Bush AC11 alignment and IFT adjusters. - UK Vintage Radio Repair and Restoration Discussion Forum

Neil Purling · 11th Nov 2007, 12:12 am

I don't have a actual Bush AC11 but I posess the complement of aerial & osc coils plus IFT's from a AC11 for a project.
Was there a special tool used to turn those tiny spindles of the IFT cores?
I expected to have to file down a plastic knitting needle to fit the hexagonal hole in a ferrite slug.
In the event that it is necessary: How does one safely free the spindles from the sealant?
Is there a lock-nut? I have the Trader sheet for the alignment procedure, if a adjustment of the cores is required.

Robert Darwent · 11th Nov 2007, 12:47 am

Hello Neil

I bought a set of ten ABS plastic trimming tools from Maplin Electronics recently, which included various sized straight edges, square, and hexagonal tips for safely adjusting IFT's and the like.

At the time I bought mine (about a month ago) they were selling the stock they had at a fraction of its listed price, because once they are all sold they won't be having any more. So if you're interested don't hang about placing an order!

Leon Crampin · 11th Nov 2007, 11:24 am

If the IF transformer adjusters on the AC11 are the same as the later Bush sets (DAC90A etc) you need to go carefully.

This type of adjuster threaded rod has 2 flats on the end to enable it to be turned and is locked with an 8 BA brass locknut. There is also a rubber washer under the locknut which enables the thread to be preloaded to permit easy adjustment. The adjuster rod is threaded in the phenolic former and this thread is fragile.

My method of dealing with these is as follows: Remove Bush locking paint with acetone. Squash a piece of car hydraulic metal brake pipe in the vice until it fits the flats on the adjuster. Slacken the 8 BA locknut. Clean the threads and tighten the locknut against the adjuster rod until the rubber washer is just compressed - little more than finger tight. Align the set, holding the locknut whilst you turn the adjuster rod. Then lock the assembly with typewriter correction fluid.

Any attempt to lock the rod after adjustment by turning the locknut will probably result in a broken coil former - the threads are very fragile.

The adjuster rods are deliberately made small to reduce eddy current losses in the transformers.

Leon.

11th Nov 2007, 12:12 am	#1
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Bush AC11 alignment and IFT adjusters. I don't have a actual Bush AC11 but I posess the complement of aerial & osc coils plus IFT's from a AC11 for a project. Was there a special tool used to turn those tiny spindles of the IFT cores? I expected to have to file down a plastic knitting needle to fit the hexagonal hole in a ferrite slug. In the event that it is necessary: How does one safely free the spindles from the sealant? Is there a lock-nut? I have the Trader sheet for the alignment procedure, if a adjustment of the cores is required.

11th Nov 2007, 12:47 am	#2
Robert Darwent Heptode Join Date: Aug 2006 Location: Sheffield, South Yorkshire, UK Posts: 990	Re: Bush AC11 alignment. Hello Neil I bought a set of ten ABS plastic trimming tools from Maplin Electronics recently, which included various sized straight edges, square, and hexagonal tips for safely adjusting IFT's and the like. At the time I bought mine (about a month ago) they were selling the stock they had at a fraction of its listed price, because once they are all sold they won't be having any more. So if you're interested don't hang about placing an order! __________________ Robert G0UHF www.wavesintheair.co.uk

11th Nov 2007, 11:24 am	#3
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Bush AC11 alignment. If the IF transformer adjusters on the AC11 are the same as the later Bush sets (DAC90A etc) you need to go carefully. This type of adjuster threaded rod has 2 flats on the end to enable it to be turned and is locked with an 8 BA brass locknut. There is also a rubber washer under the locknut which enables the thread to be preloaded to permit easy adjustment. The adjuster rod is threaded in the phenolic former and this thread is fragile. My method of dealing with these is as follows: Remove Bush locking paint with acetone. Squash a piece of car hydraulic metal brake pipe in the vice until it fits the flats on the adjuster. Slacken the 8 BA locknut. Clean the threads and tighten the locknut against the adjuster rod until the rubber washer is just compressed - little more than finger tight. Align the set, holding the locknut whilst you turn the adjuster rod. Then lock the assembly with typewriter correction fluid. Any attempt to lock the rod after adjustment by turning the locknut will probably result in a broken coil former - the threads are very fragile. The adjuster rods are deliberately made small to reduce eddy current losses in the transformers. Leon.