Repair advice needed!

[bigbandbone]

This is crazy! I repaired band instruments for 42 years. Now that I've retired and I'm only working on my own axes I find I need to ask for advice on a problem I've never encountered before!
I just bought a Conn 72H bass bone in very good condition. But I find when reaching for trigger low C in 7+ position there is a drag, but just on the upper outer slide. There is no drag when the lower outer slide tube is tested on either inner slide. But there is a drag on both inner tubes when tested with only the upper outer slide. It's in the area of the outer slide sleeves. On visual inspection there are no dents or deformations.
How would you other repair guys approach this problem? I've still got the set of three Ferree's large bore slide mandrels. Also the allied expandable large bore mandrel, but I really hate that tool.
Any advice is greatly appreciated. Thanks

[Bonearzt]

Quite possibly the hand brace has been pushed in, or under the lock lug. Sometimes hard to notice any deformations in those areas.
Could also be slightly bent.

I would start by sighting down the tube in that area from both ends of the slide, and or checking against a stone or straight edge. Then try a mandrel feeling for any hesitation.
VERY last choice, as you seem to agree, is the expanding mandrel.
Also check that the end of the tube is perfectly round.

Best of Luck!
Eric

[bigbandbone]

Quite possibly the hand brace has been pushed in, or under the lock lug. Sometimes hard to notice any deformations in those areas.
Could also be slightly bent.

I would start by sighting down the tube in that area from both ends of the slide, and or checking against a stone or straight edge. Then try a mandrel feeling for any hesitation.
VERY last choice, as you seem to agree, is the expanding mandrel.
Also check that the end of the tube is perfectly round.

Best of Luck!
Eric

Thanks for your insight Eric. It was either under the locking lug or the hand slide socket. None of my mandrels were snug enough to do the job so I had to use the dreaded expandable mandrel. That got most of it. Then I lapped the first 3-4" of the outer tub with 1200 grit lapping coumpound to get the last bit of drag out. Low trigger C is a lot easier to get to now.

[Bonearzt]

Quite possibly the hand brace has been pushed in, or under the lock lug. Sometimes hard to notice any deformations in those areas.
Could also be slightly bent.
I would start by sighting down the tube in that area from both ends of the slide, and or checking against a stone or straight edge. Then try a mandrel feeling for any hesitation.
VERY last choice, as you seem to agree, is the expanding mandrel.
Also check that the end of the tube is perfectly round.
Best of Luck!
Eric

Thanks for your insight Eric. It was either under the locking lug or the hand slide socket. None of my mandrels were snug enough to do the job so I had to use the dreaded expandable mandrel. That got most of it. Then I lapped the first 3-4" of the outer tub with 1200 grit lapping coumpound to get the last bit of drag out. Low trigger C is a lot easier to get to now.

Glad to help!!

Eric