UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Reply
 
Thread Tools
Old 10th Apr 2019, 9:41 am   #1
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Tektronix 2211 scope short-circuited

Hi all,

Recently purchased a Tektronix 2211 scope from 1990 and a T202 handheld probe as a 2 for 1 deal for a real bargain.

But the bargain was probably too good to be true.

After 30 minutes of testing it with a small wave gen the scope suddenly gave a bang sound and the power to the apartment was out. Seems my RCD blew out.

So turned it on, powered the scope again and it "blew" again immediately. You can smell a faint electrical burn.

I've opened the scope but can't seems to find at first glance any culprits (no popped caps for example). The only thing I can see is that the high-voltage transformer has some burn marks. Though this might be normal?

Tonight I'm going to dust it out and remove the boards to have a better look at the other parts.

Thanks for any tips!
Attached Thumbnails
Click image for larger version

Name:	IMG_8263.jpg
Views:	108
Size:	79.3 KB
ID:	181150   Click image for larger version

Name:	IMG_8265.jpg
Views:	110
Size:	54.8 KB
ID:	181151  
Don_Zalmrol is offline   Reply With Quote
Old 10th Apr 2019, 9:53 am   #2
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

This happened to my 2235 recently. They do like to explode!

The power supply on these is mostly the same as the 2225 if I remember correctly, so have a look at the service manual for that (available free from w140.com). Check the input board carefully (the vertical board in the rear). It's chock full of RIFAs. Those usually go first. After that it's likely the secondary caps after the big toroidal transformer. The HT on these doesn't usually fail violently but that transformer doesn't look particularly healthy. I would buzz everything out.

You can actually bring these up on a DC power supply with enough volts just by jumping the secondary cap. This is handy for debugging!

Edit: there be dragons. I spent upwards of 40 on bits for my 2235 before I got it going again and now it has an HT problem
MrBungle is online now   Reply With Quote
Old 10th Apr 2019, 9:53 am   #3
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

This thread is oddly similar!

https://groups.io/g/TekScopes2/topic...0,2,0,24975657
Don_Zalmrol is offline   Reply With Quote
Old 10th Apr 2019, 9:57 am   #4
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

Yes - I made the incendiary RIFA comments on that thread
MrBungle is online now   Reply With Quote
Old 10th Apr 2019, 9:59 am   #5
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

Thx MrBungle.

Will check those. Just need to get my hands on the service manual for the 2211 which seems to be a bit of hassle at the moment. Will check the vertical board as the mains is directly connected on that part of the board.
Don_Zalmrol is offline   Reply With Quote
Old 10th Apr 2019, 10:02 am   #6
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

AFAIK it's the same as a 2225 just with a fan and an extra board in it for the digital bits. I'd start there.
MrBungle is online now   Reply With Quote
Old 10th Apr 2019, 10:03 am   #7
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

The internet always leaves it traces Chris
Will check those, but the caps doesn't seem blown at first sight. But will test them out.
Don_Zalmrol is offline   Reply With Quote
Old 12th Apr 2019, 7:41 am   #8
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

So I've checked the PSU of the scope and it seems in rather good condition. What I do see is that the IEC socket and 230-110V switch have a blackish coloration on their leads.

The main filtercap of 2200uF 80VDC measures fine with my multimeter (2153uF and +- 6M Ohms).

The diodes measure +- 0.5V over them and in the reverse it's 0. Which means they should be ok.

In any case I will replace the components on this vertical mains inlet. The PST39 transformer (as showed earlier) have some wear and tear marks, but I believe this might be caused due to stress of a different origin.

Nowhere on the PCB(s) are there any indicators that somethings has blown a component.
So I believe the fault lays in the PSU itself.

I also believe that someone serviced it before as some of the torx screws were removed using a wrong screwdriver.

Any other things I better check out?
Attached Thumbnails
Click image for larger version

Name:	WhatsApp Image 2019-04-12 at 08.31.31.jpg
Views:	62
Size:	42.6 KB
ID:	181240   Click image for larger version

Name:	WhatsApp Image 2019-04-12 at 08.31.31(1).jpg
Views:	64
Size:	40.6 KB
ID:	181241  
Don_Zalmrol is offline   Reply With Quote
Old 12th Apr 2019, 8:29 am   #9
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

I have all the components listed of the vertical PSU board. But cannot read the Q900.
Believe this would be a voltage regulator as it's close to the leads that go towards the main PCB.

Still searching for a service manual
Don_Zalmrol is offline   Reply With Quote
Old 12th Apr 2019, 8:44 am   #10
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

2n5401. Check 2225 service manual. Same board
MrBungle is online now   Reply With Quote
Old 12th Apr 2019, 8:51 am   #11
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

Thanks!

Seems that the majority of the posts about this issue with my 2211 all point to the PSU.

Will update when I've changed the components.
Don_Zalmrol is offline   Reply With Quote
Old 12th Apr 2019, 9:52 am   #12
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

It's possible. Check all the power rails for shorts to ground as well. They are all accessible by large staple-like jumpers just outside the power supply enclosure (you will have to remove the digital board). It's possible there are tantalum or Philips capacitors on it somewhere which have gone short. The power supply will fail to start and pop the fuse then.

