review33.com: 影音天地: QUAD ESL speaker

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[#1363] Quad ESL Dear all, Thanks for your advice. The OTA sounds beautifully in my flat and the sound stage of TV (sorry I am using TV to run in my ESL as my family has to watch TV every night. This is a common problem, or norm, of a typical family in small flat) suddenly opened up wide and deep at 9:30 pm. The voices of TV people became much clearer than before. No kidding, it was TV not CD or LP. Limage and doctor John, When next visit, I am sure you will be surprised with my two new vinyl toys yet to be arrived in next week.		dkyyu 正式會員 218.xxx.xxx.221	2006-09-15 11:42

[#1364] Quad ESL
CP......Please refer to the following extracts from the user manuel of the HV probe. I think we have selected the Auto Mode which is not accurate for the reading:

"• Use a meter with an impedance of 10 MW ( ± 1% ).
Using a meter with an input impedance less than
10 MW reduces the accuracy of the reading by
causing it to be lower than the voltage present.

• DO NOT use the probe with a Fluke multimeter that
is in the kChek? or Automatic Selection mode (i.e.
Fluke 16, Fluke 12B etc.). The input impedance in
these modes is very low."

Regds

Pcs100

正式會員
219.xxx.xxx.201

2006-09-15 12:33

[#1365] Quad ESL
Hi limage,
That is true, high voltage in connection with mylar panel (capacitor) is something beyond my knowledge too. As OTL said, "You will only register the correct readings if you use an electrostatic volt meter - built a probe will do, as long as you allow for the under-readings!"

Hi Patrick,

I got two fluke meters, one is 77 and the other one is Fluke 45 (Laboratory grade). Which would you prefer?

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-15 12:46

[#1366] Quad ESL
Patrick,

That is my Fluke 45, the voltalge range can be selected manually. Any good?

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-15 12:51

[#1367] Quad ESL
Patrick,

Your choice. Fluke 77.

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-15 12:54

[#1368] Quad ESL
Your choice. Fluke 77.
-------------------

Edmond......I think Fluke 77 is fine.

Regds

Pcs100

正式會員
219.xxx.xxx.201

2006-09-15 15:30

[#1369] Quad ESL
Patrick,

Mine is the Fluke 19. The other day we were using the auto range, so that could be the problem. I've checked the online manual and note the HT probe is simply a 1000:1 divider so actually any multimeter will suit.

I doubt whether your bass panel leaks. If the EHT measurement under no load is only 2400V+, it must be the problem of the EHT. Have you decided to make a new one?

cpsjj

正式會員
219.xxx.xxx.78

2006-09-15 22:08

[#1370] Quad ESL
Dennis,

You can write a book 'The Engineer'!

jcml

正式會員
218.xxx.xxx.12

2006-09-15 22:15

[#1371] Quad ESL
Dear all,

One pair OTA in eBay, five days to go. Shipping to Hong ong is GBP240.
http://cgi.ebay.com/QUAD-ESL57-beautiful-ONE-THING-AUDIO_W0QQitemZ270029103485QQihZ017QQcategoryZ43804QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Last pair in eBay sold for GBP1500.

dkyyu

正式會員
210.xxx.xxx.217

2006-09-15 22:23

[#1372] Quad ESL
jcml,

These people are real engineer with heart and I am afraid I have to keep my mouth shout all time except baby crying for assistance.

dkyyu

正式會員
210.xxx.xxx.217

2006-09-15 22:25

[#1373] Quad ESL
Dear all

This is the scope of rebuilt quad esl57 loudspeakers by OTA:

Speakers totally stripped down to their component parts.
Frames repaired, if necessary, sanded down and re sprayed
Audio transformer tested, old components scrapped and superior modern components with a higher rating substituted. Encasement re sprayed and new 4mm sockets fitted.
Heavy duty clamp board fitted (One Thing Audio part no: CLP4
Owners's original bass panels will be re-used if after extensive work on the stators, they meet our minimum performance criteria.
Superior EHT board fitted (One Thing RBT3) with independent bass and treble drives.
New internal cabling throughout.
Cosmetics: End pieces sanded and re sprayed to their original finish (or as close we can get!). In cases where front grille is dented or unsightly, a thin cloth is fitted(black/dark brown/midnight blue) which looks most attractive. This is provided at no extra cost, but upon request only.

CP,
See, the bass panel is still original even from package of rebuilt.

dkyyu

正式會員
210.xxx.xxx.217

2006-09-15 22:28

[#1374] Quad ESL
There is a topic which are quite helpful to determine low voltage due to panels or HT circuit.

How to diagnose a Quad-57 panel or EHT block problem yourself

This method assumes one of your Quads is working properly.

The first step is to open up the backs of your Quads & measure the voltages on the EHT blocks with your high voltage
probe & meter (a must) while the speakers are energized. If you aren't comfortable at this point, especially with the
Quad's high voltages, I would pack up the bad speaker & send it to me or someone else who fixes 57's regularly.

The block measurements on both of your speakers should be the same. If not, you have to determine whether the
rectifier block is bad or panels are causing the problem. Rather than give you absolute numbers, I'll use the technique
of comparing what you measure on your good Quad with what you measure on the bad speaker. That gives you
realistic base line figures rather than simply saying "6000V on the bass & 1500V on the treble." If the numbers on the
ailing Quad don't match those on your good Quad you'll have some unsoldering to do. Ready?

Unplug the bad speaker & completely discharge the block with your probe. Unsolder the treble wire (second from
left) on the back of the block. Plug in the speaker. Measure the voltage at the pin. Has it come up now that the treble
panel is disconnected? If so, you will need to change that panel. If the voltage measurement is the same with the
panel lifted, unplug the speaker, fully discharge the block, & resolder the connection.

