So - in the case of a linear power supply - the rectified output of
the transformer typically goes straight to a big old storage cap for
smoothing purposes. My question is: how much ripple should I expect to
see across that cap if all's working well? I have to say I'm seeing a
*lot* of ripple on this cap in a Marconi RF signal generator and it's
finding its way to the RF output, which of course should ideally have
zero ripple on it. The aforementioned cap tests fine WRT ESR and
capacitance in-circuit, I should add.

Thanks,
CD.

On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>So - in the case of a linear power supply - the rectified output of
>the transformer typically goes straight to a big old storage cap for
>smoothing purposes. My question is: how much ripple should I expect to
>see across that cap if all's working well? I have to say I'm seeing a
>*lot* of ripple on this cap

Check if a diode in the bridge rectifier has failed.

On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:

>On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
>wrote:
>
>>So - in the case of a linear power supply - the rectified output of
>>the transformer typically goes straight to a big old storage cap for
>>smoothing purposes. My question is: how much ripple should I expect to
>>see across that cap if all's working well? I have to say I'm seeing a
>>*lot* of ripple on this cap
>
>Check if a diode in the bridge rectifier has failed.

Good idea! I must admit I'd overlooked that possibility. I should have
checked the frequeny of the ripple whilst I was at it.

Cursitor Doom <cd@notformail.com> wrote:

> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
>
> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
> >wrote:
> >
> >>So - in the case of a linear power supply - the rectified output of
> >>the transformer typically goes straight to a big old storage cap for
> >>smoothing purposes. My question is: how much ripple should I expect to
> >>see across that cap if all's working well? I have to say I'm seeing a
> >>*lot* of ripple on this cap
> >
> >Check if a diode in the bridge rectifier has failed.
>
> Good idea! I must admit I'd overlooked that possibility. I should have
> checked the frequeny of the ripple whilst I was at it.

The shape of the ripple will tell you if that has happened or if one of
the diodes haas gone open circuit. Another possibility is a fault in
some other part of the circuit that is drawing too much current - you
might smell something getting hot.

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

On 25 Feb 2024 at 18:01:19 GMT, "Cursitor Doom" <cd@notformail.com> wrote:

> So - in the case of a linear power supply - the rectified output of
> the transformer typically goes straight to a big old storage cap for
> smoothing purposes. My question is: how much ripple should I expect to
> see across that cap if all's working well? I have to say I'm seeing a
> *lot* of ripple on this cap in a Marconi RF signal generator and it's
> finding its way to the RF output, which of course should ideally have
> zero ripple on it. The aforementioned cap tests fine WRT ESR and
> capacitance in-circuit, I should add.
>
> Thanks,
> CD.

Usually there will either be a passive filter after the initial large
capacitor, such as an inductor in series and a further large capacitor to
earth, or an active voltage regulator circuit involving an amplifier and
series semiconductor, or both. A simple diode plus capacitor is always going
to have a huge amount of ripple, not hard to calculate if you know the current
load. But no electronic instrument is going to be powered just by a rectifier
capacitor combination. You need to look further into the circuit.

--
Roger Hayter

Cursitor Doom wrote:
> So - in the case of a linear power supply - the rectified output of
> the transformer typically goes straight to a big old storage cap for
> smoothing purposes. My question is: how much ripple should I expect to
> see across that cap if all's working well? I have to say I'm seeing a
> *lot* of ripple on this cap in a Marconi RF signal generator and it's
> finding its way to the RF output, which of course should ideally have
> zero ripple on it. The aforementioned cap tests fine WRT ESR and
> capacitance in-circuit, I should add.
>
> Thanks,
> CD.
>
In addition to the other suggestions, you might check to see if a
snubber capacitor exists across the diodes.

https://www.sciencedirect.com/topics/engineering/snubber-circuit

On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

>Cursitor Doom <cd@notformail.com> wrote:
>
>> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
>>
>> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
>> >wrote:
>> >
>> >>So - in the case of a linear power supply - the rectified output of
>> >>the transformer typically goes straight to a big old storage cap for
>> >>smoothing purposes. My question is: how much ripple should I expect to
>> >>see across that cap if all's working well? I have to say I'm seeing a
>> >>*lot* of ripple on this cap
>> >
>> >Check if a diode in the bridge rectifier has failed.
>>
>> Good idea! I must admit I'd overlooked that possibility. I should have
>> checked the frequeny of the ripple whilst I was at it.
>
>The shape of the ripple will tell you if that has happened or if one of
>the diodes haas gone open circuit. Another possibility is a fault in
>some other part of the circuit that is drawing too much current - you
>might smell something getting hot.

