which tube acts at the phase inverter for this setup?

The 6GW8s (as stated in the schematic)

I have some news! I have tracked down the intermittent right channel cutout on gram….it cut out again so I gave a little pull on each gram cable where they connect to the chassis….the ground wire popped out! Turns out it’s broken at the connector! I checked it briefly when Marc mentioned it as a suspect but I mustn’t have checked thoroughly enough that time.

I have a spare that I’ve been planning to swap - so at least I (think!) I have that one sorted!

Thanks gtc I should have looked that up….didn’t realise the 6gw8’s were a split valve….quite complicated with 1/2 of each driver/inverter & other 1/2 of each push pull….

Turns out it’s broken at the connector!

See line 4 of post #3

That’s why I come on here - you all know so much!!

Well I thought I had great news....I resoldered the earth wire and thought it was fixed.....until it cut out again playing a vinyl haha

I have noticed when it cuts out and I lift and move the turntable arm to a different spot on the record it seems to come back on....so I checked the cables from the mute switch to the tonearm but they look ok....and I tried giving them a little poke with a screwdriver while it was playing and didn't seem to bring the channel back on when it cut out.....so I don't know if it is them or not!

Big question is how on earth is the tonearm wiring replaced on a garrard at6? Is it easy to replace the wiring in the arm? I don't know how to remove the end of the arm where the headshell attaches.

Another thing I noticed (just to complicate things further) is that there are differences between the garrard's I have (I have 2 - one that originally came with this radio that has a stuffed tonearm) and this one which came from an 11-95 so it is slightly older. This one from the 11-95 one has resistors and capacitors on each channel at the mute switch whereas the later one from the 11-97 doesn't.....does anyone know the significance of this? Should I cut the leads to more closely replicate what the later model was like incase that is disturbing things?

I still have the reduced volume / slight distortion on the R channel in all modes....made no inroads there will try & check voltages later.....keep jumping between the 2 problems at the moment lol.

The Americans call that methodology "Shot gunning". In its worst case scenario people start pulling things to bits way ahead of the fault which then potentially, introduces new ones. Advised a person on the American forum (moderator) the error of his ways, for removing IF transformers , for no logical reason.

Intermittent faults were designed, to keep people amused for hours, frustrate and keep them guessing. Rule number one is to never touch the working amp in a stereo until such time as the other one is working and in the same vane, if you are changing caps do not interfere with the other one.

Some times you just need equipment. The working amp is the reference. As soon as the fault manifests, You check the voltages on the dud to see what has changed: That could be nothing. That is also where a dual trace oscilloscope is handy as you can monitor both channels, however, a single trace can be put on the input tubes plate (If it can handle the volts) and see at what point the signal dies. That sort of thing can save hours.

The input circuit is dependant on the cartridge, Magnetic and Ceramic / Crystal are not the same.

Removing a tube from push pull without result could indicate a faulty tube. If you did the same to the working amp's same tube and run quickly you should get the same result. replacing tubes to a running set, is not recommended. The other amp is the tube tester. You just swap them but mark them

Marc

Oh dear - shotgunning definitely sounds like me right now! Unfortunately I don’t quite have the knowledge or expertise…keep hoping to get lucky but to no avail.

I actually just did that again - I swapped the mute switch & all the cabling from the garrard at6 mkII over….and guess what yes the right channel still cuts out!

So I can only suspect that fault is in tonearm or pre amp - it’s not between mute switch to the pre amp input.

With the difference in volume/bass of R channel on all modes, I have a spare set of output tubes but swapping them around makes no difference.

I will measure voltages but I think I’ll save that till tomorrow now - spent all that time swapping over mute switch & wiring with no result so I’m ready to just open a beer & listen to some vinyl (which is sometimes mono sometimes stereo haha)

That methodology does sound a lot like a fishing expedition looking for the elusive "Red herring", or "The Holy Grail".

In cases like this one, where it could be as simple as a make & break. The least tampering the better. Taking all of the tubes after putting a dob of marker on one set and transferring them to the other amp is a legitimate method of finding a feral tube.

Prodding & poking the wiring & components, with a chopstick is another way that can be used to find mechanically bad jointing. The miniature tube sockets can open and careful pushing with a probe can close them back up.

Some of the fine wire used in the pick up cabling, even today, is not that good, where the fall down is with plastic wire is that with age & heat, it tends to lose its plasticiser and become more rigid. That has ramifications & why several wire runs in the Farm Utes engine have needed replacement. When the sheath became rigid it would only flex at a weak point and that's where it started to break. That behaviour also manifests in older radios and cheap modern flexible leads made for a price by reducing the expensive plasticiser.

Whilst it may be a slower process one needs to have a methodology where you work from the audio input tube. I am still not seeing a fault past there, if its not misbehaving on mono radio.

