be at best 0.8 x Vrms. You will
see a very large 60Hz ripple component on the capacitor. If it is
getting nothing, you will see, well, nothing.

-Chuck Harris

Dm Armstrong wrote:

I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .

Dm Armstrong
 

This Old Vacuum Tube Guy is assuming that like Tubes , Transistors need a
Negative Bias or feedback to get things going.
Is this -8 problem enough to keep this Scope from Tracing or might I have
other peoblems.? All I have is a New Multimeter and a Cheep conponet tester
to work with. I wish I had an Oscoloscope to fix my Oscoloscope.

On Tue, Jan 8, 2019, 10:38 AM Chuck Harris <cfharris@... wrote:

The bridge rectifier's diodes can be either: good, shorted, or open.

If they are good, no problems, the voltage on its filter capacitor
will be 1.4 x the Vrms it is being fed. There will be significant
ripple under load, but it will be at 2x the line frequency.

If any are shorted, the capacitor will be taking on the AC power line
in a fight for its life. It will get very hot very quickly. As you
might imagine, the scope will be drawing unusually high current from
the power line.... given time, fuses will blow, capacitor guts and
smoke will get released.

If any are open, the capacitor will either be fed 1/2 wave
rectified AC, or nothing. If it is fed 1/2 wave rectified AC,
the voltage on the capacitor will be at best 0.8 x Vrms. You will
see a very large 60Hz ripple component on the capacitor. If it is
getting nothing, you will see, well, nothing.

-Chuck Harris

Dm Armstrong wrote:
I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost
that
much but looks like a big PAIN to replace properly. I am hoping someone
can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .


Siggi
 

Power supply problems can cause any kind of failure, so no trace is quite
plausibly due to this failure. You might have other trouble, but there's no
point in speculating until you've brought the supplies up and into spec.

If your DMM has a diode mode, you can check the diodes in the bridge
individually with that. Each diode should measure ~0.7V in the forward
direction, and should measure open in the reverse direction.
You can also try and measure the voltage on the -8V rail with the meter in
AC mode. If you have a shorted diode, you'll see a gross AC ripple on the
"DC" rail.

On Tue, Jan 8, 2019 at 11:19 AM Dm Armstrong <dm.armstrong1@...>
wrote:

This Old Vacuum Tube Guy is assuming that like Tubes , Transistors need a
Negative Bias or feedback to get things going.
Is this -8 problem enough to keep this Scope from Tracing or might I have
other peoblems.? All I have is a New Multimeter and a Cheep conponet tester
to work with. I wish I had an Oscoloscope to fix my Oscoloscope.

On Tue, Jan 8, 2019, 10:38 AM Chuck Harris <cfharris@... wrote:

The bridge rectifier's diodes can be either: good, shorted, or open.

If they are good, no problems, the voltage on its filter capacitor
will be 1.4 x the Vrms it is being fed. There will be significant
ripple under load, but it will be at 2x the line frequency.

If any are shorted, the capacitor will be taking on the AC power line
in a fight for its life. It will get very hot very quickly. As you
might imagine, the scope will be drawing unusually high current from
the power line.... given time, fuses will blow, capacitor guts and
smoke will get released.

If any are open, the capacitor will either be fed 1/2 wave
rectified AC, or nothing. If it is fed 1/2 wave rectified AC,
the voltage on the capacitor will be at best 0.8 x Vrms. You will
see a very large 60Hz ripple component on the capacitor. If it is
getting nothing, you will see, well, nothing.

-Chuck Harris

Dm Armstrong wrote:
I am not some kind of Wizzard or Egg Head with Electronics. I hope I
know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost
that
much but looks like a big PAIN to replace properly. I am hoping someone
can
help me think this out before I do much more to it. And if I talk like
an
old Tube Guy that's because that's my first love .




Dm Armstrong
 

.008 volts AC at the -8 Volt Test Point so I am guessing that this Bridge
Rectifier is open. It is soldered so tight to the board I can't even see
Daylight under it .The only way I can test it is to Remove the whole board
. I had thoughts of cutting it out and destroying it to get to the old pins
and hoping there was enough to solder in a new one from the top without
removing the board

On Tue, Jan 8, 2019, 11:33 AM Siggi <siggi@... wrote:

Power supply problems can cause any kind of failure, so no trace is quite
plausibly due to this failure. You might have other trouble, but there's no
point in speculating until you've brought the supplies up and into spec.

If your DMM has a diode mode, you can check the diodes in the bridge
individually with that. Each diode should measure ~0.7V in the forward
direction, and should measure open in the reverse direction.
You can also try and measure the voltage on the -8V rail with the meter in
AC mode. If you have a shorted diode, you'll see a gross AC ripple on the
"DC" rail.

