Newbie with Tek 465

[Restorationnut]

Hi All,

First post on this forum. I spend all my time restoring pre WWII radios, and being active on the two main antique radio forums.

But I thought I'd take a break, and get my 465 working. Haven't done much "modern" stuff (after 1960).

So I need a little assistance. Power on, get a few lights, but display is dark. Grid illumination works. When I turn the intensity knob, I get an intermittent fuzzy dot. I should preface this by saying the last time I turned it on (a year or so ago), it worked, but any waveform wasn't really stable.

Time to play. I started by checking the fuse. It's good Then on to the voltages. All are low. +55 was around 39. Manual says it could be a leaky filter cap. I hate those can electrolytics anyway. So I thought I'd start by changing them. I removed the trigger board to get to them, and removed all 5. They are not 'lytics I use, so I had to order them. But while I wait...As I removed the trigger board, I noticed two wires (about 22 ga.) branching off. They are attached to the timing board on one end, but were broken off where they attach to the trigger board. I can't seem to find where they go, and can't easily find them in the service manual.

They are, of course, the two wires circled in red in the pic. Can someone tell me where they go? Thanks for reading.



 

[Labrat101]

this is an an oldie I would check the power section if all the voltage are low .
 and check the caps in this section first start with the big 400vdc cap and work though the power supply . Make sure you discharge the caps first .
 The other wire you marked don't know without diagram .
 its a thin wire so its probable low voltage
the power supply section sounds like your problem and a faint screen also confirms
 get the 55v sorted .
I would leave the trigger board alone until you solve the power problem

 I looked also on the manual there a few variation on this model is it the 465A ??
  as the voltages differ on versions  60v . Make sure you use the correct service manual
 its downloadable from Tektronix archive . follow there trouble section sec 40/6
 it gives all the voltages on the pins etc . be careful not to loose the NVRAM  or you will loose all the calibration and its a pain in the ass to recal . .. I have done a few TEks not this model .

[Restorationnut]

this is an an oldie I would check the power section if all the voltage are low .
 and check the caps in this section first start with the big 400vdc cap and work though the power supply . Make sure you discharge the caps first .
 The other wire you marked don't know without diagram .
 its a thin wire so its probable low voltage
the power supply section sounds like your problem and a faint screen also confirms
 get the 55v sorted .
I would leave the trigger board alone until you solve the power problem

Thanks, but I think you may have misread my post.

[Labrat101]

this is an an oldie I would check the power section if all the voltage are low .
 and check the caps in this section first start with the big 400vdc cap and work though the power supply . Make sure you discharge the caps first .
 The other wire you marked don't know without diagram .
 its a thin wire so its probable low voltage
the power supply section sounds like your problem and a faint screen also confirms
 get the 55v sorted .
I would leave the trigger board alone until you solve the power problem

Thanks, but I think you may have misread my post.

From that picture No .. maybe the black plug make a better photo of the area .
When a wire pulls off there are usually tell tell signs you will have to look close plus need the model and year is it the A does it have the option brds .. ??

to find it on the circuit one need to know where the other end goes ..

[jdragoset]

If it is not a 465 A, tell the the SN above/below.
If it's the same range as mine (recall above 22000) I will pull the cover and look

[Restorationnut]

If it is not a 465 A, tell the the SN above/below.
If it's the same range as mine (recall above 22000) I will pull the cover and look

Thanks. No, not an A. Serial # is B260117.

[med6753]

There was no "465A". There was a "465" and "465B". And the Vertical and Timing boards are vastly different.

I have a 465 carcass sitting in my spare parts stash. I'll pull it out tomorrow and see if I can identify the wiring in question.

[Restorationnut]

There was no "465A". There was a "465" and "465B". And the Vertical and Timing boards are vastly different.

I have a 465 carcass sitting in my spare parts stash. I'll pull it out tomorrow and see if I can identify the wiring in question.

Thank you.

[Labrat101]

There was no "465A". There was a "465" and "465B". And the Vertical and Timing boards are vastly different.

I have a 465 carcass sitting in my spare parts stash. I'll pull it out tomorrow and see if I can identify the wiring in question.

Thank you.

You should read the original TEK service manual the first series was not always marked with 465 (A)
 on the front panel as it was the first series .
 but its on the brd . ref.  The B serials comes after the  'A'  durr..   
 and there is a big difference between the 2 models  .. Time base board & the PSU voltages
 There were also option brds as well .
They may look similar by eye .
 
Case closed

[med6753]

There was no "465A". There was a "465" and "465B". And the Vertical and Timing boards are vastly different.

I have a 465 carcass sitting in my spare parts stash. I'll pull it out tomorrow and see if I can identify the wiring in question.

Thank you.

You should read the original TEK service manual the first series was not always marked with 465 (A)
 on the front panel as it was the first series .
 but its on the brd . ref.  The B serials comes after the  'A'  durr..   
 and there is a big difference between the 2 models  .. Time base board & the PSU voltages
 There were also option brds as well .
They may look similar by eye .
 