There's nothing getting hot, but the ripple had a definite saw-tooth
shape to it, which could be indicative of abnormal operation.
Shame there are no schematics available anywhere on the net; always
makes troubleshooting much harder.

Cursitor Doom <cd@notformail.com> wrote:

> On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
>
> >Cursitor Doom <cd@notformail.com> wrote:
> >
> >> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
> >>
> >> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
> >> >wrote:
> >> >
> >> >>So - in the case of a linear power supply - the rectified output of
> >> >>the transformer typically goes straight to a big old storage cap for
> >> >>smoothing purposes. My question is: how much ripple should I expect to
> >> >>see across that cap if all's working well? I have to say I'm seeing a
> >> >>*lot* of ripple on this cap
> >> >
> >> >Check if a diode in the bridge rectifier has failed.
> >>
> >> Good idea! I must admit I'd overlooked that possibility. I should have
> >> checked the frequeny of the ripple whilst I was at it.
> >
> >The shape of the ripple will tell you if that has happened or if one of
> >the diodes haas gone open circuit. Another possibility is a fault in
> >some other part of the circuit that is drawing too much current - you
> >might smell something getting hot.
>
> There's nothing getting hot, but the ripple had a definite saw-tooth
> shape to it, which could be indicative of abnormal operation.
> Shame there are no schematics available anywhere on the net; always
> makes troubleshooting much harder.

Is the rectifier circuit half-wave or full-wave? If the latter, is the
ripple also full wave?

Some designers allowed a larger amount of ripple on the first capacitor
to reduce the heating of the mains transformer (the copper losses are
proportional to I squared, so by allowing a longer charging time per
cycle at a lower current, they achieved lower overall resistance
losses). As long as the lowest part of the ripple was sufficiently far
above the stabilised output, a series stabiliser could cope with it.

Is the 'stabilised' line actually stable or is there ripple on it in the
form of a series of little notches?

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

On Mon, 26 Feb 2024 09:59:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

>Cursitor Doom <cd@notformail.com> wrote:
>
>> On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>> >Cursitor Doom <cd@notformail.com> wrote:
>> >
>> >> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
>> >>
>> >> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
>> >> >wrote:
>> >> >
>> >> >>So - in the case of a linear power supply - the rectified output of
>> >> >>the transformer typically goes straight to a big old storage cap for
>> >> >>smoothing purposes. My question is: how much ripple should I expect to
>> >> >>see across that cap if all's working well? I have to say I'm seeing a
>> >> >>*lot* of ripple on this cap
>> >> >
>> >> >Check if a diode in the bridge rectifier has failed.
>> >>
>> >> Good idea! I must admit I'd overlooked that possibility. I should have
>> >> checked the frequeny of the ripple whilst I was at it.
>> >
>> >The shape of the ripple will tell you if that has happened or if one of
>> >the diodes haas gone open circuit. Another possibility is a fault in
>> >some other part of the circuit that is drawing too much current - you
>> >might smell something getting hot.
>>
>> There's nothing getting hot, but the ripple had a definite saw-tooth
>> shape to it, which could be indicative of abnormal operation.
>> Shame there are no schematics available anywhere on the net; always
>> makes troubleshooting much harder.
>
>Is the rectifier circuit half-wave or full-wave? If the latter, is the
>ripple also full wave?

Marconi have used these things (not these exact components of course,
but the same footprint/pinout:

http://tinyurl.com/5ab3fd7h

So full wave. Is the ripple full wave? Well, I did mean to check the
frequency of it, but other stuff got in the way. I'm going to have to
re-investigate a bit more thoroughly later in the week.

>Some designers allowed a larger amount of ripple on the first capacitor
>to reduce the heating of the mains transformer (the copper losses are
>proportional to I squared, so by allowing a longer charging time per
>cycle at a lower current, they achieved lower overall resistance
>losses). As long as the lowest part of the ripple was sufficiently far
>above the stabilised output, a series stabiliser could cope with it.
>
>Is the 'stabilised' line actually stable or is there ripple on it in the
>form of a series of little notches?

Not sure what you mean by stabilised line. There are two secondary
windings on the mains transformer which go into separate bridge
rectifiiers of the type linked to above and then on downstream to the
first tank caps. One line has a ton of ripple on it, the other very
little indeed. Again, I'll need to go back and pay more attention to
what's going on here. I've missed out too many important details.