On Tue, Jan 8, 2019 at 11:19 AM Dm Armstrong <dm.armstrong1@...>
wrote:

This Old Vacuum Tube Guy is assuming that like Tubes , Transistors need a
Negative Bias or feedback to get things going.
Is this -8 problem enough to keep this Scope from Tracing or might I have
other peoblems.? All I have is a New Multimeter and a Cheep conponet
tester
to work with. I wish I had an Oscoloscope to fix my Oscoloscope.

On Tue, Jan 8, 2019, 10:38 AM Chuck Harris <cfharris@... wrote:

The bridge rectifier's diodes can be either: good, shorted, or open.

If they are good, no problems, the voltage on its filter capacitor
will be 1.4 x the Vrms it is being fed. There will be significant
ripple under load, but it will be at 2x the line frequency.

If any are shorted, the capacitor will be taking on the AC power line
in a fight for its life. It will get very hot very quickly. As you
might imagine, the scope will be drawing unusually high current from
the power line.... given time, fuses will blow, capacitor guts and
smoke will get released.

If any are open, the capacitor will either be fed 1/2 wave
rectified AC, or nothing. If it is fed 1/2 wave rectified AC,
the voltage on the capacitor will be at best 0.8 x Vrms. You will
see a very large 60Hz ripple component on the capacitor. If it is
getting nothing, you will see, well, nothing.

-Chuck Harris

Dm Armstrong wrote:
I am not some kind of Wizzard or Egg Head with Electronics. I hope I
know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't
cost
that
much but looks like a big PAIN to replace properly. I am hoping
someone
can
help me think this out before I do much more to it. And if I talk
like
an
old Tube Guy that's because that's my first love .






Harvey White
 

On Tue, 8 Jan 2019 10:14:35 -0500, you wrote:

I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .
ok, if you have another scope, look at the output of the bridge
rectifier, it should be pulsating DC (camel humps) with the 3000 UF
disconnected. If the capacitor is in, then you should get at least
-10 volts (more like 11 or 12, check the schematic for voltage level).

Bridges can fail in various ways, they can open (no output), one diode
can fail open (missing humps), fail short (in which case the whole
thing pretty much is shorted and fuses blow).

This sounds open.

Regulators (like the one here), take a higher voltage, typically at
least 3 volts more than the desired output, and use the big transistor
(pass transistor), as a variable resistor (think voltage divider), and
give you the desired output voltage. All those extra parts are in
there to control that transistor, and handle situations where too much
current tries to be drawn.

If you replace the bridge (and yes, most of them are nasty to
replace), try finding one with higher current ratings and higher
voltage ratings.

You really would like a scope to diagnose this scope (which is
typical).

Harvey







On Tue, Jan 8, 2019, 9:08 AM Dm Armstrong via Groups.Io <dm.armstrong1=
gmail.com@groups.io wrote:

The voltage is .79 positive. When I had the Big 3000 uf Electrolytic out I
think I measured +5 on the positive post were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ? Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <
c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there
excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to
side.
All my low voltages are right on except the -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The
Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know
how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave








John Griessen
 

On 1/8/19 10:59 AM, Dm Armstrong wrote:
.008 volts AC at the -8 Volt Test Point so I am guessing that this Bridge
Rectifier is open.
I'd interpret that as very little ripple -- and the bridge rectifier could be open. Not a lot of info yet.

Do you measure AC volts at bridge input pins? (I always consider looking for open
wires/connectors/switches as well as components)

What reading is -8 Volt Test Point on DC?

"destroying it to get to the old pins" can work well. If you later need to
replace some caps and have to pull the pcb out you can tidy it up then.

 

Definitely cut it apart with side cutters and remove the leads individually. You'll probably be able to solder in the replacement from above w/o removing the board (may need to tip over after fitting).

May be advisable to uprate the bridge rectifier current rating too.

Dave

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dm Armstrong
Sent: 08 January 2019 16:59
To: TekScopes@groups.io
Subject: Re: [TekScopes] 465 No Go

.008 volts AC at the -8 Volt Test Point so I am guessing that this Bridge
Rectifier is open. It is soldered so tight to the board I can't even see
Daylight under it .The only way I can test it is to Remove the whole board
. I had thoughts of cutting it out and destroying it to get to the old pins
and hoping there was enough to solder in a new one from the top without
removing the board

tands13462@...
 

