There haven't been any modulation changes like those affecting
wwwvb, the inconvenient hiccup when Europe and the UK switched to
9KHz channel spacing for long and medium wave AM broadcasting, and
the shift of the Droitwich frequency from 200 to 198KHz, was the
most significant change, but the Droitwich signal does also carry
phase modulated "teleswitching" data for the energy industry.


I've not noticed any significant effect from this on 198KHz
frequency references, but unlike wwwvb and MSF time and frequency
standards those locked to Droitwich do not generally attempt to
access the time of day signals but just lock to the closely
controlled carrier frequency.

After the frequency change some standards were more easily updated
than others but it seems to have been the kiss of death for the
5090, although that Radcom converter does look to be a potentially
nice solution.


There have been plenty of later designs purpose built for the
198KHz frequency, which is still rubidium locked as far as I know,
but ten or eleven years ago there were reports that the BBC had
bought all the remaining stock of the Droitwich transmitter's
output valves/tubes and was working its way through the last few
pairs.

A bit of a fallacy that those valves!, they can be rebuilt in Russia and
China where long wave is still used the UK is tiny compared with some
countries coverage needs!..

If the BBC want to carry on that service these people still make new LF
transmitters up to several hundred kilowatts and at very good efficiency
levels



The BBC no longer do their own transmission its been contracted out to
Arqiva for many years now!..

On that basis I'm pretty sure it should have shut down by now so
perhaps that story wasn't totally accurate after all.

However, aside from that it does seem that a major factor keeping
the 198 KHz transmission alive is the teleswitching data service.
This was previously destined for shut down in 2020 but extended due
to delays in the UK "smart meter" programme with the curent
contract running until the end of March 2023. Whilst no formal
announcements have been made. not that I'm aware of anyway, I've
seen plenty of suggestions that without that extra income there
would be little incentive to keep the 198 KHz service running and
that the BBC may well take the opportunity to shut it down.

It's perhaps not entirely straightforward though as the BBC also
has some contractual coverage obligations, in Scotland for example
that resulted in there being two lower powered 198KHz repeater
stations, still rubidium controlled but not locked to Droitwich or
so closely monitored, which makes traceability more of an issue
anyway as it's not always obvious which transmitter is being
received.

Whatever happens is much more likely to be a political/commercial
decision rather than technical, but I do feel that time is probably
running out for 198KHz frequency standards.

Leo Bodnar make a very good GPS based unit!...

The UK 60KHz cesium referenced time and frequency service, MSF,
which moved north from Rugby to Anthorn around fifteen years ago,
would probably be considered the go to option these days for
broadcast time and frequency references in the UK, with TDF in
France and DCF77 in Germany perhaps being other options, other than
GPS of course.





Also operating from Anthorn we do still have eLoran, experimental
and somewhat unpredictable with no warning of outages these days,
but running most of the time. If or when that signal is
discontinued I'll need to complete my version of your Loran
simulator, but for now it's a case of let's just enjoy that one
while it lasts:-)




Nigel, GM8PZR

--
Tony Sayer

PD: To not bother you, I have already get the 8566B power supply readable schematic

At 02:33 PM 2/02/2022 -0800, you wrote:

Hi Steve
The HP part number is 9100-4603
Regards,
Ruben

Not according to my 8350B service manual. 08350-90034 Jan 1983. A paper original.
There the T1 transformer is 9100-4227.

Guy

Thanks Tony! More clear than mine :D

The manual changes section shows that main transformer (mine is 9100-4603) has a few substitutes depending on the serial: 08350-60064, 9100-4277 and 9100-4337 (this last is the apropiate to my unit S/N 2642A...). It is impossible to get one of those, I only see a -4277 in USA and looks smaller and less-tapped than mine, so it don't match at all.

I located two cheap used transformers in UK: cheapest option is one from an 8566B SA, who has less taps but very powerfull ones (maybe I can use one for make various supplies if it is possible? or add an aditional little transformer I have for the +-15 volt supply); and for twice that money, one from a 8922 GSM analyzer, which has enough secondary windings, but it requires mess up with connections too (I attached a table of outputs of this instrument's power supply for reference). I suppose that feeding the rectifier board with slightly different voltages from transformer?(under certain tolerance)?doesn't affect the final result.

Can anyone send or post a photo of schematics of the main transformer, rectifier and regulator boards in the 8566B manual? Mine (I attached it) is almost not readable and I need those figures to decide which transformer I'll buy. Thanks in advance.

So maybe this adventure will continue.

Every opinion or advice is welcome, honestly. I'm here to learn :)

Regards,
Ruben

Hi Ruben,

I have a printed manual for my 8350B and I attach some pics of the manual part number and the transformer part number and part of the power supply schematics - hope this helps.

Tony

Hi again

I'm using at the same time?the op & service manual from Keysight and the same manual from KO4BB website, which has readable schematics but some missing and misplaced pages... every search is a time consuming task.?