On 26 Feb 2024 at 10:16:41 GMT, "Cursitor Doom" <cd@notformail.com> wrote:

> On Mon, 26 Feb 2024 09:59:12 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
>
>> Cursitor Doom <cd@notformail.com> wrote:
>>
>>> On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
>>> (Liz Tuddenham) wrote:
>>>
>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>
>>>>> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
>>>>>
>>>>>> On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> So - in the case of a linear power supply - the rectified output of
>>>>>>> the transformer typically goes straight to a big old storage cap for
>>>>>>> smoothing purposes. My question is: how much ripple should I expect to
>>>>>>> see across that cap if all's working well? I have to say I'm seeing a
>>>>>>> *lot* of ripple on this cap
>>>>>>
>>>>>> Check if a diode in the bridge rectifier has failed.
>>>>>
>>>>> Good idea! I must admit I'd overlooked that possibility. I should have
>>>>> checked the frequeny of the ripple whilst I was at it.
>>>>
>>>> The shape of the ripple will tell you if that has happened or if one of
>>>> the diodes haas gone open circuit. Another possibility is a fault in
>>>> some other part of the circuit that is drawing too much current - you
>>>> might smell something getting hot.
>>>
>>> There's nothing getting hot, but the ripple had a definite saw-tooth
>>> shape to it, which could be indicative of abnormal operation.
>>> Shame there are no schematics available anywhere on the net; always
>>> makes troubleshooting much harder.
>>
>> Is the rectifier circuit half-wave or full-wave? If the latter, is the
>> ripple also full wave?
>
> Marconi have used these things (not these exact components of course,
> but the same footprint/pinout:
>
> http://tinyurl.com/5ab3fd7h
>
> So full wave. Is the ripple full wave? Well, I did mean to check the
> frequency of it, but other stuff got in the way. I'm going to have to
> re-investigate a bit more thoroughly later in the week.
>
>> Some designers allowed a larger amount of ripple on the first capacitor
>> to reduce the heating of the mains transformer (the copper losses are
>> proportional to I squared, so by allowing a longer charging time per
>> cycle at a lower current, they achieved lower overall resistance
>> losses). As long as the lowest part of the ripple was sufficiently far
>> above the stabilised output, a series stabiliser could cope with it.
>>
>> Is the 'stabilised' line actually stable or is there ripple on it in the
>> form of a series of little notches?
>
> Not sure what you mean by stabilised line. There are two secondary
> windings on the mains transformer which go into separate bridge
> rectifiiers of the type linked to above and then on downstream to the
> first tank caps. One line has a ton of ripple on it, the other very
> little indeed. Again, I'll need to go back and pay more attention to
> what's going on here. I've missed out too many important details.

Older practice, when active devices were expensive and bulky was to have an
active stabiliser circuit (which also got rid of the ripple) directly after
the power supply. Nowadays they tend to have voltage regulators for each
module or circuit, local to that module. If you have the latter arrangement I
would be looking for ripple on the output of each local regulator rather than
the main power supply. Or the high ripple could be due to excessive current
being drawn from one power supply. Anything getting excessively hot?

--
Roger Hayter

Cursitor Doom <cd@notformail.com> wrote:

> On Mon, 26 Feb 2024 09:59:12 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
>
> >Cursitor Doom <cd@notformail.com> wrote:
> >
> >> On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
> >> (Liz Tuddenham) wrote:
> >>
> >> >Cursitor Doom <cd@notformail.com> wrote:
> >> >
> >> >> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
> >> >>
> >> >> >On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
> >> >> >wrote:
> >> >> >
> >> >> >>So - in the case of a linear power supply - the rectified output of
> >> >> >>the transformer typically goes straight to a big old storage cap for
> >> >> >>smoothing purposes. My question is: how much ripple should I expect to
> >> >> >>see across that cap if all's working well? I have to say I'm seeing a
> >> >> >>*lot* of ripple on this cap
> >> >> >
> >> >> >Check if a diode in the bridge rectifier has failed.
> >> >>
> >> >> Good idea! I must admit I'd overlooked that possibility. I should have
> >> >> checked the frequeny of the ripple whilst I was at it.
> >> >
> >> >The shape of the ripple will tell you if that has happened or if one of
> >> >the diodes haas gone open circuit. Another possibility is a fault in
> >> >some other part of the circuit that is drawing too much current - you
> >> >might smell something getting hot.
> >>
> >> There's nothing getting hot, but the ripple had a definite saw-tooth
> >> shape to it, which could be indicative of abnormal operation.
> >> Shame there are no schematics available anywhere on the net; always
> >> makes troubleshooting much harder.
> >
> >Is the rectifier circuit half-wave or full-wave? If the latter, is the
> >ripple also full wave?
>
> Marconi have used these things (not these exact components of course,
> but the same footprint/pinout:
>
> http://tinyurl.com/5ab3fd7h
>
> So full wave. Is the ripple full wave? Well, I did mean to check the
> frequency of it, but other stuff got in the way. I'm going to have to
> re-investigate a bit more thoroughly later in the week.
>
> >Some designers allowed a larger amount of ripple on the first capacitor
> >to reduce the heating of the mains transformer (the copper losses are
> >proportional to I squared, so by allowing a longer charging time per
> >cycle at a lower current, they achieved lower overall resistance
> >losses). As long as the lowest part of the ripple was sufficiently far
> >above the stabilised output, a series stabiliser could cope with it.
> >
> >Is the 'stabilised' line actually stable or is there ripple on it in the
> >form of a series of little notches?
>
> Not sure what you mean by stabilised line. There are two secondary
> windings on the mains transformer which go into separate bridge
> rectifiiers of the type linked to above and then on downstream to the
> first tank caps. One line has a ton of ripple on it, the other very
> little indeed. Again, I'll need to go back and pay more attention to
> what's going on here. I've missed out too many important details.

