Hi everyone
I’ve been working on a Kriesler multisonic 11-97 and need help with getting the electrostatic high frequency speakers working. The left channel works most of the time but the right channel crackles mostly. The louder the volume the more consistent the crakle. The voltages at the speakers are correct but there seems to be no audio being passed through to the right channel and left as I said is inconsistent.
Is anyone able to point me in the direction to getting it working properly.
Thanks
Scott

Hi Scotty,

I assume you have swapped right and left speakers as your first step?

Not as yet as that’s quite a production with those units. There is sound from the right high frequency speaker especially when the set is first turned on. The right high frequency channel makes a loud static noise for about 10 seconds

Have you checked the condition of the contacts in the electrostatic in/out press button switch?

With the electrostatics switched out, do the left and right channels sound OK?

Yes I checked the switch it’s working fine. No issues with the other speakers. It’s purely with the electrostatic speakers.
Am yet to try swapping them as that’s quite a production with those units. There is sound from the right high frequency speaker especially when the set is first turned

Depending on access, I think swapping over the connections on pins 3 and 4 of the electrostatic socket may be the easiest way to go for that test.

Ok, I’ll try that tomorrow. I’m still not sure how it actually works. If one of the electrostatic speakers are faulty, I wouldn’t know where to source a replacement

Be careful of the HV on those speakers.

They were Magnavox E3.5 speakers. https://www.ebay.ie/itm/MAGNAVOX-E3-5-ELECTROSTATIC-TWEETER-1960s-RARE-MATCHED-PAIR-FOR-EL84-OUTPUT/151630868179

The .01μF series caps might be suspects.

I will be looking at all the caps and resistors in this circuit over the weekend. I’m not too clear on how this part of the circuit works. I have checked the plate voltages that feed the circuit and they are correct.

Here's a description of the technology: https://en.wikipedia.org/wiki/Electrostatic_loudspeaker

Ok, well I’ve got it to work. It does appear that the 6GW8 valves are quite noisy. The unit has 4 and swapping them around moves the cracking to the other channel. I’ve cleaned the sockets which has helped a lot. Occasionally the unit lets out a few loud pops which I think is related to the valves themselves.

How did you clean the sockets -- with Deoxit or similar? Did you also clean the valve pins?

Random loud pops can be courtesy of valves, but capacitors on the way out can contribute as can bad solder joints.

Have you isolated this symptom to the audio stage -- that is, do the pops only occur when the input is radio, or gram, or both?

Hi GTC,
I used deoxit to clean the sockets and have cleaned the pins also using a contact scrub. The pops are on both radio and gram. Removing the 12ax7 pre amp doesn’t change it.?I have recapped the unit.

The problem with the electrostatic speaker was a missing plate voltage on one of the 6GW8 valves. Cleaning the sockets and pins fixed this

So, the popping is channel-specific and changes when you move the valves around?

People are asking stupid money for 6GW8s:

https://www.wagneronline.com.au/6gw8-triode-pentode/valve-tubes/electronic-components/6gw8-97563/1005422/pd/

https://www.watfordvalves.com/products.asp?search=ecl86

More reasonable: https://www.ebay.com/itm/373740895955?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338722076&toolid=10001

6GW8s were known for developing the crackles, even when quite new. I replaced many of them in "stereograms" when new, under warranty.

NOW I am showing my age!! That WAS a long time ago.