I wrote to a local custom transformer maker for an estimate. Depending on the price, I'll decide. The meanwell modules option is attractive at first because there's a lot of room for them (I remember the odissey in my 8663A a year ago to fit four bricks) once T1 and filter caps be taken out. A6 and A7 has special functions circuits?that I cannot remove from the device to avoid malfunction, but i would have to think about it when it's time comes.

Regards,
Ruben

Michael wrote: BTW I see there is a disk emulation project that simulates the HPIB floppy with an SD card. Has anyone tried this on the 8753?

I've successfully used http://www.dalton.ax/hpdisk on a 8720C.

Br
Marcus

On Wed, Feb 2, 2022 at 04:46 PM, pianovt wrote:

I don't know this for a fact, but I would guess that you can adjust the YTO pretune constants without loading all the other defaults.

OK, thanks. I think I'll try this. The worst thing that could happen is that it doesn't work and I have to do the whole procedure (assuming I can borrow an an HP power meter) but I'm no worse off.?

Yes, the new constants would be replaced by the old ones, but you would not run the risk of doing anything irreversible. My thought was that you could try to set the YTO pretune constants without wiping out any of the other adjustments. If it doesn't work, you could go back to what you had before the experiment. I don't know this for a fact, but I would guess that you can adjust the YTO pretune constants without loading all the other defaults.

Vladan

On Wed, Feb 2, 2022 at 08:54 AM, peter bunge wrote:

It is hard to guess a person's?level of expertise but since you can measure?the 3.8GHz I think you know what you are doing.

No worries.?

How and where are you measuring?the YIG output??

I'm using a spectrum analyzer to look at the output directly from the YIG. (remove the semirigid cable and connect to the spectrum analyzer)

Have you checked ALL the self tests.?The higher level ones have to be specifically called up and are not included in the normal boot up self test.

Is the analog bus working? Does the tune voltage look normal? These are a few things that can make a YIG appear dead.

I got the replacement YIG today and it works (I can see output on the spectrum analyzer) but the mounting harware went from imperial to metric. When I get some 3mm bolts tomorrow I'll mount it properly and see what needs alignment.

?

I will send you some repair logs privately that might help.

thanks!
Michael

?

On Wed, Feb 2, 2022 at 01:31 PM, pianovt wrote:

I am not sure why the 8753C manual says that all defaults must be preloaded before setting the pretune constants. I do know that this is not the case for the 8753E. I doubt that you have access to a 9122C external floppy drive (it's easier to find a GPIB power meter), but if you do, I think you may be able to back up the original eeprom. If you do that, you can always restore the settings.

Maybe because the expect the whole source module to be replaced rather than just the YIG. The output level would be a function? of the ALC which doesn't change if just the YIG is replaced.??

What happens if you just install the new YTO and turn the analyzer on without the pretune adjustment?

I'll let you know when it goes in. The replacement unit I got must be a later version ... it has metric hardware (the original is imperial). I've got to get some 3mm harware before I can put it in 8-(

No, I don't have the disk so I can't do the backup. Even if I did back up, wouldn't the new pretune constants then be overwritten when I restore??
BTW I see there is a disk emulation project that simulates the HPIB floppy with an SD card. Has anyone tried this on the 8753?

Michael

I purchased a 8601a Sweeper that arrived with major shipping damage.? The front panel controls took a direct hit.?

• The Attenuator/Vernier Output Knob and main frequency knob had actually punched thru the bubble wrap and outside of the cardboard box,
• The red Vernier Output knob was crushed and the long Vernier potentiometer shaft had been driven inward so hard that it broke the wiper and punched a major dent out the back of the potentiometer cover!
• The main frequency gear assembly was jammed and metal mounting frame was broken in half near the thinner section just below the Frequency Vernier control..
• The main power transformer was also jolted out of position, as it was cocked at an angle and contacting the pins of the rear panel transistor sockets.
• Also found loose broken plastic pieces in box...

I still want to repair and put it in use on my bench but have some questions for the group-

• The vernier output shaft passes thru the attenuator assembly and I noticed the hole on the rear of the attenuator is threaded-- Does the Vernier Output control potentiometer thread into the end of the attenuator or is it just held by the anti-rotation pin/guide?
• The brass front panel bushing for the attenuator/vernier output seems large/loose on the shaft--is this bushing supposed to have a nylon insert?
• Its an older 954- serial #, so while I have it all disassembled, are there any specific fixes/updates to go after?
  • It has the old style HP power connector, does anyone recommend a specific standard IEC replacement socket/line filter?

Sorry for the long post, Thanks in advance

DB

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That’s the HP Interface Loop so I assume the transformer noted is probably an isolation transformer for an HPIL connection but I don’t believe the 8350B had that interface capability so it is a puzzler. None of my 8350B’s have an HPIL socket or I’d be tempted to plug in a keyboard or mouse and see what happened?

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