I was assuming there would have been some sort of stabiliser after the
capacitor, so that the line downstream of it was reasonably stable and
quiet. Alternatively they might have used a series choke (or resistor)
and further capacitor to smoothout the ripple without actually
stabilising the voltage

If this is made by Marconi, the circuits for a lot of Marconi
instruments are available online but you may need to do a bit of
searching-out. If you can get hold of a handbook, that should always
have the circuit in it. What is the "TF" number of this equipment?

["TF" is Marconispeak for "Test Fixture" i.e. any sort of test gear.]

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

On 26 Feb 2024 10:51:03 GMT, Roger Hayter <roger@hayter.org> wrote:

>On 26 Feb 2024 at 10:16:41 GMT, "Cursitor Doom" <cd@notformail.com> wrote:
>
>> On Mon, 26 Feb 2024 09:59:12 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>>> Cursitor Doom <cd@notformail.com> wrote:
>>>
>>>> On Sun, 25 Feb 2024 19:16:24 +0000, liz@poppyrecords.invalid.invalid
>>>> (Liz Tuddenham) wrote:
>>>>
>>>>> Cursitor Doom <cd@notformail.com> wrote:
>>>>>
>>>>>> On Sun, 25 Feb 2024 19:40:48 +0100, HW <none@no.no> wrote:
>>>>>>
>>>>>>> On Sun, 25 Feb 2024 18:01:19 +0000, Cursitor Doom <cd@notformail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> So - in the case of a linear power supply - the rectified output of
>>>>>>>> the transformer typically goes straight to a big old storage cap for
>>>>>>>> smoothing purposes. My question is: how much ripple should I expect to
>>>>>>>> see across that cap if all's working well? I have to say I'm seeing a
>>>>>>>> *lot* of ripple on this cap
>>>>>>>
>>>>>>> Check if a diode in the bridge rectifier has failed.
>>>>>>
>>>>>> Good idea! I must admit I'd overlooked that possibility. I should have
>>>>>> checked the frequeny of the ripple whilst I was at it.
>>>>>
>>>>> The shape of the ripple will tell you if that has happened or if one of
>>>>> the diodes haas gone open circuit. Another possibility is a fault in
>>>>> some other part of the circuit that is drawing too much current - you
>>>>> might smell something getting hot.
>>>>
>>>> There's nothing getting hot, but the ripple had a definite saw-tooth
>>>> shape to it, which could be indicative of abnormal operation.
>>>> Shame there are no schematics available anywhere on the net; always
>>>> makes troubleshooting much harder.
>>>
>>> Is the rectifier circuit half-wave or full-wave? If the latter, is the
>>> ripple also full wave?
>>
>> Marconi have used these things (not these exact components of course,
>> but the same footprint/pinout:
>>
>> http://tinyurl.com/5ab3fd7h
>>
>> So full wave. Is the ripple full wave? Well, I did mean to check the
>> frequency of it, but other stuff got in the way. I'm going to have to
>> re-investigate a bit more thoroughly later in the week.
>>
>>> Some designers allowed a larger amount of ripple on the first capacitor
>>> to reduce the heating of the mains transformer (the copper losses are
>>> proportional to I squared, so by allowing a longer charging time per
>>> cycle at a lower current, they achieved lower overall resistance
>>> losses). As long as the lowest part of the ripple was sufficiently far
>>> above the stabilised output, a series stabiliser could cope with it.
>>>
>>> Is the 'stabilised' line actually stable or is there ripple on it in the
>>> form of a series of little notches?
>>
>> Not sure what you mean by stabilised line. There are two secondary
>> windings on the mains transformer which go into separate bridge
>> rectifiiers of the type linked to above and then on downstream to the
>> first tank caps. One line has a ton of ripple on it, the other very
>> little indeed. Again, I'll need to go back and pay more attention to
>> what's going on here. I've missed out too many important details.
>
>Older practice, when active devices were expensive and bulky was to have an
>active stabiliser circuit (which also got rid of the ripple) directly after
>the power supply. Nowadays they tend to have voltage regulators for each
>module or circuit, local to that module. If you have the latter arrangement I
>would be looking for ripple on the output of each local regulator rather than
>the main power supply. Or the high ripple could be due to excessive current
>being drawn from one power supply. Anything getting excessively hot?