Case closed

OK, who pissed in your wheaties this morning?

Tek was always revising their equipment resulting in boards and other assemblies possibly being labelled with an "A" revision or "B" revision but usually it just resulted in a part number change which later prints of the manuals would list and the serial numbers affected.

The point here is that there was never a 465 officially labelled and sold as a "465A". There was a "465" and "465B".

 Maybe you need to fill out one of these.

[med6753]

There was no "465A". There was a "465" and "465B". And the Vertical and Timing boards are vastly different.

I have a 465 carcass sitting in my spare parts stash. I'll pull it out tomorrow and see if I can identify the wiring in question.

Thank you.

I think this is what you are looking for. Both those wires come out of that harness and attach to that sub board under the main timing board. This 465 originally had a DM44 so there's some additional wiring that yours may not have. (Which I removed to make the picture clearer). If you need anything else let me know.

[Restorationnut]

Thanks. Well.....we're getting close. It's the OTHER end of those two wires that connect to the trigger board that I need. Even after inspecting the trigger board closely, I can't see where they attached.

[hnjmkl]

I am not aware they had NVRAM

[med6753]

Thanks. Well.....we're getting close. It's the OTHER end of those two wires that connect to the trigger board that I need. Even after inspecting the trigger board closely, I can't see where they attached.

OK, I undid the harness and here's the results. The wire from the FAR right on that sub board goes to the LEFT point as shown on the Timing board. And obviously the wire from the LEFT side of the sub board goes to that RIGHT point.




Edit....it's those two 100 ohm resistors on the top side of the timing board.

[med6753]

I am not aware they had NVRAM

The 465/465B doesn't. Just another piece of misinformation. The calibration on these scopes is old school analog twist pot.

[Restorationnut]

Thanks. Well.....we're getting close. It's the OTHER end of those two wires that connect to the trigger board that I need. Even after inspecting the trigger board closely, I can't see where they attached.

OK, I undid the harness and here's the results. The wire from the FAR right on that sub board goes to the LEFT point as shown on the Timing board. And obviously the wire from the LEFT side of the sub board goes to that RIGHT point.

Got it! Thanks for taking the time and effort. I was incorrectly assuming they went to the TOP of the board. But now I can see where they were attached to the bottom.

Thanks again.

[med6753]

Thanks. Well.....we're getting close. It's the OTHER end of those two wires that connect to the trigger board that I need. Even after inspecting the trigger board closely, I can't see where they attached.

OK, I undid the harness and here's the results. The wire from the FAR right on that sub board goes to the LEFT point as shown on the Timing board. And obviously the wire from the LEFT side of the sub board goes to that RIGHT point.

Got it! Thanks for taking the time and effort. I was incorrectly assuming they went to the TOP of the board. But now I can see where they were attached to the bottom.

Thanks again.

You're welcome.  If you need anything else post up. I have lots of experience with these scopes.

[Restorationnut]

Now that I have the caps replaced, I started checking voltages. All look O.K., EXCEPT no -8V. Looks like I need to pull the board to be able to check CR1561. Any suggestions? By the way, would the lack of -8 V be the cause of no trace?

[med6753]

Now that I have the caps replaced, I started checking voltages. All look O.K., EXCEPT no -8V. Looks like I need to pull the board to be able to check CR1561. Any suggestions? By the way, would the lack of -8 V be the cause of no trace?

Yes, without -8V chances are there would be no trace. Check to make sure the -8V bus isn't shorted to ground. If it is that would indicate a possible shorted tantalum capacitor on one of the boards. The manual does give a isolation procedure for tracking down which board has the short.

[Restorationnut]

Thanks, Already eliminated the trigger board, so I will continue!

[Restorationnut]

Not shorted, but I found C1220 had been leaking (visual). It should be 1000 mfd @ 10V, but it measures around 455. I assume this is a Tantalum (never worked with them before)? I don't see where either Mouser or Digikey has them.  Can I use a regular electrolytic?

C1220 is tied to a 22Ω resistor in the horizontal amp circuit, and has -8V applied to it. 

[med6753]

C1220 would be an aluminum electrolytic, not tantalum.

[Restorationnut]

Thanks.

[tggzzz]

Not shorted, but I found C1220 had been leaking (visual). It should be 1000 mfd @ 10V, but it measures around 455. I assume this is a Tantalum (never worked with them before)?

That will be specified in the manual.

If it is leaking then it is unlikely to be a tantalum. When very expensive milspec wet slug tants leak, PCB tracks completely disappear

[Restorationnut]

Not shorted, but I found C1220 had been leaking (visual). It should be 1000 mfd @ 10V, but it measures around 455. I assume this is a Tantalum (never worked with them before)?

That will be specified in the manual.

If it is leaking then it is unlikely to be a tantalum. When very expensive milspec wet slug tants leak, PCB tracks completely disappear

I finally found it in the manual specifying which are tantalums and which are not. So old tantalums have a habit of shorting?