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Re: HP 8566B - Can my high voltage transformer be faulty?

 

Hi Dave Casey,

The part that seems to be broken is: 0960-0383 VARO MH920E03 Do you have one of those in a good shape?
Re: HP 8566B - Can my high voltage transformer be faulty?

 

I have some new 85662- series HV assemblies of various types that I got in a parts lot awhile back. They look like they may have been part of some kind of service/upgrade kit because they also came with a new warning sticker. If you narrow the problem down to a bad assembly, post the part number and I'll see if I have it.

Dave Casey


On Thu, Jul 11, 2024 at 1:25?PM Chuck Harris via <cfharris=[email protected]> wrote:
The milling part is easy... if you have a mill.? The real
effort is disassembling the front panel so that you can do
the milling, and removing all of the CRT stuff.

It is a very good time to service the keyboard, which most
8566B's need done anyway.

-Chuck Harris


On Thu, 11 Jul 2024 12:57:50 -0500 "Steve - Home" <sw.krull@...>
wrote:
> Hey Jeff - hope you¡¯re well!
> I don¡¯t know if they still do it but SimmConn Labs used to offer a
> milled front panel in exchange for your old panel. Might be worth
> asking if one goes the LCD route.?
>
> Steve
> WB0DBS
>





How to remove the output cable of the isolator in the 8672A

 

I need to check the level coming from the isolator but the cable connecting its output to the low pass filter is very difficult to disconnect. There is very little space around the SMA connectors. The alternative is to disassemble the housing but for just checking the output level it's a huge amount of work
Is there someone in this group that can advise how best to get access to the either the output of the isolator or to the output of the low pass filter connected to the isolator output?
Re: Checking HP 8672A output level: are these drops normal?

 

The test MUST be carried out after the isolator, because in the early days of the 8672A, the 2 to 6.2 GHz amplifier was very fragile. It was theoretically designed to deliver around +23 dBm, but had difficulties doing so over the whole band. That's why there was an option 008, which enabled +8 dBm to be obtained at the generator output, because without this option the 8672A delivered barely 0 dBm at 18 GHz. Several years later, at the time the 8340/41 came out, a new, more powerful amplifier was developed, going up to 7 GHz, so as to be able to "push" the YTM (of the 8340) to 26.5 GHz. Recent 8672A models feature this amplifier (option 008 became so the standard), which can deliver +27 dBm. So the answer to the question of whether or not you can test without the isolator is as follows:
  • Old amplifier: very fragile, be careful not to have a bad connection when testing or else RIP!!!!?
  • New amplifier: less fragile, so less risk of killing it if you make a mistake.
In any case, it's best to test with the isolator, because if you want to know if there's enough power on the YTM, you need to take isolator losses into account. In all HP generators, there's such an isolator between the amplifier and the YTM, because the behavior of the SRD (and not the PIN diode, as someone wrote) is such that it induces a huge mismatch when suddenly switched on. All the more so as the bias of an SRD is difficult to adjust to obtain maximum harmonic power, and it's common at certain frequencies to obtain very high amplitude parasitic oscillations between the SRD and the YIG when the bias is pushed a little too far.

F1EKU
Re: Checking HP 8672A output level: are these drops normal?

 

There is a problem anywhere in the concatenation of amplifier, isolator, high pass filter and YTM.
It's not a problem to ensure the right load to the amplifier.
The big problem is how to disconnect the current interconnections so measurement cables can be connected without having to disassemble the whole housing, if possible at all.
Re: Checking HP 8672A output level: are these drops normal?

 

I guess that is one way to get the last word...

