On 18/05/2022 6:01 pm, tony sayer wrote:
> In article <je2nnbFgolfU1@mid.individual.net>, Trevor Wilson
> <trevor@rageaudio.com.au> scribeth thus
>> On 12/05/2022 6:56 am, tony sayer wrote:
>>> In article <jdivupFgn20U1@mid.individual.net>, Trevor Wilson
>>> <trevor@rageaudio.com.au> scribeth thus
>>>> My distortion analyser (Sound Technology 1701B) failed awhile back and
>>>> the job to repair it has proven to be quite involved. As a consequence,
>>>> I found a Japanese auction site, where I located a very impressive DA
>>>> for reasonable money. This is the device I purchased:
>>>>
>>>> https://kenrockwell.com/audio/panasonic/vp-7721a.htm
>>>>
>>>> Ken is correct. It is a brilliant DA. Fast and easy to use. Naturally, I
>>>> had to lift the lid. Construction is excellent and every one of it's 5
>>>> regulated power supplies measured within 1% of their stated figures.
>>>> Here is a graph of the oscillator distortion, plus some internal photos,
>>>> as measured with my Quantasylum QA403 (oh yeah, I bought one of those too):
>>>>
>>>> https://imgur.com/a/d7PcSDV
>>>>
>>>> I also purchased an HP339A for not much money. I must say that the
>>>>
>>>
>>>
>>>> construction quality comfortably exceeded my expectations:
>>>>
>>>> https://imgur.com/a/cX43Ydp
>>>>
>>>> A bit rough on the outside, but it works. Note the heavy gold plated PCB
>>>> traces. Colour me stunned.
>>>>
>>>>
>>>>
>>>> Of course, the Quantasylum whips the hardware analysers with ease.
>>>>
>>>>
>>>
>>> Superb bit of gear got one here and tho we have a more recent
>>> equipment's its still the go to machine!
>>>
>>> Excellent meter on it, good for peaking tuner discriminator coils and
>>> the like..
>>>
>>> Very reliable one good idea is to swap out the power supply caps with
>>> some decent ones and it will last till, well hereafter! And the
>>> performance may well improve from .00*% to .000*%!
>>
>> **Already done. Squeezed in some caps that are three times the value of
>> the originals. That said, the originals measure fine WRT stated
>> capacitance and ESR.
>>
>
> ** Bet they have already been replaced!

**Nope. They're the originals.

>>>
>>> Only issue is the control knobs are liable to fall to bits and finding
>>> new or replacements is neigh on impossible, i have heard that someone
>>> made some on the 3D printer!...
>>
>> **The knobs are an example of (rare) really crappy HP design.
>
> ** Yes not their finest hour!..
>>
>>>
>>> Quite right re the PCB's and overall build quality and even those units
>>> are now dating back since IIRC the 70's theres still a very good support
>>> newsgroup!..
>>>
>>
>> **The biggest improvement one can make (apparently) is to replace the
>> output level control with a cermet type. Measured distortion is reduced
>> significantly. When my pot arrives, I'll perform some comparison tests.
>>
>
> ** Not heard that, how would it make any real difference?, seems like
> snake Oil!..

**Nope. Carbon pots develop a range of interesting problems as the age.

>
>
>> That said, I prefer my Panasonic VP-7721A. Much faster and easier to
>> use. Plus, it resolves distortion levels 10dB lower than the HP.
>>
>
> ** Really 10 dB lower in percentage terms how low is it or are you
> claiming?..

**Not my claim. The HP resolves -80dB full scale. The Pana resolves
-90dB full scale. I haven't measured the oscillator distortion from the
HP yet, but the Pana is pretty damned good:

