Help! How to repair the toning string of a portable radio? - Page 1
Forum section: electronics / repair

author: ali6x944
author_rank: Frequent Contributor
timestamp: July 26, 2016, 02:45:25 pm
content: Hi everyone,I was trying to fix this old Nawia WR-A70 multi band radio receiver that I found in my grandfather's old stuff pile...It is functioning just fine but the string is loss and the pointer is broken, I already fixed the pointer with two component epoxy, the only thing left is to wind the string again, but I don't know how...So please help!Note:I detached the specker and the antenna to make the radio simpler to access.https://drive.google.com/folderview?id=0B5vW-k7HbsL4WmR4b1FfQVpFRTQ

author: BMack
author_rank: Regular Contributor
timestamp: July 26, 2016, 03:22:28 pm
content: It looks like it goes around the brass lug and the black lug on the lower left. It should wrap around the larger black hub once, the spring is to tension.BTW, if there's no spring, they will generally have an arm that a hub sits on, you'd bend the arm to get the tension right.

author: pinyoro
author_rank: Contributor
timestamp: July 26, 2016, 04:02:29 pm
content: Brought back memories of radios in the 70's and 80's

author: ali6x944
author_rank: Frequent Contributor
timestamp: July 26, 2016, 04:32:06 pm
content: Quote from: BMack on July 26, 2016, 03:22:28 pmI didn't quite get it...Should the string rotate around the large hub completely then go to the brass lug?

author: ali6x944
author_rank: Frequent Contributor
timestamp: July 27, 2016, 08:10:31 am
content: I think I got it right ...https://drive.google.com/folderview?id=0B5vW-k7HbsL4WmR4b1FfQVpFRTQThanks for all help

author: BMack
author_rank: Regular Contributor
timestamp: July 28, 2016, 04:56:27 am
content: Looks good, congrats! That is one of the biggest pains in the butt on receivers. I warn anyone that has a tuning issue coming into the shop that if that string is broken it will add $40-75 to the repair cost, luckily it's really rare.

author: Ian.M
author_rank: Super Contributor
timestamp: July 28, 2016, 05:40:22 am
content: Cord drive tuning systems back in the old days could have extremely complex threading. e.g. the direction and number of turns round a shaft or pulley and whether the turns were wound upwards or downwards tended to be critical. If you got it wrong, the drive would tend to slip or jam, commonly towards one limit or the other of its range. It could also judder due to the incorrect lead angle causing one turn to pile on top of another then slip off again as it starts to jam.The first rule of successful rethreading is: If you don't have a clear threading diagram from the service manual, preserve *ALL* evidence of how it was originally threaded before doing *ANYTHING* else to the receiver. e.g. photo whatever remains of the original cord, closeup and from several angles. Count turns remaining on all shafts or pulleys, noting direction and for multiple turns, which side is on top. Look for marks in dust, wear patterns, cord wear etc. that may help resolve ambiguities. Also examine the tensioner mechanism very carefully to see is there is any evidence of its original position, and measure the exact length of the cord to the break either side and the position of anything fixed to the cord (e.g. pointers) so you can check the length of the new cord to be certain you haven't got too many or too few turns around any shaft or pulley.

author: ali6x944
author_rank: Frequent Contributor
timestamp: July 28, 2016, 05:47:07 pm
content: Sorry....The old radio was working fine until my younger 1½ year old brother played with it and broke it by turning it hard causing the string to break, and the black hub to crack,so it died again, the string is now known to fix, but the hub is a different story so how to fix that:https://drive.google.com/folderview?id=0B5vW-k7HbsL4WmR4b1FfQVpFRTQ

author: Ian.M
author_rank: Super Contributor
timestamp: July 28, 2016, 09:20:55 pm
content: Show us a closeup photo of the crack!The odds of a successful repair depend on what the drive drum is made of and the precise location of the crack. ABS plastic can be glued with the right solvent glue but Nylon generally cannot. Mechanical reinforcement is essential - e.g. wrapping thread round the cracked hub annd saturating it in glue.

author: BMack
author_rank: Regular Contributor
timestamp: July 29, 2016, 06:49:52 am
content: I think you can get by with gorilla glue, but you have to be careful.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 31, 2016, 04:19:46 am
content: Gorilla Glue expands quite a bit as it cures... Just something to be aware of.

author: ali6x944
author_rank: Frequent Contributor
timestamp: May 21, 2018, 09:19:51 am
content: hi again,it have been a long while, but nevertheless I got another WR-A70 radio to be fixed with the same tuner string problem and a couple more...the toner string in this one however is badly rotted so I throw it out, in the process of removing it a brass lug fell, unlike the old radio we fixed this one has two holes for the brass lug...