WHOA....Hold on!
After repairing hundreds of Tek 465's, I've learned that the first thing to do is determine if a voltage isn't there or it's there and being pulled down by something downstream.
If you have a service manual, there are trouble shooting flow charts in the back of the manual.
Next thing is to determine which of the above conditions exist.
With the instrument off, check the resistance from the -8 volt test point to ground. You should see some resistance. If you read no resistance (dead short), that's your problem....a shorted component further downstream.
Follow the trouble shooting chart to localize the short.

HTH...Tad

Paul
 

These guys are doing a great job of helping you. I've been following along, but I did not see anything in the thread to indicate whether you have the Tek 465 manual? It has a really good troubleshooting section for the power supply with the schematic showing what voltages you should see at various points. I have a PDF of the entire 465 manual (it is 30mb), but I just made a smaller PDF of just the low voltage power supply portion (1.15mb). If you don't have it, email me at paulinsunriver2@... and I'd be happy to send you that power supply section. I'm not sure my browser will send a 30mb file attachment. If I am remembering correctly I may have found the link to it on the Tektronix 465 section of Wikipedia. Might have been somewhere else. Also, did I miss your answer about whether you have a second scope, or if you could borrow one? That is so helpful, as you know from tube radios, and true for power supplies, because you can literally see what is (is hot) happening. Those traces show you very clearly what is hard or impossible to measure with a meter. You can look at what is going into, and coming off that bridge rectifier, with and without the loads (the manual has isolation procedures to unload the different power supply sections. Anyway, no intention to step on the good coaching you are getting, but just some thoughts to try and help.

Dm Armstrong
 

I have the 465 manual the one with the Blue Cover (PDF) and a Operator Owner Manual. I have Captured a Close Up of all the Power Supplies. I have tried to follow the flow charts and will do it again before I undo more. It seems like it told me to check and repair the power supplies in an order with the -8 last.
This is what I have done so far .Replaced the 3000 uf Electrolytic and a 33 uf Tantalum in the -8 volt power section. Checked all Transistors an Resistors in this section including the Large Transistor heat sinked to the Frame. I traded places with the two Identical IC Amplifiers . Chanced two Tantalum Cap under the High Voltage cover All other power supplies are Spot On, Right On to what they are supposed to be. The Negative 8 is the only one not right. I think I said I had .79 volts dc , and maybe .008 Ac. I did check the -8 Test Point pin to ground and had 53.6 Ohms

I have a bright green Dot on the screen that I can focus and change the brightness. I can't move it up or down , left or right.
The whole unit is pulling .61 amps

John Griessen
 

On 1/8/19 4:52 PM, Dm Armstrong wrote:
The Negative 8 is the only one not right. I think I said I had .79 volts dc , and maybe .008 Ac. I did check the -8 Test Point pin to ground and had 53.6 Ohms
I have a bright green Dot on the screen that I can focus and change the brightness.

OK, lots more info. You've got clean DC of the wrong level. Other parts of the scope are working fine,
so the -8 volts is where to look. It's kind of hard without a scope though. Try measuring volts at points in the circuit,
and more checking resistors like you did so far.

John Griessen
 

On 1/8/19 5:21 PM, John Griessen wrote:
Try measuring volts at points in the circuit,
and more checking resistors like you did so far.

John Griessen
 

On 1/8/19 5:21 PM, John Griessen wrote:
Try measuring volts at points in the circuit,
and more checking resistors like you did so far.
Below is a section of the schematic to focus on:
https://www.ecosensory.com/tek/465-power-8V.png

Harvey White
 

On Tue, 08 Jan 2019 12:10:09 -0500, you wrote:

OK, you very much need another scope.

What you want is a scope that will do +/- 30 volts or so, frequency
response of 100 Khz or so to 1 Mhz. AC or DC inputs.

I've gone through amazon.com, and picked the following:

1) I don't have any of them
2) I don't especially recommend any of them
3) they are the kind of things you might consider

in no particular order:
https://www.amazon.com/Quimat-Pocket-Size-Oscilloscope-Protective-Assembled/dp/B07GRK38MS/ref=sr_1_11?s=industrial&ie=UTF8&qid=1546994823&sr=1-11&keywords=oscilloscope
https://www.amazon.com/Longruner-DSO138-Digital-Oscilloscope-Assembled/dp/B07MNK1FV4/ref=sr_1_14?s=industrial&ie=UTF8&qid=1546994823&sr=1-14&keywords=oscilloscope
https://www.amazon.com/KKmoon-Oscilloscope-Handheld-Soldered-Electronic/dp/B07C3F5BP3/ref=sr_1_30?s=industrial&ie=UTF8&qid=1546994906&sr=1-30&keywords=oscilloscope
https://www.amazon.com/Handheld-Portable-Ultra-Small-Oscilloscope-Bandwidth/dp/B07FR91QW9/ref=sr_1_58?s=industrial&ie=UTF8&qid=1546994957&sr=1-58&keywords=oscilloscope
https://www.amazon.com/Comidox-DSO138-Digital-Oscilloscope-Assembled/dp/B07J9LRKD3/ref=sr_1_125?s=industrial&ie=UTF8&qid=1546995080&sr=1-125&keywords=oscilloscope

I'd personally go for something with a case, and I like color
displays.