-Chuck Harris


On Thu, 11 Jul 2024 14:27:02 -0400 "Dave McGuire"
<mcguire@...> wrote:
On July 11, 2024 1:15:47 PM "Jeff Kruth via groups.io"
<kmec@...> wrote:
Dude, the loss of a good isolator is about a dB or less. The S11
and S22 are low reflection. The reverse isolation S12 is high and
what you want. Do you even know what an isolator is? I have built
them for Uncle Sam. And I read fine. You are worried about the
concatenated losses? Go back to sleep or just reading about
things.For more abuse about your ignorance, just keep going.
FYI, he unsubscribed right after he sent his previous message to
the list.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: Checking HP 8672A output level: are these drops normal?

 

On July 11, 2024 1:15:47 PM "Jeff Kruth via groups.io" <kmec@...> wrote:
Dude, the loss of a good isolator is about a dB or less. The S11 and S22 are low reflection. The reverse isolation S12 is high and what you want.
Do you even know what an isolator is? I have built them for Uncle Sam. And I read fine. You are worried about the concatenated losses? Go back to sleep or just reading about things.For more abuse about your ignorance, just keep going.
FYI, he unsubscribed right after he sent his previous message to the list.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: HP 8566B - Can my high voltage transformer be faulty?

 

The milling part is easy... if you have a mill. The real
effort is disassembling the front panel so that you can do
the milling, and removing all of the CRT stuff.

It is a very good time to service the keyboard, which most
8566B's need done anyway.

-Chuck Harris


On Thu, 11 Jul 2024 12:57:50 -0500 "Steve - Home" <sw.krull@...>
wrote:
Hey Jeff - hope you¡¯re well!
I don¡¯t know if they still do it but SimmConn Labs used to offer a
milled front panel in exchange for your old panel. Might be worth
asking if one goes the LCD route.?

Steve
WB0DBS
Re: HP 8566B - Can my high voltage transformer be faulty?

 

I am a fan of simmconn lab's Newscope-8 kit for the 8566B. It is
clear, bright, and very easy to read. The colors are a great
improvement.

The 50W reduction in power consumption is a great benefit.

-Chuck Harris

On Thu, 11 Jul 2024 10:34:47 -0700 "saevar" <saevartj@...> wrote:
Do you guys that have upgraded to an LCD found it worth the
400$+shipping? I am torn whether I should go that route and cough up
the cash for this old SA or buy a replacement HV multiplier. There
are a few available for 30-40$ There are more things wrong with the
SA (RF section, input signal showing very low amplitude, like 70-90dB
lower than expected) which I haven't gotten around to try and fix
since I needed a functioning display first.
Re: HP 8566B - Can my high voltage transformer be faulty?

 

¿ªÔÆÌåÓý

Hey Jeff - hope you¡¯re well!
I don¡¯t know if they still do it but SimmConn Labs used to offer a milled front panel in exchange for your old panel. Might be worth asking if one goes the LCD route.?

Steve
WB0DBS



On Jul 11, 2024, at 12:49?PM, Jeff Kruth via groups.io <kmec@...> wrote:

?
Wow, since you are not sure the RF deck works, and you MIGHT have a bad yig tuned mixer, I would go the least expensive way to get the display running. The LCD kit is nice but requires mechanical modification to the front panel of the display (milling stuff away) and the installation is not super simple. (Not bad, but takes time).

In a message dated 7/11/2024 1:34:50 PM Eastern Standard Time, saevartj@... writes:
?
Do you guys that have upgraded to an LCD found it worth the 400$+shipping?
I am torn whether I should go that route and cough up the cash for this old SA or buy a replacement HV multiplier. There are a few available for 30-40$
There are more things wrong with the SA (RF section, input signal showing very low amplitude, like 70-90dB lower than expected) which I haven't gotten around to try and fix since I needed a functioning display first.

Re: HP 8566B - Can my high voltage transformer be faulty?

 

Wow, since you are not sure the RF deck works, and you MIGHT have a bad yig tuned mixer, I would go the least expensive way to get the display running. The LCD kit is nice but requires mechanical modification to the front panel of the display (milling stuff away) and the installation is not super simple. (Not bad, but takes time).

In a message dated 7/11/2024 1:34:50 PM Eastern Standard Time, saevartj@... writes:
?

