Purple pink is likely caused by the excess gas in the tube ionizing.? Unless it's a mercury vapor tube (don't think it's likely), soot and burn marks (not a getter flash) is not a good thing to see.

I'd worry less about the tube tester and a bit more about a replacement, IMHO.

Harvey

On 10/27/2021 7:53 AM, Richard Merifield wrote:

Actually it rises to about -50V when I let things warm up.

I am thinking it may be one of the EL86 tubes. I was assuming warmth meant it was probably glowing but now I have taken the shields off I notice only one glows an nice orange and the other one flickers and glows purple/pink. I notice the purple/pink glowing one has some soot/burn marks inside the glass. Photos attached..

Anyone down under in New South Wales have a tube tester :)?

Richard

?

I would have thought so if they are alternative valves (the casing is marked for both?)

?

You’ll probably need to recalibrate after that but it ought to make it work a little better ?

Regards

Nigel

?

?

Thanks Nigel, can I mix an EL86 and 6CW5 in the one unit ?

Actually it rises to about -50V when I let things warm up.

I am thinking it may be one of the EL86 tubes. I was assuming warmth meant it was probably glowing but now I have taken the shields off I notice only one glows an nice orange and the other one flickers and glows purple/pink. I notice the purple/pink glowing one has some soot/burn marks inside the glass. Photos attached..

Anyone down under in New South Wales have a tube tester :)?

Richard

On Oct 27, 2021, at 4:23 AM, greenboxmaven via groups.io <ka2ivy@...> wrote:

?

Outside foil connection may be even more important in scopes and other test gear because of often lower signal levels being measured, and the scope containing sweep and power supply circuits that operate at high frequency and voltage levels. Audio gear, except for tuners and receivers, almost never generates signals within.

??? Bruce Gentry, KA2IVY

On 10/27/21 4:12, Dave_G0WBX via groups.io wrote:

From: byterock@...
Date: Tue, 26 Oct 2021 10:56:58 PDT
Just a general general questions on replacing the paper caps.

Does it matter if the replacement caps are placed with their foil side orientated in the same direction as the old caps?
?
I know in audio circuits it cam make a difference but does that hold true on scopes as well?

---

Hi.

This is a job I need to do as well, also on a HP-130 'scope.?? In my case, a HP 130 B sn: 0001-04304? That was used as part of the ground support for the UK's "V Bomber" fleet back in the cold war days.

(I bought it from one of the XH558 support charity auctions.? XH558 is/was the last flying Vulcan bomber.? Also the last truly 100% British designed and built 4 engine Jet aircraft.???? ? ? Sound on, and volume UP!)

All I've done so far, is find that the Power transformer is good, as are all the main tube filaments, having disconnected the HT windings to prevent electrolytic cap disasters.?? Even the front panel power indicator, and display graticule lights still work.

In general, if HP saw fit to put foil cap's in a particular way around as per the outer foil marking, it would probably be best to fit the replacements the same way.

The "Fun" bit, these days, is finding replacement caps (likely not paper dielectric) that even have the "outer foil" marked!

If you have another 'scope elsewhere, and a MF signal source that can feed a capacitive load, then you can "test" unmarked parts and find out which lead is the "Outer" foil.

Feed the cap from the signal source, via a screened lead.?? Use the 'scope as a crude 'E' field probe, and place it on the side of the cap' mid way between the leads, with the probe ground lead going to the "earthy" side of the cap' as driven by the source.

Compare the signal level with the cap' fed each way around.?? The largest signal, will indicate that the "Outer" foil is being driven, not grounded.

I have done that many times with the 1uF 2kV "Wrapped Mica" types we used in the tube based high power RF amps we support.? (RF Output and Plate-line term' Decoupling.)

I was always taught, that the "Outer" foil of such cap's should usually be connected to the lowest impedance path to "Ground", or in the case of ramp generators, the "hot" end.? (I.e.? The output side of an integrator circuit.)?? No doubt there are edge case exceptions.

One thing I could use, is a good set of schematics for the HP, all I have at present are somewhat "noisy" PDF scans.

This is one of the (several) retirement projects!? I'd like to get it going, but keep the "grubbiness" it has acquired while in decades of dry storage.?? Internally it is clean, but some of the rubber shock mountings for the input stages are "a little perished"...