The last 2225 I did had shorted Philips caps in it.

edit: actually I'd probably pull the digital board out and see if it works or not then go from there.
MrBungle is online now   Reply With Quote
Old 15th Apr 2019, 8:02 pm   #13
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

Found the culprit!
It was indeed one of the filter caps (2200nF) that was shorted.

Replacing the caps on the PSU as we speak. Though made an order mistake for the 0.15uF filter cap and ordered a 0.015uF one instead...
Attached Thumbnails
Click image for larger version

Name:	WhatsApp Image 2019-04-15 at 20.19.55.jpg
Views:	81
Size:	31.2 KB
ID:	181396   Click image for larger version

Name:	WhatsApp Image 2019-04-15 at 20.19.56.jpg
Views:	70
Size:	52.6 KB
ID:	181397  
Don_Zalmrol is offline   Reply With Quote
Old 15th Apr 2019, 8:26 pm   #14
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

Seems I can't get the 0.15uF 250V~ easily.
Would a 0.15uF be a good replacement, given the extra headroom of voltage?


https://www.gotron.be/componenten/pa...-10-p22-5.html

They do sell the 2N5401 which seems to be getting discontinued from what I can find out.
https://www.gotron.be/2n5401-pnp-160...-3w-to-92.html
Don_Zalmrol is offline   Reply With Quote
Old 15th Apr 2019, 10:21 pm   #15
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

You're lucky it didn't catch fire! Those RIFAs tend to go incendiary.

C904 has to be a Y2 class capacitor as it's between mains and earth - can't just use any film capacitor here. C903 is supposed to be the same capacitor but it looks like it has been changed before, probably explaining the last person's attack on the scope. 250V is fine. Basically these capacitors go short temporarily if there is a spike on the mains to stop it blowing up the scope.

Value isn't that important for these. They are between Live/neutral and ground and eat up noise and spikes and that's it. The manual specifies 0.022uF (2.2nF). I replaced the last scope with KEMET PME271Y422MR30. You can get these from RS locally to you: https://benl.rs-online.com/web/p/pap...itors/0210572/ (pack of 5). Replace C903 and C904 at same time.

2n5401 I'd probably hit ebay for.
MrBungle is online now   Reply With Quote
Old 15th Apr 2019, 10:44 pm   #16
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,244
Default Re: Tektronix 2211 scope short-circuited

Quote:
Originally Posted by MrBungle View Post
The manual specifies 0.022uF (2.2nF).
0.022uF is 22nF! 0.0022uF is 2.2nF....It's easy to drop a '0'!
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is online now   Reply With Quote
Old 15th Apr 2019, 10:55 pm   #17
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,112
Default Re: Tektronix 2211 scope short-circuited

Click image for larger version

Name:	Capture.PNG
Views:	27
Size:	10.4 KB
ID:	181398

Well spotted! The 0.022 I wrote down was wrong. It is supposed to be 0.0022 ... 2.2nF is the correct value.
MrBungle is online now   Reply With Quote
Old 16th Apr 2019, 12:06 am   #18
Argus25
Nonode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,119
Default Re: Tektronix 2211 scope short-circuited

Quote:
Originally Posted by Don_Zalmrol View Post

After 30 minutes of testing it with a small wave gen the scope suddenly gave a bang sound and the power to the apartment was out. Seems my RCD blew out.

Thanks for any tips!
The RCD generally only gets tripped when there is an unbalanced current (leakage to earth) from the mains input wiring. This was the big clue, along with the burning smell, that the Rifa caps on the mains input wiring were leaking to ground. Very common for these as they age. You don't want to increase their uF value too much as from the AC perspective they will tend to try to suspend the chassis at 1/2 the supply voltage, and will pass a small current to earth for that reason.
Argus25 is offline   Reply With Quote
Old 16th Apr 2019, 12:35 am   #19
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 4,038
Default Re: Tektronix 2211 scope short-circuited

Your RCD saved you from a room full of smoke.
I had one go and poked a camera into the room while the smoke was clearing.
Attached Thumbnails
Click image for larger version

Name:	DSCF0853E.jpg
Views:	65
Size:	56.0 KB
ID:	181399   Click image for larger version

Name:	DSCF0860.jpg
Views:	54
Size:	27.3 KB
ID:	181400   Click image for larger version

Name:	DSCF0864.jpg
Views:	56
Size:	53.8 KB
ID:	181401  
Refugee is offline   Reply With Quote
Old 16th Apr 2019, 7:52 am   #20
Don_Zalmrol
Hexode
 
Don_Zalmrol's Avatar
 
Join Date: May 2009
Location: Ghent, Belgium
Posts: 266
Default Re: Tektronix 2211 scope short-circuited

Quote:
Originally Posted by MrBungle View Post
C903 is supposed to be the same capacitor but it looks like it has been changed before, probably explaining the last person's attack on the scope.
That was my doing, I already swapped it for the new (green) one.
2.2nF and same ratings as the old ones.

Quote:
Originally Posted by Refugee View Post
Your RCD saved you from a room full of smoke.
I had one go and poked a camera into the room while the smoke was clearing.
Oh damn. It was in our living room and the GF was already uneasy about the tripped RCD for fire. Seems another reason for having a small workshop later

I'll see to replace the 0.15uF MKT as well to be on the safe side.
Main filter cap of 2200uF has been replaced already.
Don_Zalmrol is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 3:39 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.