https://imgur.com/a/9Ft88Dj

On 18/05/2022 6:04 pm, tony sayer wrote:
> In article <je56ktFgdgU1@mid.individual.net>, Trevor Wilson
> <trevor@rageaudio.com.au> scribeth thus
>> On 13/05/2022 5:36 am, Phil Allison wrote:
>>> Trevor Wilson wrote:
>>> =================
>>>>
>>>>>> **The knobs are an example of (rare) really crappy HP design.
>>>>>
>>>>> I do remember one aspect of crappy HP design from my days with Marconi
>>>>> Instruments. They designed their power supplies for 60Hz operation and
>>>>> neglected what happened at 50Hz if you left the things switched on for
>>>>> extended periods. They got hot - I mean failure type hot. They were
>>>>> just marginally short of primary inductance.
>>>>>
>>>>
>>>> **YIKES! That's worse than poor quality knobs. Betcha Tektronix never
>>>> made such mistakes.
>>>>
>>>
>>> ** It's a mistake I have seem many times in other gear.
>>>
>>> Some Yank transformer winders see no issue with having twin primaries on a
>> core sized for 60Hz - ie Pacific Transformers.
>>> A 20VA example dissipated 9 watts, * off load * at 240V 50Hz.
>>
>> **The worst I've seen goes to Chinese crap. One product that landed on
>> my bench had a power transformer that saturated at around 200VAC.
>>
>>>
>>> But the prize goes to a Taiwanese power amp amp that used a large toroidal,
>> about 1.2 kVA.
>>> The primary rms current rose to 8 amps at 260VAC, a common occurrence in
>> Western Australia.
>>
>
>> **YIKES! Don't get me started about WA. When I was at Marantz, our Perth
>> service agent would order spare parts that no one else in the country
>> ever ordered. When I questioned him, he explained about the wild mains
>> swings.
>>
>
> ** Just how bad are they then?..
>
> In the UK, the declared voltage and tolerance for an electricity supply
> is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2
> volts to 253.0 volts.
>
>

**Back in the 1970s, the nominal 240VAC, in Perth would hover around
260VAC for long periods and short term peaks of 270 ~ 280VAC were not
unheard of.

Trevor Wilson wrote:
=================
>
>
> **Back in the 1970s, the nominal 240VAC, in Perth would hover around
> 260VAC for long periods and short term peaks of 270 ~ 280VAC were not
> unheard of.

** I have a friend who lives in Perth.

On a visit to Sydney in 2007 he, brought me an FX unit that had a burnt out mains transformer.
The result of being left switched on overnight.

Stores in Perth and Western Australia sold 260V rated GS incandescent lamps - until the style was banned.

....... Phil

On 19/05/2022 7:29 am, Phil Allison wrote:
> Trevor Wilson wrote:
> =================
>>
>>
>> **Back in the 1970s, the nominal 240VAC, in Perth would hover around
>> 260VAC for long periods and short term peaks of 270 ~ 280VAC were not
>> unheard of.
>
> ** I have a friend who lives in Perth.
>
> On a visit to Sydney in 2007 he, brought me an FX unit that had a burnt out mains transformer.
> The result of being left switched on overnight.
>
> Stores in Perth and Western Australia sold 260V rated GS incandescent lamps - until the style was banned.
>

**Yep. Very common.

On 18/05/2022 09:04, tony sayer wrote:

> ** Just how bad are they then?..
>
> In the UK, the declared voltage and tolerance for an electricity supply
> is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2
> volts to 253.0 volts.
>
>

My Plug-in watt-o-meter showed 187V (*) once so I phoned the
EDF Emergency number and the guy who answered the phone said
"So what ?". As far as he was concerned it wasn't a problem.

(*) normally showed a reliable 243V, and I double-checked the
187V reading with my multi-meter.

Andrew wrote:
============
>
> > ** Just how bad are they then?..
> >
> > In the UK, the declared voltage and tolerance for an electricity supply
> > is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2
> > volts to 253.0 volts.
> >
> >
> My Plug-in watt-o-meter showed 187V (*) once so I phoned the
> EDF Emergency number and the guy who answered the phone said
> "So what ?". As far as he was concerned it wasn't a problem.
>
> (*) normally showed a reliable 243V, and I double-checked the
> 187V reading with my multi-meter.
>

** That reading would suggest a problem with the neutral link in a 3-phase supply to a premises.
One phase voltage goes low and the others high.
Very bad.

........ Phil

In article <b72836d2-7496-42de-a3d6-7e7a1b5260acn@googlegroups.com>,
Phil Allison <pallison49@gmail.com> wrote:
> ** That reading would suggest a problem with the neutral link in a
> 3-phase supply to a premises. One phase voltage goes low and the others
> high.

Eh? In the UK?

--
*If you can't see my mirrors, I'm doing my hair*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.