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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th May 2021, 2:12 pm   #1
Electron cloud
Diode
 
Join Date: May 2021
Location: Garstang, Lancashire, UK.
Posts: 6
Default IF transformers MK 56868 bad?

I was given a pair of these as part of a box of parts.
Wanting to throw together a radio using trannies over my hols I tried to use these as the IF, being double tuned using fets to buffer the secondary.
But I could not no matter what I tried get them to tune at anything other than around 1mc, padding them with caps just kills the peaks.
I pulled them apart, re soldered the conns but no different, all seems to be Ok internally, dc resistance Ok 7 and 4 ohms.
So I borrowed a pair from a philips B2g81 I think it was (I also have a stella 110 that has them) put them on my test jig and they resonate nicely at 370kc, Ok low in freq but more like what I expected.
So these in my junk box were duffers, but why when dc resistance being the same as good ones and the caps reading around 200pf did they do this?
So I'll carry on with the build now with the borrowed good ones.
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Old 8th May 2021, 6:02 pm   #2
Electron cloud
Diode
 
Join Date: May 2021
Location: Garstang, Lancashire, UK.
Posts: 6
Default Re: IF transformers MK 56868 bad?

They are bad.

In three of the four I have the piece of ferrite has become disconnected from the adjusting screw.
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