Do you guys that have upgraded to an LCD found it worth the 400$+shipping?
I am torn whether I should go that route and cough up the cash for this old SA or buy a replacement HV multiplier. There are a few available for 30-40$
There are more things wrong with the SA (RF section, input signal showing very low amplitude, like 70-90dB lower than expected) which I haven't gotten around to try and fix since I needed a functioning display first.

Re: HP 8566B - Can my high voltage transformer be faulty?

 

¿ªÔÆÌåÓý

I upgraded my 8566B with the NewScope LCD quite awhile ago and it has been well worth the cost for me. The 8566B is a workhorse (in both performance and weight?) and the LCD has added enough life to the SA that it will probably outlast me!


Steve
WB0DBS
EM17iq09ao


On Jul 11, 2024, at 12:34?PM, saevar via groups.io <saevartj@...> wrote:

?Do you guys that have upgraded to an LCD found it worth the 400$+shipping?
I am torn whether I should go that route and cough up the cash for this old SA or buy a replacement HV multiplier. There are a few available for 30-40$
There are more things wrong with the SA (RF section, input signal showing very low amplitude, like 70-90dB lower than expected) which I haven't gotten around to try and fix since I needed a functioning display first.

Re: HP 8566B - Can my high voltage transformer be faulty?

 

Do you guys that have upgraded to an LCD found it worth the 400$+shipping?
I am torn whether I should go that route and cough up the cash for this old SA or buy a replacement HV multiplier. There are a few available for 30-40$
There are more things wrong with the SA (RF section, input signal showing very low amplitude, like 70-90dB lower than expected) which I haven't gotten around to try and fix since I needed a functioning display first.
Re: Checking HP 8672A output level: are these drops normal?

 

Dude, the loss of a good isolator is about a dB or less. The S11 and S22 are? low reflection. The reverse isolation S12 is high and what you want.
Do you even know what an isolator is? I have built them for Uncle Sam. And I read fine. You are worried about the concatenated losses? Go back to sleep or just reading about things.
For more abuse about your ignorance, just keep going.
Re: Checking HP 8672A output level: are these drops normal?

Dave Me
 

50 years a microwave engineer
?
But poor reading skills
?
OP defined the problem as only measuring the amplifier.
?
How is it such experience cannot read and stay in context with OPs question?
?
If you are so experienced as you claim without proof (on the internet where everyone has fantastic claims o f"experience") then you know the isolator invokes its own losses.
?
These losses will vary the gain figures of the amplifier. Such an experienced expert as yourself should know that.
?
Therefore, your claim of "50 years of experience" is false.
?
See the term "Cognitive Biases" and "Logical Fallacies" of "Pointing to Oneself as an Expert"


11.07.2024, 19:12, "Jeff Kruth via groups.io" <kmec@...>:

This is not good advice. The amplifier, to a first degree,CAN be tested with the isolators intact. This is the standeard working environment and the isolator protect the amp in-situ, thats why tey are there. It has to work with the isolators If you see hoes in response, or excess gain slope, it will occur with the isolators. J. Kruth 50 years a microwave engineer.

In a message dated 7/11/2024 12:04:33 PM Eastern Standard Time, scope.project@... writes:
?
The amplifier cannot be tested thru the isolator. That is testing the sum of both characteristics. Yes, you can do the test, but the output is depending then on losses and reflections of the isolator as well. In that case, if the isolator can be swept and its graph known, it can be compared to the response of both.
?
Re: Checking HP 8672A output level: are these drops normal?

 

This is not good advice. The amplifier, to a first degree,CAN be tested with the isolators intact. This is the standeard working environment and the isolator protect the amp in-situ, thats why tey are there. It has to work with the isolators If you see hoes in response, or excess gain slope, it will occur with the isolators. J. Kruth 50 years a microwave engineer.

In a message dated 7/11/2024 12:04:33 PM Eastern Standard Time, scope.project@... writes:
?

