Author Topic: Tek 465 long term storage to operational??  (Read 855 times)

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Offline dave356

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Tek 465 long term storage to operational??
« on: September 14, 2017, 11:34:51 am »
Hi,

I have been refurb/repair old tube radios for some time but haven't been able to work on any for about 9-10 years due to job constraints. Mostly working fab 5 sets and a lot of halicrafters,  (S-19, S20, S22, S38-a-b-c, don't care much for the looks of the d or e variation)  The Tek 465 I've been using for the projects has been sitting idle for almost 10 years.  Other scope, Hitachi v-212 also sat same period.

Hitachi, all I did was plug her in and "Light the Fires" and all was good.  No problems what-so-ever. Never even blinked.  Hitachi never was finicky.

The tek 465 I feel might be a little different.

I have a variac but a person told me it is not good to bring a scope up on a variac.  Something about maybe throwing out the amp circuits and also the calibration.
Would it be wise just to power it up normally?

Would hate to damage it. It has been a very good scope for me for over 22 years.

Bought a Siglent SDS1202X-E 2 weeks ago with the EEVblog discount from SAELIG, (Thanks tautech and SAELIG) to help me get out of the stone-age, but I worry about my 465.

Any suggestions will be thankful and considered.

Thanks,  Dave





   
 

Offline helius

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Re: Tek 465 long term storage to operational??
« Reply #1 on: September 14, 2017, 12:13:40 pm »
You can use a variac to power up a 465. The switching power supply will not begin oscillating until you reach 80VAC or thereabouts. It appears to be stable in that range. You can bring the voltage up slowly over 4 hours or so and soak at 130VAC (which is near the upper limit for most variacs).
 

Offline innkeeper

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Re: Tek 465 long term storage to operational??
« Reply #2 on: September 14, 2017, 12:36:14 pm »
I acquired a NOS leader LBO-516 (was rebaged as a labvolt 789) scope

had not been fired up since it was made in ~1984, so maybe 33 years of sitting in a box.
yea i know all about that I should have reformed the caps, and i had the exact same thought if maybe bringing it up on a variac  for a few hours to reform them that way..
But i was also concerned if i might cause more issues running it at low voltage. it is one thing to reform a cap not connected to anything, and another trying to do it in a live circuit.

So I decided to fire it up at full voltage, and be ready to power it off if anything released the magic smoke.
i figured if anything popped id just fix it.

Initialy I  could notice a little noise making it to the display trace.
after a few hours that went away and its been fine ever since. so they seemed to recover ok.

i could have just as easily blown a cap, but i was prepare to deal with that if it happened.


Hobbyist and a retired engineer and possibly a test equipment addict, though, searching for the equipment to test for that.
 

Offline tautech

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Re: Tek 465 long term storage to operational??
« Reply #3 on: September 14, 2017, 12:46:33 pm »
You can use a variac to power up a 465. The switching power supply will not begin oscillating until you reach 80VAC or thereabouts. It appears to be stable in that range. You can bring the voltage up slowly over 4 hours or so and soak at 130VAC (which is near the upper limit for most variacs).
Go with this ^
There'll be no damage to Cal if all goes well.

Reforming the E caps is pretty much all you need worry about providing the selectors and switches haven't dried out through lack of use. Some switch 'exercise' can be all that's needed if things are a bit scratchy.

Good luck.
Avid Rabid Hobbyist
 

Offline David Hess

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Re: Tek 465 long term storage to operational??
« Reply #4 on: September 14, 2017, 01:07:46 pm »
If there is any danger, I suspect it is do to surge current into the large aluminum electrolytic input capacitors through the input rectifiers which were known to fail anyway.  Tektronix upgraded them or some of them later.  The regulators themselves all support current limiting.  The various solid tantalum decoupling capacitors are also known to fail however I do not think there is anything you can do about that.

So if you want to use a variac, that is up to you but there is no need to extend the ramp up time beyond seconds or 10s of seconds.  After that I would leave the oscilloscope running for several hours while supervised and without the variac.  Set the CRT to a low but visible intensity and deliberately defocus it to prevent screen damage if something goes wrong.

You can use a variac to power up a 465. The switching power supply will not begin oscillating until you reach 80VAC or thereabouts.

The Tektronix 465 has no switching power supply.  It has a high voltage inverter for the CRT circuits but it is linear as well.
 

Offline dave356

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Re: Tek 465 long term storage to operational??
« Reply #5 on: September 14, 2017, 03:11:20 pm »
Thanks Guys.

I used the variac to ramp it up starting about 50v
About every minute or so I took it up 10v.
At about 90v it had trace starting, but weak.
Once I had it up to 110v, about 8-9 minutes of ramping, I disconnected variac and plugged into mains.

All is well.  I feel so  much better about it now.

Will let it cook for 3-4 hours with weak and unfocused trace.

Everything works as designed.

I exercised it with a function gen after a few minutes, and I have clear accurate traces both channels.

Now to let it run for a few hours.

Just wasn't sure if the variac thing was the way to go.

Thanks guys. 
 


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