Yes I should definitely have adopted a more diagnostic approach.....it's a steep learning curve.....

What you say definitely makes sense - it must be a fault between cartridge and the input to preamp. I have about 4 12AX7's I've tried and all exhibit the same issue so I don't think it is the tube itself.

I think the next idea is to swap the R & L channels at the mute switch....if the fault changes channels I know it is between cartridge and mute switch.....if it doesn't change channels it must be in pre amp stage.

Actually I just worked out the darndest thing - I should have indicated how I put this setup together I bought a 11-95 which had a ruined chassis and bought a 11-97 that had a ruined cabinet. I thought I'd be clever and put the 11-97 chassis in the 11-95 cabinet which didn't require much altering at all - a cutout was required for valve no 8 which is absent on the 11-95 chassis but everything else plugged right in.

Well so I thought....I was just swapping a couple of output valves around again and noticed that the mid range speakers (bottom corners of cabinet) don't seem to be coming on when it is set to all 6 speakers.

So looking at the wiring in the cabinet the mid range speakers appear to be connected to a shared ground and receive their input seperately.

However looking at the chassis the 'input' for these speakers actually just goes through the 2 speaker switch - and this just grounds them.

So effectively both terminals of these speakers are connected to ground! I went to the garage to find the old 11-97 cabinet and sure enough the mid range speakers are wired differently - their input comes from the bass speaker input and are earthed through the chassis!

Obviously Kriesler changed how they were switched - even though all the sockets etc are the same the 11-95 must have sent seperate power to those mid range speakers compared to the 11-97 which the switch just grounded to complete the circuit! Who knew!

I just quickly cut the mid range speaker wires going to the chassis and soldered them to the bass speaker inputs which means they will always be on now even on 2 speaker mode but gees it sounds so so much better now with a full set of 6 working speakers! Channel R is still quieter than L though.....but it's mainly the bass speaker that has the noticeable difference there so it could just be the speaker.... I think it sounds so good now though that I may even leave that issue alone and only worry about the turntable R channel.....if I solve that I am just looking forward to chilling and listening

That is fascinating about the plasticiser but no surprise I guess - in this day and age everything is built cheap and imported. I have carefully checked around the wiring at the end of the tonearm which is where all the flex would occur but I can't see anything significant...but it may not be visible. Other thing I could do there is check for continuity from tonearm to the mute switch while moving the arm....but could be tricky to do may just swap R & L at mute switch first before I go further. If it is tonearm wiring I then have to work out how to disassemble the headshell connector.....I can't see any obvious way to pull apart.....steep learning curve again lol

The cartridge may not be a solder on type, it may have four slip on pins I would be tempted, if that is the case, to just do the reversal there, or at the plug. That would mean that transferring the fault, puts the fault in the wire. and is likely less risky than messing with the switch, or the head shell. Often the stylus sits in a "V" fork, make sure that's not visibly damaged.

Unfortunately the cartridge is soldered in…I have a spare head shell with its own cartridge but both exhibit same issue so it’s perhaps the tonearm wiring….I soldered in the current mute switch so it’s quite easy to swap r & l there….I could probably also bridge the 2 wires in the headshell & at mute switch to make it mono - would this sound much different do you think?

If it’s tonearm wiring I’ll try & work out how to rewire it first though before going mono…but who knows it may not even be that yet - we’ll see!

I really believe that the fault is exclusively in the path from grid to head shell. If there is no issue on radio, then clearly, one needs to mark out with coloured pencils the circuit not belonging to the radio. Switches do wear.

Rather than mess with the switch I would consider reversing at the plug and see if the fault changes channels. As proven by a 6D6 I posted, pins can look soldered, but when the envelope falls out of the base, this is not so.

Ok a quick update I swapped over the R & L channels at the headshell today but it still cut out on the R channel.

So i've removed the turntable and swapped the channels over at the mute switch.....just fired it back up so waiting to see what happens!

So far no cutting out of either - but before the R channel was quieter on radio and turntable....swapping them over at the mute switch (bearing in mind I left the grounds) seems to have made the L channel quieter and the R channel a bit louder....so they are quite similar now - although when I flick it to radio it is the same as it was with the R channel notably quieter than L.

Given removing V4 makes no difference to the sound level of the R channel something is awry there with that part of the push pull it seems but anyway it is interesting that the volume changes swapping the turntable channels so it seems maybe the R channel tonearm wire has some weakness or something dropping it's signal....which is now affecting the L channel on gram mode. Anyway lets see what happens...

Ahhh the R channel still cuts out!!!

But just as one last ditch attempt.....if it was a ground wire in the tonearm damaged it could still cut the R channel out yeah? Well I am not sure so I've just bridged the grounds in the headshell incase.....

Otherwise it's back to chassis out and trying to see what's happening there.....