I don't think anything's getting unduly warm, let alone hot. But I
can't be sure as access is impeded and they've used the most
*enormous* finned cast aluminium heatsink for only four TO-220 package
regulators. This sig gen is the 10k to 5.4Ghz one and is about 25
years old I would guess.
I agree with your approach on checking each regulator individually but
the access issue is a real pain here. They clearly haven't given much
thought to servicing with this model - and that's unusual for a
company like Marconi/Aeroflex (or whatever they call themselves now).
Plus the fact that they've never released schematics doesn't help
much either.

On 2/25/2024 1:01 PM, Cursitor Doom wrote:
> So - in the case of a linear power supply - the rectified output of
> the transformer typically goes straight to a big old storage cap for
> smoothing purposes. My question is: how much ripple should I expect to
> see across that cap if all's working well? I have to say I'm seeing a
> *lot* of ripple on this cap in a Marconi RF signal generator and it's
> finding its way to the RF output, which of course should ideally have
> zero ripple on it. The aforementioned cap tests fine WRT ESR and
> capacitance in-circuit, I should add.
>
> Thanks,
> CD.

Prior to the regulator circuit, the ripple voltage
depends upon current drawn for a given supply at a
given frequency. The higher the current drawn, the
greater the ripple for your supply. So one possibility
in your generator is that too much current is being
drawn i.e. a defect in some circuit "downstream" of
the bridge/cap.

Depending on what follows the diode/capacitor supply you
may have a regulator failure. Regulators hold the voltage
at some specific value, thus they remove ripple. Voltage
measurements usually reveal which regulator is failing to
provide the proper output voltage. Again a defect downstream
may pull the voltage down. Without a manual/schematic its
harder to diagnose - but it is still possible. And I read
somewhere that manuals are available. See the url posted
below - it may help.

Next - perhaps the ripple really isn't excessive. By that
I mean it may be within spec for your generator. You may
find this site helpful:
https://groups.io/g/Marconi-Test-Instruments

Good luck. Let us know whe you fix it!
Ed

On Tue, 27 Feb 2024 17:57:32 -0500, ehsjr <ehsjr@verizon.net> wrote:

>On 2/25/2024 1:01 PM, Cursitor Doom wrote:
>> So - in the case of a linear power supply - the rectified output of
>> the transformer typically goes straight to a big old storage cap for
>> smoothing purposes. My question is: how much ripple should I expect to
>> see across that cap if all's working well? I have to say I'm seeing a
>> *lot* of ripple on this cap in a Marconi RF signal generator and it's
>> finding its way to the RF output, which of course should ideally have
>> zero ripple on it. The aforementioned cap tests fine WRT ESR and
>> capacitance in-circuit, I should add.
>>
>> Thanks,
>> CD.
>
>
>Prior to the regulator circuit, the ripple voltage
>depends upon current drawn for a given supply at a
>given frequency. The higher the current drawn, the
>greater the ripple for your supply. So one possibility
>in your generator is that too much current is being
>drawn i.e. a defect in some circuit "downstream" of
>the bridge/cap.
>
>Depending on what follows the diode/capacitor supply you
>may have a regulator failure. Regulators hold the voltage
>at some specific value, thus they remove ripple. Voltage
>measurements usually reveal which regulator is failing to
>provide the proper output voltage. Again a defect downstream
>may pull the voltage down. Without a manual/schematic its
>harder to diagnose - but it is still possible. And I read
>somewhere that manuals are available. See the url posted
>below - it may help.
>
>Next - perhaps the ripple really isn't excessive. By that
>I mean it may be within spec for your generator. You may
>find this site helpful:
>https://groups.io/g/Marconi-Test-Instruments
>
>Good luck. Let us know whe you fix it!
>Ed

Many thanks for that, Ed. :)