Greeting All,

Would anyone know how or where I could obtain a balance control assembly for above model. Getting sound on LH channel but not on right side. Is this switch serviceable or is there a substitute that closely matches should and OEM or secondhand part be unavailable?

Look forward to any guidance and thank you in advance if you can help.

Can you be more specific about the particular model. For example, is it 11-102 or 11-103?

If so, then the balance control is a 2 megohm rotary potentiometer. These are definitely still obtainable, but there's the question of matching the shaft type and dimensions to the knob.

However, are you sure that is where the problem lies? Loss of sound in one channel can be due to a number or causes.

Is the problem evident in both radio and phono modes? Has the problem suddenly appeared or gotten worse over time?

Hi GTC,

Thanks for your prompt reply, much appreciated. I'm in the process of finalising a purchase and uncertain of model no. but have attached link below picturing the unit if that helps. Owner states that he thinks it might be the balance control as it's somewhat crackly. If you could advise I'd be most grateful.

https://www.gumtree.com.au/s-ad/mount-waverley/collectables/retro-Kriesler-master-multi-sonic/1150948600

From the look of it, that's probably an 11-102 or 11-103. The multisonic series have a very good sound, so definitely worth getting one for 'the sound of music'.

Scratchy pots are not unusual, but the problem of no sound in the right channel could be anything from a failed valve to a failed output transformer (a known weak point in the Kriesler stable), or indeed some other faulty component or combination of components.

Without the benefit of inspection, I'd say it's probably fixable.

Oddly, there seems to be a light dimmer mounted on the back.

It is a 11-103 from 1966.

This version has a meter instead of a magic-eye. Inside is brushed aluminium with glass panels on either side of a Garrard AT60 changer. Each channel has push-pull 6GW8's driving a pair of 12" & 6" x 4" speakers with an electrostat.

Very nice unit.

Schematic can be found here: http://www.kevinchant.com/uploads/7/1/0/8/7108231/11-102_11-103.pdf

Very unlikely to be the balance pot causing a dead channel.

Output transformer also unlikely unless it's O/C in two places.

Most likely in my experience of this model is the input selector switch. Often just a dry joint on a terminal. If switch itself is bad, it can usually be repaired, you won't find a direct replacement.

I have some Schadow PB switches that might fit if it's a write-off.

But test first!!!

I agree with Ian I have seen quite a few of these old switches simply repaired by lightly squeezing the contacts together or just the use of good quality contact cleaner.

Silicon chip did a good Article on this model and a few others .
I believe the back issue is still available on line .
Pete

Looking at schematic, wiring of R34b & R34d seem wrong, shouldn't they return to ground?

Looking at schematic, wiring of R34b & R34d seem wrong, shouldn't they return to ground?

In my opinion, V5A and V4A are configured as a phase splitter.
Output from V5A anode is applied to the divider R34A and R34C and the grid of V4A is connected to the mid point.
V4A is a unity gain inverter so that the amplitude at the anodes of V5A and V4A are equal but 180 degrees out of phase to drive the push/pull output valves.

Harold

Intuitively, I would prefer to see the voltage divider grounded (isolated) as here: http://www.dogstar.dantimax.dk/tubestuf/paraph.htm

Cannot see the sense of adding the newly inverted drive signal back to a resistive 'T' network.

Kriesler sometimes did some strange things. I haven't seen that arrangement before but analysis (and experience - they did make quite a few of them at the Caringbah factory by now) says it will work.

One more observation:
The manual claims the electrostatic tweeter is a Magnavox. Never knew Magnavox put out an electrostat. It's a single-ended electrostatic in that it is driven by high voltage swing of one half of push-pull primary. If we wanted to be picky, we could say this isn't exactly "hi-fi" as class AB push pull signal has asymmetry. But everybody did it, like the German radios/stereos, and an early 60s Philco console I have that uses larger parabolic electrostatic speakers above 2kHz. The Philco cleverly derives stereo & a common woofer from a single push pull transformer. It then uses movable satellite stereo speaker units that include an oval cone speaker like the Kriesler (actually it has those extreme-narrow ovals used in 60's TVs), as well as electrostats. Analysing the schematic, I traced out the Philco's complex circuitry and found it winds up having the stereo out-of-phase! Would anyone notice in the early days of stereo?

Magnavox had a factory in Sydney - Alexandria to be exact - and most if not all their designs from the 50s on were local. Yes they made electrostatic tweeters.

QUOTE: Cannot see the sense of adding the newly inverted drive signal back to a resistive 'T' network

It's a little like the way an op-amp works. The V4A tube's grid is similar to the "virtual ground" on an op-amp wired up in inverter mode. The tube creates an inverted signal nearly the same amplitude but inverted that exists on output V4B's control grid. As the 3 resistors on the T circuit are equal, you'd get almost cancellation at V4A's grid. What it does see is an "error" voltage, which V4A works hard to correct to nearly zero signal. Thus you get an out-of-phase signal to drive output V5B, which is what you need in a push-pull amp.