The next step is to take measurements on the bass side of the block & perhaps the two bass panels. The same
procedure is used but voltages are much higher. Still having the speaker unplugged & discharged, unsolder the
thicker red wire (far left) from the back of the EHT block. Energize the speaker. Take a measurement at that pin. It
should be the same as what you measure at the same pin on your "good" speaker when energized. If not, the EHT block
needs to be replaced. But if the measurement is the same as your good speaker with this fat red wire unsoldered,
your problem is not with the block but with one or both bass panels.

The last step is to determine which of the two bass panels is the culprit. Unplug the speaker. Fully discharge the
block. At the center terminal on the back of the right bass panel two fat red wires are connected. You will have to pull
back a red plastic sheath to unsolder & separate these two wires. It's a little tricky here because you don't want to
overheat the plastic post. Wiggle the wires a little as you apply heat. Once the two red wires are separated you can
determine which bass panel is causing a drag on the block by first hooking up one panel, taking measurements,
unplugging, discharging, unsoldering the red wire, & then repeating the same process with the other bass panel.

Once in a while slightly leaky treble panels don't load the high voltage rectifier block down enough to show up in
meter measurements. But rest assured, you can hear this lack of efficiency when a comparison is made to a properly
working Quad. In this case the only thing left to do is change the offending treble panel & hope for the best.

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-15 22:31

[#1375] Quad ESL
I doubt whether your bass panel leaks. If the EHT measurement under no load is only 2400V+, it must be the problem of the EHT.
-------------------------------------
CP.
How to explain why it happens to all ESL57 we have measured. totally 4 units.

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-15 22:38

[#1376] Quad ESL

Don't have a clue, Edmond. But the measurements were made under 2 different circumstances.

Measurement on Dennis' was made with bass panel connected and by the HT probe with the DMM on autorange. Reading was about 1500V but was probably faulty.

Measurement on Patrick's was with bass panel DISCONNECTED and by a HV meter directly. Reading was 2400V+.

I'll take some measurements of mine next week.

cpsjj

正式會員
219.xxx.xxx.78

2006-09-15 23:09

[#1377] Quad ESL
In responds to this ESL 57 conundrums. I make a blind guest; please make comments if you think it is not logical.
I suggest we should check the HT circuit next time. There are several safety measures in place to protect those panels and may reduce noise level by lowering HT voltage.

1, Treble panel, 1500V remains the same, but one 10M resistor is in series with the panel to limit current flow through it:. Anyhow, OTO claims the treble panels are brand new.

2. Bass panels. I read an article:
++++++++++++++++++++++++++++++++++++++
Background Noise of Quad ESL 57

One cause of background noise in the electrostatic loudspeaker is internal discharge of the EHT supply at times of high humidity, or high voltage, or both. This may be reduced by lowering the EHT voltage and a tap is provided on the EHT mains transformer for this purpose.

++++++++++++++++++++++++++++++++++++++++++

Therefore, lower the HT voltage could definitely reduce noise level.
I believe some Quad ESL 57 after being serviced. They might have purposely tuned down the HT voltage to meet some purposes.

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-16 09:10

[#1378] Quad ESL
Edmond,

We can try everything to find out. The construction is really quite simple.

The obvious flaw in your proposition is Patrick's ESL has not been serviced. The treble voltage measures exactly 1500V while the bass measures 2400V.

The EHT multipliers are in steps of 1500V so the bass voltage depends on whether you tap at 3000V, 4500V or 6000V but not on the strange figures that we have.

cpsjj

正式會員
203.xxx.xxx.124

2006-09-16 09:57

[#1379] Quad ESL
I had low voltage readings on my bass panels after restoring the HT board the first time around using the original specs.

I changed the (new) 1N4007 diodes w/ 3A ones and the readings were now ok.

Quad used the 1N4007 because they were what was available during that time but they are quite inadequate for the job.

Hope this helps.

mozilla

正式會員
210.xxx.xxx.112

2006-09-16 10:08

[#1380] Quad ESL
CP,
there is voltage divider 330K and 2.2M in the circuit. We need to check whether it is original or being modified. I query the voltage drop on both ESL 57 is symmterical.
Mozilla,
Do you remember how low was your measurement that time?

Blue-Ray

正式會員
218.xxx.xxx.17

2006-09-16 11:23

[#1381] Quad ESL
Concerning the low voltage in Dennis' bass panel, I opened up my ESL57 and ran a voltage check yesterday. To my surprise, the secondary output of the main transformer is normal at 600 volt and the treble panel is normal at 1270 volts. But the bass panel reading is very low at 2200 volts. I believe this reading is accurate because I have disconnected the bass panel. And the meter is reliable, I've been using it for almost 30 years.

My ESL57 was 1st acquired in 1980. And now is almost 26 years old. The diodes in the EHT may be very tiring and needed to be replaced. I decided it is time now to do a tune-up.

It's easy to remove both EHT from the speaker. It was full of dust but the bee wax looks beautiful. I used a toaster to melt the wax. It took less than 30 minutes and all the bee wax is gone. It looks nice and clean and is ready to do the parts replacing project. Will go buy the parts Tuesday after visit to Dennis' place. I plan to replace all the diodes, capacitors and resistors and relying on Edmond's dependable hands for the procurement.

It was funny That there were no symptom of any dissatisfaction on sound quality even on such low bass panel voltage. I thought weaker bass is normal on ESL57 and have been enjoying it for 10 years. I wonder how the new sound would be after the normal voltage on bass panel is restored.

Will update you folks on progress.

Regds