Haven't bought any of them, no idea if the vendor is good or not, do
the research

However....

A scope of this type will tell you whether a waveform is AC or DC,
where it passe the zero volts line,

You might want to have one for the following uses:

1) something where you need a portable scope
2) where it's not required to do a lot
3) where you have only one other scope
4) where you have so little space that a normal sized scope won't fit.
5) where you can live within the limitations of the scope

so what I'd want to buy....

color display (yeah, I just like them)
case... can't argue there, I like them

Note that many of these little scopes have odd input connectors, and
if the probe is not included, you need to buy one.

Internal battery might be a good idea.

Will you use it more than once? Maybe
will it be your "go to scope" Unlikely
can it answer several questions you can't answer now....

likely....

Just a suggestion.

You could always borrow the equivalent, or take it to a local "maker
space" and see what they have (seriously, look them up on the
internet). Not free, but maybe worth the money.

Harvey



On Tue, 8 Jan 2019 10:14:35 -0500, you wrote:

I am not some kind of Wizzard or Egg Head with Electronics. I hope I know
enough to keep myself from being Electrocuted.
The whole unit is drawing .61 amps . The Bridge Rectifier doesn't cost that
much but looks like a big PAIN to replace properly. I am hoping someone can
help me think this out before I do much more to it. And if I talk like an
old Tube Guy that's because that's my first love .
ok, if you have another scope, look at the output of the bridge
rectifier, it should be pulsating DC (camel humps) with the 3000 UF
disconnected. If the capacitor is in, then you should get at least
-10 volts (more like 11 or 12, check the schematic for voltage level).

Bridges can fail in various ways, they can open (no output), one diode
can fail open (missing humps), fail short (in which case the whole
thing pretty much is shorted and fuses blow).

This sounds open.

Regulators (like the one here), take a higher voltage, typically at
least 3 volts more than the desired output, and use the big transistor
(pass transistor), as a variable resistor (think voltage divider), and
give you the desired output voltage. All those extra parts are in
there to control that transistor, and handle situations where too much
current tries to be drawn.

If you replace the bridge (and yes, most of them are nasty to
replace), try finding one with higher current ratings and higher
voltage ratings.

You really would like a scope to diagnose this scope (which is
typical).

Harvey







On Tue, Jan 8, 2019, 9:08 AM Dm Armstrong via Groups.Io <dm.armstrong1=
gmail.com@groups.io wrote:

The voltage is .79 positive. When I had the Big 3000 uf Electrolytic out I
think I measured +5 on the positive post were the Cap was. After I got it
out it still was OK.
The next Question, New Old Stock or NEW from maybe Mouser? Does anyone have
some idea what I need ? Can the Bridge Rectifier be replaced without
removing the board?
The way I have it figured is 1000 parts, 5 replaced only 995 to go untill
it works.

On Tue, Jan 8, 2019 at 8:38 AM Craig Sawyers <
c.sawyers@...>
wrote:

The bridge rectifier is certainly a possibility. Tek changed the specs on
the bridges several times because of a known weakness in earlier choices.

What does the -8V read? Is it just not there at all, or is there
excessive
ripple?

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
dm.armstrong1@...
Sent: 08 January 2019 00:58
To: TekScopes@groups.io
Subject: [TekScopes] 465 No Go

I bought a very used 465 for not much money. When I got it home I found
the 1.5 amount fuse on the inside was bad . The Main fuse was OK. I
replaced two Tantalim Caps under the high voltage cover , replaced the
fuse. No more blowen fuses.
What I have is a very bright green dot. I can focus it and adjust the
brightness , but nothing else. I can't move it up or down or side to
side.
All my low voltages are right on except the -8 . I have replaced the big
3000 uf Electrolytic capacitor and a 33uf Tantalim in the -8 volt curcut.
The IC is the same as another , swap places with no change. The
Transistors
are Transistoring , and the Resistors are Resisting . All that's left is
The Bridge Rectifier, it is soldered so tight to the board I don't know
how
to check it. What the chance it is bad? Any help will be greatly
appreciated.
Thank You
Dave