Cheers.

Dave G8KBV.

-- 
Created on and sent from a Unix like PC running and using free and open source software:

?

Thanks Nigel, can I mix an EL86 and 6CW5 in the one unit ?

?

Actually it rises to about -50V when I let things warm up.

I am thinking it may be one of the EL86 tubes. I was assuming warmth meant it was probably glowing but now I have taken the shields off I notice only one glows an nice orange and the other one flickers and glows purple/pink. I notice the purple/pink glowing one has some soot/burn marks inside the glass. Photos attached..

Anyone down under in New South Wales have a tube tester :)?

Richard

From: byterock@...
Date: Tue, 26 Oct 2021 10:56:58 PDT
Just a general general questions on replacing the paper caps.

Does it matter if the replacement caps are placed with their foil side orientated in the same direction as the old caps?
?
I know in audio circuits it cam make a difference but does that hold true on scopes as well?

---

Hi.

This is a job I need to do as well, also on a HP-130 'scope.?? In my case, a HP 130 B sn: 0001-04304? That was used as part of the ground support for the UK's "V Bomber" fleet back in the cold war days.

(I bought it from one of the XH558 support charity auctions.? XH558 is/was the last flying Vulcan bomber.? Also the last truly 100% British designed and built 4 engine Jet aircraft.???? ? ? Sound on, and volume UP!)

All I've done so far, is find that the Power transformer is good, as are all the main tube filaments, having disconnected the HT windings to prevent electrolytic cap disasters.?? Even the front panel power indicator, and display graticule lights still work.

In general, if HP saw fit to put foil cap's in a particular way around as per the outer foil marking, it would probably be best to fit the replacements the same way.

The "Fun" bit, these days, is finding replacement caps (likely not paper dielectric) that even have the "outer foil" marked!

If you have another 'scope elsewhere, and a MF signal source that can feed a capacitive load, then you can "test" unmarked parts and find out which lead is the "Outer" foil.

Feed the cap from the signal source, via a screened lead.?? Use the 'scope as a crude 'E' field probe, and place it on the side of the cap' mid way between the leads, with the probe ground lead going to the "earthy" side of the cap' as driven by the source.

Compare the signal level with the cap' fed each way around.?? The largest signal, will indicate that the "Outer" foil is being driven, not grounded.

I have done that many times with the 1uF 2kV "Wrapped Mica" types we used in the tube based high power RF amps we support.? (RF Output and Plate-line term' Decoupling.)

I was always taught, that the "Outer" foil of such cap's should usually be connected to the lowest impedance path to "Ground", or in the case of ramp generators, the "hot" end.? (I.e.? The output side of an integrator circuit.)?? No doubt there are edge case exceptions.

One thing I could use, is a good set of schematics for the HP, all I have at present are somewhat "noisy" PDF scans.

This is one of the (several) retirement projects!? I'd like to get it going, but keep the "grubbiness" it has acquired while in decades of dry storage.?? Internally it is clean, but some of the rubber shock mountings for the input stages are "a little perished"...

Cheers.

Dave G8KBV.

-- 
Created on and sent from a Unix like PC running and using free and open source software:

From: [email protected] [mailto:[email protected]] On Behalf Of Xu Wang via groups.io
Sent: 27 October 2021 05:42
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] Agilent/Keysigh ESG series CLIP

?

Thanks, Paul, for the background information. I joined the Yahoo group in 2009, so I wouldn't know about what happend 15 years ago in the group.

The topic has been brought up a couple of times in here and also in the Tek group. That's how I came to know that a license exist for distributing manuals of obsolete HP test equipment. At one time I even wanted to apply for one, so that I can make avaiable some of the CLIPs that I scanned and couldn't find elsewhere online. But I didn't follow through. I still think it would be wise to 'stay on the safe side'.

The very CLIP that Milan talked about here (E4400-90336), I bought a pdf copy online in 2019 for not much money, and used it to fix my E4436B. The scan quality isn't as good as the earliver version E4400-90015 I scanned myself, but was good enough and didn't take any guesswork to read. The pdf files were dated 2018 so there may be other copies sold before mine.

-Xu

Would hope the BNC spacing is the same. Probably is. These are good from DC to 13Mhz and up to 42VDC per the manufacturer.

Regards
Tony