Sherwood RX-1010 fm tuning is off by 0.05

[balconyGardener]

I bought this in 1990, as I remember. I hope that is vintage enough for the forum. The reason why I post is that after giving it a good dusting inside. I find that when I tune the radio (it's digital), I have to tune to .05 over the correct frequency. So for example 90.30 doesn't work but 90.35 does.

I had a look inside and it contains a matsumi FE407-G60. I'm wondering if I can fix this issue by turning the 'screw' at the top right hand corner. Does anyone know if this will help?

I should also say that the radio is usable as it is. It does tune and the sound is decent, but I feel it is has a little static, but nothing disastrous. 'if it ain't broke don't fix it', so I'm checking this out before I try anything out.

Thanks in advance

[paulsherwin]

This normally happens because the discriminator transformer has drifted slightly.

This is easy to fix if you can identify the discriminator transformer. If you can't identify it with certainty, leave it alone and live with the fault. Don't twiddle transformer cores at random as you will wreck the alignment.

Tune in a station, then manually tune to the correct frequency. The stereo indicator will go out and the signal may mute. Carefully adjust the transformer core until the stereo indicator comes on. Continue to turn the core until the indicator goes out again. Now turn the core in the other direction to the midpoint between the two positions where the indicator goes out. The tuner should now tune to, and display, the correct frequency.

You may need to make further very small adjustments to make the tuner tune reliably.

And record all original positions of cores beforehand!

[balconyGardener]

Thanks Paulsherwin for your reply. And, yes, I agree with the caution.

I found a pdf of the original service manual. On page 10 it discusses 'alignment procedures'. To be honest, I don't understand a word of it. Is this any help in working out how I can tweak it?

I've made some printscreens as the pdf is too large to post.

and the link for the pdf:
https://elektrotanya.com/sherwood_rx.../download.html

Thanks again.

[paulsherwin]

I would guess that the discriminator transformer will be DET A or DET B, probably DET B looking at the snippet of the alignment instructions. I don't have time to go through the full service manual right now.

[boxdoctor]

Looks to be Detector "B", Paul.
So a careful adjustment using a non-metallic tool as Paul describes should do the trick.
I came across this problem several times when I was in the repair trade. Tony.

[balconyGardener]

Success! Thanks to all. I tweaked the DET B and it got back in order. Great

[Restoration73]

It is easy to construct a tool to effect a small change of L by proximity. A small tube, e.g.
paxolin, or even a plastic pen, has a ferrite or dust iron core screwed into one end, and
a brass or aluminium core or short rod in the other. By placing one end near the core
to be adjusted, a change of tuning is noted. The non-ferrous end reduces inductance.

[Herald1360]

Known as a "Tuning Wand" ......