The amplifier cannot be tested thru the isolator. That is testing the sum of both characteristics. Yes, you can do the test, but the output is depending then on losses and reflections of the isolator as well. In that case, if the isolator can be swept and its graph known, it can be compared to the response of both.
?
Re: Checking HP 8672A output level: are these drops normal?

Dave Me
 

"Will you destroy the amplifier if the output is not loaded with 50 ohm?"
?
This is microwave-energy. (6 GHz?) ?It is critical to have the exact characteristic else energy is reflected, not included in output measurment. Reflected power can cause heating, distortion etc problems.
?
S11 and such: "Scattering Parameters" is teh general topic
?
See
?
?
Reflection Coefficient.
?
Large errors can occur without proper matching. Even bends in a coax cable can cause microwave errors.
?
There is no way to know if it will be damaged without knowing what amplifier device is used and its tolerance to reflected power, or, having specification to the unit.
?
The amplifier cannot be tested thru the isolator. That is testing the sum of both characteristics. Yes, you can do the test, but the output is depending then on losses and reflections of the isolator as well. In that case, if the isolator can be swept and its graph known, it can be compared to the response of both.


11.07.2024, 18:19, "Erik Kaashoek" <erik@...>:

I do have a HP437B with a 18 GHz power sensor so measuring the power is not a problem. The issue is that it is not easy to disconnect the SMA connectors between the amplifier, isolator, high pass filter and YTM without disassembling a large part of the housing.
Any recommendation on how best to measure the amplifier output is recommended?
Is it possible to unscrew the amplifier from the bottom and lift it up?
Will you destroy the amplifier if the output is not loaded with 50 ohm?
Is it therefore better to measure after the isolator?
Can you bend the very thin rigid SMA coax between isolator and high pass filter easily so you can unscrew the SMA connectors?

Re: HP 8566B - Can my high voltage transformer be faulty?

 

BTW, I removed and still have the HV section from an 85662A when I upgraded to an LCD. If you need parts... J.Kruth
Re: Checking HP 8672A output level: are these drops normal?

 

I do have a HP437B with a 18 GHz power sensor so measuring the power is not a problem. The issue is that it is not easy to disconnect the SMA connectors between the amplifier, isolator, high pass filter and YTM without disassembling a large part of the housing.
Any recommendation on how best to measure the amplifier output is recommended?
Is it possible to unscrew the amplifier from the bottom and lift it up?
Will you destroy the amplifier if the output is not loaded with 50 ohm?
Is it therefore better to measure after the isolator?
Can you bend the very thin rigid SMA coax between isolator and high pass filter easily so you can unscrew the SMA connectors?
Re: HP 8566B - Can my high voltage transformer be faulty?

 

The PDA supply MUST be stable and regulated or the size of the CRT image will keep changing, Also not a good idea to operate long term without load on high voltage winding of the HV transformer.

If it is impossible to find the correct HV multiplier it may help to look for a Tektronix CRT scope one, my guess and it is only a guess without measuring the HV transformer output is that it is a X6 one.

G Edmonds
On Thursday 11 July 2024 at 15:52:48 BST, Dave Me <scope.project@...> wrote:


Idea.
?
The flyback and HVM simply make a high DC voltage and low current (milli-ampere"?)
?
Maybe this to replace a difficult to find HVM? Adjustable HV-DC output:
?
amazon DOT com/Adjustable-Voltage-Electrostatic-Precipitator-Supply/dp/B0B4ZVG3B8
?
This would assume the sweep of the flyback is still working to drive the yoke - coils or deflection plates.
?
11.07.2024, 01:09, "saevar" <saevartj@...>:

Hi George,

I couldn't wait so I tested the method you suggested immediately and you were absolutely right. There appears a small green "window" visible (like a miniature image) on the CRT in the center and the fuse is not blown. I am thoroughly impressed.
Thanks so much!

Regards
Saevar
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