Trimmer tool for adjusting skeleton pre-set potentiometers - Page 1
Forum section: electronics / rf-microwave

author: I try hard
author_rank: Newbie
timestamp: February 10, 2018, 08:57:14 pm
content: I'm currently converting a 30 year old 2 meter transciever (Yaesu FT480) to allow it to operate with UK repeaters. One necessary step is to reduce the FM deviation from the original plus/minus 5kHz to plus/minus 2.5 KHz. I'm quite comfortable with the procedure and have the necessary mod/dev meter and know clearly the trimpots and location for the adjustment. However, with this radio the trimpots have a peculiar central circular hole about 1.2mm diameter with no hex flats or screwdriver slot to allow adjustment. Has anyone come across this type before or could suggest a method of gripping the skelton wiper to enable it to be turned? Many thanks in advance...

author: floobydust
author_rank: Super Contributor
timestamp: February 10, 2018, 10:04:08 pm
content: A picture would really help.It is probably a Japanese manufacturer (Murata, TDK etc.) so sometimes you can back-track the alignment tool, if it is a specialty one.

author: I try hard
author_rank: Newbie
timestamp: February 11, 2018, 11:10:46 am
content: Thanks very much for that floobydust. It's a bit tricky for me to get a picture as there is limited scope for raising the radio casing panel due to a closely tethered wiring harness linked to the speaker and other circuitry on the inside of the panel. Obviously I will have to remove this to carry out the adjustment though so I will try. Its almost as if the accessible side of the pot is the rear face and there might be a screwdriver slot on the reverse side - but this is impossible to access without serious dismantling. Point noted about the probable source of the pot. I'll take a look on google.Kind regards

author: Ian.M
author_rank: Super Contributor
timestamp: February 11, 2018, 12:34:00 pm
content: Press a piece of plasticine into one to take an impression, or use a dental mirror.

author: I try hard
author_rank: Newbie
timestamp: February 11, 2018, 03:45:42 pm
content: Thanks Ian.M. I took a photo of a similar pot - easier to get at. I think there may be some sort of screwdriver slot after all...

author: Ian.M
author_rank: Super Contributor
timestamp: February 11, 2018, 05:34:56 pm
content: If that's got a protruding lug bent up on either side of the rotor center, then you need a piece of dowel with the end slotted to fit over the lugs, and a pin in the end of it to fit in the center hole so it doesn't slip sideways.

author: I try hard
author_rank: Newbie
timestamp: February 12, 2018, 10:57:59 am
content: OK Ian.M. Well it looks as though I could get a well fitting screwdriver blade in. It has to be a snug fit into the lugs so I may have to get the grindstone out. Point noted about the centre pin - I'll try to contrive something.Thanks again.

author: Cyberdragon
author_rank: Super Contributor
timestamp: February 23, 2018, 07:37:39 pm
content: I just use my fingers for these.(waiting for rants)

author: sidspop
author_rank: Contributor
timestamp: March 03, 2018, 01:09:57 pm
content: Tey can usually be done by carefully using an ordinary straight trimmer at the side of the centre bit, and parallel to it.