KW107 Supermatch Split stator capacitor advice - UK Vintage Radio Repair and Restoration Discussion Forum

G4_Pete · 4th Jul 2022, 7:24 pm

Hi,
I have a KW107 Supermatch ATU that I bought recently but on checking it out the split stator capacitor appears to have been distorted in that one section has even air gaps but the other section has a position offset giving a smaller air gap on one side of each vane. This is a bit odd in that I would have thought both sections would be affected but this is not the case.

my thoughts are I could try to bend the vanes to compensate for the distortion or shim the vanes tightly to maintain the gaps and re flow the solder the fixings carefully without the whole thing falling to bits. I have done the re solder trick before so I know it can work but both these options are risky and not ideal so I wanted to check if anyone had a split stator capacitor of this type they are willing to sell so that I can do a proper restore.

or any other advice accepted as these units are well worth restoring with their balanced output with no ferrites.

Pete

G4_Pete · 4th Jul 2022, 8:06 pm

HI Moderators,
sorry, re reading this I am not sure if it crosses the threshold for "wanted" so please accept apologies and move if that is the case.
Pete

Jon_G4MDC · 5th Jul 2022, 9:18 am

Since you are really asking if this one can be repaired I would think it is fine.

From photo #2 it appears that only the left hand 4 vanes or so have this problem. Those to the right seem to have fairly even spacing either side. If that is the case isn't it just those 4 rotor plates that are in need of a slight bend?

G4_Pete · 6th Jul 2022, 8:57 am

Hi Jon, The vanes on this capacitor seemed really springy and looking again at the distortion I think it may have been due to misaligned mounting brackets in the ATU applying pressure and causing solder creep and distortion over the many, many years since manufacture. I don't think it would have left the Jackson capacitor factory like this.
Therefore I did not bend the vanes and went for a full rebuild instead.

I De soldered the fixing bars as in the first photo then gapped it with 0.5mm ptfe shims and re soldered it back together. The bearings and end contact were pressure pre loaded using 1/4 inch shaft connectors tightened on the shaft against the end plates which saved making a compression jig for the whole capacitor.

The final gaps are shown in the shadow photograph and it also passes a 1Kv insulation test, the shaft has a similar torque and end float so all good now.

Pete

Jon_G4MDC · 6th Jul 2022, 10:37 am

Looks like a good job! You were brave to do that but if you have done it before...
73

4th Jul 2022, 7:24 pm	#1
G4_Pete Hexode Join Date: Feb 2014 Location: Southampton, Hampshire, UK. Posts: 419	KW107 Supermatch Split stator capacitor advice Hi, I have a KW107 Supermatch ATU that I bought recently but on checking it out the split stator capacitor appears to have been distorted in that one section has even air gaps but the other section has a position offset giving a smaller air gap on one side of each vane. This is a bit odd in that I would have thought both sections would be affected but this is not the case. my thoughts are I could try to bend the vanes to compensate for the distortion or shim the vanes tightly to maintain the gaps and re flow the solder the fixings carefully without the whole thing falling to bits. I have done the re solder trick before so I know it can work but both these options are risky and not ideal so I wanted to check if anyone had a split stator capacitor of this type they are willing to sell so that I can do a proper restore. or any other advice accepted as these units are well worth restoring with their balanced output with no ferrites. Pete Attached Thumbnails

5th Jul 2022, 9:18 am	#3
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: KW107 Supermatch Split stator capacitor advice Since you are really asking if this one can be repaired I would think it is fine. From photo #2 it appears that only the left hand 4 vanes or so have this problem. Those to the right seem to have fairly even spacing either side. If that is the case isn't it just those 4 rotor plates that are in need of a slight bend?

6th Jul 2022, 8:57 am	#4
G4_Pete Hexode Join Date: Feb 2014 Location: Southampton, Hampshire, UK. Posts: 419	Re: KW107 Supermatch Split stator capacitor advice Hi Jon, The vanes on this capacitor seemed really springy and looking again at the distortion I think it may have been due to misaligned mounting brackets in the ATU applying pressure and causing solder creep and distortion over the many, many years since manufacture. I don't think it would have left the Jackson capacitor factory like this. Therefore I did not bend the vanes and went for a full rebuild instead. I De soldered the fixing bars as in the first photo then gapped it with 0.5mm ptfe shims and re soldered it back together. The bearings and end contact were pressure pre loaded using 1/4 inch shaft connectors tightened on the shaft against the end plates which saved making a compression jig for the whole capacitor. The final gaps are shown in the shadow photograph and it also passes a 1Kv insulation test, the shaft has a similar torque and end float so all good now. Pete Attached Thumbnails

6th Jul 2022, 10:37 am	#5
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: KW107 Supermatch Split stator capacitor advice Looks like a good job! You were brave to do that but if you have done it before... 73

4th Jul 2022, 8:06 pm	#2
G4_Pete Hexode Join Date: Feb 2014 Location: Southampton, Hampshire, UK. Posts: 419	Re: KW107 Supermatch Split stator capacitor advice HI Moderators, sorry, re reading this I am not sure if it crosses the threshold for "wanted" so please accept apologies and move if that is the case. Pete