Yet another Tektronix 465 repair thread

[bd139]

Just got my hands on another dead 465. This is my 12th 4xx scope. This one looks pristine inside and out and has 3x genuine tek probes, accessory bag and cover. Untested but lights up.

Pictures

As advertised:


Post-first-fixing session and a quick wipe down. Still ch1 switch issues at the moment:


Dead bits and foreign objects so far:


Will write up any notes in here. So far issues identified:

Misc

* Latest date code is 1977 so this is quite a late model 465 non B.
* Found a scope probe tip protector. Hmm. Someone has been in it!
* Came with three Tek probes. Unfortunately two of them were 1X probes so I've only got one nice 10X probe 

HT dirt

1. Brushed out.
2. FIXED

HT protection fuse blown

1. Shorted HT tant probably.
2. Confirmed shorted. There are actually two in one pair of holes and at least one of them has gone phut.
3. C1419 replaced with 100uF 35V Panasonic E
4. FIXED

15V rail right down at 500mV

1. Confirmed shorted tant on 5V rail (not 15 as first identified!).
2. Found it. C1559. Snipped and all rails come up normal. To replace.
3. C1559 replaced with 100uF 35V Panasonic E
4. FIXED

Vertical adjustment range of both channels is way off.

1. Suspect voltages around vertical amp. WRONG
2. Leaf switches on vertical mode push pull switch were dirty. Full vertical motion now!
3. FIXED

Noisy pots and switches

1. Most of them. Will work through and clean them all.
2. Channel switches cleaned. Much improved behaviour.

One of the graticule illumination bulbs is popped.

1. Will replace

[Specmaster]

Hmm, and there's no way that could have got inside by accident other than opening it up.

[bd139]

yep exactly. Can't find any evidence of any repairs. Might have been a quick analysis and chuck in a skip job.

Rails are all in spec now. Putting HT fuse back in now. Fingers crossed!

[med6753]

Today must be Tek 465 day. I just posted final calibration results on my 465B project in the TEA thread. 

[bd139]

Yep indeed it is

Will go have a look shortly.

It's alive! But not without problems.

[Specmaster]

Yep indeed it is

Will go have a look shortly.

It's alive! But not without problems.

It's in triage now for assessment and it's fate will be sealed soon now.🤞

[bd139]

Have checked power supply out. All good now. Even ripple is in spec.

The vertical problems appear to be due to only to to dirty leaf switches.

[med6753]

Have checked power supply out. All good now. Even ripple is in spec.

The vertical problems appear to be due to only to to dirty leaf switches.

Yea, and have fun cleaning the Channel 2 leaf switches. I still have nightmares. 

[Specmaster]

Have checked power supply out. All good now. Even ripple is in spec.

The vertical problems appear to be due to only to to dirty leaf switches.

A good dose of switch cleaner should sort that then.

[bd139]

Have checked power supply out. All good now. Even ripple is in spec.

The vertical problems appear to be due to only to to dirty leaf switches.

Yea, and have fun cleaning the Channel 2 leaf switches. I still have nightmares. 

Just done them. All good now 

I haven't hit the attenuators yet. Not sure what fun that will bring.

[med6753]

Have checked power supply out. All good now. Even ripple is in spec.

The vertical problems appear to be due to only to to dirty leaf switches.

A good dose of switch cleaner should sort that then.

Believe it or not deoxit is not recommended for the input attenuators and the leaf switches. The residue can change the high frequency characteristics. IPA or physically clean them with paper.

[bd139]

That's exactly what I do. Take a piece of A4 paper and cut strips, then dip in IPA, open the leaf switch with front panel, insert paper, close leaf switch with panel and gently pull out in line with the switch lever. Repeat 5-10 times.

Deoxit / whatever is fine for the channel switch etc. I'm using WD40 contact cleaner (not normal WD40). Does the job nicely and doesn't eat any plastics I've found so far.

[Specmaster]

That's exactly what I do. Take a piece of A4 paper and cut strips, then dip in IPA, open the leaf switch with front panel, insert paper, close leaf switch with panel and gently pull out in line with the switch lever. Repeat 5-10 times.

Deoxit / whatever is fine for the channel switch etc. I'm using WD40 contact cleaner (not normal WD40). Does the job nicely and doesn't eat any plastics I've found so far.

Would have thought that switch cleaner or a spray of IPA and operating the switches would have been sufficient?

[bd139]

They are leaf switches so they aren't self cleaning like sliding contacts. You have to actually run something through the contacts.

Got most of it working. Channel switch is still dicky. Will leave that for another day. Channel 1 is not responding now 

However this is surmountable and the rest of it appears to work nicely!

[Specmaster]

They are leaf switches so they aren't self cleaning like sliding contacts. You have to actually run something through the contacts.

Got most of it working. Channel switch is still dicky. Will leave that for another day. Channel 1 is not responding now 

However this is surmountable and the rest of it appears to work nicely!

Not such a clever design then seeing as they are in a hard to reach spot, would have expected a little bit of wiping action as the contact pressure is applied?

[bd139]

The attenuator ones are well hidden. They changed this in the 465B so you can get the entire assembly out. 465, not so much. The leaf switches giving me trouble are easy to access on the vertical preamp board.

Have updated first post with pictures. This is a unicorn if I can get the channel switching sorted 

[Specmaster]

The attenuator ones are well hidden. They changed this in the 465B so you can get the entire assembly out. 465, not so much. The leaf switches giving me trouble are easy to access on the vertical preamp board.

Have updated first post with pictures. This is a unicorn if I can get the channel switching sorted 

Hope SWMBO don't dump you on the top of the horn then, it'll bring tears to your eyes will that🤣

[bd139]

Ouch! 

[tautech]

And the D83 sits forlornly waiting for some equivalent love in the cupboard. 

[bd139]

It has been promoted to the hall now. It will be repaired. I go in bursts

[Specmaster]

It's looking really good but I'm wondering where the third tant came from, you replaced 2 with 100uF 35v electrolytics, and the third?

[bd139]

There were two rammed in the same holes. Not seen that before. Replaced with one electrolytic.

[Specmaster]

Oh I see, they were 50uF each then?

[iainwhite]

I'm enjoying reading and learning.   Hope you keep fixing these 400 series scopes!

[bd139]

Oh I see, they were 50uF each then?

No 22uF each. Only one was shorted. The one with the dull top. This totals 44uF. If you swap a tant out for an electrolytic, it's good practice to double its value so I put a 100uF in. Also that was the first cap I put my hand in the box and pulled out  (there's not a lot of science to it sometimes)

I'm enjoying reading and learning.   Hope you keep fixing these 400 series scopes!

Thanks for the support

I am now looking for light bulbs. Unfortunately the only bloody place I can find some is RS an that's £7.63 for a 10 pack. I'm still deciding if this is expensive or not as I only need one of them. I did however shake my head slightly at the £6 or so I spent on a pack of fuses and this is the 4th scope that had a blown HT so far so I did ok out of them. Perhaps I should just buy them.

I did consider an LED replacement but that's not in the spirit of such a stately instrument and also the lighting is less diffused and of lower quality.